0001326190-23-000008 | 10-K | XBRL Viewer

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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2022	Feb. 24, 2023	Jun. 30, 2022
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Trading Symbol	ALT
Entity Registrant Name	ALTIMMUNE, INC.
Entity Central Index Key	0001326190
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
ICFR Auditor Attestation Flag	false
Entity Common Stock, Shares Outstanding		49,278,861
Entity Public Float			$ 537.9
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common stock, par value $0.0001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-32587
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-2726770
Entity Address, Address Line One	910 Clopper Road
Entity Address, Address Line Two	Suite 201S
Entity Address, City or Town	Gaithersburg
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	20878
City Area Code	(240)
Local Phone Number	654-1450
Document Annual Report	true
Document Transition Report	false
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	Tysons, Virginia

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 111,097	$ 190,301
Restricted cash	34	34
Total cash, cash equivalents and restricted cash	111,131	190,335
Short-term investments	73,783
Accounts receivable	173	429
Income tax and R&D incentive receivables	2,368	5,410
Prepaid expenses and other current assets	5,358	7,952
Total current assets	192,813	204,126
Property and equipment, net	1,081	1,448
Intangible assets, net	12,419	12,419
Other assets	615	872
Total assets	206,928	218,865
Current liabilities:
Accounts payable	4,804	2,034
Contingent consideration		6,090
Accrued expenses and other current liabilities	12,250	10,152
Total current liabilities	17,054	18,276
Other long-term liabilities	4,581	1,454
Total liabilities	21,635	19,730
Commitments and contingencies (Note 17)
Stockholders' equity:
Common stock, $0.0001 par value; 200,000,000 shares authorized; 49,199,845 and 40,993,768 shares issued and outstanding as of December 31, 2022 and December 31, 2021, respectively	5	4
Additional paid-in capital	568,399	497,342
Accumulated deficit	(377,884)	(293,171)
Accumulated other comprehensive loss, net	(5,227)	(5,040)
Total stockholders' equity	185,293	199,135
Total liabilities and stockholders' equity	$ 206,928	$ 218,865

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
CONSOLIDATED BALANCE SHEETS
Common stock, par or stated value per share	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	49,199,845	40,993,768
Common stock, shares outstanding	49,199,845	40,993,768

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Revenues	$ (68)	$ 4,410
Operating expenses:
Research and development	70,538	74,541
General and administrative	17,134	15,413
Impairment loss on construction-in-progress		11,370
Total operating expenses	87,672	101,324
Loss from operations	(87,740)	(96,914)
Other income (expense):
Interest expense	(8)	(5)
Interest income	2,870	203
Other income (expense), net	(32)	(374)
Total other income (expense), net	2,830	(176)
Net loss before income taxes	(84,910)	(97,090)
Income tax expense (benefit)	(197)
Net loss	(84,713)	(97,090)
Other comprehensive income - unrealized (loss) gain on short-term investments	(187)	4
Comprehensive loss	$ (84,900)	$ (97,086)
Net loss per share, basic	$ (1.81)	$ (2.35)
Net loss per share, diluted	$ (1.81)	$ (2.35)
Weighted-average common shares outstanding, basic	46,926,349	41,283,498
Weighted-average common shares outstanding, diluted	46,926,349	41,283,498

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]	Total
Beginning Balance at Dec. 31, 2020	$ 4	$ 417,337	$ (186,421)	$ (5,044)	$ 225,876
Beginning Balance (in shares) at Dec. 31, 2020	37,142,946
Stock-based compensation		5,519			5,519
Exercise of stock options		176			176
Exercise of stock options (in shares)	54,068
Vesting of restricted stock awards including withholding, net		(400)			(400)
Vesting of restricted stock awards including withholding, net (in shares)	(28,850)
Issuance of common stock from Employee Stock Purchase Plan		225			225
Issuance of common stock from Employee Stock Purchase Plan (in shares)	24,100
Retirement of common stock in exchange for common stock warrant		(7,540)	(9,660)		(17,200)
Retirement of common stock in exchange for common stock warrant (in Shares)	(1,000,000)
Issuance of common stock warrant in exchange for retirement of common stock		17,200			17,200
Issuance of common stock in at the market offerings, net		64,815			64,815
Issuance of common stock in at the market offerings, net (in shares)	4,800,454
Issuance of common stock upon cashless exercise of warrants		10			10
Issuance of common stock upon cashless exercise of warrants (in shares)	1,050
Unrealized (loss) gain on short-term investments				4	4
Net loss			(97,090)		(97,090)
Ending Balance at Dec. 31, 2021	$ 4	497,342	(293,171)	(5,040)	199,135
Ending Balance (in shares) at Dec. 31, 2021	40,993,768
Stock-based compensation		8,101			8,101
Exercise of stock options		950			$ 950
Exercise of stock options (in shares)	358,317				373,545
Vesting of restricted stock awards including withholding, net		(516)			$ (516)
Vesting of restricted stock awards including withholding, net (in shares)	8,695
Issuance of common stock from Employee Stock Purchase Plan		181			181
Issuance of common stock from Employee Stock Purchase Plan (in shares)	26,395
Issuance of common stock in at the market offerings, net	$ 1	56,165			56,166
Issuance of common stock in at the market offerings, net (in shares)	5,204,215
Issuance of common stock related to contingent consideration liability		6,176			6,176
Issuance of common stock related to contingent consideration liability (in shares)	847,444
Issuance of common stock upon cashless exercise of warrants (in shares)	1,760,854
Other increase (in shares)	157
Unrealized (loss) gain on short-term investments				(187)	(187)
Net loss			(84,713)		(84,713)
Ending Balance at Dec. 31, 2022	$ 5	$ 568,399	$ (377,884)	$ (5,227)	$ 185,293
Ending Balance (in shares) at Dec. 31, 2022	49,199,845

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (84,713)	$ (97,090)
Adjustments to reconcile net loss to net cash used in operating activities:
Change in fair value of contingent consideration liability	86	700
Impairment loss on construction-in-progress		11,370
Impairment loss on intangible assets		579
Stock-based compensation expense	8,101	5,519
Depreciation and amortization	(205)	551
Loss on foreign currency exchange	34	384
Changes in operating assets and liabilities:
Accounts receivable	256	4,181
Prepaid expenses and other assets	2,650	(5,908)
Accounts payable	2,770	1,422
Accrued expenses and other liabilities	5,393	(2,299)
Income tax and R&D incentive receivables	3,042	2,353
Net cash used in operating activities	(62,586)	(78,238)
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sales and maturities of short-term investments		107,427
Purchases of short-term investments	(73,273)	(7,592)
Purchases of property and equipment, net	(126)	(12,117)
Cash paid for internally developed patents		(195)
Net cash (used in) provided by investing activities	(73,399)	87,523
CASH FLOWS FROM FINANCING ACTIVITIES:
Payments of deferred offering costs		(118)
Proceeds from issuance of common stock in at-the-market offerings, net	56,166	64,815
Proceeds from issuance of common stock from Employee Stock Purchase Plan	181	225
Proceeds from exercises of stock options, net	434	176
Net cash provided by financing activities	56,781	65,098
Net (decrease) increase in cash and cash equivalents and restricted cash	(79,204)	74,383
Cash, cash equivalents and restricted cash at beginning of period	190,335	115,952
Cash, cash equivalents and restricted cash at end of period	111,131	190,335
SUPPLEMENTAL NON-CASH ACTIVITIES:
Fair value of common stock retired in exchange for issuance of common stock warrant		17,200
Common stock issued related to contingent consideration liability	$ 6,176
Operating lease liability and right of use asset addition		$ 72

Nature of Business and Organization

12 Months Ended

Dec. 31, 2022

Nature of Business and Organization

Nature of Business and Organization

1. Nature of Business and Organization

Altimmune, Inc., headquartered in Gaithersburg, Maryland, United States, together with its subsidiaries (collectively, the “Company” or “Altimmune”) is a clinical stage biopharmaceutical company incorporated under the laws of the State of Delaware.

The Company is focused on developing treatments for obesity and liver diseases. The Company’s pipeline includes next generation peptide therapeutics for obesity and non-alcoholic steatohepatitis (“NASH”) (for both, pemvidutide, formerly known as ALT-801), and for chronic hepatitis B (HepTcell). Since its inception, the Company has devoted substantially all of its efforts to business planning, research and development, recruiting management and technical staff and raising capital, and has financed its operations through the issuance of common and preferred stock, long-term debt and proceeds from research grants and government contracts. The Company has not generated any revenues from the sale of any products to date, and there is no assurance of any future revenues from product sales.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2022

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

The accompanying consolidated financial statements are prepared in conformity with generally accepted accounting principles in the United States (“U.S. GAAP”) and in accordance with the rules and regulations of the United States Securities and Exchange Commission (“SEC”). The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. Significant estimates relied upon in preparing the accompanying consolidated financial statements were related to the fair value of common stock and other equity instruments, accounting for stock-based compensation, income taxes, useful lives of long-lived assets, fair value of contingent consideration, impairment of long-lived assets, and accounting for project development and certain accruals. The Company assesses the above estimates on an ongoing basis; however, actual results could differ materially from those estimates.

Segment Information

The Company is managed and operates as a single business focused on the research and development of treatments for various diseases and disorders, and vaccines. The Company is managed by a single management team, and consistent with its organizational structure, the Chief Executive Officer manages and allocates resources at a consolidated level. Accordingly, the Company views its business as one operating segment.

Cash Equivalents

The Company considers all highly liquid investments purchased with remaining maturities of 90 days or less on the purchase date to be cash equivalents, and includes amounts held in money market funds which are actively traded (a Level 1 input).

Restricted Cash

The Company had restricted cash of $34,000 as of both December 31, 2022 and 2021, held in money market savings accounts as collateral. The restricted cash as of December 31, 2022 and 2021 is for the Company’s facility lease obligation. Restricted cash is classified as a component of cash, cash equivalents, and restricted cash in the accompanying consolidated balance sheets and consolidated statements of cash flows.

Short-term Investments

The Company’s short-term investments are comprised of U.S. Treasury, corporate debt securities and certificate of deposit that have original maturities less than or equal to one year and are classified as available-for-sale securities. Such securities are carried at estimated fair value, with any unrealized holding gains or losses reported as accumulated other comprehensive income or loss, which is a separate component of stockholders’ equity. Realized gains and losses and declines in value judged to be other-than-temporary, if any, are included in other income (expenses), net in the consolidated results of operations. The Company reviews its investment portfolio for impairment quarterly or more frequently if circumstances warrant. In determining whether a decline in the value of an investment is other-than-temporary, the Company evaluates currently available factors that may include, among others: (1) general market conditions; (2) the duration and extent to which fair value has been less than the carrying value; (3) the investment issuer’s financial condition and business outlook; and (4) its assessment as to whether it is more likely than not that the Company will be required to sell a security prior to recovery of its amortized cost basis. A decline in the market value of any available-for-sale security below cost that is deemed to be other-than-temporary results in a reduction in fair value charged to earnings in that period, and a new cost basis for the security is established. Dividend and interest income are recognized in other income when earned. The cost of securities sold is calculated using the specific identification method. The Company places all investments with government agencies, or corporate institutions whose debt is rated as investment grade.

Fair Value Measurements

The Company records certain financial assets and liabilities at fair value in accordance with the guidance in Financial Accounting Standards Board (“FASB”) Accounting Standard Codification Topic 820, Fair Value Measurements and Disclosures (“ASC 820”), which defines fair value and establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are described below:

Level 1 — Quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company can access at the measurement date.

Level 2 — Inputs other than quoted prices included within Level 1 that are either directly or indirectly observable. If the asset or liability has a specified (contractual) term, a Level 2 input must be observable for substantially the full term.

Level 3 — Unobservable inputs developed using estimates of assumptions developed by the Company, which reflect those that a market participant would use.

To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. There were no transfers into or out of Level 3 of the fair value hierarchy during the years ended December 31, 2022 and 2021.

Financial Instruments

The Company’s financial instruments consist of cash, cash equivalents, restricted cash, accounts receivable, short-term investments, accounts payable, accrued expenses, and common stock warrants classified as equity. The carrying amounts of cash, cash equivalents, restricted cash, accounts receivable, accounts payable, and accrued expenses approximate their fair value due to the short-term nature of those financial instruments. Short-term investments are

recorded at fair value, with any unrealized holding gains or losses reported as accumulated other comprehensive income or loss. For those warrants with a down round feature, if the down round feature is triggered, the Company would remeasure those instruments at that time with changes recorded as a deemed dividend all within equity.

Accounts Receivable

Accounts receivable includes both billed and unbilled amounts. The Company makes judgments as to its ability to collect outstanding receivables and provides an allowance for receivables when collection becomes doubtful. Provisions are made based upon a specific review of all significant outstanding invoices and the overall quality and age of those invoices not specifically reviewed. The Company’s receivables represent amounts reimbursed under its government grants and contracts. The Company believes that credit risks associated with these government grants and contracts is not significant. To date, the Company has not experienced any losses associated with accounts receivable and does not maintain an allowance for doubtful accounts.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents, restricted cash, short-term investments and accounts receivable. Periodically, the Company maintains deposits in financial institutions in excess of government insured limits. Management believes that the Company is not exposed to significant credit risk as the Company’s deposits are held at financial institutions that management believes to be of high credit quality. The Company has not experienced any losses in these deposits.

Property and Equipment, Net

The Company records property and equipment at cost less accumulated depreciation and amortization. Expenditures for maintenance and repairs are charged to operations as incurred, whereas major improvements are capitalized as additions to property and equipment. Costs of assets under construction are capitalized but are not depreciated until the construction is substantially complete and the assets being constructed are ready for their intended use.

Depreciation and amortization are recorded using the straight-line method over the estimated useful lives of the assets, as follows:


Asset Category		Estimated Useful Life
Computer and telecommunications		3 – 5 years
Software		3 years
Furniture, fixtures and equipment		5 years
Laboratory equipment		7 years
Leasehold improvements		Lesser of lease term or estimated useful lives

Intangible Assets

The Company records intangible assets acquired in a business combination based on fair value on the date of acquisition. Acquired in-process research and development (“IPR&D”) assets that have alternative future use at the time of acquisition are capitalized as an indefinite-lived intangible asset and tested for impairment until the project is completed or abandoned. Upon completion of the project, the indefinite-lived intangible asset will be accounted for as a finite-lived intangible asset and amortized on a straight-line basis over its estimated useful life. If the project is abandoned, the indefinite-lived intangible asset will be charged to expense.

Intangible assets acquired in other transactions are recorded at cost. The Company capitalizes costs incurred in the course of obtaining patents and license issuance fees for the use of proprietary technologies. Costs incurred for obtaining patents are amortized on a straight-line basis over the estimated useful lives of the assets from the time of approval of the patent. Prior to approval, these costs are carried on the balance sheets and not amortized. In the event approval is denied, the cost of the denied application is expensed. License issuance fees are amortized on a straight-line basis over the estimated useful lives of the underlying licensed technology. Amortization costs are classified as research and development expenses.

Impairment of Long-lived Assets

The Company evaluates its long-lived tangible and intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Impairment of long-lived assets other than goodwill and indefinite lived intangibles is assessed by comparing the undiscounted cash flows expected to be generated by the asset group to its carrying value.

The Company has one IPR&D asset, HepTcell, that was acquired in 2015. This candidate is a viral pathogen immunotherapy product for the treatment of chronic HBV. The IPR&D asset is currently non-amortizing. Until such time as the project is either completed or abandoned, the Company tests this asset for impairment at least annually at year end, or more frequently at interim periods, by evaluating qualitative factors which could be indicative of impairment. Qualitative factors being considered include, but are not limited to, the current project status, forecasted changes in the timing or amounts required to complete the project, forecasted changes in timing or changes in the future cash flows to be generated by the completed product, a probability of success of the ultimate project and changes to other market-based assumptions, such as discount rates. If impairment indicators are present as a result of the Company’s qualitative assessment, the Company will test the asset for impairment by comparing the fair value of the asset to its carrying value. Upon completion or abandonment, the value of the IPR&D asset will be amortized to expense over the anticipated useful life of the developed product, if completed, or charged to expense when abandoned if no alternative future use exists. Key assumptions used in the Company’s impairment analysis tests include projected cash flows, a probability of success of the ultimate project, and the discount rate.

The Company performed a qualitative assessment for the IPR&D impairment testing for the year ended December 31, 2022 and 2021 and determined that no impairment indicators were present.

Leases

The Company determines if an arrangement is a lease at inception. Operating leases are recorded as a current and long-term lease obligation, with a corresponding right of use lease assets.

Lease liabilities represent the Company’s obligation to make lease payments arising from leases. Right of use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term. Lease liabilities and ROU assets are recognized at the lease commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the lease commencement date in determining the present value of lease payments. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise those options. Lease expense for lease payments is recognized on a straight-line basis over the lease term.

Short-term leases are leases having a term of twelve months or less. The Company recognizes short-term leases on a straight-line basis and does not record a related lease asset or liability for such leases.

Lease incentives and allowance provided by our landlord for the construction of leasehold improvements are recorded as lease incentive obligations as the related construction costs are incurred, up to the maximum allowance.

Contingent Consideration

The Company records contingent consideration associated with development and regulatory milestones that meets the definition of a liability under FASB Accounting Standards Codification Topic 480, Distinguishing Liabilities From Equity (“ASC 480”) at fair value. The fair value model used to calculate this obligation is based on the Monte Carlo simulation that has been risk adjusted based on the probability of achievement of the milestones. The inputs the Company uses for determining the fair value of the contingent consideration associated with development and regulatory milestones are Level 3 fair value measurements. The Company re-evaluates the fair value on a quarterly basis. Changes in the fair value can result from adjustments to the probability of achievement of the milestones, stock price, volatility and the risk-free interest rate.

The change in the Company’s estimates associated with payments for development and regulatory milestones could change the fair value of contingent consideration, resulting in a charge or contra expense to research and development expense in the period in which the increase or decrease is determined.

Warrants

Common stock warrants issued in connection with the 2018 Unit Offering, the 2018 and 2019 Registered Direct Offerings, and the 2020 Public Offering (all terms defined in Note 10 and Note 11), were classified as a component of permanent equity because they are freestanding financial instruments that were legally detachable and separately exercisable from other debt and equity instruments, are contingently exercisable, do not embody an obligation for the Company to repurchase its shares, and permits the holders to receive a fixed number of common shares upon exercise. In addition, such warrants did not provide any guarantee of value or return. The 2018 Registered Direct Offering and 2019 Registered Direct Offering triggered down round adjustments to the exercise price of warrants issued in connection with the 2018 Unit Offering. In the event that down round adjustment is triggered, the Company treats the value of the effect of the reduction in exercise price as a deemed dividend, resulting in a reduction to income available to common shareholders.

Stock-based Compensation

The Company accounts for all stock-based compensation granted to employees and non-employees using a fair value method. The Company estimates the fair value of stock options granted using the Black-Scholes option pricing model on the dates of grant. For restricted stock and restricted stock units granted, fair value is determined based on the grant date closing price of the Company’s common stock.

Stock-based compensation awarded to employees is measured at the grant date fair value of stock option grants and is recognized over the requisite service period of the awards, usually the vesting period, on a straight-line basis, net of estimated forfeitures.

If awards are modified, the Company compares the fair value of the affected award measured immediately prior to modification to its value after modification. To the extent that the fair value of the modified award exceeds the original award, the incremental fair value of the modified award is recognized as compensation expense on the date of modification for vested awards, and over the remaining vesting period for unvested awards.

Revenue

The Company’s revenue consists primarily of government and foundation grants and contracts that support the Company’s efforts on specific research projects. The Company has determined that the government agencies and foundations providing grants and contracts to the Company are not customers. These grants and contracts generally provide for reimbursement of approved costs as those costs are incurred by the Company. Research grants and contracts and the related accounts receivable are recognized as earned in proportion to when reimbursable expenses are incurred in performance of the contract. Payments received in advance of services being provided are recorded as deferred revenue. The Company anticipates that these government and foundation grants will decline in future periods.

Research and Development

Research and development costs are expensed as incurred. Research and development costs consist of payroll and personnel expense, consulting costs, external contract research and development expenses, which includes fees paid to other entities that conduct certain research and development activities on the Company’s behalf, such as clinical research organizations (“CROs”) and contract manufacturing organizations (“CMOs”), raw materials, drug product manufacturing costs, laboratory supplies and allocated overhead, including depreciation and amortization, rent and utilities. Material research and development costs that are paid in advance of performance are capitalized as a prepaid expense and amortized over the service period as the services are provided.

Clinical trial costs are a significant component of research and development expenses, and the Company outsources a significant portion of these costs to third parties. Third party clinical trial expenses include investigator fees, site and patient costs, CRO costs, costs for central laboratory testing, data management and CMO costs. The accrual for

site and patient costs includes inputs such as estimates of patient enrollment, patient cycles incurred, clinical site activations and other pass-through costs. These inputs are required to be estimated due to a lag in receiving the actual clinical information from third parties. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected on the consolidated balance sheets as a prepaid asset or accrued expenses. These third-party agreements are generally cancelable, and related costs are recorded as research and development expenses as incurred. Material advance payments for goods or services that will be used or rendered for future research and development activities are recorded as a prepaid asset and recognized as expense as the related goods are delivered or the related services are performed. When evaluating the adequacy of the accrued expenses, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates may be made in determining the accrued balances at the end of any reporting period.

Research and Development Incentive Credits

The Company is eligible to obtain certain research and development (“R&D”) incentive credits, through the participation in the U.K. R&D Small and Medium Enterprise tax relief program (“U.K. R&D credit”) and the Australian research and development incentive credit (the “Australia R&D credit”) program administered through the Australian Tax Office (the “ATO”).

The U.K. R&D credits are calculated as a percentage of qualifying R&D expenses and are payable in cash by the U.K. government to the Company. Qualifying R&D expenses consist of employment costs for research staff, consumables, a proportion of relevant, permitted sub-contract costs and certain internal overhead costs incurred as part of research projects for which the Company does not receive income. The Australia R&D credits provide for a cash refund based on a percentage of certain research and development activities undertaken in Australia by the Company’s wholly owned subsidiary, Altimmune AU Pty, Limited. Qualifying R&D expenses must be incurred within the country.

The U.K. and Australian incentive credits are available on the basis of specific criteria with which the Company must comply. The incentive credits are subject to future audits by the government authorities and a statute of limitations. Although the incentive credits may be administered through the local tax authority, the Company has accounted for the incentives outside of the scope of FASB Accounting Standards Codification Topic 740, Income Taxes (“ASC 740”), since the incentives are not linked to the Company’s taxable income and can be realized regardless of whether the Company has generated taxable income in the respective jurisdictions. The Company accounts for these incentive credits as a government grant which analogizes with International Accounting Standards 20 (“IAS 20”), Accounting for Government Grants and Disclosure of Government Assistance.

The Company records qualifying U.K. R&D expenses as receivable and a corresponding reduction to R&D expense in the consolidated statement of operations and comprehensive loss. During the years ended December 31, 2022 and 2021, the Company recognized $1.8 million and $1.9 million, respectively, of R&D credits as a reduction to R&D expense in the consolidated statement of operations and comprehensive loss. As of December 31, 2022 and 2021, the Company had $1.6 million and $1.8 million, respectively, of R&D credits included in “Income tax and R&D incentive receivables” on the accompanying consolidated balance sheets.

The Company records qualifying Australian R&D as receivable with a full valuation reserve. Cash receipts for Australia R&D credits are recorded as long-term liability until it either passes an audit performed by the Australian Tax Office, or the statute of limitations ends, whichever occurs first. Upon successfully passing an audit or the expiration of the statute of limitations, the Company will clear the liability and a corresponding reduction to R&D expense unless recognition criteria is met in a later year, in which case the R&D credit will be recorded as other income in the consolidated statement of operations and comprehensive loss. During the year ended December 31, 2022, the Company received a total of $3.6 million in cash for R&D incentive credit related to R&D costs that the Company incurred during the fiscal years 2021 and 2020 through the participation in the Australian R&D credit program, and is included in “Other long-term liabilities” on the accompanying consolidated balance sheets.

Income Taxes

The Company accounts for income taxes in accordance with ASC 740. ASC 740 uses the asset and liability approach, which requires the recognition of future tax benefits or liabilities on the temporary differences between the

financial reporting and tax bases of our assets and liabilities. Deferred tax assets and liabilities represent future tax consequences of temporary differences between the financial statement carrying amounts and the tax basis of assets and liabilities and for loss carryforwards using enacted tax rates expected to be in effect in the years in which the differences reverse. A valuation allowance is established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company also recognizes a tax benefit from uncertain tax positions only if it is “more likely than not” that the position is sustainable based on its technical merits. The Company accounts for interest and penalties related to uncertain tax positions as part of its provision for income taxes. To date, the Company has not incurred interest and penalties related to uncertain tax positions. Should such costs be incurred, they would be classified as a component of provision for income taxes.

The Company conducts R&D activities potentially qualified to claim research tax credits for U.S. federal and state purposes under Internal Revenue Code Section 41. The Company has not performed a formal study claiming these credits in the tax returns because the Company does not yet have taxable profits. Once the Company becomes profitable, it will likely have a study prepared, and the amount of R&D tax credits available could generate income tax benefit, subject to an annual Section 383 limitation and valuation allowance for realizability of the deferred tax asset.

Comprehensive Loss

For the years presented, the total comprehensive loss includes net loss and other comprehensive income (loss) which represents unrealized gains or losses on short-term investments.

Net Loss per Share

Basic net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding for the period without consideration for potentially dilutive securities.

The Company computes diluted net loss per common share after giving consideration to all potentially dilutive common equivalents, including all unvested restricted stock, common stock warrants, and common stock options outstanding during the period except where the effect of such non-participating securities would be anti-dilutive.

Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and dilutive common stock equivalents outstanding for the period determined using the treasury-stock and if-converted methods.

Recently Issued Accounting Pronouncements not yet adopted

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU No. 2016-13”). ASU No. 2016-13 requires financial assets measured at amortized cost to be presented at the net amount expected to be collected and any unrealized loss relating to available-for-sale debt securities that is a result of credit losses be recorded through an allowance for credit losses. The Company will adopt this new accounting standard on January 1, 2023 using a modified retrospective method. Adoption of this update is not expected to have a material impact on the Company’s financial statements and related disclosures.

Fair Value Measurements

12 Months Ended

Dec. 31, 2022

Fair Value Measurements

Fair Value Measurements

3. Fair Value Measurement

The Company records cash equivalents, short-term investments and contingent consideration liability at fair value on a recurring basis. Fair value is an exit price, representing the amount that would be received from the sale of an asset or paid to transfer a liability in an orderly transaction between market participants based on assumptions that market participants would use in pricing an asset or liability.

The Company’s assets and liabilities measured at fair value on a recurring basis as of December 31, 2022 consisted of the following (in thousands):


	Fair Value Measurement at December 31, 2022
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents - money market funds	$	105,794	$	105,794	$	—	$	—
Short-term investments		73,783		—		73,783		—
Total	$	179,577	$	105,794	$	73,783	$	—

The Company’s assets and liabilities measured at fair value on a recurring basis as of December 31, 2021 consisted of the following (in thousands):


	Fair Value Measurement at December 31, 2021
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents - money market funds	$	65,634	$	65,634	$	—	$	—
Total	$	65,634	$	65,634	$	—	$	—
Liabilities:
Contingent consideration liability (see Note 8)	$	6,090	$	—	$	—	$	6,090
Total	$	6,090	$	—	$	—	$	6,090

As described in Note 8 the remaining milestone payment underlying the contingent consideration liability was fully settled during 2022 in shares of the Company’s common stock. As of December 31, 2022, the Company had no contingent consideration liability.

Short-term investments have been initially valued at the transaction price and subsequently valued at the end of each reporting period utilizing third party pricing services or other market observable data (Level 2). The pricing services utilize industry standard valuation models, including both income and market-based approaches and observable market inputs to determine value.

Short-term investments with quoted prices at December 31, 2022 as shown below (in thousands):


	December 31, 2022
	Amortized Cost		Unrealized (Loss) Gain		Market Value
United States treasury securities	$	15,868	$	(86)	$	15,782
Commercial paper and corporate debt securities		50,747		(71)		50,676
Asset backed securities		5,427		(35)		5,392
Agency debt securities		1,928		5		1,933
Total	$	73,970	$	(187)	$	73,783

As of December 31, 2021, the fair value of contingent payments classified as a liability was based on the regulatory milestones described in Note 8 and was estimated using the Monte Carlo simulation valuation model with Level 3 inputs.

The assumptions used to estimate the fair value of contingent payments that were classified as a liability at December 31, 2021 include the following significant unobservable inputs:


Unobservable input	Value or Range	Weighted-Average
Expected volatility	80.1%	80.1%
Risk-free interest rate	0.26%	0.26%
Cost of capital	30%	30%
Discount for lack of marketability	8%‑13%	11%
Probability of payment	88%	88%
Projected year of payment	2022	2022

Separate disclosure is required for assets and liabilities measured at fair value on a recurring basis from those measured at fair value on a non-recurring basis. Assets recorded at fair value on a non-recurring basis, such as property and equipment and intangible assets are recognized at fair value when they are impaired. During the year ended December 31, 2022, the Company had no significant assets or liabilities that were measured at fair value on a non-recurring basis. During the year ended December 31, 2021, the Company recorded non-cash impairment charges to property and equipment, net on a non-recurring basis (see below).

Lonza Manufacturing Agreement

In March 2021, the Company expanded its manufacturing collaboration with Lonza Houston, Inc. (“Lonza”) for the manufacture of AdCOVID or other adenovirus-based vaccines. Under the expanded agreement, the Company had committed approximately $23.0 million to Lonza to procure long-lead equipment and construct a dedicated manufacturing suite for clinical and commercial production of adenovirus-based vaccines. In June 2021, the Company announced the discontinuation of further development of AdCOVID following the Company’s review of findings from its Phase 1 clinical trial. Construction continued at Lonza, and the Company assessed its strategic options with respect to the suite. This work was completed during the fourth quarter of 2021. The Company capitalized a total of $11.4 million as construction-in-progress (“CIP”) during the nine months ended September 30, 2021 under this expanded agreement.

In connection with the discontinuation of further development of AdCOVID, the Company recorded a non-cash impairment charge of $8.1 million in the unaudited consolidated statements of operations and comprehensive loss for the nine months ended September 30, 2021 to write-down the CIP associated with the construction of the Lonza facility to its fair value of $3.3 million as of September 30, 2021. As of September 30, 2021, the fair value of the CIP related assets was primarily determined utilizing the cost approach, which reflected the replacement cost of the asset being appraised, adjusted for contractual restrictions on the assets, the probability of satisfying the contractual restrictions, physical deterioration, functional obsolescence and economic obsolescence. The fair value measurement was considered a Level 3 measurement within the valuation hierarchy.

Furthermore, the remaining $3.3 million CIP was fully charged to impairment during the three months ended December 31, 2021 upon termination of the agreement.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Property and Equipment, Net

12 Months Ended

Dec. 31, 2022

Property and Equipment, Net

Property and Equipment, Net

4. Property and Equipment, Net

Property and equipment, net consists of the following (in thousands):


	December 31,
	2022		2021
Furniture, fixtures and equipment	$	163		222
Laboratory equipment		295		1,040
Computers and telecommunications		194		291
Software		178		148
Leasehold improvements		1,749		1,794
Property and equipment, at cost		2,579		3,495
Less: accumulated depreciation and amortization		(1,498)		(2,047)
Property and equipment, net	$	1,081	$	1,448

Depreciation expense related to property and equipment for the years ended December 31, 2022 and 2021 was $0.5 million and $0.4 million, respectively.

Intangible Assets

12 Months Ended

Dec. 31, 2022

Intangible Assets

Intangible Assets

5. Intangible Assets

The Company’s intangible assets consist of the following (in thousands):


		Gross
	Estimated	Carrying		Accumulated				Net Book
	Useful Lives	Value		Amortization		Impairment		Value
December 31, 2022:
IPR&D assets	Indefinite	$	12,419	$	—	$	—	$	12,419
Total		$	12,419	$	—	$	—	$	12,419
December 31, 2021:
Internally developed patents	6–20 years	$	1,079	$	(500)	$	(579)	$	—
Acquired licenses	16–20 years		285		(285)		—		—
Total intangible assets subject to amortization			1,364		(785)		(579)		—
IPR&D assets	Indefinite		12,419		—		—		12,419
Total		$	13,783	$	(785)	$	(579)	$	12,419

As of December 31, 2021, the Company recorded an impairment loss of $0.6 million for the remaining net book value of the internally developed patents that are associated with the Company's discontinued development programs. The impairment loss has been recorded to research and development expenses in the accompanying audited consolidated statements of operations and comprehensive loss. There was no IPR&D impairment loss during the years ended December 31, 2022 and 2021

Leases

12 Months Ended

Dec. 31, 2022

Leases

Leases

6. Leases

The Company rents office and laboratory space in the United States, which are operating leases and expire in April 2025. Rent expense under these leases during each of the years ended December 31, 2022 and 2021 was $0.5 million, which includes short-term leases and variable lease costs that are not included in the lease obligation.

The office space lease provides for increases in future minimum annual rental payments as defined in the lease agreements. The office space lease also includes an option to renew the lease as of the end of the term. The Company has determined that the lease renewal option is not reasonably certain of being exercised.

The cash paid for operating lease liabilities for each of the years ended December 31, 2022 and 2021 was $0.5 million.

Supplemental balance sheet information related to the operating leases is as follows (in thousands):


	December 31,
	2022			2021
Operating lease obligations (see Note 7 and 9)	$	1,124		$	1,535
Operating lease right-of-use assets (included in "Other assets" in Balance Sheet)	$	596		$	798
Weighted-average remaining lease term (years)		2.3			3.3
Weighted-average discount rate		7.2	%		7.2	%

Maturities of operating lease liabilities are as follows (in thousands):


Year ending December 31,
2023	$	515
2024		526
2025		176
Total operating lease payments		1,217
Less: imputed interest		(93)
Total operating lease liabilities (see Note 7 and 9)	$	1,124

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2022

Accrued Expenses and Other Current Liabilities.

Accrued Expenses and Other Current Liabilities

7. Accrued Expenses and Other Current Liabilities

Accrued expense and other current liabilities consist of the following (in thousands):


	December 31,
	2022		2021
Accrued professional services	$	276	$	396
Accrued payroll and employee benefits		2,955		2,313
Accrued research and development		7,295		6,988
Lease obligation, current portion (see Note 6)		452		411
Excess tax refund payable		1,169		—
Accrued interest and other		103		44
Total accrued expenses and other current liabilities	$	12,250	$	10,152

Contingent Consideration

12 Months Ended

Dec. 31, 2022

Contingent Consideration

Contingent consideration

8. Contingent Consideration

The Company entered into an Agreement and Plan of Merger and Reorganization, dated July 8, 2019, by and among the Company, Springfield Merger Sub, Inc., Springfield Merger Sub, LLC, Spitfire Pharma, Inc. and David Collier, as the Stockholder Representative (the “Spitfire Merger Agreement”) to acquire all of the equity interests of Spitfire Pharma, Inc. (“Spitfire”). Spitfire was a privately held, preclinical pharmaceutical company developing a novel GLP-1/glucagon receptor dual agonist for the treatment of NASH.

The transaction closed on July 12, 2019. The Company issued 1,887,250 unregistered shares of its common stock as upfront consideration to certain former securityholders of Spitfire, representing an amount equal to $5.0 million less working capital and transaction expense adjustment amounts as defined in the agreement.

The acquisition of Spitfire was accounted for as an asset acquisition instead of a business combination because substantially all of the fair value of the gross assets acquired was concentrated in a single identifiable asset or group of similar identifiable assets, and therefore, the asset was not considered a business. The Company expensed the acquired intellectual property as of the acquisition date as in-process research and development with no alternative future uses.

The Spitfire Merger Agreement also includes future contingent payments up to $88.0 million payable in either cash or shares of the Company’s common stock as follows:

●

a one-time payment of $5.0 million (the “IND Milestone Consideration Amount”) within sixty days of the submission of an Investigational New Drug Application (“IND”) to the United States Food and Drug Administration (the “FDA”) or other applicable governmental authority in a foreign jurisdiction, which IND has not been rejected or placed on clinical hold by the FDA or such applicable foreign governmental authority within time specified in the Spitfire Merger Agreement;

●

a one-time payment of $3.0 million (the “Phase 2 Milestone Consideration Amount” and together with the IND Milestone Consideration Amount, the “Regulatory Milestones”) within sixty days of the initiation (first patient, first dosing) of the first Phase 2 clinical trial of a product candidate anywhere in the world; and

●

payments of up to $80.0 million upon the achievement of specified worldwide net sales (the “Sales Milestones”) of all products developed using the technology acquired in the License Agreement within ten years following the approval of a new drug application filed with the FDA.

The Regulatory Milestones were payable in shares of the Company’s Common Stock, with the number of shares of the Company’s common stock issued in connection with each milestone amount, if any, dependent on the share price at the time of achievement. The number of shares issued in consideration for the IND Milestone Consideration Amount was determined based on the lower of (A) the average of the closing prices of the Company’s common stock as reported on the Nasdaq Global Market for the twenty (20) consecutive trading days prior to the IND Reference Date or (B) $2.95. The number of shares issued in consideration for the Phase 2 Milestone Consideration Amount was determined based on the lower of (A) the average of the closing trading prices of the Company’s common stock as reported on the Nasdaq

Global Market for the twenty (20) consecutive trading days immediately preceding the date of the occurrence of the Phase 2 Milestone Event or (B) $3.54.

The contingent payments related to the Sales Milestones are predominately cash-based payments accounted for under FASB Accounting Standards Codification Topic 450, Contingencies. Accordingly, the Company will recognize the Sales Milestones when the contingency is probable and the amount can be reasonably estimated.

In November 3, 2020, the Company issued 1,694,906 shares of its common stock valued at $9.57 per share for the amount value of $13.6 million to the former Spitfire stockholders to satisfy the obligations under IND Milestone.

On April 26, 2022, the Company dosed the first patient in the Phase 2 MOMENTUM trial of pemvidutide in obesity, which triggered the obligation to pay the Phase 2 Milestone Consideration Amount to the former owners. As a result, on June 10, 2022, the Company issued 847,444 shares of its common stock valued at $8.55 per share for the amount value of $7.2 million to the former Spitfire stockholders. From the last valuation date on March 31, 2022 through June 10, 2022, the date of issuance, the Company recognized an increase in the fair value of the Phase 2 Milestone Consideration Amount of $1.9 million to research and development expense and reclassified the balance in the contingent consideration liability to equity in the Company’s consolidated balance sheet. As of December 31, 2022, the Company had no contingent consideration liability.

Below is a summary of the contingent consideration activity (in thousands):


	Year Ended December 31,
	2022		2021
Beginning balance	$	6,090	$	5,390
Change in fair value		86		700
Fair value of payments settled in common stock (Phase II Milestone)		(6,176)		—
Ending balance	$	—	$	6,090

Other Long-Term Liabilities

12 Months Ended

Dec. 31, 2022

Other Long-Term Liabilities

Other Long-Term Liabilities

9. Other Long-Term Liabilities

The Company’s other long-term liabilities are summarized as follows (in thousands):


	December 31,
	2022		2021
Research and development incentive credit	$	3,599	$	—
Lease obligation, long-term portion (see Note 6)		672		1,124
Conditional economic incentive grants		250		250
Other		60		80
Total other long-term liabilities	$	4,581	$	1,454

R&D incentive credit Program

During the year ended December 31, 2022, the Company received a total of $3.6 million in cash for research and development (“R&D”) incentive credit related to R&D costs that the Company incurred during the fiscal years 2021 and 2020 through the participation in the Australian research and development incentive credit program administered through the Australian Tax Office. The Company recorded the receipt as long-term liability until there is reasonable assurance that the Company will comply with the conditions attached to the incentive credit.

Economic Incentive Grants

The Company has two conditional economic incentive grants for a total of $250,000 from Montgomery County, Maryland and the State of Maryland. The Montgomery County grant was received in May 2018, with a term expiring on February 28, 2028. The State of Maryland grant was received in October 2019, with a 10-year term expiring on December 31, 2029. These grants are conditional primarily based on the Company maintaining its current headquarter locations in addition to employing a required number of employees at different reporting dates through the term of the

grants. The Company is accruing 3% interest on both grants and has recorded approximately $8,000 in interest expense for each of the years ended December 31, 2022 and 2021.

Common Stock

12 Months Ended

Dec. 31, 2022

Common Stock

Common Stock

10. Common Stock

The Amended and Restated Certificate of Incorporation, as amended (“Charter”), authorized the Company to issue 200,000,000 shares of common stock, par value $0.0001 per share. As of December 31, 2022, the Company had 49,199,845 shares of common stock issued and outstanding.

The Charter also authorized the Company to issue 1,000,000 shares of preferred stock, par value $0.0001 per share. As of December 31, 2022, the Company had no shares of preferred stock issued and outstanding.

At-the-Market Offerings

On February 25, 2021, the Company entered into an Equity Distribution Agreement (the “2021 Agreement”) with Piper Sandler & Co., Evercore Group L.L.C., and B. Riley Securities, Inc., serving as sales agents (the “Sales Agents”) with respect to an at-the-market offerings program under which the Company offered and sold shares of its common stock, par value $0.0001 per share (the “Common Stock”), having an aggregate offering price of up to $125.0 million (the “Shares”) through the Sale Agents (the “2021 Offering”). All Shares offered and sold in the 2021 Offering were issued pursuant to the Company’s Registration Statement on Form S-3 filed with the SEC on December 31, 2020, which was declared effective on January 11, 2021 (“2021 Shelf”), the prospectus supplement relating to the 2021 Offering filed with the SEC on February 25, 2021 and any applicable additional prospectus supplements related to the 2021 Offering that form a part of the Registration Statement.

During the year ended December 31, 2022, the Company sold 5,204,415 shares of Common Stock under the 2021 Agreement resulting in approximately $56.2 million in proceeds, net of $1.9 million commission and other offering cost. As of December 31, 2022, the Company has sold 10,004,869 shares of Common Stock under the 2021 Agreement resulting in approximately $121.0 million in proceeds, net of $4.0 million commission and other offering costs. As of December 31, 2022, there were no remaining shares available under the 2021 Agreement. The Company recorded approximately $0.3 million of other offering costs which offset the proceeds received from the shares sold through December 31, 2022.

Exchange Agreement

On February 25, 2021, the Company entered into an exchange agreement (the “Exchange Agreement”) with an Investor and its affiliates (the “Exchanging Stockholders”), pursuant to which the Company exchanged an aggregate of 1,000,000 shares of the Company’s common stock, par value $0.0001 per share, owned by the Exchanging Stockholders for pre-funded warrants (the “Exchange Warrants”) to purchase an aggregate of 1,000,000 shares of common stock (subject to adjustment in the event of any stock dividends and splits, reverse stock split, recapitalization, reorganization or similar transaction, as described in the Exchange Warrants), with an exercise price of $0.0001 per share. On January 24, 2022, the Exchange Warrants to purchase 1,000,000 shares were net exercised, resulting in the issuance of 999,984 shares of common stock, and no Exchange Warrants remain outstanding (see Note 11).

Public Offering

On July 16, 2020, the Company offered and sold (i) 3,369,564 shares of common stock, at a price to the public of $23.00 per share, and (ii) pre-funded warrants of the Company to purchase 1,630,436 shares of common stock at an exercise price equal to $0.0001 per share (the “Pre-Funded Warrants”), at a price to the public of $22.9999 per share of common stock underlying the Pre-Funded Warrants (equal to the public offering price per share of Common Stock, minus the exercise price of each Pre-Funded Warrant). The Pre-Funded Warrants are exercisable at any time, provided that each Pre-Funded Warrant holder will be prohibited from exercising such Pre-Funded Warrants into shares of the Company’s common stock if, as a result of such exercise, the holder, together with its affiliates, would own more than 4.99% of the total number of shares of the Company’s common stock then issued and outstanding, which percentage may change at the holders’ election to any other number less than or equal to 19.99% upon 61 days’ notice to the Company.

The Company has assessed the Pre-Funded Warrants for appropriate equity or liability classification and determined that the Pre-Funded Warrants are freestanding instruments that do not meet the definition of a liability pursuant to ASC 480 and do not meet the definition of a derivative pursuant to FASB Accounting Standards Codification Topic 815, Derivatives and Hedging (“ASC 815”). The Pre-Funded Warrants are indexed to the Company’s common stock and meet all other conditions for equity classification under ASC 480 and ASC 815. Accordingly, the Pre-Funded Warrants are classified as equity and were accounted for as a component of additional paid-in capital at the time of issuance. As of December 31, 2022, 760,870 of the Pre-Funded Warrants were exercised, leaving 869,566 remaining Pre-Funded Warrants unexercised (see Note 11).

Warrants

12 Months Ended

Dec. 31, 2022

Warrants

Warrants

11. Warrants

The following common stock warrants were outstanding at December 31, 2022:


	Number of
	Common	Per Share
	Stock	Exercise
	Warrants	Price		Issuance Date	Expiration Date
Issued with common units in the 2018 Unit Offering	3,300		2.7568	October 2, 2018	October 2, 2023
Issued with common units in the 2018 Registered Direct Offering	92,300		5.40	October 10, 2018	October 10, 2023
Issued with common units in the 2019 Registered Direct Offering	50,000		3.21	March 12, 2019	March 12, 2024
Issued with common units in the 2020 Public Offering (see Note 10)	869,566		0.0001	July 16, 2020	—
Total	1,015,166

The following common stock warrants were outstanding at December 31, 2021:


	Number of
	Common	Per Share
	Stock	Exercise
	Warrants	Price		Issuance Date	Expiration Date
Replacement warrants	155	$	483.00	March 3, 2012	March 3, 2022
Issued with common units in the 2018 Unit Offering	3,300		2.7568	October 2, 2018	October 2, 2023
Issued with common units in the 2018 Registered Direct Offering	92,300		5.40	October 10, 2018	October 10, 2023
Issued with common units in the 2019 Registered Direct Offering	50,000		3.21	March 12, 2019	March 12, 2024
Issued with common units in the 2020 Public Offering (see Note 10)	1,630,436		0.0001	July 16, 2020	—
Issued in exchange for retirement of common stock per the Exchange Agreement (see Note 10)	1,000,000		0.0001	February 25, 2021	—
Total	2,776,191

The following is a description of the common stock warrants issued prior to January 1, 2020:

2019 Registered Direct Offering

On March 12, 2019, the Company issued a combined total of 4,361,370 common units and pre-funded units to certain institutional investors in a registered direct offering (the “Registered Direct Offering”). Each common unit in the Registered Direct Offering was sold at a price of $3.21 and consisted of one share of common stock and 0.70 of a warrant to purchase one share of common stock at an exercise price of $3.21. Each warrant sold in the Registered Direct Offering was exercisable immediately and expired five years from the date of issuance. All of the pre-funded warrants were exercised during 2019. The warrants issued in the Registered Direct Offering were recognized as equity classified

freestanding financial instruments. As of December 31, 2022, there were 50,000 unexercised warrants issued under the 2019 Registered Direct Offering.

2018 Unit Offering

On October 2, 2018, the Company issued a combined total of 2,400,000 common units and pre-funded units in a public offering (the “2018 Unit Offering”). Each common unit in the 2018 Unit Offering was sold at a public offering price of $5.00 and consisted of one share of common stock and a warrant to purchase one share of common stock at an exercise price of $6.00. Each warrant sold in the 2018 Unit Offering was exercisable immediately and expired five years from the date of issuance. All of the pre-funded warrants were exercised prior to December 31, 2018.

The warrants issued in the 2018 Unit Offering are each subject to anti-dilution protection. Accordingly, to the extent the Company was to issue additional common stock or securities convertible into common stock at an issuance price lower than exercise price of the warrants, the exercise price of the warrants would be adjusted to the lower of (i) the issuance price or (ii) the lowest volume weighted-average price of the Company’s common stock on the five trading days following the announcement of the new offering. The 2018 Registered Direct Offering triggered a down round adjustment to the exercise price of the warrants issued in the 2018 Unit Offering from $6.00 to $4.1798. In addition, the 2019 Registered Direct Offering triggered a down round adjustment to the exercise price of the warrants issued in the 2018 Unit Offering from $4.1798 to $2.7568. As of December 31, 2022, there were 3,300 unexercised warrants issued under the 2018 Unit Offering.

2018 Registered Direct Offering

On October 10, 2018, the Company issued a combined total of 4,629,630 common units and pre-funded units to certain institutional investors in a registered direct offering (the “2018 Registered Direct Offering”). Each common unit in the 2018 Registered Direct Offering was sold at a price of $5.40 and consisted of one share of common stock and a warrant to purchase one share of common stock at an exercise price of $5.40. Each warrant sold in the 2018 Registered Direct Offering was exercisable immediately and expired five years from the date of issuance. All of the pre-funded warrants were exercised prior to December 31, 2018. As of December 31, 2022, there were 92,300 unexercised warrants issued under the 2018 Registered Direct Offering.

A summary of warrant activity is as follows:


				Weighted-Average
			Weighted	Remaining
	Number of		Average	Contractual Term
	Warrants		Exercise Price	(Years)
Warrants outstanding, December 31, 2021	2,776,191
Expired	(155)
Exercises (see Note 10)	(1,760,870)
Warrants outstanding, December 31, 2022	1,015,166	$	0.66	0.9

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-URI https://asc.fasb.org/topic&trid=2208762

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)
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+ Details

Stock-Based Compensation

12 Months Ended

Dec. 31, 2022

Stock-Based Compensation

Stock-Based Compensation

12. Stock-Based Compensation

Stock Options

The Company established the 2001 Employee Stock Option Plan to provide incentive stock options and non-qualified stock options to employees, and the 2001 Non-employee Stock Option Plan to provide non-qualified stock options to the members of the board of directors and advisory board, and non-employees. The 2001 Employee Stock Option Plan and the 2001 Non-employee Stock Option Plan are collectively referred to as the “2001 Plans.” In connection with the Company’s merger with PharmAthene, Inc. in 2017, the Company issued options from its 2001 Plans to replace options previously granted. The Company de-designated common stock available for issuance under the 2001 Plans. No additional options or restricted stock will be granted under these plans. Options outstanding and unvested restricted stock granted or replaced under these plans will continue to vest over the remaining vesting period through the earlier of exercise, expiration or forfeiture. The replacement options issued after the 2017 mergers will continue to vest over the remaining

vesting period through the earlier of exercise, expiration or forfeiture. Also, in connection with the 2017 mergers, the 2001 Plans were assumed by the Company.

In addition, the Company assumed the PharmAthene, Inc. Amended and Restated 2007 Long-Term Incentive Compensation Plan (the “2007 Plan”). Awards outstanding under the 2007 Plan remained outstanding in accordance with their applicable terms and conditions. No additional awards will be made under the 2007 Plan.

The Company established the 2017 Omnibus Incentive Plan (the “Omnibus Plan”) to provide incentive stock options, non-qualified stock options, restricted stock, and other stock-based awards denominated in shares of the Company’s common stock, and performance-based cash awards to eligible employees, consultants and directors. In 2018, the Company’s shareholders approved an amendment to the Omnibus Plan to increase the number of shares reserved for issuance from 1,500,000 to 5,000,000. The aggregate share reserve will be increased on January 1 of each year commencing in 2018 and ending on and including January 1, 2027 up to an amount equal to the lowest of (i) 4% of the total number of shares of common stock outstanding on a fully diluted basis as of December 31 of the immediately preceding calendar year, and (ii) such number of shares of common stock, if any, determined by the Company’s board of directors. Accordingly, on January 1, 2023, the number of shares of Common Stock reserved and available for issuance under the Omnibus Plan increased by 2,160,537. The maximum shares of common stock that may be granted to each employee or consultant in any fiscal year under the Omnibus Plan is the lesser of 800,000 shares per type of award or a maximum compensation amount of $5,000,000 under a Black-Scholes valuation model. The maximum common stock that may be granted to directors under the Omnibus Plan during any fiscal year is 500,000 shares.

On November 29, 2018, the Board approved and adopted the Altimmune Inc. 2018 Inducement Grant Plan (the “Inducement Plan”). The Inducement Plan provides for the grant of equity or equity-based awards in the form of non-qualified stock options, restricted stock awards and other stock-based awards. The Inducement Plan was adopted by the Board without stockholder approval pursuant to Rule 5635(c)(4) of the NASDAQ Listing Rules.

The Board has reserved 2,000,000 shares of the Company’s common stock for issuance pursuant to awards granted under the Inducement Plan (subject to customary adjustments in the event of a change in capital structure of the Company), and the Inducement Plan will be administered by the Compensation Committee. In accordance with Rule 5635(c)(4) of the NASDAQ Listing Rules, awards under the Inducement Plan may be only made to an employee who has not previously been an employee or member of the Board or any parent or subsidiary, or following a bona fide period of non-employment by the Company or a parent or subsidiary, if he or she is granted such award in connection with his or her commencement of employment with the Company or a subsidiary and such grant is an inducement material to his or her entering into employment with the Company or such subsidiary.

The 2001 Plans, the 2007 Plan, the Omnibus Plan and the Inducement Plan are collectively referred to as the “Plans.” During the year ended December 31, 2022 under the Plans, a total of 1,473,427 options to purchase shares of common stock were granted. As of December 31, 2022, there were 1,368,689 and 1,309,275 shares of common stock available for future grants under the Omnibus Plan and the Inducement Plan, respectively.

The fair value of stock option issued to employees was estimated at the date of grant using Black-Scholes with the following weighted-average assumptions:


	Year Ended December 31,
	2022		2021
Expected volatility	110.1	%	109.6	%
Expected term (years)	6.0		6.0
Risk-free interest rate	2.4	%	0.8	%
Expected dividend yield	0.0	%	0.0	%

Expected volatility: As there is not sufficient historical volatility for the expected term of the stock options, the Company uses an average historical share price volatility, inclusive of its own volatility, based on an analysis of reported data for a peer group of comparable companies which were selected based upon industry similarities.

Expected term (years): Expected term represents the number of years that the Company’s option grants are expected to be outstanding. There is not sufficient historical share exercise data to calculate the expected term of the stock

options; therefore, the Company elected to utilize the simplified method to value option grants. Under this approach, the weighted-average expected life is presumed to be the average of the vesting term and the contractual term of the option.

Risk-free interest rate: The Company determined the risk-free interest rate by using a weighted-average equivalent to the expected term based on the daily U.S. Treasury yield curve rate in effect as of the date of grant.

Expected dividend yield: The Company does not anticipate paying any dividends in the foreseeable future.

The fair value of each non-employee stock option is estimated at the date of grant using Black-Scholes with assumptions generally consistent with those used for employee stock options, with the exception of expected term, which is over the contractual life.

A summary of stock option activity under the Plans is presented below (in thousands, except share and per share data):


				Weighted-Average
		Weighted-		Remaining
	Number of	Average		Contractual Term	Aggregate Intrinsic
	Stock Options	Exercise Price		(Years)	Value
Outstanding, December 31, 2021	2,583,443	$	8.63	5.9	$	8,460
Granted	1,473,427	$	8.48
Exercised	(373,545)	$	2.65
Forfeited or expired	(299,388)	$	8.92
Outstanding, December 31, 2022	3,383,937	$	9.20	5.9	$	25,724
Exercisable, December 31, 2022	1,523,504	$	9.00	5.8	$	12,292
Vested and expected to vest, December 31, 2022	3,197,894	$	9.19	5.9	$	25,724

The per share weighted-average grant date fair value of stock options granted during the years ended December 31, 2022 and 2021 were $7.07 and $11.79 per share, respectively. The total intrinsic value of stock options exercised during the years ended December 31, 2022 and 2021 was $4.4 million and $0.7 million, respectively. The total fair value of options vested during the years ended December 31, 2022 and 2021 was $6.8 million and $4.7 million, respectively. As of December 31, 2022, there was $11.7 million of unrecognized compensation cost related to stock options, which is expected to be recognized over a weighted-average period of 2.6 years.

Restricted Stock

In November 2018, the Company authorized and granted the Chief Executive Officer a restricted stock award of 322,907 shares on his date of hire. The weighted-average grant date fair value of the restricted stock award was $3.59 per share. The restricted stock vested over a four-year period, 25% of the shares vesting on the one-year anniversary, and the remaining 75% vesting in 36 substantially equal monthly installments. The restricted stock was fully vested on November 30, 2022. During the year ended December 31, 2022, the Company issued 41,572 of unrestricted common stock as a result of the vesting of 74,000 restricted stock net of 32,428 shares of common stock withheld to satisfy tax withholding obligations. The fair value of restricted stock awards vested during the years ended December 31, 2022 and 2021 was $0.7 million and $1.0 million, respectively. As of December 31, 2022, there was no unrecognized compensation expense related to restricted stock.

A summary of restricted stock activities is presented below:


		Weighted-
		average
		Grant Date
	Shares	Fair Value
Unvested, December 31, 2021	74,000	$	3.59
Vested	(74,000)		3.59
Unvested, December 31, 2022	—	$

Restricted Stock Units (RSUs)

During the year ended December 2022, the Company granted 285,000 shares of RSUs with a weighted-average grant date fair value of $7.11 per share which vest over four years. During the year ended December 31, 2022, the Company issued 41,123 shares of unrestricted common stock as a result of the vesting of 61,028 RSUs net of 19,905 shares of common stock withheld to satisfy tax withholding obligations. The fair value of RSUs vested during the years ended December 31, 2022 and 2021 was $0.6 million and $0.1 million, respectively.

A summary of RSUs activities is presented below:


		Weighted-
		average
		Grant Date
	Shares	Fair Value
Unvested, December 31, 2021	231,928	$	14.53
Granted	285,000		7.11
Vested	(61,028)		14.39
Forfeited or expired	(41,415)		10.95
Unvested, December 31, 2022	414,485	$	9.81

As of December 31, 2022, total unrecognized compensation expense related to RSUs was $2.8 million, which the Company expects to recognize over a weighted-average period of approximately 2.8 years.

2019 Employee Stock Purchase Plan

On March 29, 2019, the Board adopted the 2019 Employee Stock Purchase Plan (the “2019 ESPP”). A total of 403,500 shares of the Company’s common stock have been reserved for issuance under the 2019 ESPP. Subject to any plan limitations, the 2019 ESPP allows eligible employees to contribute through payroll deductions up to 10% of their earnings for the purchase of the Company’s common stock at a discounted price per share. The offering periods begin in February and August of each year, with the initial offering period started on August 1, 2019. The common shares issuable under the 2019 ESPP were registered pursuant to a registration statement on Form S-8 on April 4, 2019.

Unless otherwise determined by the administrator, the Company’s common stock will be purchased for the accounts of employees participating in the 2019 ESPP at a price per share that is the lesser of 85% of the fair market value of the Company’s common stock on the first trading day of the offering period or 85% of the fair market value of the Company’s common stock on the last trading day of the offering period. The 2019 ESPP estimated shares to be purchased fair value is included in stock-based compensation expense.

Employees have the ability to purchase shares of the Company’s common stock at a price equal to the lower of the first or last trading day of the offering period, which represents an option and, therefore, the 2019 ESPP is a compensatory plan under ASC 718-50, Employee Stock Purchase Plans. Accordingly, stock-based compensation expense is determined based on the option’s grant-date fair value, employee contributions, and the Company’s stock price and is recognized over the requisite service period of the option. The Company used the Black-Scholes valuation model to determine the fair value of ESPP.

During the year ended December 31, 2022, employees purchased 26,395 shares for $0.2 million under the 2019 ESPP. As of December 31, 2022, there were 260,344 shares of common stock available for future issuance under the 2019 ESPP Plan. The Company recognized stock-based compensation expense related to this plan of $0.3 million for each of the years ended December 31, 2022 and 2021, respectively.

Stock-based Compensation Expense

Stock-based compensation expense is classified in the accompanying consolidated statements of operations and comprehensive loss for the years ended December 31, 2022 and 2021 as follows (in thousands):



	Year Ended December 31,
	2022		2021
Research and development	$	2,835	$	1,656
General and administrative		5,266		3,863
Total	$	8,101	$	5,519

U.S. Government Contracts and Grants

12 Months Ended

Dec. 31, 2022

U.S. Government Contracts and Grants

U.S. Government Contracts and Grants

13. U.S. Government Contracts and Grants

In June 2020, the Company was awarded $4.7 million from the U.S. Army Medical Research & Development Command (“USAMRDC”) to fund its Phase 1/2 clinical trial of T-COVID. The competitive award was granted by USAMRDC in collaboration with the Medical Technology Enterprise Consortium (“MTEC”), a 501(c)(3) biomedical technology consortium working in partnership with the Department of Defense (“DoD”). Under the contract, MTEC paid the Company a firm fixed fee based upon the achievement of certain milestones for conduct and completion of a Phase 1/2 study and research and development work on the replication-deficient adenovirus 5 (“RD-Ad5”) vector vaccine platform. For the year ended December 31, 2021, the Company has recognized $0.5 million of grant revenue under this contract, which completed the full recognition of this award. No revenue was recognized for this contract for the year ended December 31, 2022.

In July 2016, the Company signed a five-year contract with Biomedical Advanced Research and Development Authority (“BARDA”). The contract, as amended, had a total value of up to $136.8 million and is used to fund clinical development of NasoShield. Under the contract, BARDA paid the Company a fixed fee and reimburses certain costs for the research and development of an Ad5-vectored, protective antigen-based intranasal anthrax vaccine through cGMP manufacture and conduct of a Phase 1 clinical trial dose ranging assessment of safety and immunogenicity. The contract consisted of an initial base performance period providing approximately $30.9 million in funding for the period July 2016 through December 2021. BARDA had seven options to extend the contract to fund certain continued development and manufacturing activities for the anthrax vaccine, including Phase 2 clinical studies. Each option, if exercised by BARDA, would have provided additional funding ranging from approximately $1.1 million to $34.4 million for a three-year period beginning in 2021. For the year ended December 31, 2021, the Company has recognized $3.7 million of grant revenue under the current BARDA contract. For the year ended December 31, 2022, the Company has recognized de minimis grant revenue related to the close-out of the BARDA contract. BARDA did not extend the contract beyond the end of December 2021.

The Company accounts for these contracts as a government grant which analogizes with International Accounting Standards 20 (“IAS 20”), Accounting for Government Grants and Disclosure of Government Assistance.

Employee Benefit Plans

12 Months Ended

Dec. 31, 2022

Employee Benefit Plans

Employee Benefit Plans

14. Employee Benefit Plans

The Company has a 401(k)-retirement plan in which substantially all of our employees in the United States are eligible to participate in. Eligible employees may elect to contribute up to the maximum limits, as set by the Internal Revenue Service, of their eligible compensation. During each of the years ended December 31, 2022 and 2021, the Company made discretionary plan contributions of $0.3 million.

- Definition

The entire disclosure for retirement benefits.

+ References

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+ Details

Income Taxes

12 Months Ended

Dec. 31, 2022

Income Taxes

Income Taxes

15. Income Taxes

The components of net loss before income tax benefit are as follows (in thousands):


	Year Ended December 31,
	2022		2021
U.S. operations	$	(72,750)	$	(78,583)
Non-U.S. operations		(12,160)		(18,507)
Net loss before income tax benefit	$	(84,910)	$	(97,090)

The components of the income tax expense (benefit) are as follows (in thousands):


	Year Ended December 31,
	2022		2021
U.S. federal
Current	$	(144)	$	—
U.S. state and local
Current		(53)		—
Income tax expense (benefit)	$	(197)	$	—

Reconciliation between the effect of applying the federal statutory rate and the effective income tax rate used to calculate the Company’s income tax benefit is as follows:


	Year Ended December 31,
	2022		2021
Federal statutory rate	21.00	%	21.00	%
State income taxes, net of federal benefit	(0.12)		4.71
Research and development tax credit	(2.22)		(2.30)
Acquired in process research and development	(0.02)		(0.15)
Rate change	1.29		—
Other	0.21		(0.47)
Change in valuation allowance	(19.91)		(22.79)
Effective tax rate	0.23	%	—	%

Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income and for tax carryforwards. Significant components of the Company’s deferred tax assets and liabilities are as follows (in thousands):


	December 31,
	2022		2021
Deferred tax assets:
Net operating losses	$	44,606	$	37,229
Accrued expenses		523		352
Amortization		540		746
Stock compensation		2,193		1,276
Lease liability		309		422
Asset impairment		—		3,129
Capitalized research and development costs		11,996		—
Other		107		109
Total deferred tax assets		60,274		43,263
Valuation allowance		(57,245)		(40,584)
Deferred tax assets, net		3,029		2,679
Deferred tax liabilities:
IPR&D assets		(2,847)		(2,360)
Right of use asset		(164)		(220)
Depreciation		(18)		(99)
Total deferred tax liabilities		(3,029)		(2,679)
Total deferred tax assets (liabilities), net	$	—	$	—

The Company assesses the need for a valuation allowance against our deferred tax assets and considers both positive and negative evidence related to the likelihood of realization of the deferred tax assets to determine, based on the weight of available evidence, whether it is more-likely-than-not that some or all of the deferred tax assets will not be realized. This determination requires significant judgment, including assumptions about future taxable income that are based on historical and projected information. The increase in the valuation allowance during the year ended December 31, 2022 primarily relates to increases for current year losses in both the U.S. and foreign locations. The Company has recorded a valuation allowance against its net U.S. and net non-U.S. deferred tax assets as it believes are not more likely than not realizable. Deferred tax liabilities, consist primarily of indefinite life IPR&D assets located in a foreign subsidiary, which will be applied in the future to offset against net operating losses (“NOLs”) that have an indefinite life.

The Company has U.S. federal and state net operating loss carryforwards of approximately $134.3 million and $103.7 million, respectively, as of December 31, 2022, of which a portion of the federal and state amount of $7.1 million and $103.7 million, respectively, has a 20-year carry forward period that will expire at various dates beginning in 2024. Under current law, the remaining federal amount of $127.2 million has an indefinite life and amounts utilized in the future may not exceed 80% of taxable income. The Company also has foreign net operating loss carryforward of approximately $38.6 million which carryforward indefinitely.

Under Section 382 of the Internal Revenue Code of 1986 (“IRC 382”), as amended, substantial changes in the Company’s ownership may limit the amount of NOLs that can be utilized annually in the future to offset its U.S. federal and state taxable income. Specifically, this limitation may arise in the event of a cumulative change in ownership of the Company of more than 50% within any three-year period. The amount of the annual limitation is determined based on the value of the Company immediately before the ownership change. The Company has reduced the NOL and related valuation allowance in historical periods.

The Company’s existing NOLs are subject to limitations arising from previous ownership changes from 2020 and prior that impact the timing and amount. In addition, future changes in the Company’s stock ownership, many of which are outside of the Company’s control, could result in an ownership change. We have not determined if we have experienced Section 382 ownership changes in the past and if a portion of our NOL and tax credit carryforwards are subject to an annual limitation under Section 382. Accordingly, the Company may not be able to utilize a material portion of its NOLs and this could harm the Company’s future operating results by effectively increasing the Company’s future tax obligations.

Significant judgment is required in evaluating tax positions and determining the provision for income taxes. The Company establishes liabilities for tax-related uncertainties based on estimates of whether, and the extent to which, additional taxes may be due. These liabilities are established when the Company believes that certain positions might be challenged despite its belief that its tax return positions are fully supportable. The Company adjusts these liabilities in light of changing facts and circumstances, such as the outcome of a tax audit. The provision for income taxes includes the impact of changes to these liabilities.

The amount of unrecognized tax benefits was $0.7 million and $0.2 million as of December 31, 2022 and 2021, respectively. Any changes in the next twelve months are not anticipated to have a significant impact on the results of operations, financial position or cash flows of the Company. All of the Company’s uncertain tax positions, if recognized, would affect its income tax expense, although the net impact would be zero due to the Company’s valuation allowance position.

The Company has elected an accounting policy to classify interest and penalties related to unrecognized tax benefits as a component of income tax expense. During the year ended December 31, 2022, the company recorded income tax benefit of $0.2 million related to interest received and receivable on income tax refunds. As of December 31, 2021, potential interest and penalties on unrecognized tax benefits were not significant.

The following is a tabular reconciliation of the total amounts of unrecognized tax benefits excluding related interest and penalties (in thousands):


	Year Ended December 31,
	2022		2021
Beginning balance	$	237	$	711
Increases for prior year tax positions		474		—
Decreases for prior year tax positions		—		(474)
Ending balance	$	711	$	237

The Company files income tax returns in the United States, various U.S. states, U.K. and Australia. The Company is still open to examination by the applicable taxing authorities from 2010 forward, although tax attributes that were generated prior to 2010 may still be adjusted upon examination by federal, state, foreign or local tax authorities if they either have been or will be used in a future period.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI https://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI https://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI https://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Net Loss Per Share

12 Months Ended

Dec. 31, 2022

Net Loss Per Share

Net Loss Per Share

16. Net Loss Per Share

Because the Company has reported net loss attributable to common stockholders for the years ended December 31, 2022 and 2021, basic and diluted net loss per share attributable to common stockholders in each year are the same.

Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted-average numbers of shares of common stock outstanding for the period. Basic shares outstanding includes the weighted-average effect of the Company’s outstanding pre-funded warrants, the exercise of which requires little or no consideration for the delivery of shares of common stock.

Diluted net loss per share is calculated by adjusting weighted-average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period. As such, all unvested restricted stock, common stock warrants, and stock options have been excluded from the computation of diluted weighted-average shares outstanding because such securities would have an anti-dilutive impact for all periods presented.

Potential common shares issuable upon conversion, vesting or exercise of unvested restricted stock, common stock warrants, and stock options that are excluded from the computation of diluted weighted-average shares outstanding, as they are anti-dilutive, are as follows:


	Year Ended December 31,
	2022	2021
Common stock warrants	145,600	145,755
Common stock options	3,397,998	2,594,177
Restricted stock units	414,485	231,928
Restricted stock	—	74,000

Commitments and Contingencies

12 Months Ended

Dec. 31, 2022

Commitments And Contingencies.

Commitments and Contingencies

17. Commitments and Contingencies

License Obligations

PER.C6 Cell Line - Janssen Vaccines & Prevention B.V.

The Company has a royalty-bearing, worldwide non-exclusive license agreement with Janssen Vaccines & Prevention B.V. (formerly known as Crucell Holland B.V.) (“Janssen”) for use of its vaccine technology. The Company may terminate the license agreement without cause, and the agreement contains customary provisions for either party to terminate prior to the expiration of the agreement. The amended license agreement expires on a product-by-product and country-by-country basis on the later of the date upon which the last of the licensed patents applicable to the relevant product expires or 15 years from the date of first commercial sale of the relevant product. The Janssen patent rights include patents issued in the United States with an expected expiration date no earlier than April 2020, in each case not giving effect to any potential extensions and assuming payment of all associated fees. Upon expiration of the amended license agreement, or if the Company terminates the amended license agreement for Janssen’s material breach, the Company retains the right to exploit the rights granted. Under the agreement, the Company is required to pay an annual license fee and annual royalty fees upon reaching certain milestones in an amount that equals the greater of a low single digit percentage of net sales or $150,000.

On April 2, 2020, the Company entered into Amendment No. 3 to the Second Restated License Agreement and additionally entered into Amendment No. 4, 5 and 6 throughout 2020 (collectively, the “Amendments”), by and between the Company and Janssen (as amended by Amendment No. 1 to Second Restated License Agreement and Amendment No. 2 to Second Restated License Agreement, together with the Amendments, the “License Agreement”). Pursuant to the Amendment, the field of licenses granted to the Company for the use of the PER.C6 cell line under the License Agreement is expanded to cover COVID-19 caused by SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), in addition to the existing licenses related to Bacillus anthracis and influenza virus. All capitalized terms not defined herein shall have the meanings assigned to them in the Amendment or the License Agreement, as applicable.

Pursuant to the Amendment, the Company agreed to pay certain additional development-based milestone payments through approval of licensed products by the FDA for the treatment or prevention of COVID-19, up to an aggregate amount of $1.2 million. The Company also agreed to pay royalty payments as a percentage of net sales of products to a royalty stacking reduction and minimum annual royalty payments, until the expiration of the term of the License Agreement, as amended. Fees incurred under the Janssen agreement totaled $0.1 million and $0.2 million for the years ended December 31, 2022 and 2021, respectively, and are included in research and development expenses in the accompanying consolidated statements of operations and comprehensive loss. The agreement’s current maintenance fee term is set to expire on April 2, 2023, and the Company has provided notice to Janssen that it does not intend to renew the agreement.

Spitfire Acquisition

As disclosed in Note 8, the Company is obligated to make payments of up to $80.0 million upon the achievement of specified worldwide net sales of all products developed using the technology acquired from Spitfire Pharma Inc. within ten years following the approval of a new drug application filed with the FDA.

Litigation

In December 2019, a complaint was filed by Dr. De-chu Christopher Tang (“Plaintiff”) against the Company, which the Company removed to the United States District Court for the Eastern District of Texas. The Plaintiff amended the complaint in February 2020 to include Vipin K. Garg and David J. Drutz as defendants, in addition to the Company (Dr. Garg, Dr. Drutz, and the Company are collectively referred to as “Defendants”). In March 2020 the Defendants filed a motion to dismiss the complaint. On March 25, 2021, the court granted the motion and dismissed the action for lack of personal jurisdiction. In December 2021, the Plaintiff refiled the case in the United States District Court for the District of Maryland, captioned Tang v. Altimmune, Inc., et al., Case No. 8:21-cv-03283 (D. Md.). Plaintiff, who is representing himself, asserts two causes of action: (1) breach of a prior settlement agreement by “robbing Plaintiff’s properties”; and (2) use by the Company of the “AdHigh system,” which Plaintiff claims is “proprietary.” On April 4, 2022, Defendants filed a motion to dismiss all claims in Plaintiff’s operative complaint, which motion is pending. The Company believes the allegations in the operative complaint are without merit and intend to vigorously defend the litigation.

The Company is a party in various contracts and subject to disputes, litigation, and potential claims arising in the ordinary course of business none of which are currently reasonably possible or probable of material loss.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2022

Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

Short-term Investments

Fair Value Measurements

Level 1 — Quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company can access at the measurement date.

Level 3 — Unobservable inputs developed using estimates of assumptions developed by the Company, which reflect those that a market participant would use.

Financial Instruments

Accounts Receivable

Concentrations of Credit Risk

Property and Equipment, Net

Depreciation and amortization are recorded using the straight-line method over the estimated useful lives of the assets, as follows:


Asset Category		Estimated Useful Life
Computer and telecommunications		3 – 5 years
Software		3 years
Furniture, fixtures and equipment		5 years
Laboratory equipment		7 years
Leasehold improvements		Lesser of lease term or estimated useful lives

Intangible Assets

Impairment of Long-lived Assets

The Company performed a qualitative assessment for the IPR&D impairment testing for the year ended December 31, 2022 and 2021 and determined that no impairment indicators were present.

Leases

The Company determines if an arrangement is a lease at inception. Operating leases are recorded as a current and long-term lease obligation, with a corresponding right of use lease assets.

Contingent Consideration

Contingent Consideration

Warrants

Stock-based Compensation

Revenue

Research and Development

Research and Development Incentive Credits

Research and Development Incentive Credits

Income Taxes

Comprehensive Loss

For the years presented, the total comprehensive loss includes net loss and other comprehensive income (loss) which represents unrealized gains or losses on short-term investments.

Net Loss per Share

Recently Issued Accounting Pronouncements

Recently Issued Accounting Pronouncements not yet adopted

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2022

Summary of Significant Accounting Policies

Summary of Depreciation and Amortization Recorded using Straight-line Method over Estimated Useful Lives

Depreciation and amortization are recorded using the straight-line method over the estimated useful lives of the assets, as follows:


Asset Category		Estimated Useful Life
Computer and telecommunications		3 – 5 years
Software		3 years
Furniture, fixtures and equipment		5 years
Laboratory equipment		7 years
Leasehold improvements		Lesser of lease term or estimated useful lives

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2022

Fair Value Measurements

Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis

The Company’s assets and liabilities measured at fair value on a recurring basis as of December 31, 2022 consisted of the following (in thousands):


	Fair Value Measurement at December 31, 2022
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents - money market funds	$	105,794	$	105,794	$	—	$	—
Short-term investments		73,783		—		73,783		—
Total	$	179,577	$	105,794	$	73,783	$	—

The Company’s assets and liabilities measured at fair value on a recurring basis as of December 31, 2021 consisted of the following (in thousands):


	Fair Value Measurement at December 31, 2021
	Total		Level 1		Level 2		Level 3
Assets:
Cash equivalents - money market funds	$	65,634	$	65,634	$	—	$	—
Total	$	65,634	$	65,634	$	—	$	—
Liabilities:
Contingent consideration liability (see Note 8)	$	6,090	$	—	$	—	$	6,090
Total	$	6,090	$	—	$	—	$	6,090

Schedule of Short Term Investments

Short-term investments with quoted prices at December 31, 2022 as shown below (in thousands):


	December 31, 2022
	Amortized Cost		Unrealized (Loss) Gain		Market Value
United States treasury securities	$	15,868	$	(86)	$	15,782
Commercial paper and corporate debt securities		50,747		(71)		50,676
Asset backed securities		5,427		(35)		5,392
Agency debt securities		1,928		5		1,933
Total	$	73,970	$	(187)	$	73,783

Summary of Assumptions Used to Estimate Fair Value of Contingent Payments


Unobservable input	Value or Range	Weighted-Average
Expected volatility	80.1%	80.1%
Risk-free interest rate	0.26%	0.26%
Cost of capital	30%	30%
Discount for lack of marketability	8%‑13%	11%
Probability of payment	88%	88%
Projected year of payment	2022	2022

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2022

Property and Equipment, Net

Summary of Property and Equipment, Net

Property and equipment, net consists of the following (in thousands):


	December 31,
	2022		2021
Furniture, fixtures and equipment	$	163		222
Laboratory equipment		295		1,040
Computers and telecommunications		194		291
Software		178		148
Leasehold improvements		1,749		1,794
Property and equipment, at cost		2,579		3,495
Less: accumulated depreciation and amortization		(1,498)		(2,047)
Property and equipment, net	$	1,081	$	1,448

Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2022

Intangible Assets

Schedule of Intangible Assets

The Company’s intangible assets consist of the following (in thousands):


		Gross
	Estimated	Carrying		Accumulated				Net Book
	Useful Lives	Value		Amortization		Impairment		Value
December 31, 2022:
IPR&D assets	Indefinite	$	12,419	$	—	$	—	$	12,419
Total		$	12,419	$	—	$	—	$	12,419
December 31, 2021:
Internally developed patents	6–20 years	$	1,079	$	(500)	$	(579)	$	—
Acquired licenses	16–20 years		285		(285)		—		—
Total intangible assets subject to amortization			1,364		(785)		(579)		—
IPR&D assets	Indefinite		12,419		—		—		12,419
Total		$	13,783	$	(785)	$	(579)	$	12,419

Leases (Tables)

12 Months Ended

Dec. 31, 2022

Leases

Summary of Supplemental other Information Related to Operating Leases Balance Sheet

Supplemental balance sheet information related to the operating leases is as follows (in thousands):


	December 31,
	2022			2021
Operating lease obligations (see Note 7 and 9)	$	1,124		$	1,535
Operating lease right-of-use assets (included in "Other assets" in Balance Sheet)	$	596		$	798
Weighted-average remaining lease term (years)		2.3			3.3
Weighted-average discount rate		7.2	%		7.2	%

Summary of Maturities of Operating Leases Liabilities

Maturities of operating lease liabilities are as follows (in thousands):


Year ending December 31,
2023	$	515
2024		526
2025		176
Total operating lease payments		1,217
Less: imputed interest		(93)
Total operating lease liabilities (see Note 7 and 9)	$	1,124

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2022

Accrued Expenses and Other Current Liabilities.

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expense and other current liabilities consist of the following (in thousands):


	December 31,
	2022		2021
Accrued professional services	$	276	$	396
Accrued payroll and employee benefits		2,955		2,313
Accrued research and development		7,295		6,988
Lease obligation, current portion (see Note 6)		452		411
Excess tax refund payable		1,169		—
Accrued interest and other		103		44
Total accrued expenses and other current liabilities	$	12,250	$	10,152

Contingent Consideration (Tables)

12 Months Ended

Dec. 31, 2022

Contingent Consideration

Summary of Fair Value of Contingent Consideration

Below is a summary of the contingent consideration activity (in thousands):


	Year Ended December 31,
	2022		2021
Beginning balance	$	6,090	$	5,390
Change in fair value		86		700
Fair value of payments settled in common stock (Phase II Milestone)		(6,176)		—
Ending balance	$	—	$	6,090

Other Long-Term Liabilities (Tables)

12 Months Ended

Dec. 31, 2022

Other Long-Term Liabilities

Summary of Other Long-Term Liabilities

The Company’s other long-term liabilities are summarized as follows (in thousands):


	December 31,
	2022		2021
Research and development incentive credit	$	3,599	$	—
Lease obligation, long-term portion (see Note 6)		672		1,124
Conditional economic incentive grants		250		250
Other		60		80
Total other long-term liabilities	$	4,581	$	1,454

Warrants (Tables)

12 Months Ended

Dec. 31, 2022

Warrants

Summary of Common Stock Warrants Outstanding

The following common stock warrants were outstanding at December 31, 2022:


	Number of
	Common	Per Share
	Stock	Exercise
	Warrants	Price		Issuance Date	Expiration Date
Issued with common units in the 2018 Unit Offering	3,300		2.7568	October 2, 2018	October 2, 2023
Issued with common units in the 2018 Registered Direct Offering	92,300		5.40	October 10, 2018	October 10, 2023
Issued with common units in the 2019 Registered Direct Offering	50,000		3.21	March 12, 2019	March 12, 2024
Issued with common units in the 2020 Public Offering (see Note 10)	869,566		0.0001	July 16, 2020	—
Total	1,015,166

The following common stock warrants were outstanding at December 31, 2021:


	Number of
	Common	Per Share
	Stock	Exercise
	Warrants	Price		Issuance Date	Expiration Date
Replacement warrants	155	$	483.00	March 3, 2012	March 3, 2022
Issued with common units in the 2018 Unit Offering	3,300		2.7568	October 2, 2018	October 2, 2023
Issued with common units in the 2018 Registered Direct Offering	92,300		5.40	October 10, 2018	October 10, 2023
Issued with common units in the 2019 Registered Direct Offering	50,000		3.21	March 12, 2019	March 12, 2024
Issued with common units in the 2020 Public Offering (see Note 10)	1,630,436		0.0001	July 16, 2020	—
Issued in exchange for retirement of common stock per the Exchange Agreement (see Note 10)	1,000,000		0.0001	February 25, 2021	—
Total	2,776,191

Summary of Warrant Activity

A summary of warrant activity is as follows:


				Weighted-Average
			Weighted	Remaining
	Number of		Average	Contractual Term
	Warrants		Exercise Price	(Years)
Warrants outstanding, December 31, 2021	2,776,191
Expired	(155)
Exercises (see Note 10)	(1,760,870)
Warrants outstanding, December 31, 2022	1,015,166	$	0.66	0.9

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2022

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Summary of Fair Value of Stock Options Issued to Employees

The fair value of stock option issued to employees was estimated at the date of grant using Black-Scholes with the following weighted-average assumptions:


	Year Ended December 31,
	2022		2021
Expected volatility	110.1	%	109.6	%
Expected term (years)	6.0		6.0
Risk-free interest rate	2.4	%	0.8	%
Expected dividend yield	0.0	%	0.0	%

Schedule of Information Related to Stock Options Outstanding

A summary of stock option activity under the Plans is presented below (in thousands, except share and per share data):


				Weighted-Average
		Weighted-		Remaining
	Number of	Average		Contractual Term	Aggregate Intrinsic
	Stock Options	Exercise Price		(Years)	Value
Outstanding, December 31, 2021	2,583,443	$	8.63	5.9	$	8,460
Granted	1,473,427	$	8.48
Exercised	(373,545)	$	2.65
Forfeited or expired	(299,388)	$	8.92
Outstanding, December 31, 2022	3,383,937	$	9.20	5.9	$	25,724
Exercisable, December 31, 2022	1,523,504	$	9.00	5.8	$	12,292
Vested and expected to vest, December 31, 2022	3,197,894	$	9.19	5.9	$	25,724

Summary of Restricted Stock Activity

A summary of restricted stock activities is presented below:


		Weighted-
		average
		Grant Date
	Shares	Fair Value
Unvested, December 31, 2021	74,000	$	3.59
Vested	(74,000)		3.59
Unvested, December 31, 2022	—	$

Schedule of Stock-based Compensation Expense



	Year Ended December 31,
	2022		2021
Research and development	$	2,835	$	1,656
General and administrative		5,266		3,863
Total	$	8,101	$	5,519

Restricted Stock Units [Member]

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Summary of Restricted Stock Activity


		Weighted-
		average
		Grant Date
	Shares	Fair Value
Unvested, December 31, 2021	231,928	$	14.53
Granted	285,000		7.11
Vested	(61,028)		14.39
Forfeited or expired	(41,415)		10.95
Unvested, December 31, 2022	414,485	$	9.81

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

Income Taxes

Components of Net Loss Before Income Tax Benefit

The components of net loss before income tax benefit are as follows (in thousands):


	Year Ended December 31,
	2022		2021
U.S. operations	$	(72,750)	$	(78,583)
Non-U.S. operations		(12,160)		(18,507)
Net loss before income tax benefit	$	(84,910)	$	(97,090)

Components of Income Tax Benefits

The components of the income tax expense (benefit) are as follows (in thousands):


	Year Ended December 31,
	2022		2021
U.S. federal
Current	$	(144)	$	—
U.S. state and local
Current		(53)		—
Income tax expense (benefit)	$	(197)	$	—

Reconciliation Between Effect of Applying Federal Statutory Rate and Effective Income Tax Rate Used to Calculate Income Tax Benefit

Reconciliation between the effect of applying the federal statutory rate and the effective income tax rate used to calculate the Company’s income tax benefit is as follows:


	Year Ended December 31,
	2022		2021
Federal statutory rate	21.00	%	21.00	%
State income taxes, net of federal benefit	(0.12)		4.71
Research and development tax credit	(2.22)		(2.30)
Acquired in process research and development	(0.02)		(0.15)
Rate change	1.29		—
Other	0.21		(0.47)
Change in valuation allowance	(19.91)		(22.79)
Effective tax rate	0.23	%	—	%

Components of Deferred Tax Assets and Liabilities


	December 31,
	2022		2021
Deferred tax assets:
Net operating losses	$	44,606	$	37,229
Accrued expenses		523		352
Amortization		540		746
Stock compensation		2,193		1,276
Lease liability		309		422
Asset impairment		—		3,129
Capitalized research and development costs		11,996		—
Other		107		109
Total deferred tax assets		60,274		43,263
Valuation allowance		(57,245)		(40,584)
Deferred tax assets, net		3,029		2,679
Deferred tax liabilities:
IPR&D assets		(2,847)		(2,360)
Right of use asset		(164)		(220)
Depreciation		(18)		(99)
Total deferred tax liabilities		(3,029)		(2,679)
Total deferred tax assets (liabilities), net	$	—	$	—

Reconciliation of Unrecognized Tax Benefits

The following is a tabular reconciliation of the total amounts of unrecognized tax benefits excluding related interest and penalties (in thousands):


	Year Ended December 31,
	2022		2021
Beginning balance	$	237	$	711
Increases for prior year tax positions		474		—
Decreases for prior year tax positions		—		(474)
Ending balance	$	711	$	237

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2022

Net Loss Per Share

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share


	Year Ended December 31,
	2022	2021
Common stock warrants	145,600	145,755
Common stock options	3,397,998	2,594,177
Restricted stock units	414,485	231,928
Restricted stock	—	74,000

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2022 USD ($) segment	Dec. 31, 2021 USD ($)
Significant Accounting Policies [Line Items]
Number of operating segments \| segment	1
Impairments		$ 579,000
Fair value transfers into Level 3	$ 0	0
Fair value transfers out of Level 3	0	0
Restricted cash	34,000	34,000
United Kingdom
Significant Accounting Policies [Line Items]
Research and Development Credits	1,800,000	1,900,000
R&D credits receivable	1,600,000	1,800,000
Australian Taxation Office
Significant Accounting Policies [Line Items]
Research and development incentive credit earned	3,600,000
Money Market Funds [Member]
Significant Accounting Policies [Line Items]
Restricted cash	34,000	34,000
IPR&D [Member]
Significant Accounting Policies [Line Items]
Impairments	$ 0	$ 0

Summary of Significant Accounting Policies - Summary of Depreciation and Amortization Recorded using Straight-line Method over Estimated Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2022
Computers and Telecommunications [Member] \| Minimum [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	3 years
Computers and Telecommunications [Member] \| Maximum [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	5 years
Software [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	3 years
Furniture, Fixtures and Equipment [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	5 years
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	7 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Estimated useful lives of assets	Lesser of lease term or estimated useful lives

Fair Value Measurements - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	$ 73,783
Contingent consideration liability (see Note 8)		$ 6,090	$ 5,390
Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	73,783
Total	179,577	65,634
Contingent consideration liability (see Note 8)		6,090
Total		6,090
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	105,794	65,634
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	73,783
Total	73,783
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration liability (see Note 8)		6,090
Total		6,090
Money Market Funds [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	105,794	65,634
Money Market Funds [Member] \| Fair Value, Measurements, Recurring [Member] \| Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 105,794	$ 65,634

Fair Value Measurements - Schedule of Short Term Investments (Detail) $ in Thousands	Dec. 31, 2022 USD ($)
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 73,970
Unrealized Loss	(187)
Market Value	73,783
United States Treasury Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	15,868
Unrealized Loss	(86)
Market Value	15,782
Commercial Paper and Corporate Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	50,747
Unrealized Loss	(71)
Market Value	50,676
Asset Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	5,427
Unrealized Loss	(35)
Market Value	5,392
Agency Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,928
Unrealized Loss	5
Market Value	$ 1,933

Fair Value Measurements - Summary of Assumptions Used to Estimate Fair Value of Contingent Payments (Detail) - Level 3 [Member]	12 Months Ended
	Dec. 31, 2021
Expected Volatility [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assumptions used to estimate fair value of contingent payments	80.1
Risk-free Interest Rate [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assumptions used to estimate fair value of contingent payments	0.26
Cost of Capital [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assumptions used to estimate fair value of contingent payments	30
Probability of Payment [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assumptions used to estimate fair value of contingent payments	88
Projected Year of Payment [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assumptions used to estimate fair value of contingent payments	2022
Minimum [Member] \| Discount for Lack of Marketability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assumptions used to estimate fair value of contingent payments	8
Maximum [Member] \| Discount for Lack of Marketability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assumptions used to estimate fair value of contingent payments	13
Weighted Average [Member] \| Expected Volatility [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assumptions used to estimate fair value of contingent payments	80.1
Weighted Average [Member] \| Risk-free Interest Rate [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assumptions used to estimate fair value of contingent payments	0.26
Weighted Average [Member] \| Cost of Capital [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assumptions used to estimate fair value of contingent payments	30
Weighted Average [Member] \| Discount for Lack of Marketability [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assumptions used to estimate fair value of contingent payments	11
Weighted Average [Member] \| Probability of Payment [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assumptions used to estimate fair value of contingent payments	88
Weighted Average [Member] \| Projected Year of Payment [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assumptions used to estimate fair value of contingent payments	2022

Fair Value Measurements - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2022	Dec. 31, 2021
Fair value transfers into Level 3				$ 0	$ 0
Fair value transfers out of Level 3				0	0
Assets or liabilities measured at fair value on a non-recurring basis.				$ 0
Non-cash impairment charge					$ 11,370,000
Lonza Manufacturing Agreement [Member]
Non-cash impairment charge			$ 8,100,000
Commitment to procure equipment and construction	$ 23,000,000.0
Lonza Manufacturing Agreement [Member] \| Construction-In-Progress
Non-cash impairment charge		$ 3,300,000
Capitalized costs			11,400,000
Lonza Manufacturing Agreement [Member] \| Construction-In-Progress \| Fair Value, Nonrecurring [Member] \| Level 3 [Member]
Fair value of impaired assets			$ 3,300,000

Property and Equipment, Net - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property Plant And Equipment [Line Items]
Property and equipment, at cost	$ 2,579	$ 3,495
Less: accumulated depreciation and amortization	(1,498)	(2,047)
Property and equipment, net	1,081	1,448
Furniture, Fixtures and Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, at cost	163	222
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, at cost	295	1,040
Computers and Telecommunications [Member]
Property Plant And Equipment [Line Items]
Property and equipment, at cost	194	291
Software [Member]
Property Plant And Equipment [Line Items]
Property and equipment, at cost	178	148
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, at cost	$ 1,749	$ 1,794

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Property and Equipment, Net
Depreciation	$ 0.5	$ 0.4

Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Schedule Of Intangible Assets [Line Items]
Intangible assets subject to amortization, Gross Carrying Value		$ 1,364
Intangible assets subject to amortization, Accumulated Amortization		(785)
Total intangible assets, Gross Carrying Value	$ 12,419	13,783
Indefinite-lived intangible assets, Impairment		(579)
Finite-lived intangible assets, Impairment		$ (579)
Impairment, Intangible Asset, Finite-Lived, Statement of Income or Comprehensive Income [Extensible Enumeration]		Impairment of Long-Lived Assets Held-for-use
Intangible Assets, Impairment		$ (579)
Total intangible assets, Net Book Value	12,419
Total intangible assets, Net Book Value	12,419	12,419
IPR&D [Member]
Schedule Of Intangible Assets [Line Items]
Total intangible assets, Gross Carrying Value	12,419	12,419
Indefinite-lived intangible assets, Impairment	0	0
Total intangible assets, Net Book Value	$ 12,419	12,419
Internally Developed Patents [Member]
Schedule Of Intangible Assets [Line Items]
Intangible assets subject to amortization, Gross Carrying Value		1,079
Intangible assets subject to amortization, Accumulated Amortization		(500)
Indefinite-lived intangible assets, Impairment		(600)
Finite-lived intangible assets, Impairment		(579)
Internally Developed Patents [Member] \| Minimum [Member]
Schedule Of Intangible Assets [Line Items]
Estimated Useful Lives	6 years
Internally Developed Patents [Member] \| Maximum [Member]
Schedule Of Intangible Assets [Line Items]
Estimated Useful Lives	20 years
Acquired Licenses [Member]
Schedule Of Intangible Assets [Line Items]
Intangible assets subject to amortization, Gross Carrying Value		285
Intangible assets subject to amortization, Accumulated Amortization		$ (285)
Acquired Licenses [Member] \| Minimum [Member]
Schedule Of Intangible Assets [Line Items]
Estimated Useful Lives	16 years
Acquired Licenses [Member] \| Maximum [Member]
Schedule Of Intangible Assets [Line Items]
Estimated Useful Lives	20 years

Leases - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Leases
Operating lease rent expense	$ 0.5	$ 0.5
Cash paid for operating lease liabilities	$ 0.5	$ 0.5

Leases - Summary of Supplemental other Information Related to Operating Leases Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Leases
Operating lease obligations (see Note 7 and 9)	$ 1,124	$ 1,535
Operating lease right-of-use assets (included in "Other assets" in Balance Sheet)	$ 596	$ 798
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other Assets Noncurrent	Other Assets Noncurrent
Weighted-average remaining lease term (years)	2 years 3 months 18 days	3 years 3 months 18 days
Weighted-average discount rate	7.20%	7.20%

Leases - Summary of Maturities of Lease Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Leases
2023	$ 515
2024	526
2025	176
Total operating lease payments	1,217
Less: imputed interest	(93)
Total operating lease liabilities (see Note 7 and 9)	$ 1,124	$ 1,535

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expense and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accrued Liabilities And Other Liabilities [Abstract]
Accrued professional services	$ 276	$ 396
Accrued payroll and employee benefits	2,955	2,313
Accrued research and development	7,295	6,988
Lease obligation, current portion (see Note 6)	$ 452	$ 411
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Total accrued expenses and other current liabilities	Total accrued expenses and other current liabilities
Excess tax refund payable	$ 1,169
Accrued interest and other	103	$ 44
Total accrued expenses and other current liabilities	$ 12,250	$ 10,152

Contingent Consideration - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				2 Months Ended	12 Months Ended
	Apr. 26, 2022	Nov. 03, 2020	Jul. 12, 2019	Jun. 10, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Estimated future contingent consideration						$ 6,090	$ 5,390
Change in value of contingent consideration for acquired in-process research and development					$ 86	700
Contingent consideration						$ 6,090
Common Stock Issued Related To Contingent Consideration Liability					6,176
Clinical Trial Notification [Member]
Business Acquisition [Line Items]
Shares issued for contingent milestone payment		1,694,906
Common Stock Issued Related To Contingent Consideration Liability		$ 13,600
Spitfire Pharma, Inc. [Member]
Business Acquisition [Line Items]
Agreement date			Jul. 08, 2019
Unregistered shares of common stock			1,887,250
Up-front consideration			$ 5,000
Spitfire Pharma, Inc. [Member] \| Clinical Trial Notification [Member]
Business Acquisition [Line Items]
Consideration amount		$ 9.57
Spitfire Pharma, Inc. [Member] \| Investigational New Drug Application Milestone [Member]
Business Acquisition [Line Items]
Estimated future contingent consideration			$ 5,000
Estimated future contingent consideration term			60 days
Number of consecutive trading days			20 days
Consideration amount			$ 2.95
Spitfire Pharma, Inc. [Member] \| Investigational New Drug Application and Regulatory Milestones [Member]
Business Acquisition [Line Items]
Estimated future contingent consideration			$ 3,000
Estimated future contingent consideration term			60 days
Number of consecutive trading days			20 days
Consideration amount			$ 3.54
Spitfire Pharma, Inc. [Member] \| Sales Milestones [Member]
Business Acquisition [Line Items]
Estimated future contingent consideration			$ 80,000
License agreement term			10 years
Spitfire Pharma, Inc. [Member] \| Phase Two Milestone [Member]
Business Acquisition [Line Items]
Estimated future contingent consideration					$ 0
Consideration amount	$ 8.55
Shares issued for contingent milestone payment	847,444
Change in value of contingent consideration for acquired in-process research and development				$ 1,900
Common Stock Issued Related To Contingent Consideration Liability	$ 7,200
Spitfire Pharma, Inc. [Member] \| Common Stock [Member] \| Maximum [Member]
Business Acquisition [Line Items]
Estimated future contingent consideration			$ 88,000

Contingent Consideration - Summary of Fair Value of Contingent Consideration (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Contingent Consideration
Beginning balance	$ 6,090	$ 5,390
Change in fair value	86	700
Fair value of payments settled in common stock (Phase II Milestone)	$ (6,176)
Ending balance		$ 6,090

Other Long-Term Liabilities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2022 USD ($) item	Dec. 31, 2021 USD ($)
Debt Instrument [Line Items]
Conditional economic incentive grants	$ 250,000	$ 250,000
Interest expense	$ 8,000	5,000
Montgomery County [Member]
Debt Instrument [Line Items]
Expiration date of economic conditional incentive grant	Feb. 28, 2028
State of Maryland [Member]
Debt Instrument [Line Items]
Expiration date of economic conditional incentive grant	Dec. 31, 2029
Economic incentive grant term	10 years
Montgomery County and State of Maryland [Member]
Debt Instrument [Line Items]
Conditional economic incentive grants	$ 250,000
Number of economic conditional incentive grants \| item	2
Interest expense	$ 8,000	$ 8,000
Accrued interest rate on grant	3.00%	3.00%

Other Long-Term Liabilities - Summary of Long-term Portion of Outstanding Notes Payable as well as Other Long-Term Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Other Long-Term Liabilities
Research and development incentive credit	$ 3,599
Lease obligation, long-term portion (see Note 6)	$ 672	$ 1,124
Operating lease, liability, statement of financial position [extensible list]	Other long-term liabilities	Other long-term liabilities
Conditional economic incentive grants	$ 250	$ 250
Other	60	80
Total other long-term liabilities	$ 4,581	$ 1,454

Common Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Jan. 24, 2022	Feb. 25, 2021	Jul. 16, 2020	Dec. 31, 2022	Dec. 31, 2021
Changes In Equity And Comprehensive Income Line Items [Line Items]
Proceeds from issuance of common stock in public offering				$ 56,166	$ 64,815
Common stock, shares authorized				200,000,000	200,000,000
Common stock, par or stated value per share				$ 0.0001	$ 0.0001
Common stock, shares issued				49,199,845	40,993,768
Common stock, shares outstanding				49,199,845	40,993,768
Preferred stock, shares authorized				1,000,000
Preferred stock, par or stated value per share				$ 0.0001
Preferred stock, shares issued				0
Preferred stock, shares outstanding				0
Warrants outstanding				1,015,166	2,776,191
Exercise price of warrants or rights				$ 0.66
Pre-Funded Warrants [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Number of securities called by warrants or rights				760,870
Warrants outstanding				869,566
Common Stock [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Shares of common stock sold				5,204,215	4,800,454
Exchange Warrants [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Number of securities called by warrants or rights		1,000,000
Common stock, par or stated value per share		$ 0.0001
Number Of Warrants Exercised	1,000,000
Common stock exchanged for pre-funded warrants		1,000,000
Shares of common stock sold	999,984
Warrants outstanding	0
Exercise price of warrants or rights		$ 0.0001
Public Offering [Member] \| Pre-Funded Warrants [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Purchase price of warrants issued			$ 22.9999
Ownership percentage on exercise of warrants without notice, minimum			4.99%
Ownership percentage on exercise of warrants with notice, maximum			19.99%
Notice period to increase ownership percentage on exercise of warrants			61 days
Exercise price of warrants or rights			$ 0.0001
Public Offering [Member] \| Common Stock [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Public offering price, per share			$ 23.00
Shares of common stock sold			3,369,564
Public Offering [Member] \| Common Stock [Member] \| Pre-Funded Warrants [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Number of securities called by warrants or rights			1,630,436
At-The-Market Offering [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Proceeds from issuance of common stock in public offering				$ 56,200
Shares of common stock sold				5,204,415
Issuance costs				$ 1,900
At-The-Market Offering [Member] \| Equity Distribution Agreement [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Common stock, par or stated value per share		$ 0.0001
Remaining shares available for issuance				0
At-The-Market Offering [Member] \| Equity Distribution Agreement [Member] \| Piper Sandler company and evercore group limited liability company and B Riley Securities inc [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Deferred Offering Costs				$ 300
Proceeds from issuance of common stock in public offering				$ 121,000
Aggregate offering price		$ 125,000
Shares of common stock sold				10,004,869
Issuance costs				$ 4,000

Warrants - Summary of Common Stock Warrants Outstanding (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Class Of Warrant Or Right [Line Items]
Number of Common Stock Warrants	1,015,166	2,776,191
Per Share Exercise Price	$ 0.66
Replacement Warrants [Member]
Class Of Warrant Or Right [Line Items]
Number of Common Stock Warrants		155
Per Share Exercise Price		$ 483.00
Issuance Date		Mar. 03, 2012
Expiration Date		Mar. 03, 2022
Warrants Issued With Common Units In 2018 Unit Offering [Member]
Class Of Warrant Or Right [Line Items]
Number of Common Stock Warrants	3,300	3,300
Per Share Exercise Price	$ 2.7568	$ 2.7568
Issuance Date	Oct. 02, 2018	Oct. 02, 2018
Expiration Date	Oct. 02, 2023	Oct. 02, 2023
Issued With Common Units In 2018 Registered Direct Offering [Member]
Class Of Warrant Or Right [Line Items]
Number of Common Stock Warrants	92,300	92,300
Per Share Exercise Price	$ 5.40	$ 5.40
Issuance Date	Oct. 10, 2018	Oct. 10, 2018
Expiration Date	Oct. 10, 2023	Oct. 10, 2023
Issued With Common Units In 2019 Registered Direct Offering [Member]
Class Of Warrant Or Right [Line Items]
Number of Common Stock Warrants	50,000	50,000
Per Share Exercise Price	$ 3.21	$ 3.21
Issuance Date	Mar. 12, 2019	Mar. 12, 2019
Expiration Date	Mar. 12, 2024	Mar. 12, 2024
Issued with Common Units in the 2020 Public Offering [Member]
Class Of Warrant Or Right [Line Items]
Number of Common Stock Warrants	869,566	1,630,436
Per Share Exercise Price	$ 0.0001	$ 0.0001
Issuance Date	Jul. 16, 2020	Jul. 16, 2020
Issued in Exchange for Retirement of Common Stock per the Exchange Agreement [Member]
Class Of Warrant Or Right [Line Items]
Number of Common Stock Warrants		1,000,000
Per Share Exercise Price		$ 0.0001
Issuance Date		Feb. 25, 2021

Warrants - Additional Information (Detail) - $ / shares	Mar. 12, 2019	Oct. 10, 2018	Oct. 02, 2018	Dec. 31, 2022	Dec. 31, 2021
Class Of Warrant Or Right [Line Items]
Warrants outstanding				1,015,166	2,776,191
Common stock, shares issued				49,199,845	40,993,768
Exercise price of warrants or rights				$ 0.66
Number of Common Stock Warrants				1,015,166	2,776,191
2018 Unit Offering [Member]
Class Of Warrant Or Right [Line Items]
Common units outstanding			2,400,000
Issuance of transaction date			Oct. 02, 2018
2018 Unit Offering [Member] \| Common Units [Member]
Class Of Warrant Or Right [Line Items]
Public offering price per share			$ 5.00
Exercise price of warrants or rights			$ 6.00
Warrant expiration period			5 years
Two Thousand Eighteen Registered Direct Offering
Class Of Warrant Or Right [Line Items]
Common units outstanding		4,629,630
Issuance of transaction date		Oct. 10, 2018
Two Thousand Eighteen Registered Direct Offering \| Common Units [Member]
Class Of Warrant Or Right [Line Items]
Public offering price per share		$ 5.40
Exercise price of warrants or rights		$ 5.40
Warrant expiration period		5 years
Registered Direct Offering [Member]
Class Of Warrant Or Right [Line Items]
Warrants outstanding				50,000
Common units outstanding	4,361,370
Issuance of transaction date	Mar. 12, 2019
Warrant expiration period	5 years
Number of Common Stock Warrants				50,000
Registered Direct Offering [Member] \| Common Units [Member]
Class Of Warrant Or Right [Line Items]
Public offering price per share	$ 3.21
Number of securities called by warrants or rights	0.70
Per share exercise price	$ 3.21
Issued With Common Units In 2018 Registered Direct Offering [Member]
Class Of Warrant Or Right [Line Items]
Warrants outstanding				92,300	92,300
Exercise price of warrants or rights				$ 5.40	$ 5.40
Number of Common Stock Warrants				92,300	92,300
Issued With Common Units In 2018 Registered Direct Offering [Member] \| Minimum [Member]
Class Of Warrant Or Right [Line Items]
Exercise price of warrants or rights	4.1798	$ 6.00
Issued With Common Units In 2018 Registered Direct Offering [Member] \| Maximum [Member]
Class Of Warrant Or Right [Line Items]
Exercise price of warrants or rights	$ 2.7568	$ 4.1798
Issued With Common Units In 2018 Registered Direct Offering [Member] \| Two Thousand Eighteen Registered Direct Offering
Class Of Warrant Or Right [Line Items]
Warrants outstanding				92,300
Number of Common Stock Warrants				92,300
Warrants Issued With Common Units In 2018 Unit Offering [Member]
Class Of Warrant Or Right [Line Items]
Warrants outstanding				3,300	3,300
Exercise price of warrants or rights				$ 2.7568	$ 2.7568
Number of Common Stock Warrants				3,300	3,300

Warrants - Summary of Warrant Activity (Detail)	12 Months Ended
Warrants - Summary of Warrant Activity (Detail)	Dec. 31, 2022 $ / shares shares
Warrants
Warrants outstanding, December 31, 2021	2,776,191
Expired	(155)
Exercises (see Note 10)	(1,760,870)
Warrants outstanding, December 31, 2022	1,015,166
Weighted Average Exercise Price \| $ / shares	$ 0.66
Weighted-Average Remaining Contractual Term (Years)	10 months 24 days

Stock-Based Compensation - Additional Information (Detail)			1 Months Ended	12 Months Ended
	Jan. 01, 2023 shares	Mar. 29, 2019 shares	Nov. 30, 2018 installment $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Nov. 29, 2018 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Stock Options, Granted				1,473,427
Issuance of common stock from Employee Stock Purchase Plan \| $				$ 181,000	$ 225,000
Stock-based compensation expense \| $				$ 8,101,000	$ 5,519,000
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value of stock options granted \| $ / shares				$ 7.07	$ 11.79
Weighted-average Intrinsic Value, Exercised \| $				$ 4,400,000	$ 700,000
Fair value of award vested \| $				6,800,000	4,700,000
Unrecognized compensation cost, stock options \| $				$ 11,700,000
Unrecognized stock-based compensation expense, period for recognition				2 years 7 months 6 days
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrestricted common stock				41,572
Common stock withheld to satisfy tax withholding obligations.				32,428
Unrecognized compensation expense \| $				$ 0
Restricted Stock [Member] \| November 30, 2018 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of restricted shares that vested \| $				$ 700,000	1,000,000.0
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense, period for recognition				2 years 9 months 18 days
Restricted stock authorized and granted				285,000
Weighted average grant date fair value of restricted stock award \| $ / shares				$ 7.11
Unrestricted common stock				41,123
Fair value of restricted shares that vested \| $				$ 600,000	$ 100,000
Common stock withheld to satisfy tax withholding obligations.				19,905
Unrecognized compensation expense \| $				$ 2,800,000
Restricted stock vesting period				4 years
Executive Officer [Member] \| Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock authorized and granted			322,907
Weighted average grant date fair value of restricted stock award \| $ / shares			$ 3.59
Share-based compensation arrangement by share-based payment award, shares vesting date			Nov. 30, 2022
Restricted stock vesting period			4 years
Executive Officer [Member] \| Restricted Stock [Member] \| One Year Anniversary [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage			25.00%
Executive Officer [Member] \| Restricted Stock [Member] \| 36 Substantially Equal Monthly Installments
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights, percentage			75.00%
Number of substantially equal monthly installments \| installment			36
Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Stock Options, Granted				1,473,427
Unrestricted common stock				8,695	(28,850)
2001 Employee Stock Option Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Stock Options, Granted				0
2007 Long Term Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Stock Options, Granted				0
2017 Omnibus Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future issuance, description				The aggregate share reserve will be increased on January 1 of each year commencing in 2018 and ending on and including January 1, 2027 up to an amount equal to the lowest of (i) 4% of the total number of shares of common stock outstanding on a fully diluted basis as of December 31 of the immediately preceding calendar year, and (ii) such number of shares of common stock, if any, determined by the Company’s board of directors.
Percentage of additional shares from common stock available for stock-based compensation				4.00%
2017 Omnibus Incentive Plan [Member] \| Subsequent Event [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of additional shares authorized	2,160,537
2017 Omnibus Incentive Plan [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance				1,500,000
2017 Omnibus Incentive Plan [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance				5,000,000
2017 Omnibus Incentive Plan [Member] \| Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance				1,368,689
2017 Omnibus Incentive Plan [Member] \| Common Stock [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock granted, shares				800,000
Stock granted value \| $				$ 5,000,000
2017 Omnibus Incentive Plan [Member] \| Common Stock [Member] \| Maximum [Member] \| Director [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock granted, shares				500,000
2018 Inducement Grant Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance						2,000,000
2018 Inducement Grant Plan [Member] \| Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance				1,309,275
2019 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance		403,500		260,344
Percent of payroll deductions		10.00%
Percentage of discount from fair market value of common stock on first or last trading day of offering period		85.00%
Stock purchased by employee				26,395
Issuance of common stock from Employee Stock Purchase Plan \| $				$ 200,000
Stock-based compensation expense \| $				$ 300,000	$ 300,000

Stock-Based Compensation - Summary of Fair Value of Stock Options Issued to Employees (Detail)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]
Expected volatility	110.10%	109.60%
Expected term (years)	6 years	6 years
Risk-free interest rate	2.40%	0.80%
Expected dividend yield	0.00%	0.00%

Stock-Based Compensation - Schedule of Information Related to Stock Options Outstanding (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Stock-Based Compensation
Number of Stock Options, Outstanding	2,583,443
Number of Stock Options, Granted	1,473,427
Number of Stock Options, Exercised	(373,545)
Number of Stock Options, Forfeited or expired	(299,388)
Number of Stock Options, Outstanding	3,383,937	2,583,443
Number of Stock Options, Exercisable	1,523,504
Number of Stock Options, Expected to vest	3,197,894
Weighted-average Exercise Price, Outstanding	$ 8.63
Weighted-average Exercise Price, Granted	8.48
Weighted-average Exercise Price, Exercised	2.65
Weighted-average Exercise Price, Forfeited or expired	8.92
Weighted-average Exercise Price, Outstanding	9.20	$ 8.63
Weighted-average Exercise Price, Exercisable	9.00
Weighted-average Exercise Price, Expected to vest	$ 9.19
Weighted-average Remaining Contractual Term, Outstanding	5 years 10 months 24 days	5 years 10 months 24 days
Weighted-average Remaining Contractual Term, Exercisable	5 years 9 months 18 days
Weighted-average Remaining Contractual Term, Expected to vest	5 years 10 months 24 days
Weighted-average Intrinsic Value, Outstanding	$ 8,460
Weighted-average Intrinsic Value, Outstanding	25,724	$ 8,460
Aggregate Intrinsic Value, Exercisable	12,292
Weighted-average Intrinsic Value, Expected to vest	$ 25,724

Stock-Based Compensation - Summary of Restricted Stock Activity (Detail) - $ / shares	1 Months Ended	12 Months Ended
	Nov. 30, 2018	Dec. 31, 2022
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vested Shares		(74,000)
Restricted Stock [Member] \| Executive Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested Shares, Beginning balance		74,000
Shares granted	322,907
Vested Shares		(74,000)
Weighted-average Grant Date Fair Value Unvested, beginning balance		$ 3.59
Weighted-average Grant Date Fair Value Granted	$ 3.59
Weighted-average Grant Date Fair Value Vested		$ 3.59
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested Shares, Beginning balance		231,928
Shares granted		285,000
Vested Shares		(61,028)
Forfeited or expired		(41,415)
Unvested Shares, Ending balance		414,485
Weighted-average Grant Date Fair Value Unvested, beginning balance		$ 14.53
Weighted-average Grant Date Fair Value Granted		7.11
Weighted-average Grant Date Fair Value Vested		14.39
Weighted-average Grant Date Fair Value Forfeited or expired		10.95
Weighted-average Grant Date Fair Value Unvested, Ending balance		$ 9.81

Stock-Based Compensation - Schedule of Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock based compensation expense	$ 8,101	$ 5,519
Research and Development [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock based compensation expense	2,835	1,656
General and Administrative [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock based compensation expense	$ 5,266	$ 3,863

U.S. Government Contracts and Grants - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended		12 Months Ended
	Jan. 01, 2021	Jun. 30, 2020	Jul. 31, 2016	Dec. 31, 2022	Dec. 31, 2021
Revenues				$ (68)	$ 4,410
BARDA Contract [Member]
Duration of contract	3 years		5 years
Amount used to fund clinical development			$ 136,800
BARDA Contract [Member] \| Minimum [Member]
Additional funding for development and manufacturing activities	$ 1,100
BARDA Contract [Member] \| Maximum [Member]
Additional funding for development and manufacturing activities	$ 34,400
MTEC Collaborative Arrangement [Member]
Revenues		$ 4,700
Grant [Member] \| BARDA Contract [Member]
Revenues					3,700
Grant [Member] \| MTEC Collaborative Arrangement [Member]
Revenues				$ 0	$ 500
Investment Performance [Member] \| BARDA Contract [Member]
Revenues			$ 30,900

Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Employee Benefit Plans
Discretionary plan contributions	$ 0.3	$ 0.3

Income Taxes - Components of Net Loss Before Income Tax Benefit (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Taxes
U.S. operations	$ (72,750)	$ (78,583)
Non-U.S. operations	(12,160)	(18,507)
Net loss before income taxes	$ (84,910)	$ (97,090)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8906-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8933-108599

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 940
-SubTopic 20
-Section 25
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=126941158&loc=d3e41242-110953

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
-Paragraph 22
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8736-108599

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(10))
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(8))
-URI https://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-URI https://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
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-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8924-108599

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
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-Section S99
-Paragraph 1
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-URI https://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

Income Taxes - Components of Income Tax Benefits (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
U.S. federal
Current	$ (144)
U.S. state and local
Current	(53)
Income Tax Expense (Benefit), Total	$ (197)

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Income Taxes - Reconciliation Applying Federal Statutory Rate and Effective Income Tax Rate Used to Calculate Income Tax Benefit (Detail)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Corporate federal income tax rate	21.00%	21.00%
State income taxes, net of federal benefit	(0.12%)	4.71%
Research and development tax credit	(2.22%)	(2.30%)
Acquired in process research and development	(0.02%)	(0.15%)
Rate change	1.29%
Other	0.21%	(0.47%)
Change in valuation allowance	(19.91%)	(22.79%)
Effective tax rate	0.23%

Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Net operating losses	$ 44,606	$ 37,229
Accrued expenses	523	352
Amortization	540	746
Stock compensation	2,193	1,276
Lease liability	309	422
Asset impairment		3,129
Capitalized research and development costs	11,996
Other	107	109
Total deferred tax assets	60,274	43,263
Valuation allowance	(57,245)	(40,584)
Deferred tax assets, net	3,029	2,679
Deferred tax liabilities:
IPR&D assets	(2,847)	(2,360)
Right of use asset	(164)	(220)
Depreciation	(18)	(99)
Total deferred tax liabilities	$ (3,029)	$ (2,679)

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Taxes [Line Items]
Testing period	3 years
Unrecognized Tax Benefits	$ 711	$ 237	$ 711
Income tax expense
Income Taxes [Line Items]
Unrecognized Tax Benefits	$ 200
Minimum [Member]
Income Taxes [Line Items]
Ownership percentage	50.00%
U.S. Federal and State [Member]
Income Taxes [Line Items]
Operating loss carry forwards expiration period	20 years
Net operating loss carryforwards, expiration date	Jan. 01, 2024
U.S. Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 134,300
Operating Loss carryforwards, subject to expiration	7,100
Operating loss carryforwards not subject to expiration	127,200
State [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	103,700
Operating Loss carryforwards, subject to expiration	103,700
Foreign [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 38,600

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Taxes
Beginning balance	$ 237	$ 711
Increases for prior year tax positions	474
Decreases for prior year tax positions	0	(474)
Ending balance	$ 711	$ 237

Net Loss Per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Common Stock Warrants [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	145,600	145,755
Stock Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	3,397,998	2,594,177
Restricted Stock Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	414,485	231,928
Restricted Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share		74,000

Commitments and Contingencies - Additional Information (Details) - USD ($)			12 Months Ended
	Apr. 02, 2020	Jul. 12, 2019	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Commitments And Contingencies [Line Items]
Estimated future contingent consideration				$ 6,090,000	$ 5,390,000
Sales Milestones [Member] \| Spitfire Pharma, Inc. [Member]
Commitments And Contingencies [Line Items]
License agreement term		10 years
Estimated future contingent consideration		$ 80,000,000.0
Janssen Vaccines and Prevention Bv [Member] \| Research and Development [Member]
Commitments And Contingencies [Line Items]
License fee costs			$ 100,000	$ 200,000
Janssen Vaccines and Prevention Bv [Member] \| License [Member] \| Maximum [Member]
Commitments And Contingencies [Line Items]
Development Based Milestone Payments	$ 1,200,000
Janssen Vaccines and Prevention Bv [Member] \| License And Royalty Fees \| Sales Milestones [Member]
Commitments And Contingencies [Line Items]
License agreement term	15 years
Amount required to be pay upon reaching certain milestone	$ 150,000