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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2019	Aug. 13, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Trading Symbol	ALT
Entity Registrant Name	Altimmune, Inc.
Entity Central Index Key	0001326190
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		15,338,001
Entity File Number	001-32587
Entity Tax Identification Number	202726770
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	Maryland
Entity Address, Postal Zip Code	20878
City Area Code	(240)
Local Phone Number	654-1450

Consolidated Balance Sheets - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 41,671,738	$ 33,718,713
Restricted cash	34,174	634,416
Total cash, cash equivalents and restricted cash	41,705,912	34,353,129
Accounts receivable	2,629,840	3,461,938
Tax refund receivable	1,080,559	1,008,973
Prepaid expenses and other current assets	688,862	548,094
Total current assets	46,105,173	39,372,134
Property and equipment, net	1,222,130	1,342,802
Right of use asset	732,380
Intangible assets, net	13,760,216	13,851,924
Other assets	156,115	183,682
Total assets	61,976,014	54,750,542
Current liabilities:
Notes payable	163,724	71,596
Accounts payable	270,097	372,860
Accrued expenses and other current liabilities	3,046,567	4,082,949
Total current liabilities	3,480,388	4,527,405
Deferred income taxes	58,500	58,500
Other long-term liabilities	2,212,104	1,852,071
Total liabilities	5,750,992	6,437,976
Commitments and contingencies (Note 12)
Stockholders’ equity:
Common stock, $0.0001 par value; 200,000,000 shares authorized; 13,451,106 and 9,078,735 shares issued; 13,450,751 and 9,078,238 shares outstanding at June 30, 2019 and December 31, 2018, respectively	1,313	876
Additional paid-in capital	183,604,057	170,207,844
Accumulated deficit	(122,340,185)	(116,855,991)
Accumulated other comprehensive loss – foreign currency translation adjustments	(5,040,163)	(5,040,163)
Total stockholders’ equity	56,225,022	48,312,566
Total liabilities and stockholders’ equity	$ 61,976,014	$ 54,750,542

Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
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	13,451,106	9,078,735
Common stock, shares outstanding	13,450,751	9,078,238

Consolidated Statements of Operations and Comprehensive Loss - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenue	$ 1,626,029	$ 2,417,140	$ 4,581,622	$ 5,108,121
Operating expenses:
Research and development	2,945,096	4,918,961	6,162,768	10,665,890
General and administrative	2,231,817	2,933,982	4,298,299	5,381,917
Impairment charges				490,676
Total operating expenses	5,176,913	7,852,943	10,461,067	16,538,483
Loss from operations	(3,550,884)	(5,435,803)	(5,879,445)	(11,430,362)
Other income (expense):
Changes in fair value of warrant liability	(46,000)	(5,228,691)	(46,000)	(3,680,709)
Changes in fair value of embedded derivatives		4,912		(2,130)
Interest expense	(748)	(1,921)	(1,488)	(2,791)
Interest income	239,964	25,617	425,211	57,206
Other income (expense)	(29,220)	(49)	17,528	257,675
Total other income (expense)	163,996	(5,200,132)	395,251	(3,370,749)
Net loss before income tax benefit	(3,386,888)	(10,635,935)	(5,484,194)	(14,801,111)
Income tax benefit		1,497,093		2,488,731
Net loss	(3,386,888)	(9,138,842)	(5,484,194)	(12,312,380)
Other comprehensive income (loss) – foreign currency translation adjustments		(1,078,648)		(463,177)
Comprehensive loss	(3,386,888)	(10,217,490)	(5,484,194)	(12,775,557)
Net loss	(3,386,888)	(9,138,842)	(5,484,194)	(12,312,380)
Preferred stock accretion and other deemed dividends		(700,093)	(452,925)	(2,591,414)
Net loss attributed to common stockholders	$ (3,386,888)	$ (9,838,935)	$ (5,937,119)	$ (14,903,794)
Weighted-average common shares outstanding, basic and diluted	13,127,773	956,057	11,318,819	817,077
Net loss per share attributed to common stockholders, basic and diluted	$ (0.26)	$ (10.29)	$ (0.52)	$ (18.24)

Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity - USD ($)	Total	Public Offering [Member]	Series B Redeemable Convertible Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member] Public Offering [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] Public Offering [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2017	$ 39,395,823			$ 61		$ 121,657,587		$ (77,684,839)	$ (4,576,986)
Beginning Balance (in shares) at Dec. 31, 2017				608,499
Beginning Balance (in shares) at Dec. 31, 2017			12,177
Beginning Balance at Dec. 31, 2017			$ 9,281,767
Stock based compensation and vesting of restricted stock	356,737					356,737
Stock based compensation and vesting of restricted stock (in shares)				71
Exercises of stock options	18,488			$ 1		18,487
Exercises of stock options (in shares)				7,703
Accretion of Series B redeemable convertible preferred stock	(1,891,321)					(1,891,321)
Accretion of Series B redeemable convertible preferred stock			$ 1,891,321
Conversion of Series B convertible preferred stock into common stock	5,218,572			$ 13		5,218,559
Conversion of Series B convertible preferred stock into common stock (in shares)			(5,219)
Conversion of Series B convertible preferred stock into common stock			$ (5,218,572)
Conversion of Series B convertible preferred stock into common stock (in shares)				130,447
Other comprehensive income (loss) – foreign currency translation adjustments	615,471								615,471
Net loss	(3,173,538)							(3,173,538)
Ending Balance at Mar. 31, 2018	40,540,232			$ 75		125,360,049		(80,858,377)	(3,961,515)
Ending Balance (in shares) at Mar. 31, 2018				746,720
Ending Balance (in shares) at Mar. 31, 2018			6,958
Ending Balance at Mar. 31, 2018			$ 5,954,516
Beginning Balance at Dec. 31, 2017	39,395,823			$ 61		121,657,587		(77,684,839)	(4,576,986)
Beginning Balance (in shares) at Dec. 31, 2017				608,499
Beginning Balance (in shares) at Dec. 31, 2017			12,177
Beginning Balance at Dec. 31, 2017			$ 9,281,767
Other comprehensive income (loss) – foreign currency translation adjustments	(463,177)
Net loss	(12,312,380)
Ending Balance at Jun. 30, 2018	35,809,989			$ 125		130,847,246		(89,997,219)	(5,040,163)
Ending Balance (in shares) at Jun. 30, 2018				1,250,508
Ending Balance (in shares) at Jun. 30, 2018			558
Ending Balance at Jun. 30, 2018			$ 510,083
Beginning Balance at Mar. 31, 2018	40,540,232			$ 75		125,360,049		(80,858,377)	(3,961,515)
Beginning Balance (in shares) at Mar. 31, 2018				746,720
Beginning Balance (in shares) at Mar. 31, 2018			6,958
Beginning Balance at Mar. 31, 2018			$ 5,954,516
Stock based compensation and vesting of restricted stock	252,156					252,156
Stock based compensation and vesting of restricted stock (in shares)				71
Exercises of stock options	4,410					4,410
Exercises of stock options (in shares)				1,837
Accretion of Series B redeemable convertible preferred stock	(956,150)					(956,150)
Accretion of Series B redeemable convertible preferred stock			$ 956,150
Conversion of Series B convertible preferred stock into common stock	4,036,539			$ 33		4,036,506
Conversion of Series B convertible preferred stock into common stock (in shares)			(4,036)
Conversion of Series B convertible preferred stock into common stock			$ (4,036,539)
Conversion of Series B convertible preferred stock into common stock (in shares)				334,180
Redemption of Series B redeemable convertible preferred stock for cash and release of embedded derivative	23,292					23,292
Redemption of Series B redeemable convertible preferred stock for cash and release of embedded derivative (in shares)			(2,364)
Redemption of Series B redeemable convertible preferred stock for cash and release of embedded derivative			$ (2,364,044)
Issuance of common stock for the exchange of warrants	2,127,000			$ 17		2,126,983
Issuance of common stock for the exchange of warrants (in shares)				167,700
Other comprehensive income (loss) – foreign currency translation adjustments	(1,078,648)								(1,078,648)
Net loss	(9,138,842)							(9,138,842)
Ending Balance at Jun. 30, 2018	35,809,989			$ 125		130,847,246		(89,997,219)	(5,040,163)
Ending Balance (in shares) at Jun. 30, 2018				1,250,508
Ending Balance (in shares) at Jun. 30, 2018			558
Ending Balance at Jun. 30, 2018			$ 510,083
Beginning Balance at Dec. 31, 2018	48,312,566			$ 876		170,207,844		(116,855,991)	(5,040,163)
Beginning Balance (in shares) at Dec. 31, 2018				9,078,239
Stock based compensation and vesting of restricted stock	407,742					407,742
Stock based compensation and vesting of restricted stock (in shares)				71
Issuance of common stock in registered direct offering, net of offering costs		$ 12,668,784			$ 436		$ 12,668,348
Issuance of common stock in registered direct offering, net of offering costs (in shares)					4,361,370
Issuance of common stock upon exercise of warrants	30,324			$ 1		30,323
Issuance of common stock upon exercise of warrants (in shares)				11,000
Net loss	(2,097,306)							(2,097,306)
Ending Balance at Mar. 31, 2019	59,322,110			$ 1,313		183,314,257		(118,953,297)	(5,040,163)
Ending Balance (in shares) at Mar. 31, 2019				13,450,680
Beginning Balance at Dec. 31, 2018	48,312,566			$ 876		170,207,844		(116,855,991)	(5,040,163)
Beginning Balance (in shares) at Dec. 31, 2018				9,078,239
Net loss	(5,484,194)
Ending Balance at Jun. 30, 2019	56,225,022			$ 1,313		183,604,057		(122,340,185)	(5,040,163)
Ending Balance (in shares) at Jun. 30, 2019				13,450,751
Beginning Balance at Mar. 31, 2019	59,322,110			$ 1,313		183,314,257		(118,953,297)	(5,040,163)
Beginning Balance (in shares) at Mar. 31, 2019				13,450,680
Stock based compensation and vesting of restricted stock	289,800					289,800
Stock based compensation and vesting of restricted stock (in shares)				71
Net loss	(3,386,888)							(3,386,888)
Ending Balance at Jun. 30, 2019	$ 56,225,022			$ 1,313		$ 183,604,057		$ (122,340,185)	$ (5,040,163)
Ending Balance (in shares) at Jun. 30, 2019				13,450,751

Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Jun. 30, 2019	Jun. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (5,484,194)	$ (12,312,380)
Adjustments to reconcile net loss to net cash used in operating activities:
Impairment charges		490,676
Stock-based compensation	697,486	608,893
Depreciation	121,899	77,528
Amortization	107,580	29,446
Unrealized gains on foreign currency exchange	(24,943)
Changes in fair value of warrant liability	46,000	3,680,709
Changes in fair value of embedded derivatives		2,130
Changes in operating assets and liabilities:
Accounts receivable	832,098	951,727
Prepaid expenses and other current assets	(113,200)	479,600
Accounts payable	(102,763)	115,452
Accrued expenses and other current liabilities	(1,094,831)	1,160,415
Deferred revenue	2,802	2,614
Lease obligation	(89,428)	765,239
Tax refund receivable	(71,586)	2,244,751
Deferred taxes		(1,507,358)
Net cash used in operating activities	(5,173,080)	(3,210,558)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(1,226)	(811,646)
Additions to intangible assets	(15,874)	(27,505)
Net cash used in investing activities	(17,100)	(839,151)
CASH FLOWS FROM FINANCING ACTIVITIES:
Redemption of preferred stock		(2,364,044)
Cash paid in conjunction with warrant exchange		(1,100,000)
Proceeds from issuance of common units, net of issuance costs	12,668,784
Proceeds from exercise of warrants	30,324
Payments of notes payable	(156,145)
Proceeds from exercise of stock options		22,898
Net cash provided by (used in) financing activities	12,542,963	(3,441,146)
EFFECT OF EXCHANGE RATES ON CASH		(50,365)
Net increase (decrease) in cash and cash equivalents and restricted cash	7,352,783	(7,541,220)
Cash, cash equivalents and restricted cash, beginning of period	34,353,129	12,303,639
Cash, cash equivalents and restricted cash, end of period	$ 41,705,912	4,762,419
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid for interest		1,791
SUPPLEMENTAL NON-CASH FINANCING ACTIVITIES:
Notes payable issued in conjunction with the exchange of warrants		1,500,000
Addition of property and equipment not yet paid		139,349
Addition of intangible assets not yet paid		5,763
Lease incentive billed but not yet received		139,349
Series B Redeemable Convertible Preferred Stock [Member]
SUPPLEMENTAL NON-CASH FINANCING ACTIVITIES:
Conversion of Series B redeemable convertible preferred stock into common stock		9,255,111
Accretion of Series B redeemable convertible preferred stock		$ 2,847,471

Nature of Business and Basis of Presentation

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Nature of Business and Basis of Presentation

1.Nature of Business and Basis of Presentation

Nature of Business

Altimmune, Inc., headquartered in Gaithersburg, Maryland, 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 discovering and developing immunotherapies and vaccines to address significant unmet medical needs. 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.

The accompanying unaudited consolidated financial statements are prepared pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Accordingly, they do not include all of the information and disclosures required by accounting principles generally accepted in the United States for complete consolidated financial statements and should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2018 included in the annual report on Form 10-K which was filed with the SEC on April 1, 2019. In the opinion of management, the Company has prepared the accompanying unaudited consolidated financial statements on the same basis as the audited consolidated financial statements, and these consolidated financial statements include all adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation of the results of the interim periods presented. The operating results for the interim periods presented are not necessarily indicative of the results expected for the full year 2019 or any future years or periods.

Basis of presentation

The unaudited consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities in the ordinary course of business. The financial statements do not include any adjustments relating to the recoverability and classification of recorded assets and liabilities that might be necessary should we be unable to continue as a going concern.

On September 13, 2018, the Company filed Certificates of Amendment to its Amended and Restated Certificate of Incorporation with the Secretary of State of Delaware to increase the number of authorized shares of the Company’s common stock, par value $0.0001 per share, from 100,000,000 to 200,000,000 shares and to effect a reverse stock split of the Company’s common stock at a ratio of 1-for-30 (the “Reverse Stock Split”). All references set forth in this quarterly report to number of shares or per share data have been presented retroactively on a post Reverse Stock Split basis.

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.Summary of Significant Accounting Policies

During the six months ended June 30, 2019, there have been no significant changes to the Company’s summary of significant accounting policies contained in the Company’s Annual report on Form 10-K for the year ended December 31, 2018 as filed with the SEC, except for the recently adopted accounting standard for leases.

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.

The lease obligations represent the Company’s obligation to make lease payments arising from the lease. The right of use lease assets represent the Company’s right to use an underlying asset for the lease term. The lease obligations and the operating right of use lease assets are recognized at the 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 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 that option. 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.

Recently Issued Accounting Pronouncements - Adopted

In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-02, Leases (“ASU 2016-02”). ASU 2016-02 requires a lessee to separate the lease components from the non-lease components in a contract and recognize in the statement of financial position a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018. The standard requires a modified retrospective approach or an optional transition to apply the new guidance in the year of transition rather than at the beginning of the earliest period presented. The Company adopted ASU 2016-02 in the first quarter of 2019 under the optional transition method. The Company’s current operating leases will be accounted for as operating lease liabilities and right of use assets upon adoption. The Company has elected the package of practical expedients permitted. Accordingly, the Company accounted for its existing operating leases as operating leases under the new guidance, without reassessing (a) whether the contracts contain a lease, (b) whether classification of the operating leases would be different in accordance, or (c) whether the unamortized initial direct costs before transition adjustments would have met the definition of initial direct costs at lease commencement. In addition, the Company does not allocate the consideration between lease and non-lease components. On January 1, 2019, the Company recorded a lease liability and a corresponding right of use asset. The adjustment resulted in an increase of $756,347 to total assets and total liabilities on the January 1, 2019 consolidated balance sheet. The adoption will not have a material impact on the consolidated statement of operations or consolidated statement of cash flows.

In June 2018, FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718)—Improvements to Nonemployee Share-Based Payment Accounting (“ASU 2018-07”). ASU 2018-07 expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The Company adopted ASU 2018-07 in the first quarter of 2019. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements.

Recently Issued Accounting Pronouncements - Pending Adoption

In August 2018, FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820) – Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement, was issued to modify and enhance the disclosure requirements for fair value measurements. This update is effective in fiscal years, including interim periods, beginning after December 15, 2019, and early adoption is permitted. The Company is still completing its assessment of the impacts and anticipated adoption date of this guidance.

Acquisitions

6 Months Ended

Jun. 30, 2019

Business Combinations [Abstract]

Acquisitions

3.Acquisitions

Subsequent to the quarter ended June 30, 2019, the Company entered into a definitive agreement to acquire all of the equity interests of Spitfire Pharma, Inc. (“Spitfire”) on July 8, 2019. Spitfire was a privately held, preclinical pharmaceutical company developing a novel dual GLP-1/glucagon receptor agonist for the treatment of non-alcoholic steatohepatitis.

The transaction closed on July 12, 2019. The Company issued 1,887,250 unregistered shares of its common stock (the “Shares”) as upfront consideration to certain former securityholders of Spitfire (collectively, the “Spitfire Equityholders”), representing an amount equal to $5,000,000 less working capital and transaction expense adjustment amounts as defined in the agreement (the “Closing Consideration”). The number of Shares issued as payment of the Closing Consideration was determined based on 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 and including July 8, 2019, the date on which the parties entered into the Agreement and Plan of Merger and Reorganization (the “Merger Agreement”).

The Merger Agreement includes $88,000,000 in future contingent payments for regulatory, clinical and sales milestones using the acquired intellectual property. The Company will record the contingent consideration when and if the milestones are achieved and the milestone payments become payable.

The Company determined that the acquisition of Spitfire should be accounted for as an asset acquisition instead of a business combination because substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets, and therefore, the asset is not considered a business. The Company plans to expense the acquired intellectual property as of the acquisition date as in-process research and development with no alternative future uses. The Company expects to record an in-process research and development expense for the up-front consideration during the third quarter of 2019. Transaction costs of $618,417 are recorded within research and development expense on the Consolidated Statements of Operations and Comprehensive Loss during the three and six months ended June 30, 2019

Net Loss Per Share

6 Months Ended

Jun. 30, 2019

Earnings Per Share [Abstract]

Net Loss Per Share

4.Net Loss Per Share

Because the Company has reported a net loss attributable to common stockholders for all periods presented, basic and diluted net loss per share attributable to common stockholders are the same for all periods presented. For periods presented, all preferred stock, 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 antidilutive impact.

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

	As of June 30,
	2019		2018
Redeemable preferred stock		-		6,966
Common stock warrants		10,386,256		25,211
Common stock options		873,066		53,846
Restricted stock		323,262		639

Goodwill and Intangible Assets

6 Months Ended

Jun. 30, 2019

Goodwill And Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

5.Goodwill and Intangible Assets

Goodwill

In May 2017, the Company closed on a business combination and recorded an initial purchase price allocation including goodwill. During the six months ended June 30, 2018 and prior to the end of the measurement period for accounting for the business combination, the Company recorded adjustments to the purchase price allocation resulting in a net decrease in tax refunds receivable, with a corresponding net increase in goodwill, of $490,676. As goodwill related to this transaction had previously been determined to be fully impaired, the Company recognized an impairment charge of $490,676 as a result of these purchase price allocation adjustments during the six months ended June 30, 2018. The purchase price allocation was considered final in May 2018, and no further adjustments were recorded.

Intangibles assets

The Company’s intangible assets consisted of the following:

	June 30, 2019
	Estimated Useful Lives	Gross Carrying Value		Accumulated Amortization			Net Book Value
Internally developed patents	6-10 years	$	734,432	$	(416,857	)	$	317,575
Acquired licenses	16-20 years		285,000		(261,326	)		23,674
Total intangible assets subject to amortization			1,019,432		(678,183	)		341,249
IPR&D assets	Indefinite		13,418,967		—			13,418,967
Total		$	14,438,399	$	(678,183	)	$	13,760,216

	December 31, 2018
	Estimated Useful Lives	Gross Carrying Value		Accumulated Amortization			Impairment			Net Book Value
Internally developed patents	6-10 years	$	718,559	$	(317,172	)	$	—		$	401,387
Acquired licenses	16-20 years		285,000		(253,430	)		—			31,570
Total intangible assets subject to amortization		$	1,003,559	$	(570,602	)	$	—		$	432,957
IPR&D assets	Indefinite		37,868,978		—			(24,450,011	)		13,418,967
Total		$	38,872,537	$	(570,602	)	$	(24,450,011	)	$	13,851,924

Amortization expense of intangible assets subject to amortization was $14,836 and $14,972 for the three months ended June 30, 2019 and 2018, and $107,580 and $29,446 for the six months ended June 30, 2019 and 2018, respectively. Amortization expense was classified as research and development expenses in the accompanying unaudited consolidated statements of operations and comprehensive loss.

As of June 30, 2019, future estimated amortization expense was as follows:

Years ending December 31,
The remainder of 2019	$	29,690
2020		45,933
2021		25,375
2022		25,375
2023		25,375
2024 and thereafter		189,501
Total	$	341,249

Accrued Expenses

6 Months Ended

Jun. 30, 2019

Payables And Accruals [Abstract]

Accrued Expenses

6.Accrued Expenses

Accrued expenses and other current liabilities consist of the following:

	June 30, 2019		December 31, 2018
Accrued professional services	$	417,618	$	552,619
Accrued payroll and employee benefits		808,585		1,257,191
Accrued interest		2,685		1,192
Accrued research and development		1,539,045		2,076,704
Lease obligation, current portion		246,193		—
Deferred rent, current portion		—		175,490
Deferred revenue		32,441		19,753
Total accrued expenses	$	3,046,567	$	4,082,949

Notes Payable and Other Long-Term Liabilities

6 Months Ended

Jun. 30, 2019

Notes Payable And Other Liabilities Disclosure [Abstract]

Notes Payable and Other Liabilities

7.Notes Payable and Other Long-Term Liabilities

The Company’s current portion of outstanding notes payable are summarized as follows:

June 30,

2019

December 31,

2018

BPI France notes, short-term portion

163,724

71,596

Total notes payable

163,724

71,596

The Company’s long-term portion of outstanding notes payable as well as other long-term liabilities are summarized as follows:

	June 30, 2019		December 31, 2018
BPI France notes, long-term portion	$	252,902	$	501,174
Lease obligation, long-term portion (see Note 11)		1,618,055		—
Deferred rent, long-term portion		—		1,045,807
Common stock warrant liability (see Note 9)		111,000		65,000
Other		230,147		240,090
Total other long-term liabilities	$	2,212,104	$	1,852,071

Line of Credit

On July 27, 2018, the Company renewed its existing line of credit agreement for a six-month term with an increase to the borrowing capacity from $250,000 to $1,750,000, subject to a minimum liquidity requirement equal to the outstanding balance of the line. The line of credit was not renewed and expired in January 2019. There was no balance on this credit facility as of December 31, 2018 or for the period within 2019 prior to its expiration.

BPI France Notes

Altimmune France has two non-interest-bearing research and development funding arrangements with BPI France that were entered into in December 2013 to provide Altimmune France up to €750,000 in research funding in the first arrangement and up to €250,000 in the second arrangement. Altimmune France was permitted to draw 50% of the funds upon the signing of the arrangements, an additional 30% contingent upon a financial audit and technical progress report, and the remaining amounts at the completion of the research and development project being funded by the arrangements. In October 2016, the Company and BPI France agreed to extend the term on the arrangement by two years. Each of the two obligations is repayable in sixteen quarterly installments from June 2019 through March 2023. The total amount advanced under the arrangements was €500,000 as of June 30, 2019 ($568,321 as of June 30, 2019). In April 2019, the Company was notified that €102,951 ($117,018 as of June 30, 2019) exceeded the allowable funding in accordance with the arrangement and made payment of this amount on June 5, 2019. The remaining balance is repayable in sixteen quarterly installments from June 2019 through March 2023, and the Company paid €31,250 ($35,520) during the six months ended June 30, 2019. As of June 30, 2019, $163,724 on this note is classified as short term, and $252,902 as long term. The BPI France notes are recorded at their repayment value which approximates fair value.

Common Stock

6 Months Ended

Jun. 30, 2019

Text Block [Abstract]

Common Stock

8.Common Stock

On March 12, 2019, the Company issued a combined total of 1,500,000 common units and 2,861,370 pre-funded units to two 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. Each pre-funded unit in the Registered Direct Offering was sold at a public offering price of $3.20 and consisted of a pre-funded warrant to purchase one share of common stock at an exercise price of $0.01 per share and 0.70 of a warrant to purchase one share of common stock at an exercise price of $3.21. The pre-funded warrants were immediately exercisable and were able to be exercised at any time until all of the pre-funded warrants were exercised in full. All of the pre-funded warrants were exercised prior to March 31, 2019. The net proceeds of the Registered Direct Offering were approximately $12,668,784, after deducting the underwriting discount and offering expenses payable by the Company.

The warrants issued in the Registered Direct Offering were concluded to be equity classified freestanding financial instruments. The Registered Direct Offering triggered a down round adjustment to the exercise price of warrants previously issued in an October 2018 public offering from $4.1798 to $2.7568. The Company treated the value of the effect of the reduction in exercise price as a deemed dividend of $452,925 during the six months ended June 30, 2019, which reduced income available to common shareholders.

Warrants

6 Months Ended

Jun. 30, 2019

Federal Home Loan Banks [Abstract]

Warrants

9.Warrants

A summary of warrant activity during the six months ended June 30, 2019 is as follows:



Warrants outstanding, beginning of period	7,344,297
Issuances	3,052,959
Exercises and conversions	(11,000	)
Warrants outstanding, end of period	10,386,256

For warrants classified as a liability, the following is a summary of the periodic changes in their fair value during the six months ended June 30, 2019:

Balance, January 1, 2019	$	65,000
Changes in fair value (Monte Carlo simulation valuation)		46,000
Balance, June 30, 2019	$	111,000

The fair value of common warrants classified as a liability was estimated using the Monte Carlo simulation valuation model with Level 3 inputs. The following assumptions were used to estimate the fair value of warrants that were classified as a liability at June 30, 2019.


Expected volatility	96.3	%
Expected term (years)	3.10
Risk-free interest rate	1.7	%
Expected dividend yield	0.0	%

Stock-Based Compensation

6 Months Ended

Jun. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

10.Stock-Based Compensation

Stock Options

The Company’s stock option awards generally vest over four years and typically have a contractual life of ten years. At June 30, 2019, there was $1,579,524 of unrecognized compensation cost related to stock options, which is expected to be recognized over a weighted-average period of 3.39 years. During the six months ended June 30, 2019, the Company granted 618,000 stock options with a weighted average price of $2.76 and per share weighted average grant date fair value of $2.09.

Information related to stock options outstanding at June 30, 2019 is as follows:

	Number of Stock Options		Weighted- average Exercise Price		Weighted- average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding		873,066	$	5.67		5.89	$	2,000
Exercisable		112,944	$	18.97		5.18	$	-
Unvested		760,122	$	3.69		5.99	$	2,000

Restricted Stock

At June 30, 2019, the Company had unvested restricted stock of 323,262 shares with total unrecognized compensation expense of $990,288, which the Company expects to recognize over a weighted average period of approximately 3.42 years. During the six months ended June 30, 2019, the Company released 71 shares of common stock from restriction as a result of the vesting of restricted stock.

Stock-based compensation expense

Stock-based compensation expense is classified in the unaudited consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2019 and 2018 as follows:

	For the Three Months Ended June 30,				For the Six Months Ended June 30,
	2019		2018		2019		2018
Research and development	$	92,060	$	108,276	$	168,684	$	197,312
General and administrative		197,712		143,850		528,802		411,581
Total	$	289,772	$	252,126	$	697,486	$	608,893

2019 Employee Stock Purchase Plan

On March 29, 2019, the board of directors 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 commencing 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.

Operating Leases

6 Months Ended

Jun. 30, 2019

Leases [Abstract]

Operating Leases

11.Operating Leases

The Company rents office and laboratory space in the United States. The Company also leases office equipment under a non-cancellable equipment lease through December 2022. Rent expense during the three and six months ended June 30, 2019 under all of the Company’s operating leases was $83,903 and $174,079, respectively, which includes short-term leases and variable lease costs 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 Company has determined the lease renewal option is not reasonably certain.

The operating cash outflows related to operating leases for the six months ended June 30, 2019 was $89,428.

Supplemental other information related to the operating leases balance sheet information is as follows:

	June 30, 2019
Operating lease obligations	$	1,864,248
Operating lease right-of-use assets	$	732,380
Weighted-average remaining lease term		5.83
Weighted-average discount rate		8.0	%

Maturities of lease liabilities is as follows:

Year ending December 31,
The remainder of 2019	$	191,428
2020		387,079
2021		393,542
2022		400,198
2023		407,054
2024 and thereafter		552,948
Total lease payments		2,332,249
Less imputed interest		(468,001	)
Total	$	1,864,248

Commitments and Contingencies

6 Months Ended

Jun. 30, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

12.Commitments and Contingencies

The Company is a party in various other contractual disputes, litigation, and potential claims arising in the ordinary course of business. The Company does not believe that the resolution of these matters will have a material adverse effect on its financial position or results of operations.

Subsequent events

6 Months Ended

Jun. 30, 2019

Subsequent Events [Abstract]

Subsequent Events

13.Subsequent Events

Refer to Note 3 for a description of the Merger Agreement entered into on July 8, 2019.

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2019
Accounting Policies [Abstract]
Leases	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. The lease obligations represent the Company’s obligation to make lease payments arising from the lease. The right of use lease assets represent the Company’s right to use an underlying asset for the lease term. The lease obligations and the operating right of use lease assets are recognized at the 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 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 that option. 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.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements - Adopted In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-02, Leases (“ASU 2016-02”). ASU 2016-02 requires a lessee to separate the lease components from the non-lease components in a contract and recognize in the statement of financial position a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018. The standard requires a modified retrospective approach or an optional transition to apply the new guidance in the year of transition rather than at the beginning of the earliest period presented. The Company adopted ASU 2016-02 in the first quarter of 2019 under the optional transition method. The Company’s current operating leases will be accounted for as operating lease liabilities and right of use assets upon adoption. The Company has elected the package of practical expedients permitted. Accordingly, the Company accounted for its existing operating leases as operating leases under the new guidance, without reassessing (a) whether the contracts contain a lease, (b) whether classification of the operating leases would be different in accordance, or (c) whether the unamortized initial direct costs before transition adjustments would have met the definition of initial direct costs at lease commencement. In addition, the Company does not allocate the consideration between lease and non-lease components. On January 1, 2019, the Company recorded a lease liability and a corresponding right of use asset. The adjustment resulted in an increase of $756,347 to total assets and total liabilities on the January 1, 2019 consolidated balance sheet. The adoption will not have a material impact on the consolidated statement of operations or consolidated statement of cash flows. In June 2018, FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718)—Improvements to Nonemployee Share-Based Payment Accounting (“ASU 2018-07”). ASU 2018-07 expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The Company adopted ASU 2018-07 in the first quarter of 2019. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements. Recently Issued Accounting Pronouncements - Pending Adoption In August 2018, FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820) – Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement, was issued to modify and enhance the disclosure requirements for fair value measurements. This update is effective in fiscal years, including interim periods, beginning after December 15, 2019, and early adoption is permitted. The Company is still completing its assessment of the impacts and anticipated adoption date of this guidance.

Net Loss Per Share (Tables)

6 Months Ended

Jun. 30, 2019

Earnings Per Share [Abstract]

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

	As of June 30,
	2019		2018
Redeemable preferred stock		-		6,966
Common stock warrants		10,386,256		25,211
Common stock options		873,066		53,846
Restricted stock		323,262		639

Goodwill and Intangible Assets (Tables)

6 Months Ended

Jun. 30, 2019

Goodwill And Intangible Assets Disclosure [Abstract]

Schedule of Intangible Assets

The Company’s intangible assets consisted of the following:

	June 30, 2019
	Estimated Useful Lives	Gross Carrying Value		Accumulated Amortization			Net Book Value
Internally developed patents	6-10 years	$	734,432	$	(416,857	)	$	317,575
Acquired licenses	16-20 years		285,000		(261,326	)		23,674
Total intangible assets subject to amortization			1,019,432		(678,183	)		341,249
IPR&D assets	Indefinite		13,418,967		—			13,418,967
Total		$	14,438,399	$	(678,183	)	$	13,760,216

	December 31, 2018
	Estimated Useful Lives	Gross Carrying Value		Accumulated Amortization			Impairment			Net Book Value
Internally developed patents	6-10 years	$	718,559	$	(317,172	)	$	—		$	401,387
Acquired licenses	16-20 years		285,000		(253,430	)		—			31,570
Total intangible assets subject to amortization		$	1,003,559	$	(570,602	)	$	—		$	432,957
IPR&D assets	Indefinite		37,868,978		—			(24,450,011	)		13,418,967
Total		$	38,872,537	$	(570,602	)	$	(24,450,011	)	$	13,851,924

Schedule of Future Estimated Amortization Expense

As of June 30, 2019, future estimated amortization expense was as follows:

Years ending December 31,
The remainder of 2019	$	29,690
2020		45,933
2021		25,375
2022		25,375
2023		25,375
2024 and thereafter		189,501
Total	$	341,249

Accrued Expenses (Tables)

6 Months Ended

Jun. 30, 2019

Payables And Accruals [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following:

	June 30, 2019		December 31, 2018
Accrued professional services	$	417,618	$	552,619
Accrued payroll and employee benefits		808,585		1,257,191
Accrued interest		2,685		1,192
Accrued research and development		1,539,045		2,076,704
Lease obligation, current portion		246,193		—
Deferred rent, current portion		—		175,490
Deferred revenue		32,441		19,753
Total accrued expenses	$	3,046,567	$	4,082,949

Notes Payable and Other Long-Term Liabilities (Tables)

6 Months Ended

Jun. 30, 2019

Notes Payable And Other Liabilities Disclosure [Abstract]

Summary of Current Portion of Outstanding Notes Payable

The Company’s current portion of outstanding notes payable are summarized as follows:

June 30,

2019

December 31,

2018

BPI France notes, short-term portion

163,724

71,596

Total notes payable

163,724

71,596

Summary of Long-term Portion of Outstanding Notes Payable as well as Other Long-Term Liabilities

The Company’s long-term portion of outstanding notes payable as well as other long-term liabilities are summarized as follows:

	June 30, 2019		December 31, 2018
BPI France notes, long-term portion	$	252,902	$	501,174
Lease obligation, long-term portion (see Note 11)		1,618,055		—
Deferred rent, long-term portion		—		1,045,807
Common stock warrant liability (see Note 9)		111,000		65,000
Other		230,147		240,090
Total other long-term liabilities	$	2,212,104	$	1,852,071

Warrants (Tables)

6 Months Ended

Jun. 30, 2019

Summary of Warrant Activity

A summary of warrant activity during the six months ended June 30, 2019 is as follows:



Warrants outstanding, beginning of period	7,344,297
Issuances	3,052,959
Exercises and conversions	(11,000	)
Warrants outstanding, end of period	10,386,256

Summary of Periodic Changes in Fair Value of Warrant Liability

For warrants classified as a liability, the following is a summary of the periodic changes in their fair value during the six months ended June 30, 2019:

Balance, January 1, 2019	$	65,000
Changes in fair value (Monte Carlo simulation valuation)		46,000
Balance, June 30, 2019	$	111,000

Monte Carlo Simulation Model [Member]

Assumptions Used to Estimate Fair Value of Embedded Redemption Derivative Financial Instrument


Expected volatility	96.3	%
Expected term (years)	3.10
Risk-free interest rate	1.7	%
Expected dividend yield	0.0	%

- Definition

Tabular disclosure of warrants or rights issued. Warrants and rights outstanding are derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months. Disclose the title of issue of securities called for by warrants and rights outstanding, the aggregate amount of securities called for by warrants and rights outstanding, the date from which the warrants or rights are exercisable, and the price at which the warrant or right is exercisable.

+ References + Details

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Information Related to Stock Options Outstanding

Information related to stock options outstanding at June 30, 2019 is as follows:

	Number of Stock Options		Weighted- average Exercise Price		Weighted- average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding		873,066	$	5.67		5.89	$	2,000
Exercisable		112,944	$	18.97		5.18	$	-
Unvested		760,122	$	3.69		5.99	$	2,000

Schedule of Stock-based Compensation Expense

Stock-based compensation expense is classified in the unaudited consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2019 and 2018 as follows:

	For the Three Months Ended June 30,				For the Six Months Ended June 30,
	2019		2018		2019		2018
Research and development	$	92,060	$	108,276	$	168,684	$	197,312
General and administrative		197,712		143,850		528,802		411,581
Total	$	289,772	$	252,126	$	697,486	$	608,893

Operating Leases (Tables)

6 Months Ended

Jun. 30, 2019

Leases [Abstract]

Summary of Supplemental other Information Related to Operating Leases Balance Sheet

Supplemental other information related to the operating leases balance sheet information is as follows:

	June 30, 2019
Operating lease obligations	$	1,864,248
Operating lease right-of-use assets	$	732,380
Weighted-average remaining lease term		5.83
Weighted-average discount rate		8.0	%

Summary of Maturities of Lease Liabilities

Maturities of lease liabilities is as follows:

Year ending December 31,
The remainder of 2019	$	191,428
2020		387,079
2021		393,542
2022		400,198
2023		407,054
2024 and thereafter		552,948
Total lease payments		2,332,249
Less imputed interest		(468,001	)
Total	$	1,864,248

Nature of Business and Basis of Presentation - Additional Information (Detail)	Sep. 13, 2018 $ / shares shares	Jun. 30, 2019 $ / shares shares	Dec. 31, 2018 $ / shares shares	Sep. 12, 2018 shares
Accounting Policies [Abstract]
Common stock, par or stated value per share \| $ / shares	$ 0.0001	$ 0.0001	$ 0.0001
Common stock, shares authorized \| shares	200,000,000	200,000,000	200,000,000	100,000,000
Reverse split	1-for-30
Reverse split conversion ratio	0.03

Summary of Significant Accounting Policies - Additional Information (Detail) - ASU 2016-02 [Member]	Jan. 01, 2019 USD ($)
Significant Accounting Policies [Line Items]
Increase in total assets on the consolidated balance sheet due to adoption of ASU 2016-02	$ 756,347
Increase in total liabilities on the consolidated balance sheet due to adoption of ASU 2016-02	$ 756,347

Acquisitions - Additional Information (Detail) - Spitfire Pharma, Inc. [Member] - USD ($)		3 Months Ended	6 Months Ended
	Jul. 12, 2019	Jun. 30, 2019	Jun. 30, 2019
Business Acquisition [Line Items]
Transaction cost recorded within research and development expense		$ 618,417	$ 618,417
Subsequent Event [Member]
Business Acquisition [Line Items]
Agreement date	Jul. 08, 2019
Unregistered shares of common stock	1,887,250
Up-front consideration	$ 5,000,000
Number of consecutive trading days	20 days
Future contingent payments	$ 88,000,000

Net Loss Per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Series B Redeemable Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share		6,966
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	10,386,256	25,211
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	873,066	53,846
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	323,262	639

Goodwill and Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Schedule Of Intangible Assets [Line Items]
Increase in goodwill from recorded adjustments				$ 490,676
Impairment charges				490,676
Research and Development [Member]
Schedule Of Intangible Assets [Line Items]
Amortization expense of intangible assets	$ 14,836	$ 14,972	$ 107,580	$ 29,446

Goodwill and Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Schedule Of Intangible Assets [Line Items]
Intangible assets subject to amortization, Gross Carrying Value	$ 1,019,432	$ 1,003,559
Intangible assets subject to amortization, Accumulated Amortization	(678,183)	(570,602)
Intangible assets subject to amortization, Net Book Value	341,249	432,957
Total intangible assets, Gross Carrying Value	14,438,399	38,872,537
Intangible Assets, Impairment		24,450,011
Total intangible assets, Net Book Value	13,760,216	13,851,924
Intangible Assets, Impairment		(24,450,011)
IPR&D [Member]
Schedule Of Intangible Assets [Line Items]
Total intangible assets, Gross Carrying Value	13,418,967	37,868,978
Total intrangible assets, Impairment		(24,450,011)
Total intangible assets, Net Book Value	13,418,967	13,418,967
Internally Developed Patents [Member]
Schedule Of Intangible Assets [Line Items]
Intangible assets subject to amortization, Gross Carrying Value	734,432	718,559
Intangible assets subject to amortization, Accumulated Amortization	(416,857)	(317,172)
Intangible assets subject to amortization, Net Book Value	$ 317,575	$ 401,387
Internally Developed Patents [Member] \| Minimum [Member]
Schedule Of Intangible Assets [Line Items]
Estimated Useful Lives	6 years	6 years
Internally Developed Patents [Member] \| Maximum [Member]
Schedule Of Intangible Assets [Line Items]
Estimated Useful Lives	10 years	10 years
Acquired Licenses [Member]
Schedule Of Intangible Assets [Line Items]
Intangible assets subject to amortization, Gross Carrying Value	$ 285,000	$ 285,000
Intangible assets subject to amortization, Accumulated Amortization	(261,326)	(253,430)
Intangible assets subject to amortization, Net Book Value	$ 23,674	$ 31,570
Acquired Licenses [Member] \| Minimum [Member]
Schedule Of Intangible Assets [Line Items]
Estimated Useful Lives	16 years	16 years
Acquired Licenses [Member] \| Maximum [Member]
Schedule Of Intangible Assets [Line Items]
Estimated Useful Lives	20 years	20 years

Goodwill and Intangible Assets - Schedule of Future Estimated Amortization Expense (Detail) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
The remainder of 2019	$ 29,690
2020	45,933
2021	25,375
2022	25,375
2023	25,375
2024 and thereafter	189,501
Intangible assets subject to amortization, Net Book Value	$ 341,249	$ 432,957

Accrued Expenses - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Accrued Liabilities And Other Liabilities [Abstract]
Accrued professional services	$ 417,618	$ 552,619
Accrued payroll and employee benefits	808,585	1,257,191
Accrued interest	2,685	1,192
Accrued research and development	1,539,045	2,076,704
Lease obligation, current portion	246,193
Deferred rent, current portion		175,490
Deferred revenue	32,441	19,753
Total accrued expenses	$ 3,046,567	$ 4,082,949

Notes Payable and Other Long-Term Liabilities - Summary of Current Portion of Outstanding Notes Payable (Detail) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total notes payable	$ 163,724	$ 71,596
BPI France Notes [Member]
Debt Instrument [Line Items]
Total notes payable	$ 163,724	$ 71,596

Notes Payable and Other Long-Term Liabilities - Summary of Long-term Portion of Outstanding Notes Payable as well as Other Long-Term Liabilities (Detail) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Lease obligation, long-term portion (see Note 11)	$ 1,618,055
Deferred rent, long-term portion		$ 1,045,807
Common stock warrant liability (see Note 9)	111,000	65,000
Other	230,147	240,090
Total other long-term liabilities	2,212,104	1,852,071
BPI France Notes [Member]
Debt Instrument [Line Items]
BPI France notes, long-term portion	$ 252,902	$ 501,174

Notes Payable and Other Long-Term Liabilities - Additional Information (Detail)		6 Months Ended
	Jul. 11, 2018	Jun. 30, 2019 USD ($) FundingArrangement	Jun. 30, 2019 EUR (€) FundingArrangement	Jun. 30, 2019 EUR (€)	Jan. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jul. 27, 2018 USD ($)	Jul. 26, 2018 USD ($)
Debt Instrument [Line Items]
Line of credit facility, renewed credit agreement expiration period	6 months
Line of credit facility, maximum borrowing capacity							$ 1,750,000	$ 250,000
Line of credit facility, remaining balance					$ 0	$ 0
Line of Credit Facility Expiration		2019-01	2019-01
Total long-term debt		$ 568,321		€ 500,000
Repayments of notes payable		156,145
Note classified as short term		$ 163,724				71,596
BPI France Notes [Member]
Debt Instrument [Line Items]
Number of non-interest bearing research and development funding arrangements \| FundingArrangement		2	2
Percentage of fund to be withdrawn upon signing of arrangements		50.00%	50.00%
Additional percentage of fund to be withdrawn, contingent upon financial audit and technical progress report		30.00%	30.00%
Research and development funding arrangements extended period		2 years	2 years
Method of repayment		sixteen quarterly installments from June 2019 through March 2023	sixteen quarterly installments from June 2019 through March 2023
Long-term debt, unrecognized as grant funds and stands payable		$ 117,018		102,951
Repayments of notes payable		35,520	€ 31,250
Note classified as short term		163,724				71,596
Note classified as long term		$ 252,902				$ 501,174
BPI France Notes [Member] \| Research Funding First Arrangement [Member]
Debt Instrument [Line Items]
Debt instrument, face amount \| €				750,000
Method of repayment		sixteen quarterly installments from June 2019 through March 2023	sixteen quarterly installments from June 2019 through March 2023
BPI France Notes [Member] \| Research Funding Second Arrangement [Member]
Debt Instrument [Line Items]
Debt instrument, face amount \| €				€ 250,000
Method of repayment		sixteen quarterly installments from June 2019 through March 2023	sixteen quarterly installments from June 2019 through March 2023

Common Stock - Additional Information (Detail) - Registered Direct Offering [Member]	Mar. 12, 2019 USD ($) Investor $ / shares shares	Jun. 30, 2019 USD ($)
Changes In Equity And Comprehensive Income Line Items [Line Items]
Sale of transaction date	Mar. 12, 2019
Number of institutional investors involved in offering \| Investor	2
Common units outstanding \| shares	1,500,000
Warrant expiration period	5 years
Net proceeds from offering \| $	$ 12,668,784
Deemed dividend \| $		$ 452,925
Maximum [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Per share exercise price	$ 4.1798
Minimum [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Per share exercise price	2.7568
Common Units
Changes In Equity And Comprehensive Income Line Items [Line Items]
Public offering price per share	$ 3.21
Shares of common stock called by warrants \| shares	0.70
Per share exercise price	$ 3.21
Pre-funded Units [Member]
Changes In Equity And Comprehensive Income Line Items [Line Items]
Common units outstanding \| shares	2,861,370
Public offering price per share	$ 3.20
Shares of common stock called by warrants \| shares	0.70
Per share exercise price	$ 3.21
Per share exercise price	$ 0.01

Warrants - Summary of Warrant Activity (Detail)	6 Months Ended
Warrants - Summary of Warrant Activity (Detail)	Jun. 30, 2019 shares
Warrants And Rights Note Disclosure [Abstract]
Warrants outstanding, beginning of period	7,344,297
Issuances	3,052,959
Exercises and conversions	(11,000)
Warrants outstanding, end of period	10,386,256

Warrants - Summary of Periodic Changes in Fair Value of Warrant Liability (Detail) - Level 3 [Member] - Common Stock Warrants [Member]	6 Months Ended
	Jun. 30, 2019 USD ($)
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Balance, January 1, 2019	$ 65,000
Changes in fair value	46,000
Balance, June 30, 2019	$ 111,000

Warrants - Summary of Assumptions Used to Estimate Fair Value of Warrants (Detail) - Common Stock Warrants [Member]	Jun. 30, 2019
Expected Volatility [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of warrants, measurement input	96.3
Expected Term (Years) [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of warrants, measurement input, expected term (years)	3 years 1 month 6 days
Risk-free Interest Rate [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of warrants, measurement input	1.7
Expected Dividend Yield [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair value of warrants, measurement input	0.0

Stock-Based Compensation - Additional Information (Detail) - USD ($)		6 Months Ended
	Mar. 29, 2019	Jun. 30, 2019
2019 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance	403,500
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 Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting Period		4 years
Stock option expiration Period		10 years
Unrecognized compensation cost, stock options		$ 1,579,524
Unrecognized stock-based compensation expense, period for recognition		3 years 4 months 20 days
Number of Stock Options, Granted		618,000
Stock options granted, weighted-average exercise price		$ 2.76
Weighted-average grant date fair value of stock options granted		$ 2.09
Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense, period for recognition		3 years 5 months 1 day
Unvested restricted stock, shares		323,262
Unrecognized compensation expense		$ 990,288
Common stock issued as result of vesting of restricted stock		71

Stock-Based Compensation - Schedule of Information Related to Stock Options Outstanding (Detail)	6 Months Ended
	Jun. 30, 2019 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Stock Options, Outstanding \| shares	873,066
Number of Stock Options, Exercised \| shares	112,944
Number of Stock Options, Unvested \| shares	760,122
Weighted-average Exercise Price, Outstanding \| $ / shares	$ 5.67
Weighted-average Exercise Price, Exercised \| $ / shares	18.97
Weighted-average Exercise Price, Unvested \| $ / shares	$ 3.69
Weighted-average Remaining Contractual Term, Outstanding	5 years 10 months 20 days
Weighted-average Remaining Contractual Term, Exercisable	5 years 2 months 4 days
Weighted-average Remaining Contractual Term, Unvested	5 years 11 months 26 days
Weighted-average Intrinsic Value, Outstanding \| $	$ 2,000
Weighted-average Intrinsic Value, Unvested \| $	$ 2,000

Stock-Based Compensation - Schedule of Stock-based Compensation Expense (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	$ 289,772	$ 252,126	$ 697,486	$ 608,893
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	92,060	108,276	168,684	197,312
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	$ 197,712	$ 143,850	$ 528,802	$ 411,581

Operating Leases - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Leases [Abstract]
Non-cancellable lease maturity period		2022-12
Operating lease rent expense	$ 83,903	$ 174,079
Operating cash outflows related to operating leases		$ 89,428

Operating Leases - Summary of Supplemental other Information Related to Operating Leases Balance Sheet (Detail)	Jun. 30, 2019 USD ($)
Leases [Abstract]
Operating lease obligations	$ 1,864,248
Operating lease right-of-use assets	$ 732,380
Weighted-average remaining lease term	5 years 9 months 29 days
Weighted-average discount rate	8.00%

Operating Leases - Summary of Maturities of Lease Liabilities (Detail)	Jun. 30, 2019 USD ($)
Leases [Abstract]
The remainder of 2019	$ 191,428
2020	387,079
2021	393,542
2022	400,198
2023	407,054
2024 and thereafter	552,948
Total lease payments	2,332,249
Less imputed interest	(468,001)
Total	$ 1,864,248

Subsequent Events - Additional Information (Detail)	Jul. 12, 2019
Spitfire Pharma, Inc. [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Agreement date	Jul. 08, 2019