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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2017	Nov. 09, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Trading Symbol	ALT
Entity Registrant Name	ALTIMMUNE, INC.
Entity Central Index Key	0001326190
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Accelerated Filer
Entity Common Stock, Shares Outstanding		15,652,640

Condensed Consolidated Balance Sheets - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 17,116,845	$ 2,876,113
Restricted cash	34,174
Accounts receivable	2,902,503	383,046
Prepaid expenses and other current assets	1,007,032	420,424
Tax refund receivable	5,061,920	807,507
Total current assets	26,122,474	4,487,090
Property and equipment, net	280,093	177,859
Intangible assets, net	38,586,399	14,954,717
Other assets	22,248	22,248
Goodwill	9,334,904	18,758,421
Total assets	74,346,118	38,400,335
Current liabilities:
Notes payable	49,702	458,629
Accounts payable	495,064	2,005,208
Accrued expenses and other current liabilities	3,597,313	2,972,745
Current portion of deferred revenue	19,753	19,753
Current portion of deferred rent	18,626	14,388
Total current liabilities	4,180,458	5,470,723
Unvested restricted stock liability	343	1,001
Long-term debt	590,185	525,950
Deferred revenue, long-term portion	164,609	179,424
Deferred rent, long-term portion	1,591	15,914
Deferred tax liability	8,312,426
Other long-term liabilities	4,027,962
Total liabilities	17,277,574	6,193,012
Contingencies (Note 12)
Stockholders' equity:
Common stock, $0.0001 par value; 100,000,000 shares authorized; 15,652,640 and 6,991,749 shares issued; 15,627,081 and 6,917,204 shares outstanding at September 30, 2017 and December 31, 2016, respectively	1,563	692
Additional paid-in capital	122,392,504	71,034,899
Accumulated deficit	(68,853,850)	(31,259,449)
Accumulated other comprehensive loss - foreign currency translation adjustments	(4,709,973)	(7,574,812)
Total stockholders' equity	48,830,244	32,207,323
Total liabilities, redeemable convertible preferred stock, and stockholders' equity	74,346,118	38,400,335
Series B Redeemable Convertible Preferred Stock [Member]
Current liabilities:
Series B redeemable convertible preferred stock; $0.0001 par value; 16,000 shares designated; 15,656 and zero shares issued and outstanding at September 30, 2017 and December 31, 2016, respectively; aggregate liquidation and redemption value of $8,238,300 at September 30, 2017	$ 8,238,300
Series B Preferred Stock [Member]
Stockholders' equity:
Series B convertible preferred stock; $0.01 par value; zero and 599,285 shares authorized, issued and outstanding at September 30, 2017 and December 31, 2016, respectively		5,993
Total stockholders' equity		$ 5,993

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Common stock, par or stated value per share	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	15,652,640	6,991,749
Common stock, shares outstanding	15,627,081	6,917,204
Series B Redeemable Convertible Preferred Stock [Member]
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares designated	16,000	16,000
Convertible preferred stock, shares issued	15,656	0
Convertible preferred stock, shares outstanding	15,656	0
Convertible preferred stock, aggregate liquidation	$ 8,238,300
Convertible preferred stock, redemption value	$ 8,238,300
Series B Preferred Stock [Member]
Preferred stock, par or stated value per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	0	599,285
Preferred stock, shares issued	0	599,285
Preferred stock, shares outstanding	0	599,285

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
License revenue	$ 26,689	$ 4,938	$ 36,565	$ 168,341
Research grants and contracts	4,565,251	896,101	7,892,919	1,983,574
Total revenue and grants and contracts	4,591,940	901,039	7,929,484	2,151,915
Operating expenses
Research and development	5,905,552	2,400,914	13,946,403	4,845,045
General and administrative	3,038,756	3,289,647	6,863,782	5,301,444
Goodwill impairment charges	26,600,000		26,600,000
Total operating expenses	35,544,308	5,690,561	47,410,185	10,146,489
Loss from operations	(30,952,368)	(4,789,522)	(39,480,701)	(7,994,574)
Other income (expense):
Change in fair value of warrant liabilities	(508,316)		(508,316)
Change in fair value of embedded derivative	(1,157)		(1,157)
Interest expense	(2,344)	(9,408)	(160,103)	(28,858)
Interest income	15,372		19,538	1,047
Other income (expense)	10,786	3,871	9,839	(2,600)
Total other income (expense), net	(485,659)	(5,537)	(640,199)	(30,411)
Net loss before income tax benefit	(31,438,027)	(4,795,059)	(40,120,900)	(8,024,985)
Income tax benefit	1,532,790		2,526,499
Net loss	(29,905,237)	(4,795,059)	(37,594,401)	(8,024,985)
Other comprehensive loss - foreign currency translation adjustments	(1,028,033)	(1,316,787)	(2,864,839)	(5,121,081)
Total comprehensive loss	(30,933,270)	(6,111,846)	(40,459,240)	(13,146,066)
Net loss	(29,905,237)	(4,795,059)	(37,594,401)	(8,024,985)
Preferred stock accretion and dividends	(1,962,072)	(104,548)	(2,125,141)	(247,562)
Net loss attributed to common stockholders	$ (31,867,309)	$ (4,899,607)	$ (39,719,542)	$ (8,272,547)
Weighted-average common shares outstanding, basic and diluted	15,527,867	6,911,715	11,595,698	6,911,366
Net loss per share attributed to common stockholders, basic and diluted	$ (2.05)	$ (0.71)	$ (3.43)	$ (1.20)

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity - 9 months ended Sep. 30, 2017 - USD ($)	Total	Series B Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]	Series B Redeemable Convertible Preferred Stock [Member]
Beginning Balance at Dec. 31, 2016							$ 0
Beginning Balance (in shares) at Dec. 31, 2016							0
Issuance of Series B redeemable convertible preferred stock and warrants, net of issuance costs and discounts							$ 6,276,228
Issuance of Series B redeemable convertible preferred stock and warrants, net of issuance costs and discounts (in shares)							15,656
Accretion of Series B redeemable convertible preferred stock							$ 1,962,072
Ending Balance at Sep. 30, 2017							$ 8,238,300
Ending Balance (in shares) at Sep. 30, 2017							15,656
Beginning Balance at Dec. 31, 2016	$ 32,207,323	$ 5,993	$ 692	$ 71,034,899	$ (31,259,449)	$ (7,574,812)
Beginning Balance (in shares) at Dec. 31, 2016		599,285	6,917,204
Stock based compensation	905,230			905,230
Vesting and accelerated vesting of restricted stock	231,900		$ 5	231,895
Vesting and accelerated vesting of restricted stock (in shares)			48,988
Exercises of stock options	16,455		$ 20	16,435
Exercises of stock options (in shares)			200,657
Warrant issuance, net of issuance costs	548,956			548,956
Conversion of Series B convertible preferred stock into common stock		$ (5,993)	$ 60	5,933
Conversion of Series B convertible preferred stock into common stock (in shares)		(599,285)	599,285
Conversion of convertible notes and accrued interest into common stock	3,645,424		$ 32	3,645,392
Conversion of convertible notes and accrued interest into common stock (in shares)			316,734
Warrant exercises			$ 66	(66)
Warrant exercises (in shares)			660,715
Issuance of common stock for the acquisition of subsidiaries	44,742,737		$ 688	44,742,049
Issuance of common stock for the acquisition of subsidiaries (in shares)			6,883,498
Issuance of Series B redeemable convertible preferred stock and warrants, net of issuance costs and discounts	3,223,853			3,223,853
Accretion of Series B redeemable convertible preferred stock	(1,962,072)			(1,962,072)
Foreign currency translation adjustments	2,864,839					2,864,839
Net loss	(37,594,401)				(37,594,401)
Ending Balance at Sep. 30, 2017	$ 48,830,244		$ 1,563	$ 122,392,504	$ (68,853,850)	$ (4,709,973)
Ending Balance (in shares) at Sep. 30, 2017			15,627,081

Condensed Consolidated Statements of Cash Flows - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (37,594,401)	$ (8,024,985)
Adjustments to reconcile net loss to net cash used in operating activities:
Goodwill impairment charges	26,600,000
Stock-based compensation	1,137,125	584,784
Depreciation	61,191	47,276
Amortization	40,409	60,552
Debt discount and deferred financing cost accretion	98,060	1,950,159
Loss on disposal of property and equipment	3,745
Change in fair value of warrant liabilities	508,316
Change in fair value of embedded derivatives	1,157
Changes in operating assets and liabilities:
Accounts receivable	(1,393,988)	(103,308)
Prepaid expenses and other current assets	(150,524)	67,465
Accounts payable	(2,273,397)	925,664
Accrued expenses and other current liabilities	(34,680)	80,668
Deferred revenue	(14,815)	(70,705)
Deferred rent	(10,085)	(5,971)
Tax refund receivable	(2,142,987)	(371,715)
Deferred tax liability	(243,056)
Net cash used in operating activities	(15,407,930)	(4,860,116)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(89,849)	(113,040)
Proceeds from sale of property and equipment	7,531
Additions to intangible assets	(47,634)	(66,307)
Refund of cash held in escrow	200,000
Cash assumed from acquiring subsidiaries	13,684,535
Net cash provided by (used in) investing activities	13,754,583	(179,347)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments of notes payable	(212,431)	(99)
Proceeds from issuance of convertible notes, net of issuance costs	3,018,780	531
Proceeds from issuance of preferred stock and warrants, net of issuance costs	13,018,570	5,673,680
Proceeds from exercise of stock options	16,455	300
Net cash provided by financing activities	15,841,374	5,674,412
EFFECT OF EXCHANGE RATES ON CASH	86,879	(170,048)
Net increase in cash and cash equivalents and restricted cash	14,274,906	464,901
Cash and cash equivalents and restricted cash, beginning of period	2,876,113	4,638,711
Cash and cash equivalents and restricted cash, end of period	17,151,019	5,103,612
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid for interest	5,882	2,424
SUPPLEMENTAL NON-CASH FINANCING ACTIVITIES:
Accrued expenses and notes payable modified and replaced with convertible notes	1,077,540
Conversion of convertible notes into common stock	3,645,424
Common stock warrants issued in connection with convertible notes, net of issuance costs	$ 548,956
Preferred stock subscription reclassified as additional paid-in capital upon preferred stock issuance		$ 325,280

Nature of Business and Basis of Presentation	9 Months Ended
Nature of Business and Basis of Presentation	Sep. 30, 2017
Accounting Policies [Abstract]
Nature of Business and Basis of Presentation	1. Nature of Business and Basis of Presentation Altimmune, Inc., headquartered in Gaithersburg, Maryland, United States, together with its subsidiaries (collectively, “Altimmune”) is a clinical stage biopharmaceutical company incorporated in 1997 under the laws of the State of Delaware. Altimmune is focused on discovering and developing immunotherapies and vaccines to address significant unmet medical needs. Since its inception, Altimmune 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 convertible preferred stock, long-term debt, and proceeds from research grants and government contracts. Altimmune 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. Pursuant to an Agreement and Plan of Merger and Reorganization (the “Merger Agreement”) dated January 18, 2017, PharmAthene, Inc. (“PharmAthene”), its wholly owned acquisition subsidiaries Mustang Merger Sub Corp I Inc. (“Merger Sub Corp”) and Mustang Merger Sub II LLC (“Merger Sub LLC”) agreed to acquire 100% of the outstanding capital stock of Altimmune in a reverse triangular merger and reorganization pursuant to section 368(a) of the Internal Revenue Code (the “Mergers”) (Note 3). As a condition for the Mergers, in January 2017, prior to the Mergers, Altimmune entered into a Convertible Promissory Note Purchase Agreement (the “Note Agreement”) for the private placement of $8.6 million of 6% convertible notes (the “Notes”) (See Note 7) to be issued in two separate closings. The initial closing dated March 9, 2017 resulted in $3,150,630 of gross proceeds. The initial closing also included $196,496 of certain existing outstanding notes payable and $881,044 of certain accrued expenses that were modified and became a component of the Notes on March 9, 2017. In connection with the Notes, Altimmune issued warrants to purchase 49,776 shares of Altimmune’s common stock to certain noteholders, with an exercise price of $0.01 per share. These warrants are classified as permanent equity (see Note 10). The second closing was included in the sale of Series B redeemable convertible preferred stock (“redeemable preferred stock”) that closed on August 16, 2017 (see Note 9). On May 4, 2017, Altimmune and PharmAthene closed the Mergers in accordance with the terms of the Merger Agreement. Upon the closing of the Mergers, (i) Merger Sub Corp merged with and into Altimmune, with Altimmune remaining as the surviving corporation; (ii) Altimmune then merged with and into Merger Sub LLC, with Merger Sub LLC (renamed as “Altimmune LLC”) remaining as the surviving entity; and (iii) PharmAthene was renamed as “Altimmune, Inc.” Upon closing of the Mergers, all equity instruments of Altimmune were exchanged for corresponding equity instruments of PharmAthene (see Note 3). Altimmune and PharmAthene and its subsidiaries are hereinafter collectively referred to as the “Company” or “we”. The accompanying unaudited condensed 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 Altimmune’s audited consolidated financial statements for the year ended December 31, 2016 included in the Registration Statement on Form S-4/A which was filed with the SEC on March 31, 2017. In the opinion of management, we have prepared the accompanying unaudited condensed consolidated financial statements on the same basis as our audited consolidated financial statements, and these condensed 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 2017 or any future years or periods. The unaudited condensed 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.

Going Concern	9 Months Ended
Going Concern	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Going Concern	2. Going Concern The accompanying condensed consolidated financial statements have been prepared assuming we will continue as a going concern. We have experienced recurring losses in past years and incurred a net loss of $37,594,401 and used $15,407,930 in cash to fund operations during the nine months ended September 30, 2017, and had an accumulated deficit of $68,853,850 as of September 30, 2017. We expect to incur additional losses in the future in connection with our research and development activities. Since inception, we have financed our activities principally from the issuance of equity and debt securities and the receipt of proceeds from research grants and government contracts. Our ability to continue as a going concern is dependent upon our ability to raise additional debt and equity capital. There can be no assurance that such capital will be available in sufficient amounts or on terms acceptable to us. These factors raise substantial doubt about our ability to continue as a going concern. The accompanying condensed consolidated financial statements do not include any adjustments relating to the recoverability of the recorded assets or the classification of liabilities that may be necessary should we be unable to continue as a going concern. As capital resources are consumed to fund our research and development activities, we may not have sufficient capital to fund our plan of operations. In order to address our capital needs, including our planned clinical trials, we must continue to actively pursue additional equity or debt financing. Adequate financing opportunities might not be available to us, when and if needed, on acceptable terms, or at all. If we are unable to obtain additional financing in sufficient amounts or on acceptable terms under such circumstances, our operating results and prospects will be adversely affected. As more fully described in Note 3, in January 2017, in connection with the Mergers, Altimmune entered into the Note Agreement for the private placement of the Notes. In addition, as more fully described in Note 9, in August 2017, we issued shares of redeemable preferred stock and the related common stock warrants for an aggregate net proceeds of $13.0 million. We expect that the combination of the net proceeds from the Notes, cash assumed from the Mergers, the anticipated receipt of tax refunds (Note 3), redeemable preferred financing, and revenue from our government sponsored contracts will be insufficient to fund our operations and research and development efforts for at least twelve months from the expected issuance date of our September 2017 financial statements.

Business Combination

9 Months Ended

Sep. 30, 2017

Business Combinations [Abstract]

Business Combination

3. Business Combination

On May 4, 2017, we closed the Mergers with PharmAthene. In accordance with the terms of the Merger Agreement, PharmAthene issued 0.749106 (the “share exchange ratio”) of a share of PharmaAthene common stock for each share of Altimmune’s $0.0001 par value common stock (“common stock”) outstanding as of the closing date. All historical share and per share information including common and preferred stock, common stock warrants, and stock options, has been retroactively adjusted to reflect the impact of the share exchange ratio. In addition, Altimmune’s stock options and warrants were also replaced with options and warrants to purchase PharmAthene’s common stock at the same share exchange ratio of 0.749106 share. Immediately prior to closing, 599,285 shares of Series B convertible preferred stock (“convertible preferred stock”) converted into Altimmune common stock on a 1-for-1 basis. Due to the convertible preferred stock having unique terms and conditions, the convertible preferred stock outstanding in periods prior to the Mergers continues to be presented separately on our balance sheet for periods prior to conversion. In addition, outstanding principal and accrued interest on the Notes converted into 316,734 shares of Altimmune common stock. Further, 39,758 shares of Altimmune common stock were issued pursuant to the accelerated vesting of restricted stock, and 660,715 shares of Altimmune common stock were issued as a result of warrant exercises, both in accordance with their original terms. Upon the closing of the Mergers, Altimmune common stock totaling 6,883,498 shares were exchanged for 6,883,498 shares of PharmAthene common stock.

Although PharmAthene was the issuer of the shares and considered the legal acquirer in the Mergers, following the closing, shareholders of Altimmune held 58.2% of the equity interest of the combined entity and assumed control of the combined entity. As a result, the transaction has been accounted for as a reverse merger, with Altimmune considered the accounting acquirer, and the assets and liabilities of PharmAthene have been recorded at their estimated fair value. The unadjusted purchase price allocated to PharmAthene’s assets and liabilities was estimated to be $44,742,737 as of the closing date and consisted of the shares of the combined company retained by PharmAthene shareholders, and the estimated fair value of vested PharmAthene stock options and warrants which remained outstanding as of the closing date. Also at the closing, 7,569 outstanding unvested options of PharmAthene with an estimated fair value of $15,173 remained subject to vesting and service requirements. These unvested options will be recorded as operating expense in future periods as the services are delivered and the options vest.

Headquartered in Annapolis, Maryland, PharmAthene was incorporated in Delaware in April 2005. PharmAthene was a biodefense company engaged in Phase II clinical trials in developing a next generation anthrax vaccine. The next generation vaccine is intended to have more rapid time to protection, fewer doses for protection and less stringent requirements for temperature controlled storage and handling than the currently used vaccine. The Mergers enable the combined company to become a fully integrated, commercially-focused immunotherapeutics company with the ability to create more value than either company could achieve individually. As a publicly listed entity, the Mergers also provide us with additional capital financing alternatives to support the combined entity’s planned research and development activities.

In addition to the operating assets and liabilities of PharmAthene, Altimmune also acquired PharmAthene’s tax attributes, which primarily consisted of a tax refund receivable and approximately $1 million of net operating losses which were limited under Section 382 of the U.S. Internal Revenue Service and were fully reserved, which begin to expire in 2023. We recorded a deferred tax liability related to future tax benefits arising from an in-process research and development asset (“IPR&D”) acquired in the Mergers. Goodwill generated from the Mergers is not expected to be deductible for tax purposes.

For accounting purposes, the historical financial statements of Altimmune have not been adjusted to reflect the Mergers, other than adjustments to the capital structure of Altimmune to reflect the historical capital structure of PharmAthene. Altimmune incurred $1,673,695 of transaction costs, which have been expensed as incurred in the accompanying condensed consolidated financial statements.

The following table lists the various securities of PharmAthene which were outstanding as of May 4, 2017 and whose rights and obligations were assumed by Altimmune following the Mergers:


Outstanding PharmAthene common stock		6,883,498
Outstanding PharmAthene stock options		123,003
Outstanding PharmAthene stock warrants		4,658
Per share fair value of PharmAthene common stock	$	6.50
Weighted average per share fair value of PharmAthene stock options	$	0.26
Per share fair value of PharmAthene stock warrants	$	0.01
Aggregate fair value of consideration	$	44,757,910
Less fair value of unvested common stock options		(15,173	)

Total fair value of consideration	$	44,742,737

Since the acquisition date, we have recorded adjustments to the allocation of the purchase consideration that included a $44,700 adjustment to increase our tax refund receivable and a $4,535 adjustment to reduce our deferred tax liabilities, with a total adjustment of $49,235 resulting in an increase in goodwill. The adjustments were the result of a change in the tax rate being applied from 34% to 35%. These purchase price adjustments were reflected in the accompanying condensed consolidated balance sheet as of September 30, 2017. The adjusted allocation of the purchase consideration to the assets acquired and liabilities assumed of PharmAthene in these financial statements is still preliminary and subject to change as management gathers information regarding these items. The adjusted allocation of the purchase consideration was as follows:


Cash and cash equivalents	$	13,684,535
Accounts receivable		1,124,462
Prepaid expenses and other current assets		597,172
Tax refund receivable		2,047,234
Property and equipment		75,779
IPR&D		22,389,000
Goodwill		15,573,822

Total assets acquired		55,492,004

Accounts payable and accrued expenses		(2,193,785	)
Deferred tax liability		(8,555,482	)

Total liabilities assumed		(10,749,267	)

Net assets acquired	$	44,742,737

We relied on significant Level 3 unobservable inputs to estimate the fair value of acquired IPR&D assets using management’s estimate of future revenue and expected profitability of the products after taking into account an estimate of future expenses necessary to bring the products to completion. These projected cash flows were then discounted to their present values using a discount rate of 23%, which was considered commensurate with the risks and stages of development of the products.

The operating activities of PharmAthene have been included in the accompanying condensed consolidated financial statements from the date of the Mergers. For the period from May 4, 2017 to September 30, 2017, revenues and net loss of PharmAthene included in the accompanying condensed consolidated financial statements aggregated $1,052,007 and $343,509, respectively.

The following unaudited pro forma information for the nine months ended September 30, 2017 and 2016 gives effect to the acquisition of PharmAthene as if the Mergers had occurred at the beginning of the respective full annual reporting period:


	Nine Months Ended September 30,
	2017			2016
Pro forma revenue and grants and contracts	$	9,035,435		$	6,262,748
Pro forma net (loss) income attributable to common stockholders	$	(39,277,568	)	$	111,784,503
Pro forma weighted average common shares outstanding, basic		15,218,542			14,268,717
Pro forma net (loss) income per share, basic	$	(2.58	)	$	7.83
Pro forma weighted average common shares outstanding, diluted		15,218,542			15,107,312
Pro forma net (loss) income per share, diluted	$	(2.58	)	$	7.40

Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Sep. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	4. Summary of Significant Accounting Policies Segment information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, our Chief Executive Officer, in making decisions regarding resource allocation and assessing performance. We view our operations and manage our business in one operating segment, the research and development of immunotherapies and vaccines. Business combination We use our best estimates and assumptions to accurately assign fair value to the tangible and intangible assets acquired and liabilities assumed at the acquisition date. Our estimates are inherently uncertain and subject to refinement. During the measurement period, which may be up to one year from the acquisition date, we may record adjustments to the fair value of these tangible and intangible assets acquired and liabilities assumed, with the corresponding offset to goodwill. In addition, uncertain tax positions and tax-related valuation allowances are initially established in connection with a business combination as of the acquisition date. Our management collects information and reevaluates these estimates and assumptions quarterly and records any adjustments to our preliminary estimates to goodwill during the measurement period. Upon the conclusion of the measurement period or final determination of the fair value of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to our consolidated statements of operations and comprehensive loss. Amounts paid for acquisitions are allocated to the assets acquired and liabilities assumed based on their estimated fair values at the date of acquisition. We allocate the purchase price in excess of net tangible assets acquired to identifiable intangible assets, including purchased IPR&D assets. The fair value of identifiable intangible assets is based on detailed valuations that use information and assumptions provided by management. We allocate any excess purchase price over the fair value of the net tangible and intangible assets acquired to goodwill. Our IPR&D assets represent the estimated fair value as of the acquisition date of substantive in-process projects that have not reached technological feasibility. The primary basis for determining technological feasibility of these projects is obtaining regulatory approval. The valuation of IPR&D assets is determined using the discounted cash flow method. In determining the value of IPR&D assets, management considers, among other factors, the stage of completion of the projects, the technological feasibility of the projects, whether the projects have an alternative future use and the estimated residual cash flows that could be generated from the various projects and technologies over their respective projected economic lives. The discount rate used is determined at the time of acquisition and includes a rate of return which accounts for the time value of money, as well as risk factors that reflect the economic risk that the cash flows projected may not be realized. Impairment of long-lived assets and goodwill We evaluate our long-lived tangible and intangible assets, including IPR&D assets and goodwill, 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 to its carrying value. Goodwill is tested for impairment by comparing the estimated fair value of our single reporting unit to its carrying value. From the date of the Mergers through September 30, 2017, we experienced a decline in the trading price of our common stock. As of September 30, 2017, our one reporting unit had an estimated average market capitalization through September 30, 2017, before adjusting for an estimated control premium, of approximately $36,200,000 as compared to the unadjusted carrying value of the reporting unit of $75,430,244, which is an impairment indicator. As a result, we conducted an interim impairment review and test. Our IPR&D assets are currently non-amortizing. Until such time as the projects are either completed or abandoned, we test those assets for impairment annually by comparing the fair value of such assets to their carrying value. On an interim basis, we consider qualitative factors which could be indicative of impairment; these factors include the current project status, forecasted changes in the timing or amounts required to complete the project, forecasted changes in the future cash flows to be generated by the completed products, and changes to other market based assumptions, such as discount rates. Upon completion or abandonment, the value of the IPR&D assets will be amortized to expense or the anticipated useful life of the developed products, if completed, or charged to expense when abandoned if no alternative future use exists. As of September 30, 2017, the projects continue to progress as originally anticipated, and no significant changes to the estimated timing or amount of cash flows or any other market assumptions have occurred. We performed an interim qualitative assessment of our long-lived assets, including IPR&D, as of September 30, 2017, and have determined that our long-lived assets, including IPR&D, are not impaired at September 30, 2017. We test goodwill for impairment during the fourth quarter of each year, or more frequently if impairment indicators arise. During the nine months ended September 30, 2017, we adopted the Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) No. 2017-04, Simplifying the Test for Goodwill Impairment (“ASU 2017-04”), which provides for a one-step quantitative test. We early adopted ASU 2017-04 to simplify our goodwill impairment analysis. If the carrying value of a reporting unit exceeds its fair value, the amount of goodwill impairment is the excess of the reporting unit’s carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. We consider multiple methods including both market and income approaches to determine fair value of our one reporting unit, and primarily relied on fair value estimated based on our market capitalization (a Level 1 input) as of or near the testing date, adjusted for an estimated control premium. As noted, due to the decline in the market value of our common stock which indicated potential impairment, we performed an interim impairment test on our goodwill as of September 30, 2017, using a volume weighted average price (“VWAP”) of $2.31 per share at September 30, 2017 and a control premium of 35%. Based on the result of our impairment test, the carrying value of our reporting unit exceeded its estimated fair value at September 30, 2017. As a result, we have concluded that our goodwill was impaired at September 30, 2017 and an impairment charge of $26,600,000 was recorded during the three and nine months ended September 30, 2017, and was classified as a component of operating expenses. We will continue to evaluate our goodwill for impairment based on factors including the overall movements of our market capitalization. Any sustained declines in our stock price from the September 30, 2017 level could result in a future impairment and the overall amount of impairment loss could be material. Income Taxes We account for income taxes using 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. A valuation allowance is established when necessary to reduce deferred tax assets to the amounts expected to be realized. We also recognize 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. Pursuant to federal and state tax regulations with respect to carryback periods of certain net operating losses (“NOLs”), in 2017, as a result of the Mergers, we anticipate that we will be able to carryback 2017 NOLs to 2016, which we expect will allow us to recover previously paid federal and state income taxes by PharmAthene and other tax credits of approximately $5.1 million. These anticipated refunds generated through September 30, 2017, are included as a component of tax refund receivable on the condensed consolidated balance sheet at September 30, 2017 and an income tax benefit during the three and nine months ended September 30, 2017. Preferred Stock Convertible preferred stock outstanding prior to the Mergers were classified as permanent equity, with the net issuance price in excess of par value recorded as additional paid-in capital. Redeemable preferred stock issued in August 2017 are classified as temporary equity and were initially recorded at their original issuance price, net of issuance costs and discounts. Discounts included common stock warrants issued as part of the financing which were required to be classified as a liability and recorded at fair value (Note 10), an embedded derivative related to certain redemption features which was classified as a liability and recorded at fair value (Note 9), and the intrinsic value of a beneficial conversion feature present in the instrument at issuance (Note 9). The carrying value of redeemable preferred stock will be accreted over the term of the redeemable preferred stock up to their redemption value, using the interest method with the amount of the accretion recorded as a reduction of additional paid-in capital. Warrants Common stock warrants issued in connection with the convertible preferred stock and the Notes were classified as a component of permanent equity because they were freestanding financial instruments that were legally detachable and separately exercisable from other debt and equity instruments, were contingently exercisable, did not embody an obligation for us to repurchase our own shares, and permitted the holders to receive a fixed number of common shares upon exercise. In addition, such warrants required physical settlement and do not provide any guarantee of value or return. These warrants were valued using the Black Scholes option pricing model (“Black-Scholes”). Common stock warrants issued in connection with the redeemable preferred stock are classified as a liability because the warrants may be net share settled at the holders option. Such warrants contain terms which could, in certain circumstances, require the Company to settle the instruments for cash and such circumstances are outside the Company’s control. Common stock warrants classified as a liability are initially recorded at their issuance date fair value and are remeasured on each subsequent balance sheet date with changes in fair value recorded as a component of other income (expenses), net. These common stock warrants were valued using the Monte Carlo simulation valuation model. Stock Compensation We adopted FASB’s ASU No. 2016-09, Compensation – Stock Compensation (“ASU 2016-09”) on January 1, 2017. The adoption of ASU 2016-09 did not have a material impact on our financial statements. We elected to adopt the cash flow presentation of the excess tax benefits prospectively, commencing with our statement of cash flows for the three months ended March 31, 2017. We have elected to continue to estimate the number of stock-based awards expected to vest, rather than electing to account for forfeitures as they occur to determine the amount of compensation cost to be recognized in each period. There was no impact to our computation of dilutive EPS as all securities were considered anti-dilutive. Recently issued accounting pronouncements In May 2014, FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), as amended, which amends the guidance for revenue recognition to replace numerous industry specific requirements. ASU 2014-09, as amended, implements a five-step process for customer contract revenue recognition that focuses on transfer of control, as opposed to transfer of risk and rewards. ASU 2014-09, as amended, also requires enhanced disclosures regarding the nature, amount, timing, and uncertainty of revenues and cash flows from contracts with customers. Other major provisions include ensuring the time value of money is considered in the transaction price, and allowing estimates of variable consideration to be recognized before contingencies are resolved in certain circumstances. ASU 2014-09, as amended, is effective for reporting periods beginning after December 15, 2017. Early adoption is permitted, but not before December 15, 2016. Entities can transition to the standard either retrospectively or as a cumulative-effect adjustment as of the date of adoption. We are currently in the process of evaluating the effect the adoption of ASU 2014-09, as amended, may have on our financial statements. As the majority of our revenues relate to research grants and government contracts, we do not expect the adoption of ASU 2014-09, as amended, will have a material impact on our financial statements. In February 2016, FASB issued 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. It also aligns lease accounting for lessors with the revenue recognition guidance in ASU 2014-09. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, and is to be applied at the beginning of the earliest period presented using a modified retrospective approach. We do not expect the adoption of ASU 2016-02 will have a material impact on our financial statements.

Net Loss Per Share

9 Months Ended

Sep. 30, 2017

Earnings Per Share [Abstract]

Net Loss Per Share

5. Net Loss Per Share

Because we have 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.

The following table sets forth the computation of basic and diluted net loss per share:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
Numerator:
Net loss	$	(29,905,237	)	$	(4,795,059	)	$	(37,594,401	)	$	(8,024,985	)
Less: preferred stock accretion and dividends		(1,962,072	)		(104,548	)		(2,125,141	)		(247,562	)

Net loss attributed to common stockholders	$	(31,867,309	)	$	(4,899,607	)	$	(39,719,542	)	$	(8,272,547	)

Denominator:
Weighted-average common shares outstanding, basic and diluted		15,527,867			6,911,715			11,595,698			6,911,366

Net loss per share attributed to common stockholders, basic and diluted	$	(2.05	)	$	(0.71	)	$	(3.43	)	$	(1.20	)

Potential common shares issuable upon conversion, vesting or exercise of convertible preferred stock, redeemable 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:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Convertible preferred stock		—		517,860		—		411,736
Redeemable preferred stock		5,863,564		—		5,863,564		—
Common stock warrants		2,350,085		538,003		2,350,085		442,910
Common stock options		1,720,004		831,248		1,720,004		838,595
Restricted stock		25,559		—		25,559		—

Goodwill and Intangible Assets

9 Months Ended

Sep. 30, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

6. Goodwill and Intangible Assets

Changes in the carrying amounts of IPR&D assets and goodwill for the nine months ended September 30, 2017 were:


	IPR&D		Goodwill
Balance, beginning of period	$	14,477,019	$	18,758,421
Additions from the Mergers		22,389,000		15,573,822
Foreign currency translation adjustments		1,235,457		1,602,661
Impairment charges		—		(26,600,000	)

Balance, end of period	$	38,101,476	$	9,334,904

Our intangible assets consisted of the following:


	December 31, 2016
	Estimated Useful Lives		Gross Carrying Value		Accumulated Amortization			Net Book Value
Internally developed patents		6-10 years	$	624,454	$	(211,956	)	$	412,498
Acquired licenses		16-20 years		285,000		(219,800	)		65,200

Total intangible assets subject to amortization				909,454		(431,756	)		477,698
IPR&D assets		Indefinite		14,477,019		—			14,477,019

Total			$	15,386,473	$	(431,756	)	$	14,954,717


	September 30, 2017
	Estimated Useful Lives		Gross Carrying Value		Accumulated Amortization			Net Book Value
Internally developed patents		6-10 years	$	672,088	$	(239,211	)	$	432,877
Acquired licenses		16-20 years		285,000		(232,954	)		52,046

Total intangible assets subject to amortization				957,088		(472,165	)		484,923


	September 30, 2017
	Estimated Useful Lives		Gross Carrying Value		Accumulated Amortization			Net Book Value
IPR&D assets		Indefinite		38,101,476		—			38,101,476

Total			$	39,058,564	$	(472,165	)	$	38,586,399

Amortization expense of intangible assets subject to amortization totaled $14,257 and $11,764 for the three months ended September 30, 2017 and 2016, respectively, and $40,409 and $60,552 for the nine months ended September 30, 2017 and 2016, respectively. Amortization expense was classified as research and development expenses in the accompanying condensed consolidated statements of operations and comprehensive loss.

As of September 30, 2017, future estimated amortization expense is as follows:


Years ending December 31,
The remainder of 2017	$	14,257
2018		53,027
2019		48,227
2020		34,781
2021		14,222
2022 and thereafter		320,409

Total	$	484,923

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Notes Payable	9 Months Ended
Notes Payable	Sep. 30, 2017
Debt Disclosure [Abstract]
Notes Payable	7. Notes Payable As a condition for the Mergers as described in Note 3, Altimmune entered into the Note Agreement on January 18, 2017. The Notes bore interest at a rate of 6% per annum, compounded annually. On February 28, 2017, as part of the initial closing, $196,496 of the Notes were issued upon the conversion of outstanding principal of certain prior notes payable, and $881,044 of the Notes were issued upon the conversion of certain outstanding accrued expenses. The conversion of the prior notes payable into the Notes was accounted for as a modification with no resulting gains or losses being recognized. On March 9, 2017, the remainder of the initial closing of the Notes was issued for an aggregate of $3,150,630 in gross proceeds. In connection with the issuance of the Notes, we granted warrants for the purchase of up to 49,776 shares of our common stock to certain noteholders. The allocated fair value of the warrants on the issuance date of $566,793 was accounted for as a debt issuance discount and was accreted over the term of the Notes using the interest method. All outstanding principal and accrued interest on the Notes were converted into our common stock upon the close of the Mergers. On May 4, 2017, upon the close of the Mergers, outstanding principal and accrued interest, net of unamortized discount and deferred financing costs totaling $3,645,424 were converted into 316,734 shares of our common stock. Interest expense incurred on the Notes prior to conversion totaled $83,207 and $136,629 for the three and nine months ended September 30, 2017, respectively.

Accrued Expenses and Other Current Liabilities

9 Months Ended

Sep. 30, 2017

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

8. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following:


	September 30,		December 31,
	2017		2016
Accrued professional services	$	885,549	$	689,135
Accrued board of director compensation		81,414		606,199
Accrued payroll and employee benefits		1,070,006		957,719
Accrued interest		536		169,790
Accrued research and development costs		1,559,808		549,902

Total	$	3,597,313	$	2,972,745

Redeemable Convertible Preferred Stock

9 Months Ended

Sep. 30, 2017

Text Block [Abstract]

Redeemable Convertible Preferred Stock

9. Redeemable Convertible Preferred Stock

On August 16, 2017, we issued 15,656 shares of $0.0001 par value, redeemable preferred stock and warrants to purchase up to 2,345,427 shares of our common stock (see Note 10) for total gross proceeds of $14,716,370, and incurred issuance costs totaling $1,697,800. The redeemable preferred stock matures on August 16, 2018. The maturity date may be extended at the option of the holders to ten trading days after the curing of a triggering event (as defined), or ten business days after the consummation of a change of control. In addition, the redeemable preferred stock agreements require that we reserve a sufficient number of common shares to cover at least 150% of the common shares expected to be issued upon the conversion of the redeemable preferred stock at the then current conversion price, and the exercises of common stock warrants issued in connection with the redeemable preferred stock.

The rights, preferences, and privileges of redeemable preferred stock are summarized below:

Voting – Holders of redeemable preferred stock have no voting rights, except as required by law.

Dividends – Holders of redeemable preferred stock are entitled to participate in dividends, when and if declared by our board of directors, on an as converted basis at the initial conversion price of $2.67 per share, not to exceed the maximum ownership percentages (as defined).

Optional conversion – Holders of redeemable preferred stock have the option to convert redeemable preferred stock into shares of common stock, rounded up to the nearest whole shares, at any time, not to exceed the maximum ownership percentages (as defined), at the conversion rate calculated as (1) whole shares of redeemable preferred shares to be converted at $1,000 per share, plus any accrued but unpaid dividends, and any accrued but unpaid late charges, divided by (2) the conversion price which is $2.67 per share initially, or as adjusted for any dilutive events and down rounds.

Mandatory conversion – If for any ten consecutive trading days after the redeemable preferred stock issuance date, the weighted average price of our common stock equals or exceeds 200% of the then current conversion price (initially $2.67 per share, subject to adjustment for stock dividends, stock splits, or a stock combination), we have the option to require all holders of redeemable preferred stock to convert all or a pro rata portion of their outstanding unconverted redeemable preferred stock (plus accrued and unpaid dividends and accrued and unpaid late charges) into common stock at the then current conversion rate (initially $2.67 per share), up to the maximum ownership percentage (as defined).

Triggering event conversion – Upon a triggering event, holders of redeemable preferred stock may elect to convert all, or a portion of, the outstanding conversion amount at the triggering event conversion price determined based on the lowest of (1) the conversion price then in effect (initially $2.67 per share), (2) 75% of the lowest VWAP during the 20-day period prior to the triggering event conversion date, and (3) 75% of the VWAP on the triggering event conversion date, adjusted for any share dividend, share split, or share combination.

Installment – On each of the nine specified installment dates beginning in December 2017 through maturity, we are required to convert, redeem, or a combination, one-ninth of the originally issued number of redeemable preferred shares at their stated value of $1,000 per share, for an aggregate value of $1,739,524 at each installment. If we elect to convert the installment shares, the conversion price is determined based on the lowest of (i) the then applicable conversion price (initially $2.67 per share), (ii) 85% of the average of the three lowest weighted-average prices of the common stock during the ten trading days up to the installment date, and (iii) 85% of the weighted average price of common stock on the trading day immediately before the installment date. If we elect cash redemption, the redemption amount is $1,000 per share, plus any accrued but unpaid dividends and any accrued but unpaid late charges.

Liquidation preference – In the event of a voluntary or involuntary liquidation, dissolution, or winding up of business involving substantially all of our assets, holders of redeemable preferred stock are entitled to receive cash payments in priority to holders of common stock in the amount that equals the sum of any outstanding shares at $1,000 per share, plus any accrued and unpaid dividends, and any accrued and unpaid late charges. If assets available for distribution are insufficient to satisfy the liquidation payment in full, funds available for distribution shall be allocated pari passu among holders of redeemable preferred stock, and other equity classes equal in preference, based on their relative shareholdings. When the holders of redeemable preferred stock are satisfied in full, any excess assets available for distribution will be allocated ratably among holders of common stock and holders of redeemable preferred stock based on the number of common shares held by each holders of redeemable preferred stock on an as-converted basis.

Mandatory redemption – Upon maturity, we are required redeem any remaining outstanding redeemable preferred stock in cash at $1,000 per share, plus any accrued and unpaid dividends, and any accrued and unpaid late charges.

Change of control redemption or triggering event redemption – In the event of a change of control or upon a triggering event, holders of redeemable preferred stock may redeem for cash all or a portion of their outstanding redeemable preferred stock at the greater of (i) 125% of the amount to be redeemed, or (ii) the amount to be redeemed multiplied by the quotient of the highest closing sale price during the period from the earlier of consummation or public announcement of the change of control to the date of the redemption notice, divided by the lowest conversion price in effect during such period. If we are unable to redeem all redeemable preferred stock submitted for redemption, we may be required to pay a penalty until the redemption amount is paid in full.

Stock purchasing rights – Holders of redeemable preferred stock are entitled to the same stock purchasing rights granted to holders of common stock.

Late charges – We may be required to pay a late charge for any amounts due to the holders of redeemable preferred stock that are not paid timely, at 12% per annum on the unpaid amount, until it is paid in full.

Because the securities contain contingencies which could require the Company to redeem the shares for cash, and such contingencies are outside the control of the Company, the redeemable convertible preferred stock must be classified outside of permanent equity. Because a substantive conversion feature is present at issuance, the redeemable convertible preferred stock is only contingently redeemable and therefore is classified as temporary equity and carried on the balance sheet in between liabilities and equity at its accreted redemption value.

In addition, certain features present in the redeemable convertible preferred stock require separate recognition. For purposes of this evaluation, we have determined that the redeemable preferred instrument is more akin to a debt host because the installment conversion feature, as the primary settlement mechanism, settles in variable shares. Because the potential contingent redemption price contains a significant premium over the issuance price, the redemption feature is not clearly and closely related to the debt-like host instrument. All redemption features (including the change of control redemption, triggering event redemption, mandatory redemption, and installment redemption) have been determined to be a single, compound embedded derivative financial instrument to be bifurcated and separately accounted for as a liability. The embedded derivative financial instrument was initially recorded at its fair value on the redeemable preferred stock issuance date, and is being remeasured on each subsequent balance date with changes in fair value classified as a component of other income (expenses), net. The embedded derivative is classified as a component of other long-term liabilities.

The redeemable convertible preferred stock also contains a beneficial conversion element at issuance. The conversion feature was “in-the-money” as of the commitment date as the fair value of the underlying common share was greater than the effective conversion price. The beneficial conversion feature, measured as the intrinsic value of the feature, totaled $3,223,853 and is classified as a component of additional paid-in capital. This amount was allocated from the net proceeds of the financing. The beneficial conversion feature will not be remeasured in subsequent periods.

The net proceeds from the financing were allocated as follows:


Common stock warrant liability	$	3,498,632
Embedded derivative, redemption features		19,857
Beneficial conversion feature		3,223,853
Initial carrying value of redeemable preferred stock		6,276,228

Net proceeds from redeemable preferred stock issuance	$	13,018,570

The periodic changes in the fair value of the embedded redemption derivative financial instrument measured using Level 3 inputs, is as follows:


Balance, beginning of period	$	—
Issuance		19,857
Change in fair value		1,157

Balance, end of period	$	21,014

The fair value used to determine the initial carrying value of the embedded redemption derivative financial instrument was measured using Level 3 inputs and was estimated using the Monte Carlo simulation valuation model. The assumptions used to estimate the fair value of the embedded redemption derivative financial instrument as September 30, 2017 and as of the redeemable preferred stock issuance date were as follows:


	September 30, 2017			August 16, 2017
Expected volatility		52.00	%		56.00	%
Incremental borrowing rate		12.00	%		12.00	%
Risk-free interest rate		1.28	%		1.24	%

Warrants

9 Months Ended

Sep. 30, 2017

Equity [Abstract]

Warrants

10. Warrants

As of December 31, 2016, there were 616,770 warrants outstanding. In March 2017, we issued warrants to purchase up to 49,776 shares of common stock in connection with the Notes (see Note 1). The warrants were classified as permanent equity, and were recorded at the issuance date using a relative fair value allocation method, and were not subsequently remeasured. In connection with the Mergers, 660,715 shares of common stock were issued as a result of cashless exercises of such warrants.

In August 2017, in connection with the redeemable preferred stock issuance (Note 9), we granted warrants to holders of redeemable preferred stock to purchase up to 2,345,427 shares of our common stock. Warrants issued with the redeemable preferred stock are classified as a liability and are initially recorded at their grant date fair value, to be remeasured on each subsequent balance sheet date. The warrant liability is classified as component of other long-term liabilities.

A summary of warrant activity during the three and nine months ended September 30, 2017 and 2016 is as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017			2016
Warrants outstanding, beginning of period		4,658		477,613		616,770			208.614
Issuances		2,345,427		134,499		2,395,203			403,498
Exercises and conversions		—		—		(661,888	)		—

Warrants outstanding, end of period		2,350,085		612,112		2,350,085			612,112

Warrants outstanding at September 30, 2017 have an aggregate grant date fair value of $3,498,720 with a weighted average exercise price of $2.70.

The periodic changes in the fair value of the warrant liability, measured using Level 3 inputs, is as follows:


Balance, beginning of period	$	—
Issuance		3,498,632
Change in fair value		508,316

Balance, end of period	$	4,006,948

The fair value used to determine the initial carrying value of warrants classified as permanent equity was measured using Level 3 inputs and was estimated using the Black-Scholes option pricing model. 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 during the three and nine months ended September 30, 2017 and 2016:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
Expected volatility		87.00	%		71.00	%		87.00	%		75.00	%
Expected term (years)		5.00			4.22			5.00			4.54
Risk-free interest rate		1.76	%		1.08	%		1.76	%		1.29	%
Expected dividend yield		0.00	%		0.00	%		0.00	%		0.00	%

Stock-Based Compensation

9 Months Ended

Sep. 30, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

11. Stock-Based Compensation

Stock Options

Our stock option awards generally vest over four years and typically have a contractual life of ten years. At September 30, 2017, there was $2,227,080 of unrecognized compensation cost related to stock options, which is expected to be recognized over a weighted-average period of 2.45 years. During the three and nine months ended September 30, 2017, we issued 200,060 and 200,657 shares, respectively, of common stock as a result of option exercises.

Information related to stock options outstanding at September 30, 2017 is as follows:


	Number of Stock Options		Weighted- average Exercise Price		Weighted- average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding		1,720,004	$	4.73		4.93	$	883,740

Exercisable		971,221	$	4.44		4.41	$	857,749

Expected to vest		748,783	$	5.11		5.61	$	25,991

Restricted Stock

At September 30, 2017, we had unvested restricted stock of 25,559 shares with total unrecognized compensation expense of $33,618, which we expect to recognize over a weighted average period of approximately 1.86 years. During the three and nine months ended September 30, 2017, we released 2,130 and 48,987 shares of common stock, respectively, from restriction as a result of the vesting and accelerated vesting of restricted stock.

Stock-based compensation expense

Stock-based compensation expense is classified in the accompanying condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2017 and 2016 as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Research and development	$	93,821	$	62,871	$	250,061	$	215,596
General and administrative		359,216		132,185		887,064		369,189

Total	$	453,037	$	195,056	$	1,137,125	$	584,784

Contingencies	9 Months Ended
Contingencies	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Contingencies	12. Contingencies We are a party in various other contractual disputes, litigation, and potential claims arising in the ordinary course of business. We do not believe that the resolution of these matters will have a material adverse effect on our financial position or results of operations.

Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2017
Accounting Policies [Abstract]
Segment information	Segment information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, our Chief Executive Officer, in making decisions regarding resource allocation and assessing performance. We view our operations and manage our business in one operating segment, the research and development of immunotherapies and vaccines.
Business combination	Business combination We use our best estimates and assumptions to accurately assign fair value to the tangible and intangible assets acquired and liabilities assumed at the acquisition date. Our estimates are inherently uncertain and subject to refinement. During the measurement period, which may be up to one year from the acquisition date, we may record adjustments to the fair value of these tangible and intangible assets acquired and liabilities assumed, with the corresponding offset to goodwill. In addition, uncertain tax positions and tax-related valuation allowances are initially established in connection with a business combination as of the acquisition date. Our management collects information and reevaluates these estimates and assumptions quarterly and records any adjustments to our preliminary estimates to goodwill during the measurement period. Upon the conclusion of the measurement period or finaldetermination of the fair value of assets acquired or liabilities assumed, whichever comes first, any subsequent adjustments are recorded to our consolidated statements of operations and comprehensive loss. Amounts paid for acquisitions are allocated to the assets acquired and liabilities assumed based on their estimated fair values at the date of acquisition. We allocate the purchase price in excess of net tangible assets acquired to identifiable intangible assets, including purchased IPR&D assets. The fair value of identifiable intangible assets is based on detailed valuations that use information and assumptions provided by management. We allocate any excess purchase price over the fair value of the net tangible and intangible assets acquired to goodwill. Our IPR&D assets represent the estimated fair value as of the acquisition date of substantive in-process projects that have not reached technological feasibility. The primary basis for determining technological feasibility of these projects is obtaining regulatory approval. The valuation of IPR&D assets is determined using the discounted cash flow method. In determining the value of IPR&D assets, management considers, among other factors, the stage of completion of the projects, the technological feasibility of the projects, whether the projects have an alternative future use and the estimated residual cash flows that could be generated from the various projects and technologies over their respective projected economic lives. The discount rate used is determined at the time of acquisition and includes a rate of return which accounts for the time value of money, as well as risk factors that reflect the economic risk that the cash flows projected may not be realized.
Impairment of long-lived assets and goodwill	Impairment of long-lived assets and goodwill We evaluate our long-lived tangible and intangible assets, including IPR&D assets and goodwill, 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 to its carrying value. Goodwill is tested for impairment by comparing the estimated fair value of our single reporting unit to its carrying value. From the date of the Mergers through September 30, 2017, we experienced a decline in the trading price of our common stock. As of September 30, 2017, our one reporting unit had an estimated average market capitalization through September 30, 2017, before adjusting for an estimated control premium, of approximately $36,200,000 as compared to the unadjusted carrying value of the reporting unit of $75,430,244, which is an impairment indicator. As a result, we conducted an interim impairment review and test. Our IPR&D assets are currently non-amortizing. Until such time as the projects are either completed or abandoned, we test those assets for impairment annually by comparing the fair value of such assets to their carrying value. On an interim basis, we consider qualitative factors which could be indicative of impairment; these factors include the current project status, forecasted changes in the timing or amounts required to complete the project, forecasted changes in the future cash flows to be generated by the completed products, and changes to other market based assumptions, such as discount rates. Upon completion or abandonment, the value of the IPR&D assets will be amortized to expense or the anticipated useful life of the developed products, if completed, or charged to expense when abandoned if no alternative future use exists. As of September 30, 2017, the projects continue to progress as originally anticipated, and no significant changes to the estimated timing or amount of cash flows or any other market assumptions have occurred. We performed an interim qualitative assessment of our long-lived assets, including IPR&D, as of September 30, 2017, and have determined that our long-lived assets, including IPR&D, are not impaired at September 30, 2017. We test goodwill for impairment during the fourth quarter of each year, or more frequently if impairment indicators arise. During the nine months ended September 30, 2017, we adopted the Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) No. 2017-04, Simplifying the Test for Goodwill Impairment (“ASU 2017-04”), which provides for a one-step quantitative test. We early adopted ASU 2017-04 to simplify our goodwill impairment analysis. If the carrying value of a reporting unit exceeds its fair value, the amount of goodwill impairment is the excess of the reporting unit’s carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. We consider multiple methods including both market and income approaches to determine fair value of our one reporting unit, and primarily relied on fair value estimated based on our market capitalization (a Level 1 input) as of or near the testing date, adjusted for an estimated control premium. As noted, due to the decline in the market value of our common stock which indicated potential impairment, we performed an interim impairment test on our goodwill as of September 30, 2017, using a volume weighted average price (“VWAP”) of $2.31 per share at September 30, 2017 and a control premium of 35%. Based on the result of our impairment test, the carrying value of our reporting unit exceeded its estimated fair value at September 30, 2017. As a result, we have concluded that our goodwill was impaired at September 30, 2017 and an impairment charge of $26,600,000 was recorded during the three and nine months ended September 30, 2017, and was classified as a component of operating expenses. We will continue to evaluate our goodwill for impairment based on factors including the overall movements of our market capitalization. Any sustained declines in our stock price from the September 30, 2017 level could result in a future impairment and the overall amount of impairment loss could be material.
Income Taxes	Income Taxes We account for income taxes using 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. A valuation allowance is established when necessary to reduce deferred tax assets to the amounts expected to be realized. We also recognize 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. Pursuant to federal and state tax regulations with respect to carryback periods of certain net operating losses (“NOLs”), in 2017, as a result of the Mergers, we anticipate that we will be able to carryback 2017 NOLs to 2016, which we expect will allow us to recover previously paid federal and state income taxes by PharmAthene and other tax credits of approximately $5.1 million. These anticipated refunds generated through September 30, 2017, are included as a component of tax refund receivable on the condensed consolidated balance sheet at September 30, 2017 and an income tax benefit during the three and nine months ended September 30, 2017.
Preferred Stock	Preferred Stock Convertible preferred stock outstanding prior to the Mergers were classified as permanent equity, with the net issuance price in excess of par value recorded as additional paid-in capital. Redeemable preferred stock issued in August 2017 are classified as temporary equity and were initially recorded at their original issuance price, net of issuance costs and discounts. Discounts included common stock warrants issued as part of the financing which were required to be classified as a liability and recorded at fair value (Note 10), an embedded derivative related to certain redemption features which was classified as a liability and recorded at fair value (Note 9), and the intrinsic value of a beneficial conversion feature present in the instrument at issuance (Note 9). The carrying value of redeemable preferred stock will be accreted over the term of the redeemable preferred stock up to their redemption value, using the interest method with the amount of the accretion recorded as a reduction of additional paid-in capital.
Warrants	Warrants Common stock warrants issued in connection with the convertible preferred stock and the Notes were classified as a component of permanent equity because they were freestanding financial instruments that were legally detachable and separately exercisable from other debt and equity instruments, were contingently exercisable, did not embody an obligation for us to repurchase our own shares, and permitted the holders to receive a fixed number of common shares upon exercise. In addition, such warrants required physical settlement and do not provide any guarantee of value or return. These warrants were valued using the Black Scholes option pricing model (“Black-Scholes”). Common stock warrants issued in connection with the redeemable preferred stock are classified as a liability because the warrants may be net share settled at the holders option. Such warrants contain terms which could, in certain circumstances, require the Company to settle the instruments for cash and such circumstances are outside the Company’s control. Common stock warrants classified as a liability are initially recorded at their issuance date fair value and are remeasured on each subsequent balance sheet date with changes in fair value recorded as a component of other income (expenses), net. These common stock warrants were valued using the Monte Carlo simulation valuation model.
Stock Compensation	Stock Compensation We adopted FASB’s ASU No. 2016-09, Compensation – Stock Compensation (“ASU 2016-09”) on January 1, 2017. The adoption of ASU 2016-09 did not have a material impact on our financial statements. We elected to adopt the cash flow presentation of the excess tax benefits prospectively, commencing with our statement of cash flows for the three months ended March 31, 2017. We have elected to continue to estimate the number of stock-based awards expected to vest, rather than electing to account for forfeitures as they occur to determine the amount of compensation cost to be recognized in each period. There was no impact to our computation of dilutive EPS as all securities were considered anti-dilutive.
Recently issued accounting pronouncements	Recently issued accounting pronouncements In May 2014, FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“ASU 2014-09”), as amended, which amends the guidance for revenue recognition to replace numerous industry specific requirements. ASU 2014-09, as amended, implements a five-step process for customer contract revenue recognition that focuses on transfer of control, as opposed to transfer of risk and rewards. ASU 2014-09, as amended, also requires enhanced disclosures regarding the nature, amount, timing, and uncertainty of revenues and cash flows from contracts with customers. Other major provisions include ensuring the time value of money is considered in the transaction price, and allowing estimates of variable consideration to be recognized before contingencies are resolved in certain circumstances. ASU 2014-09, as amended, is effective for reporting periods beginning after December 15, 2017. Early adoption is permitted, but not before December 15, 2016. Entities can transition to the standard either retrospectively or as a cumulative-effect adjustment as of the date of adoption. We are currently in the process of evaluating the effect the adoption of ASU 2014-09, as amended, may have on our financial statements. As the majority of our revenues relate to research grants and government contracts, we do not expect the adoption of ASU 2014-09, as amended, will have a material impact on our financial statements. In February 2016, FASB issued 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. It also aligns lease accounting for lessors with the revenue recognition guidance in ASU 2014-09. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, and is to be applied at the beginning of the earliest period presented using a modified retrospective approach. We do not expect the adoption of ASU 2016-02 will have a material impact on our financial statements.

- Definition

Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.

+ References + Details

Business Combination (Tables)

9 Months Ended

Sep. 30, 2017

Business Combinations [Abstract]

Schedule of Lists of Various Securities

The following table lists the various securities of PharmAthene which were outstanding as of May 4, 2017 and whose rights and obligations were assumed by Altimmune following the Mergers:


Outstanding PharmAthene common stock		6,883,498
Outstanding PharmAthene stock options		123,003
Outstanding PharmAthene stock warrants		4,658
Per share fair value of PharmAthene common stock	$	6.50
Weighted average per share fair value of PharmAthene stock options	$	0.26
Per share fair value of PharmAthene stock warrants	$	0.01
Aggregate fair value of consideration	$	44,757,910
Less fair value of unvested common stock options		(15,173	)

Total fair value of consideration	$	44,742,737

Schedule of Purchase Price Allocation

The adjusted allocation of the purchase consideration to the assets acquired and liabilities assumed of PharmAthene in these financial statements is still preliminary and subject to change as management gathers information regarding these items. The adjusted allocation of the purchase consideration was as follows:


Cash and cash equivalents	$	13,684,535
Accounts receivable		1,124,462
Prepaid expenses and other current assets		597,172
Tax refund receivable		2,047,234
Property and equipment		75,779
IPR&D		22,389,000
Goodwill		15,573,822

Total assets acquired		55,492,004

Accounts payable and accrued expenses		(2,193,785	)
Deferred tax liability		(8,555,482	)

Total liabilities assumed		(10,749,267	)

Net assets acquired	$	44,742,737

Summary of Unaudited Pro Forma Information


	Nine Months Ended September 30,
	2017			2016
Pro forma revenue and grants and contracts	$	9,035,435		$	6,262,748
Pro forma net (loss) income attributable to common stockholders	$	(39,277,568	)	$	111,784,503
Pro forma weighted average common shares outstanding, basic		15,218,542			14,268,717
Pro forma net (loss) income per share, basic	$	(2.58	)	$	7.83
Pro forma weighted average common shares outstanding, diluted		15,218,542			15,107,312
Pro forma net (loss) income per share, diluted	$	(2.58	)	$	7.40

Net Loss Per Share (Tables)

9 Months Ended

Sep. 30, 2017

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net Loss Per Share

The following table sets forth the computation of basic and diluted net loss per share:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
Numerator:
Net loss	$	(29,905,237	)	$	(4,795,059	)	$	(37,594,401	)	$	(8,024,985	)
Less: preferred stock accretion and dividends		(1,962,072	)		(104,548	)		(2,125,141	)		(247,562	)

Net loss attributed to common stockholders	$	(31,867,309	)	$	(4,899,607	)	$	(39,719,542	)	$	(8,272,547	)

Denominator:
Weighted-average common shares outstanding, basic and diluted		15,527,867			6,911,715			11,595,698			6,911,366

Net loss per share attributed to common stockholders, basic and diluted	$	(2.05	)	$	(0.71	)	$	(3.43	)	$	(1.20	)

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share


	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Convertible preferred stock		—		517,860		—		411,736
Redeemable preferred stock		5,863,564		—		5,863,564		—
Common stock warrants		2,350,085		538,003		2,350,085		442,910
Common stock options		1,720,004		831,248		1,720,004		838,595
Restricted stock		25,559		—		25,559		—

Goodwill and Intangible Assets (Tables)

9 Months Ended

Sep. 30, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Changes in Carrying Amounts of IPR&D Assets and Goodwill

Changes in the carrying amounts of IPR&D assets and goodwill for the nine months ended September 30, 2017 were:


	IPR&D		Goodwill
Balance, beginning of period	$	14,477,019	$	18,758,421
Additions from the Mergers		22,389,000		15,573,822
Foreign currency translation adjustments		1,235,457		1,602,661
Impairment charges		—		(26,600,000	)

Balance, end of period	$	38,101,476	$	9,334,904

Schedule of Intangible Assets

Our intangible assets consisted of the following:


	December 31, 2016
	Estimated Useful Lives		Gross Carrying Value		Accumulated Amortization			Net Book Value
Internally developed patents		6-10 years	$	624,454	$	(211,956	)	$	412,498
Acquired licenses		16-20 years		285,000		(219,800	)		65,200

Total intangible assets subject to amortization				909,454		(431,756	)		477,698
IPR&D assets		Indefinite		14,477,019		—			14,477,019

Total			$	15,386,473	$	(431,756	)	$	14,954,717


	September 30, 2017
	Estimated Useful Lives		Gross Carrying Value		Accumulated Amortization			Net Book Value
Internally developed patents		6-10 years	$	672,088	$	(239,211	)	$	432,877
Acquired licenses		16-20 years		285,000		(232,954	)		52,046

Total intangible assets subject to amortization				957,088		(472,165	)		484,923


	September 30, 2017
	Estimated Useful Lives		Gross Carrying Value		Accumulated Amortization			Net Book Value
IPR&D assets		Indefinite		38,101,476		—			38,101,476

Total			$	39,058,564	$	(472,165	)	$	38,586,399

Schedule of Future Estimated Amortization Expense

As of September 30, 2017, future estimated amortization expense is as follows:


Years ending December 31,
The remainder of 2017	$	14,257
2018		53,027
2019		48,227
2020		34,781
2021		14,222
2022 and thereafter		320,409

Total	$	484,923

Accrued Expenses and Other Current Liabilities (Tables)

9 Months Ended

Sep. 30, 2017

Payables and Accruals [Abstract]

Schedule of Accrued Expenses and Other Liabilities

Accrued expenses and other current liabilities consist of the following:


	September 30,		December 31,
	2017		2016
Accrued professional services	$	885,549	$	689,135
Accrued board of director compensation		81,414		606,199
Accrued payroll and employee benefits		1,070,006		957,719
Accrued interest		536		169,790
Accrued research and development costs		1,559,808		549,902

Total	$	3,597,313	$	2,972,745

Redeemable Convertible Preferred Stock (Tables)

9 Months Ended

Sep. 30, 2017

Text Block [Abstract]

Allocation of Net Proceeds From Financing

The net proceeds from the financing were allocated as follows:


Common stock warrant liability	$	3,498,632
Embedded derivative, redemption features		19,857
Beneficial conversion feature		3,223,853
Initial carrying value of redeemable preferred stock		6,276,228

Net proceeds from redeemable preferred stock issuance	$	13,018,570

Summary of Periodic Changes Fair Value of Embedded Redemption Derivative Financial Instrument

The periodic changes in the fair value of the embedded redemption derivative financial instrument measured using Level 3 inputs, is as follows:


Balance, beginning of period	$	—
Issuance		19,857
Change in fair value		1,157

Balance, end of period	$	21,014

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


	September 30, 2017			August 16, 2017
Expected volatility		52.00	%		56.00	%
Incremental borrowing rate		12.00	%		12.00	%
Risk-free interest rate		1.28	%		1.24	%

Warrants (Tables)

9 Months Ended

Sep. 30, 2017

Equity [Abstract]

Summary of Warrant Activity

A summary of warrant activity during the three and nine months ended September 30, 2017 and 2016 is as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017			2016
Warrants outstanding, beginning of period		4,658		477,613		616,770			208.614
Issuances		2,345,427		134,499		2,395,203			403,498
Exercises and conversions		—		—		(661,888	)		—

Warrants outstanding, end of period		2,350,085		612,112		2,350,085			612,112

Summary of Periodic Changes in Fair Value of Warrant Liability

The periodic changes in the fair value of the warrant liability, measured using Level 3 inputs, is as follows:


Balance, beginning of period	$	—
Issuance		3,498,632
Change in fair value		508,316

Balance, end of period	$	4,006,948

Summary of Fair Value Used to Determine Warrants' Initial Carrying Value


	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
Expected volatility		87.00	%		71.00	%		87.00	%		75.00	%
Expected term (years)		5.00			4.22			5.00			4.54
Risk-free interest rate		1.76	%		1.08	%		1.76	%		1.29	%
Expected dividend yield		0.00	%		0.00	%		0.00	%		0.00	%

- 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

- 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)

9 Months Ended

Sep. 30, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Information Related to Stock Options Outstanding

Information related to stock options outstanding at September 30, 2017 is as follows:


	Number of Stock Options		Weighted- average Exercise Price		Weighted- average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding		1,720,004	$	4.73		4.93	$	883,740

Exercisable		971,221	$	4.44		4.41	$	857,749

Expected to vest		748,783	$	5.11		5.61	$	25,991

Schedule of Stock-based Compensation Expense


	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Research and development	$	93,821	$	62,871	$	250,061	$	215,596
General and administrative		359,216		132,185		887,064		369,189

Total	$	453,037	$	195,056	$	1,137,125	$	584,784

Nature of Business and Basis of Presentation - Additional Information (Detail) - USD ($)		9 Months Ended
	Mar. 09, 2017	Sep. 30, 2017	Mar. 31, 2017	Jan. 31, 2017
Business And Basis Of Presentation [Line Items]
Shares of common stock called by warrants			49,776
Warrants exercise price per share		$ 2.70	$ 0.01
Merger Agreement [Member]
Business And Basis Of Presentation [Line Items]
Agreement of reorganization and merger date		Jan. 18, 2017
Merger Agreement [Member] \| Merger Sub Corp I Inc and Mustang Merger Sub II LLC [Member]
Business And Basis Of Presentation [Line Items]
Business acquisition, percentage of voting interest acquired		100.00%
Convertible Promissory Note Purchase Agreement [Member] \| 6% Convertible Notes [Member]
Business And Basis Of Presentation [Line Items]
Notes payable				$ 8,600,000
Notes payable, interest rate				6.00%
Description of second closing		The second closing was included in the sale of Series B redeemable convertible preferred stock (“redeemable preferred stock”) that closed on August 16, 2017 (see Note 9).
Convertible Promissory Note Purchase Agreement [Member] \| 6% Convertible Notes [Member] \| Convertible Promissory Note Purchase Agreement Initial Closing [Member]
Business And Basis Of Presentation [Line Items]
Gross proceeds from notes payable	$ 3,150,630
Notes payable modified and replaced with convertible notes	196,496
Accrued expenses modified and replaced with convertible notes	$ 881,044

Going Concern - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended
	Aug. 16, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss		$ (29,905,237)	$ (4,795,059)	$ (37,594,401)	$ (8,024,985)
Cash used to fund operations				(15,407,930)	(4,860,116)
Accumulated deficit		$ (68,853,850)		(68,853,850)		$ (31,259,449)
Proceeds from issuance of preferred stock and related common stock warrants, net of issuance costs	$ 13,018,570			$ 13,018,570	$ 5,673,680

Business Combination - Additional Information (Detail)		3 Months Ended		5 Months Ended	9 Months Ended		12 Months Ended
Business Combination - Additional Information (Detail)	May 04, 2017 USD ($) $ / shares shares	Sep. 30, 2017 USD ($) $ / shares	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) $ / shares	Sep. 30, 2017 USD ($) $ / shares	Sep. 30, 2016 USD ($)	Dec. 31, 2016 $ / shares
Business Acquisition [Line Items]
Share exchange ratio					1-for-1 basis
Debt converted in to equity	316,734
Conversion of stock \| shares	6,883,498
Common stock, par value \| $ / shares	$ 0.0001	$ 0.0001		$ 0.0001	$ 0.0001		$ 0.0001
Transaction costs	$ 1,673,695
Discount rate	23.00%
Revenue		$ 4,591,940	$ 901,039		$ 7,929,484	$ 2,151,915
Net loss		(29,905,237)	$ (4,795,059)		(37,594,401)	$ (8,024,985)
Restricted Stock Units (RSUs) [Member]
Business Acquisition [Line Items]
Conversion of stock \| shares	39,758
Series B Preferred Stock [Member]
Business Acquisition [Line Items]
Conversion of preferred stock	$ 599,285
Common Stock Class A [Member]
Business Acquisition [Line Items]
Common stock issued \| shares	6,883,498
United States [Member]
Business Acquisition [Line Items]
Operating loss carryforwards		$ 1,000,000		$ 1,000,000	$ 1,000,000
Operating loss carryforwards, expiration date					Jan. 01, 2023
Common Stock Warrants [Member]
Business Acquisition [Line Items]
Conversion of stock \| shares	660,715
PharmAthene [Member]
Business Acquisition [Line Items]
Reverse stock split of common stock	0.749106
Equity interests acquired	58.20%
Total fair value of consideration	$ 44,742,737
Outstanding unvested options \| shares	7,569
Stock options estimated fair value	$ 15,173
Increase tax refund receivable due to adjustments to the allocation of the purchase consideration				44,700
Reduce deferred tax liability due to adjustments to the allocation of the purchase consideration				4,535
Increase in goodwill due to adjustments to the allocation of the purchase consideration				49,235
Change in tax rate					35.00%		34.00%
Revenue				1,052,007
Net loss				$ 343,509

Business Combination - Schedule of Lists of Various Securities (Detail) - USD ($)	May 04, 2017	Sep. 30, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Outstanding PharmAthene common stock		15,627,081	6,917,204
Outstanding PharmAthene stock options		1,720,004
Weighted average per share fair value of PharmAthene stock options		$ 4.73
PharmAthene [Member]
Business Acquisition [Line Items]
Outstanding PharmAthene common stock	6,883,498
Outstanding PharmAthene stock options	123,003
Outstanding PharmAthene stock warrants	4,658
Per share fair value of PharmAthene common stock	$ 6.50
Weighted average per share fair value of PharmAthene stock options	0.26
Per share fair value of PharmAthene stock warrants	$ 0.01
Aggregate fair value of consideration	$ 44,757,910
Less fair value of unvested common stock options	(15,173)
Total fair value of consideration	$ 44,742,737

Business Combination - Schedule of Purchase Price Allocation (Detail) - USD ($)	Sep. 30, 2017	May 04, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 9,334,904		$ 18,758,421
PharmAthene [Member]
Business Acquisition [Line Items]
Cash and cash equivalents		$ 13,684,535
Accounts receivable		1,124,462
Prepaid expenses and other current assets		597,172
Tax refund receivable		2,047,234
Property and equipment		75,779
IPR&D		22,389,000
Goodwill		15,573,822
Total assets acquired		55,492,004
Accounts payable and accrued expenses		(2,193,785)
Deferred tax liability		(8,555,482)
Total liabilities assumed		(10,749,267)
Net assets acquired		$ 44,742,737

Business Combination - Summary of Unaudited Pro Forma Information (Detail) - PharmAthene [Member] - USD ($)	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition [Line Items]
Pro forma revenue and grants and contracts	$ 9,035,435	$ 6,262,748
Pro forma net (loss) income attributable to common stockholders	$ (39,277,568)	$ 111,784,503
Pro forma weighted average common shares outstanding, basic	15,218,542	14,268,717
Pro forma net (loss) income per share, basic	$ (2.58)	$ 7.83
Pro forma weighted average common shares outstanding, diluted	15,218,542	15,107,312
Pro forma net (loss) income per share, diluted	$ (2.58)	$ 7.40

Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended	9 Months Ended
	Sep. 30, 2017 USD ($) $ / shares	Sep. 30, 2017 USD ($) Reporting_Unit Segment $ / shares
Significant Accounting Policies [Line Items]
Number of operating segments \| Segment		1
Number of reporting units \| Reporting_Unit		1
Estimated average market capitalization		$ 36,200,000
Carrying value of the reporting unit		$ 75,430,244
Control premium percentage		35.00%
Goodwill impairment charges	$ 26,600,000	$ 26,600,000
Weighted Average [Member]
Significant Accounting Policies [Line Items]
Initial conversion price \| $ / shares	$ 2.31	$ 2.31
PharmAthene [Member]
Significant Accounting Policies [Line Items]
Income tax expense recoverable		$ 5,100,000

Net Loss Per Share - Schedule of Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net loss	$ (29,905,237)	$ (4,795,059)	$ (37,594,401)	$ (8,024,985)
Less: preferred stock accretion and dividends	(1,962,072)	(104,548)	(2,125,141)	(247,562)
Net loss attributed to common stockholders	$ (31,867,309)	$ (4,899,607)	$ (39,719,542)	$ (8,272,547)
Denominator:
Weighted-average common shares outstanding, basic and diluted	15,527,867	6,911,715	11,595,698	6,911,366
Net loss per share attributed to common stockholders, basic and diluted	$ (2.05)	$ (0.71)	$ (3.43)	$ (1.20)

Net Loss Per Share - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share		517,860		411,736
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	5,863,564		5,863,564
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	1,720,004	831,248	1,720,004	838,595
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	2,350,085	538,003	2,350,085	442,910
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	25,559		25,559

Goodwill and Intangible Assets - Schedule of Changes in Carrying Amounts of IPR&D Assets and Goodwill (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Indefinite-lived Intangible Assets [Line Items]
Goodwill Balance, beginning of period		$ 18,758,421
Goodwill, Additions from the Mergers		15,573,822
Goodwill, Foreign currency translation adjustments		1,602,661
Goodwill, Impairment charges	$ (26,600,000)	(26,600,000)
Goodwill Balance, end of period	9,334,904	9,334,904
IPR&D [Member]
Indefinite-lived Intangible Assets [Line Items]
IPR&D Balance, beginning of period		14,477,019
IPR&D, Additions from the Mergers		22,389,000
IPR&D, Foreign currency translation adjustments		1,235,457
IPR&D Balance, end of period	$ 38,101,476	$ 38,101,476

Goodwill and Intangible Assets - Schedule of Intangible Assets (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Schedule Of Intangible Assets [Line Items]
Total intangible assets, Gross Carrying Value	$ 39,058,564	$ 15,386,473
Intangible assets subject to amortization, Gross Carrying Value	957,088	909,454
Intangible assets subject to amortization, Accumulated Amortization	(472,165)	(431,756)
Intangible assets subject to amortization, Net Book Value	484,923	477,698
Total intangible assets, Net Book Value	38,586,399	14,954,717
IPR&D [Member]
Schedule Of Intangible Assets [Line Items]
Intangible assets, Net Book Value	38,101,476	14,477,019
Internally Developed Patents [Member]
Schedule Of Intangible Assets [Line Items]
Intangible assets subject to amortization, Gross Carrying Value	672,088	624,454
Intangible assets subject to amortization, Accumulated Amortization	(239,211)	(211,956)
Intangible assets subject to amortization, Net Book Value	$ 432,877	$ 412,498
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	(232,954)	(219,800)
Intangible assets subject to amortization, Net Book Value	$ 52,046	$ 65,200
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 - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Research and Development [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense of intangible assets	$ 14,257	$ 11,764	$ 40,409	$ 60,552

Goodwill and Intangible Assets - Schedule of Future Estimated Amortization Expense (Detail) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
The remainder of 2017	$ 14,257
2018	53,027
2019	48,227
2020	34,781
2021	14,222
2022 and thereafter	320,409
Intangible assets subject to amortization, Net Book Value	$ 484,923	$ 477,698

Notes Payable - Additional Information (Detail) - USD ($)			1 Months Ended	3 Months Ended		9 Months Ended
	May 04, 2017	Mar. 09, 2017	Aug. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Feb. 28, 2017	Jan. 18, 2017
Debt Instrument [Line Items]
Warrants issued on debt issuance			2,345,427	2,345,427	134,499	2,395,203	403,498
Debt Instrument, unamortized discount						$ 98,060	$ 1,950,159
Debt conversion, converted instrument, amount						$ 3,645,424
Notes Payable [Member]
Debt Instrument [Line Items]
Debt instrument, issuance date						Jan. 18, 2017
Debt instrument, interest rate, stated percentage									6.00%
Debt instrument, offering date						Feb. 28, 2017
Gain (loss) on extinguishment of debt						$ 0
Gross proceeds from notes payable		$ 3,150,630
Debt Instrument, unamortized discount		$ 566,793
Debt conversion, converted instrument, amount	$ 3,645,424
Debt conversion, shares converted	316,734
Interest expense, debt				$ 83,207		$ 136,629
Notes Payable [Member] \| Common Stock Class A [Member]
Debt Instrument [Line Items]
Warrants issued on debt issuance		49,776
Notes Payable [Member] \| Prior Note Payable [Member]
Debt Instrument [Line Items]
Debt instrument, face amount								$ 196,496
Notes Payable [Member] \| Accrued Expenses [Member]
Debt Instrument [Line Items]
Debt instrument, face amount								$ 881,044

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Liabilities (Detail) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Accrued Liabilities and Other Liabilities [Abstract]
Accrued professional services	$ 885,549	$ 689,135
Accrued board of director compensation	81,414	606,199
Accrued payroll and employee benefits	1,070,006	957,719
Accrued interest	536	169,790
Accrued research and development costs	1,559,808	549,902
Total	$ 3,597,313	$ 2,972,745

Redeemable Convertible Preferred Stock - Additional Information (Detail)		9 Months Ended
	Aug. 16, 2017 USD ($) Installments $ / shares shares	Sep. 30, 2017 $ / shares shares	Dec. 31, 2016 $ / shares shares
Temporary Equity [Line Items]
Number of installments \| Installments	9
Percentage of average of three lowest weighted-average prices of common stock	85.00%
Percentage of redeemable preferred stock to be redeemed	125.00%
Late charge percentage per annum on unpaid amount	12.00%
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible preferred shares, shares issued \| shares	15,656	15,656	0
Convertible preferred shares, par value	$ 0.0001	$ 0.0001	$ 0.0001
Stock issued for exchange of warrants \| $	$ 14,716,370
Issuance costs incurred \| $	$ 1,697,800
Redeemable preferred stock redemption date	Aug. 16, 2018
Percentage of common stock in reserve for issue on conversion	150.00%
Redeemable Preferred stock, voting rights		Holders of redeemable preferred shares have no voting rights.
Initial conversion price	$ 2.67
Mandatory redeemable preferred stock shares in cash	$ 1,000
Aggregate value of redeemable preferred stock converted on each installment \| $	$ 1,739,524
Series B Redeemable Convertible Preferred Stock [Member] \| Fair Value, Inputs, Level 3 [Member]
Temporary Equity [Line Items]
Beneficial conversion feature \| $	$ 3,223,853
Series B Redeemable Convertible Preferred Stock [Member] \| Dividend [Member]
Temporary Equity [Line Items]
Initial conversion price	$ 2.67
Series B Redeemable Convertible Preferred Stock [Member] \| Maximum [Member]
Temporary Equity [Line Items]
Stock issued for exchange of warrants, shares \| shares	2,345,427
Series B Redeemable Convertible Preferred Stock [Member] \| Mandatory Conversion [Member]
Temporary Equity [Line Items]
Number of days after preferred stock issuance date that trigger conversion price	10 days
Percentage of current conversion price trigger	200.00%
Mandatorily Redeemable Preferred Stock [Member]
Temporary Equity [Line Items]
Mandatory redeemable preferred stock shares in cash	$ 1,000

Redeemable Convertible Preferred Stock - Allocation of Net Proceeds From Financing (Detail) - USD ($)		9 Months Ended
	Aug. 16, 2017	Sep. 30, 2017	Sep. 30, 2016
Allocation Of Net Proceeds From Redeemable Convertible Preferred Stock Financing [Line Items]
Common stock warrant liability	$ 3,498,632
Embedded derivative, redemption features	19,857
Initial carrying value of redeemable preferred stock	6,276,228
Net proceeds from redeemable preferred stock issuance	13,018,570	$ 13,018,570	$ 5,673,680
Series B Redeemable Convertible Preferred Stock [Member] \| Fair Value, Inputs, Level 3 [Member]
Allocation Of Net Proceeds From Redeemable Convertible Preferred Stock Financing [Line Items]
Beneficial conversion feature	$ 3,223,853

Redeemable Convertible Preferred Stock - Summary of Periodic Changes Fair Value of Embedded Redemption Derivative Financial Instrument (Detail)	Aug. 16, 2017 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Abstract]
Issuance	$ 19,857
Change in fair value	1,157
Balance, end of period	$ 21,014

Redeemable Convertible Preferred Stock - Assumptions Used to Estimate Fair Value of Embedded Redemption Derivative Financial Instrument (Detail) - Fair Value, Inputs, Level 3 [Member]		9 Months Ended
	Aug. 16, 2017	Sep. 30, 2017
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Expected volatility	56.00%	52.00%
Incremental borrowing rate	12.00%	12.00%
Risk-free interest rate	1.24%	1.28%

Warrants - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
Warrants - Additional Information (Detail) - USD ($)	Aug. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Class of Warrant or Right [Line Items]
Warrants outstanding		2,350,085	612,112	2,350,085	612,112	4,658.000		616,770	477,613.000	208.614
Shares of common stock called by warrants							49,776
Issuances	2,345,427	2,345,427	134,499	2,395,203	403,498
Warrants right grant date fair value		$ 3,498,720		$ 3,498,720
Warrants right weighted average exercise price		$ 2.70		$ 2.70			$ 0.01
Merger Agreement [Member]
Class of Warrant or Right [Line Items]
Number of warrants exercised				660,715
Maximum [Member]
Class of Warrant or Right [Line Items]
Shares of common stock called by warrants							49,776

Warrants - Summary of Warrant Activity (Detail) - shares	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Warrants and Rights Note Disclosure [Abstract]
Warrants outstanding, beginning of period		4,658.000	477,613.000	616,770	208.614
Issuances	2,345,427	2,345,427	134,499	2,395,203	403,498
Exercises and conversions				(661,888)
Warrants outstanding, end of period		2,350,085	612,112	2,350,085	612,112

Warrants - Summary of Periodic Changes in Fair Value of Warrant Liability (Detail) - USD ($)		3 Months Ended	9 Months Ended
	Aug. 16, 2017	Sep. 30, 2017	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Issuance	$ (3,498,632)
Change in fair value		$ (508,316)	$ (508,316)
Fair Value, Inputs, Level 3 [Member] \| Common Stock Warrants [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Balance, beginning of period			0
Issuance			3,498,632
Change in fair value			508,316
Balance, end of period		$ 4,006,948	$ 4,006,948

Warrants - Summary of Fair Value Used to Determine Warrants' Initial Carrying Value (Detail) - Common Stock Warrants [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Expected volatility	87.00%	71.00%	87.00%	75.00%
Expected term (years)	5 years	4 years 2 months 19 days	5 years	4 years 6 months 14 days
Risk-free interest rate	1.76%	1.08%	1.76%	1.29%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%

Stock-Based Compensation - Additional Information (Detail)	3 Months Ended	9 Months Ended
	Sep. 30, 2017 USD ($) shares	Sep. 30, 2017 USD ($) shares
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 \| $	$ 2,227,080	$ 2,227,080
Unrecognized stock-based compensation expense, period for recognition		2 years 5 months 12 days
Common stock issued as result of option exercises	200,060	200,657
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense, period for recognition		1 year 10 months 10 days
Unvested restricted stock, shares	25,559	25,559
Unrecognized compensation expense \| $	$ 33,618	$ 33,618
Common stock issued as result of vesting of restricted stock	2,130	48,987

Stock-Based Compensation - Schedule of Information Related to Stock Options Outstanding (Detail)	9 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Stock Options, Outstanding \| shares	1,720,004
Number of Stock Options, Exercisable \| shares	971,221
Number of Stock Options, Expected to vest \| shares	748,783
Weighted- average Exercise Price, Outstanding \| $ / shares	$ 4.73
Weighted- average Exercise Price, Exercisable \| $ / shares	4.44
Weighted- average Exercise Price, Expected to vest \| $ / shares	$ 5.11
Weighted- average Remaining Contractual Term, Outstanding	4 years 11 months 4 days
Weighted- average Remaining Contractual Term, Exercisable	4 years 4 months 28 days
Weighted- average Remaining Contractual Term, Expected to vest	5 years 7 months 10 days
Aggregate Intrinsic Value, Outstanding \| $	$ 883,740
Aggregate Intrinsic Value, Exercisable \| $	857,749
Aggregate Intrinsic Value, Expected to vest \| $	$ 25,991

Stock-Based Compensation - Schedule of Stock-based Compensation Expense (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	$ 453,037	$ 195,056	$ 1,137,125	$ 584,784
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	93,821	62,871	250,061	215,596
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock based compensation expense	$ 359,216	$ 132,185	$ 887,064	$ 369,189