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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2017	Mar. 02, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	Axsome Therapeutics, Inc.
Entity Central Index Key	0001579428
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 85.5
Entity Common Stock, Shares Outstanding		25,492,992
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash	$ 34,021,123	$ 36,618,497
Prepaid and other current assets	1,278,418	1,380,560
Total current assets	35,299,541	37,999,057
Equipment, net	68,071	100,730
Other assets	187,952	112,821
Total assets	35,555,564	38,212,608
Current liabilities:
Accounts payable	3,435,456	4,081,173
Accrued expenses and other current liabilities	2,679,534	2,820,377
Loan payable, current portion	3,269,346	269,162
Warrant liability	2,791,000
Total current liabilities	12,175,336	7,170,712
Loan payable, long-term	6,663,005	9,470,445
Total liabilities	18,838,341	16,641,157
Stockholders? equity:
Common stock, $0.0001 par value per share (150,000,000 shares authorized, 25,492,992 and 19,158,417 shares issued and outstanding at December 31, 2017 and December 31, 2016, respectively)	2,549	1,916
Additional paid-in capital	93,299,517	69,210,986
Accumulated deficit	(76,584,843)	(47,641,451)
Total stockholders? equity	16,717,223	21,571,451
Total liabilities and stockholders? equity	$ 35,555,564	$ 38,212,608

Consolidated Statements of Operations - USD ($)	12 Months Ended
Consolidated Statements of Operations - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating expenses:
Research and development	$ 19,957,616	$ 21,199,860	$ 6,776,987
General and administrative	7,206,691	6,343,648	2,419,289
Total operating expenses	27,164,307	27,543,508	9,196,276
Loss from operations	(27,164,307)	(27,543,508)	(9,196,276)
Interest and amortization of debt discount/premium (expense) income	(1,340,199)	(132,424)	(736,048)
Tax credit	207,114	474,279
Change in fair value of warrant liability	(646,000)		(108,539)
Change in fair value of embedded derivative liabilities			274,800
Loss on extinguishment of debt			(2,444,516)
Net loss	$ (28,943,392)	$ (27,201,653)	$ (12,210,579)
Net loss per common share, basic and diluted	$ (1.27)	$ (1.42)	$ (1.02)
Weighted average common shares outstanding, basic and diluted	22,764,606	19,150,690	11,945,318

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($)	Common Stock	Additional paid-in capital	Accumulated deficit	Total
Beginning balance at Dec. 31, 2014	$ 1,111	$ 5,025,533	$ (8,229,219)	$ (3,202,575)
Balance (in shares) at Dec. 31, 2014	11,108,144
Stock-based compensation		803,279		803,279
Issuance of common stock in initial public offering, net of expense	$ 567	45,505,934		45,506,501
Issuance of common stock in initial public offering, net of expense (in shares)	5,666,667
Issuance of common stock for conversion of convertible notes	$ 237	15,302,624		15,302,861
Issuance of common stock for conversions of convertible notes (in shares)	2,374,606
Reclassification of warrant liability		244,774		244,774
Net loss			(12,210,579)	(12,210,579)
Ending balance at Dec. 31, 2015	$ 1,915	66,882,144	(20,439,798)	46,444,261
Balance (in shares) at Dec. 31, 2015	19,149,417
Stock-based compensation		2,031,418		2,031,418
Issuance of common stock in initial public offering, net of expense	$ 1	33,029		33,030
Issuance of common stock in initial public offering, net of expense (in shares)	9,000
Issuance of warrants		264,395		264,395
Net loss			(27,201,653)	(27,201,653)
Ending balance at Dec. 31, 2016	$ 1,916	69,210,986	(47,641,451)	$ 21,571,451
Balance (in shares) at Dec. 31, 2016	19,158,417			19,158,417
Stock-based compensation		2,072,210		$ 2,072,210
Proceeds from exercise of options	$ 9	316,710		$ 316,719
Proceeds from exercise of options (in shares)	88,922			88,922
Issuance of warrants	$ 13	167,881		$ 167,894
Issuance of warrants (in shares)	129,149
Issuance of stock upon financing	$ 611	21,531,730		21,532,341
Issuance of common stock upon financing (in shares)	6,116,504
Net loss			(28,943,392)	(28,943,392)
Ending balance at Dec. 31, 2017	$ 2,549	$ 93,299,517	$ (76,584,843)	$ 16,717,223
Balance (in shares) at Dec. 31, 2017	25,492,992			25,492,992

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net loss	$ (28,943,392)	$ (27,201,653)	$ (12,210,579)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	2,072,210	2,031,418	803,279
Amortization of debt (premium) discount	470,521	68,930	42,202
Amortization of debt issuance costs			7,757
Non-cash interest expense			698,826
Change in fair value of warrants	646,000		108,539
Change in fair value of warrant and embedded derivative liabilities			(274,800)
Loss on extinguishment of debt			2,444,516
Depreciation	42,557	20,484	3,542
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	102,143	(383,942)	(870,673)
Other assets	(75,131)	(86,196)	(26,625)
Accounts payable	(645,717)	2,188,810	1,134,204
Accrued expenses and other current liabilities	(140,843)	2,080,845	700,821
Net cash used in operating activities	(26,471,652)	(21,281,304)	(7,438,991)
Cash flows from investing activities
Purchases of equipment	(9,898)	(104,561)	(20,195)
Net cash used in investing activities	(9,898)	(104,561)	(20,195)
Cash flows from financing activities
Proceeds from issuance of convertible notes			7,382,468
Proceeds from issuance of term loan		10,000,000
Payment of debt issuance costs		(64,928)	(12,489)
Repayment of principal on term loan	(277,778)
Proceeds from issuance of initial public offering, net			45,549,121
Procceds from issuance of common stock upon financing, net	23,677,341
Proceeds issuance of common stock upon exercise of warrants	167,894	33,030
Proceeds from issuance of common stock upon exercise of options	316,719
Payment of loan from related party			(41,469)
Net cash provided by financing activities	23,884,176	9,968,102	52,877,631
Net (decrease) increase in cash	(2,597,374)	(11,417,763)	45,418,445
Cash at beginning of period	36,618,497	48,036,260	2,617,815
Cash at end of period	34,021,123	36,618,497	48,036,260
Supplemental disclosures of non-cash financing activity:
Establishment of warrant liabilities in connection with common stock issuance	$ 2,145,000
Issuance of warrants in connection with debt financing		$ 264,395
Conversion of convertible notes to common stock			$ 15,302,861

Nature of Business and Basis of Presentation	12 Months Ended
Nature of Business and Basis of Presentation	Dec. 31, 2017
Nature of Business and Basis of Presentation
Nature of Business and Basis of Presentation	Note 1.Nature of Business and Basis of Presentation Axsome Therapeutics, Inc. (“Axsome” or the “Company”) is a clinical stage biopharmaceutical company developing novel therapies for central nervous system, or CNS, disorders for which there are limited treatment options. By focusing on this therapeutic area, the Company is addressing significant and growing markets where current treatment options are limited or inadequate. The Company’s product candidate portfolio includes five product candidates, AXS‑05, AXS-09, AXS-02, AXS-07, and AXS‑06, which are being developed for multiple indications. The Company aims to become a fully integrated biopharmaceutical company that develops and commercializes differentiated therapies that expand the treatment options available to caregivers and improve the lives of patients living with CNS disorders. The Company was incorporated on January 12, 2012 in the State of Delaware and now has operations in the United States and Australia. The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and include all adjustments necessary for the fair presentation of the Company’s financial position for the periods presented. The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All material intercompany accounts and transactions have been eliminated during the consolidation process. Amendment to Certificate of Incorporation On October 30, 2015, the Company filed an amendment to its Certificate of Incorporation whereby the Company (i) increased the number of authorized shares of common stock to 25,000,000 shares and (ii) effectuated a 7.3445‑for‑1 forward stock split of its common stock. Fractional shares resulting from the stock split were rounded down to the next whole share and in lieu of any fractional shares the Company will pay a cash amount to the holder of such fractional share equal to the fair market value of such fractional share as determined by the Company’s board of directors. The accompanying audited financial statements and notes to the financial statements give retroactive effect to this stock split for all periods presented. In connection with the completion of the Company’s initial public offering (“IPO”) on November 24, 2015, the Company’s stockholders approved an amended and restated Certificate of Incorporation, in which its authorized capital stock consists of 150,000,000 shares of common stock, par value $0.0001 per share, and 10,000,000 shares of preferred stock, par value $0.0001 per share. Liquidity and Capital Resources The Company has incurred operating losses since its inception, and expects to continue to incur operating losses for the foreseeable future and may never become profitable. As of December 31, 2017, the Company had an accumulated deficit of $76.6 million. In November 2015, the Company completed its IPO, whereby it sold 5,666,667 shares of common stock at a public offering price of $9.00 per share. The Company received gross proceeds of approximately $51.0 million and net proceeds of approximately $45.5 million, after deducting underwriting discounts and commissions and offering-related transaction costs. In November 2016, the Company entered into a loan and security agreement with Silicon Valley Bank (“SVB”) for a term loan of up to $20.0 million. The initial tranche of $10.0 million was funded shortly after executing the loan agreement. The Company did not achieve the conditional criteria to access the second and third tranches before the specified dates and the $10.0 million in additional term loan advances have expired. In March 2017, the Company completed an underwritten public offering, whereby it sold 4,304,813 shares of common stock at a public offering price of $3.74 per share. The Company received gross proceeds of approximately $16.1 million and net proceeds of approximately $14.8 million, net of underwriting discounts and offering expenses. In October 2017, the Company entered into a sales agreement (the “Sales Agreement”) with Leerink Partners LLC ("Leerink"), pursuant to which the Company may sell up to $30 million in shares of its common stock from time to time through Leerink, acting as its sales agent, in one or more at-the-market offerings. Leerink is entitled to receive a commission of 3.0% of the gross proceeds for any shares sold under the Sales Agreement. Gross sales of $0.1 million were made under the Sales Agreement during the year ended December 31, 2017. In December 2017, the Company completed a registered direct offering priced at the market, whereby it sold 1,783,587 shares of common stock and warrants to purchase up to an aggregate of 1,783,587 shares of its common stock at a combined purchase price of $5.325 per share. The Company received gross proceeds of approximately $9.5 million and net proceeds of approximately $8.8 million, net of underwriting discounts and offering expenses. The Company’s primary sources of cash have been proceeds from the issuance and sale of its common stock in public offerings. The Company has not yet commercialized any of its product candidates and cannot be sure if it will ever be able to do so. Even if the Company commercializes one or more of its product candidates, it may not become profitable. The Company’s ability to achieve profitability depends on a number of factors, including its ability to obtain regulatory approval for its product candidates, successfully complete any post-approval regulatory obligations and successfully commercialize its product candidates alone or in partnership. The Company may continue to incur substantial operating losses even if it begins to generate revenues from its product candidates. As of December 31, 2017, the Company had $34.0 million in cash. The Company currently anticipates its cash to be sufficient to fund its anticipated operating cash requirements into the third quarter of 2019. The actual amount of cash that the Company will need to operate is subject to many factors, including, but not limited to, the timing, design and conduct of clinical trials for its product candidates. The Company is dependent upon significant future financing to provide the cash necessary to execute its current operations, including the commercialization of any of its product candidates. The Company’s common stock is listed on the Nasdaq Global Market and trades under the symbol “AXSM”.

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2017
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	Note 2.Summary of Significant Accounting Policies Significant Risks and Uncertainties The Company’s operations are subject to a number of factors that can affect its operating results and financial condition. Such factors include, but are not limited to: the results of clinical testing and trial activities of the Company’s product candidates; the Company’s ability to obtain regulatory approval to market its products, if approved; competition from products manufactured and sold or being developed by other companies; the price of, and demand for, Company products, if approved; the Company’s ability to negotiate favorable licensing or other manufacturing and marketing agreements for its products, if approved; and the Company’s ability to raise additional financing. If the Company does not successfully commercialize any of its product candidates, it will be unable to generate recurring product revenue or achieve and maintain profitability. Use of Estimates Management considers many factors in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. This process may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements if these results differ from historical experience, or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. In preparing these financial statements, management used significant estimates in the following areas, among others: stock‑based compensation expense; the determination of the fair value of the warrant and embedded derivative liabilities; the accounting for research and development costs; and the recoverability of the Company’s net deferred tax assets and related valuation allowance. Prior to being a public company, the Company utilized significant estimates and assumptions in determining the fair value of its common stock. The Company granted stock options at exercise prices not less than the fair market value of its common stock as determined by the board of directors, with input from management. The board of directors determined the estimated fair value of the Company’s common stock based on a number of objective and subjective factors, including external market conditions affecting the biotechnology industry, the prices at which the Company issued convertible notes, and the likelihood of achieving a liquidity event, such as an IPO or sale of the Company. Foreign Currency Translation Expenses denominated in foreign currency are translated into U.S. dollars at the exchange rate on the date the expense is incurred. Assets and liabilities of foreign operations are translated at period-end exchange rates. The effect of exchange rate fluctuations on translating foreign currency into U.S. dollars is included in the Statements of Operations and is not material to the Company’s financial statements. Segment and Geographic Information Operating segments are defined as components of an enterprise for which separate discrete information is available for evaluation by the chief operating decision maker or decision making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business as one operating segment, which is the business of developing novel therapies for the management of CNS disorders. Cash Equivalents The Company considers all highly liquid investments that have maturities of three months or less when acquired to be cash equivalents. Cash equivalents are valued at cost, which approximates their fair value. There were no cash equivalents at December 31, 2017 and 2016. Concentration of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash. The Company maintains its cash at financial institutions, which at times, exceed federally insured limits. At December 31, 2017, the majority of the Company’s cash was held by one financial institution and the amount on deposit was in excess of Federal Deposit Insurance Corporation insurance limits. The Company has not recognized any losses from credit risks on such accounts since inception. The Company believes it is not exposed to significant credit risk on cash. Fair Value of Financial Instruments Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Assets and liabilities that are measured at fair value are reported using a three‑level fair value hierarchy that prioritizes the inputs used to measure fair value. This hierarchy maximizes the use of observable inputs and minimizes the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows: Level 1—Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Inputs other than quoted prices in active markets that are observable for the asset or liability, either directly or indirectly. Level 3—Inputs that are unobservable for the asset or liability. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts reported in the accompanying consolidated financial statements for accounts payable and accrued expenses approximate their respective fair values due to their short‑term maturities. The fair value of the warrant and embedded derivative liabilities are discussed in Note 3, “Fair Value Measurements.” Debt Issuance Costs The Company incurred third‑party costs in connection with the Company’s convertible notes and term loan as described in Note 6 and Note 7, respectively. These costs are classified on the consolidated balance sheet as a direct deduction from the debt liability. The Company amortizes these costs over the term of its debt agreements as interest expense in the consolidated statement of operations. Equipment Equipment consists primarily of computer equipment and is recorded at cost. Equipment is depreciated on a straight‑line basis over its estimated useful life, which the Company estimates to be three years. When equipment is sold or otherwise disposed of, the cost and related accumulated depreciation are removed from the accounts and the resulting gain or loss is included in operating expenses. Research and Development Costs Research and development expenses primarily consist of costs incurred in performing research and development activities, including preclinical studies, clinical trials, manufacturing costs, employee salaries and benefits, stock‑based compensation expense, contract services, including external research and development expenses incurred under arrangements with third parties, such as contract research organizations (“CROs”), facilities costs, overhead costs, depreciation, and other related costs. Generally, research and development costs are expensed as incurred. Nonrefundable advance payments for goods or services that will be used or rendered for future research and development activities are deferred and amortized over the period that the goods are delivered or the related services are performed, subject to an assessment of recoverability. The Company makes estimates of costs incurred in relation to external CROs, and clinical site costs. The Company analyzes the progress of clinical trials, including levels of patient enrollment, invoices received and contracted costs when evaluating the adequacy of the amount expensed and the related prepaid asset and accrued liability. Significant judgments and estimates must be made and used in determining the accrued balance and expense in any accounting period. The Company reviews and accrues CRO expenses and clinical trial study expenses based on work performed and relies upon estimates of those costs applicable to the stage of completion of a study. Accrued CRO costs are subject to revisions as such trials progress to completion. Revisions are charged to expense in the period in which the facts that give rise to the revision become known. With respect to clinical site costs, the financial terms of these agreements are subject to negotiation and vary from contract to contract. Payments under these contracts may be uneven, and depend on factors such as the achievement of certain events, the successful recruitment of patients, the completion of portions of the clinical trial or similar conditions. The objective of our policy is to match the recording of expenses in our financial statements to the actual services received and efforts expended. As such, expense accruals related to clinical site costs are recognized based on our estimate of the degree of completion of the event or events specified in the specific clinical study or trial contract. Income Taxes Income taxes are accounted for under the asset and liability method. Under this method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases, operating losses, and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Valuation allowances are provided if, based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not to be sustained upon examination based on the technical merits of the position as well as consideration of the available facts and circumstances. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. As of December 31, 2017, the Company does not believe any material uncertain tax positions are present. In the event the Company determines that accrual of interest or penalties are necessary in the future, the amount will be presented as a component of income tax expense. Stock‑Based Compensation For stock options issued to employees and members of the Company’s board of directors for their services, the Company estimates the grant date fair value of each option using the Black‑Scholes option pricing model. The Black-Scholes model takes into account the expected volatility of the Company’s common stock, the risk-free interest rate, the estimated life of the option, the closing market price of the Company’s common stock and the exercise price. The estimates utilized in the Black-Scholes calculation involve inherent uncertainties and the application of management judgment. In addition, the Company recognizes expense for equity awards expected to vest and accounts for forfeitures as they occur. For awards subject to service-based vesting conditions, the Company recognizes stock-based compensation expense on a straight-line basis over the requisite service period, which is generally the vesting term. For awards subject to performance-based vesting conditions, the Company recognizes stock-based compensation expense using the accelerated attribution method when it is probable that the performance condition will be achieved. The expense related to the stock-based compensation is recorded within the financial statement line item the grantee’s cash compensation is recorded in. For stock‑based payments issued to non‑employees, compensation expense is determined at the “measurement date,” which is the earlier of (i) the date at which a commitment for performance by the counterparty to earn the equity instrument is reached or (ii) the date at which the counterparty’s performance is complete. The expense is recognized over the vesting period of the award. Until the measurement date is reached, the total amount of compensation expense remains uncertain. The Company records compensation expense based on the fair value of the award at the reporting date. The awards to non‑employees are then revalued, or the total compensation is recalculated based on the then‑current fair value, at each subsequent reporting date. Tax Credit The tax credit represents the receipt of the New York City Biotechnology Tax Credit, or NYC Biotech credit, and receipt by Axsome Therapeutics Australia PTY, LTD, our Australian subsidiary, of the Australia Tax Incentive Credit, related to our research and development expenses incurred for our product candidates. These expenses were incurred in prior periods and therefore the grant income was recorded when the funds were received. Basic and Diluted Net Loss per Common Share Basic net loss per share of common stock is computed by dividing net loss by the weighted average number of shares of common stock outstanding during the period. Diluted net loss per share of common stock includes the effect, if any, from the potential exercise or conversion of securities, such as convertible notes, warrants, and stock options, which would result in the issuance of incremental shares of common stock. As the impact of these items is anti‑dilutive during periods of net loss, there was no difference between basic and diluted net loss per share of common stock for the years ended December 31, 2017, 2016, and 2015. Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842), which supersedes FASB Topic 840, Leases (Topic 840) and provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than twelve months regardless of classification. Leases with a term of twelve months or less will be accounted for similarly to existing guidance for operating leases. The standard will be effective for annual and interim periods beginning after December 15, 2018, with early adoption permitted upon issuance. The Company is currently evaluating the potential impact of the new guidance. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) – Classification of Certain Cash Receipts and Cash Payments, which is guidance to address diversity in practice with respect to how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The updated guidance addresses eight specific cash flow issues with the objective of reducing the existing diversity that occurs in practice. The guidance is effective for annual and interim periods beginning after December 15, 2017. The Company will adopt this guidance effective January 1, 2018 and the adoption of the guidance is not anticipated to have a material impact on the Company’s financial statements. In May 2017, the FASB issued No. ASU 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting. ASU 2017-09 provides clarity and reduces both (1) diversity in practice and (2) cost and complexity when applying the guidance in Topic 718, to a change to the terms or conditions of a share-based payment award. The amendments in ASU 2017-09 should be applied prospectively to an award modified on or after the adoption date. This ASU is effective for fiscal years beginning after December 15, 2017, including interim periods within those years. The Company will adopt this guidance effective January 1, 2018 and the adoption of the guidance is not anticipated to have a material impact on the Company’s financial statements.

Fair Value Measurements

12 Months Ended

Dec. 31, 2017

Fair Value Measurements

Fair Value Measurements

Note 3.Fair Value Measurements

2017 Warrants associated with Registered Direct Offering

In accordance with ASC820, Fair Value Measurements and Disclosures, financial instruments were measured at fair value using a three-level hierarchy which maximizes use of observable inputs and minimizes use of unobservable inputs:

Level 1—Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

Level 2—Inputs other than quoted prices in active markets that are observable for the asset or liability, either directly or indirectly.

Level 3—Inputs that are unobservable for the asset or liability.

In connection with the Company’s December 4, 2017 registered direct offering (the “Registered Direct Offering”), the Company issued common stock warrants (“Common Warrants”) to certain investors to purchase an aggregate of 1,783,587 shares of its common stock. The Common Warrants are exercisable at $5.25 per share and expire on December 11, 2018. Additionally, as part of the Registered Direct Offering, the Company issued warrants (the “Placement Agent Warrants’) to certain investors affiliated with H.C. Wainwright & Co., LLC, the placement agent in the Registered Direct Offering to purchase an aggregate of 107,015 shares of its common stock. The Placement Agent Warrants are exercisable at $6.6562 and expire on December 11, 2018. The Common Warrants and Placement Agent Warrants were analyzed and it was determined that they require liability treatment. Under ASC 815, registered common stock warrants that require the issuance of registered shares upon exercise and do not expressly preclude an implied right to cash settlement are accounted for as derivative liabilities. The Company classifies these derivative warrant liabilities on the consolidated balance sheet as a current liability.

The fair value of the Common Warrants at December 4, 2017, the date these warrants were issued, and December 31, 2017 were determined to be approximately $2,064,000 and $2,683,000, respectively, as calculated using Black-Scholes with the following assumptions: (1) stock price of $5.00 and $5.60, respectively; (2) a risk-free rate of 1.66% and 1.76%, respectively; and (3) an expected volatility of 61% and 62%, respectively. The fair value of the Common Warrants were reported as a warrant liability on the balance sheet and the change in the fair value between December 4, 2017 and December 31, 2017 is reported as a change in fair value of the warrant liability on the statement of operations.

The fair value of the Placement Agent Warrants at December 4, 2017, the date these warrants were issued, and December 31, 2017 were determined to be approximately $81,000 and $108,000, respectively, as calculated using Black-Scholes with the following assumptions: (1) stock price of $5.00 and $5.60, respectively; (2) a risk-free rate of 1.66% and 1.76%, respectively; and (3) an expected volatility of 61% and 62%, respectively. The fair value of the Placement Agent Warrants were reported as a warrant liability on the balance sheet and the change in the fair value between December 4, 2017 and December 31, 2017 is reported as a change in fair value of the warrant liability on the statement of operations.

Level 3 Fair Value Sensitivity

Warrant liability

As of December 31, 2017, the fair value of the warrant liability utilizes inputs including: share price, expected volatility and risk-free rate.

A 10% plus/minus change in share price will result in an estimated increase/decrease of $0.7 million in the value of the warrant liability,

A 10% plus/minus change in the expected volatility will result in an estimated increase/decrease of $0.2 million in the value of the warrant liability, and

A 10% plus/minus change in the risk-free interest rate will result in an immaterial change in the value of the warrant liability.

There were no financial liabilities measured at fair value on a recurring basis as of December 31, 2016 and 2015.

The following table sets forth a summary of changes in the fair value of Level 3 liabilities for the years ended December 31, 2017, 2016, and 2015:



December 31, 2017	Beginning of period		Issuances		Change in fair value (3)		Extinguishments		End of period
Warrant liability	$	—	$	2,145,000	$	646,000	$	—	$	2,791,000
Embedded derivative liabilities		—		—		—		—		—
Total	$	—	$	2,145,000	$	646,000	$	—	$	2,791,000

December 31, 2016	Beginning of period		Issuances		Change in fair value (3)		Extinguishments		End of period
Warrant liability	$	—	$	—	$	—	$	—	$	—
Embedded derivative liabilities		—		—		—		—		—
Total	$	—	$	—	$	—	$	—	$	—


December 31, 2015	Beginning of period		Issuances		Change in fair value (3)		Extinguishments		End of period
Warrant liability (1)	$	136,235	$	—	$	108,539	$	(244,774)	$	—
Embedded derivative liabilities (2)		496,400		871,000		(274,800)		(1,092,600)		—
Total	$	632,635	$	871,000	$	(166,261)	$	(1,337,374)	$	—

(1) Prior to the close of the Company’s IPO on November 24, 2015, the Company considered its convertible note related warrant liability as a Level 3 financial instrument. On the grant date and in subsequent periods, the Company estimated the fair value of the warrant liability using the Black‑Scholes option pricing model, which requires inputs such as the expected volatility based on comparable public companies, the estimated fair value of the common stock, and the estimated time to liquidity. The Company determined the fair value of the liability immediately prior to the Company’s IPO and then reclassified the balance to additional paid-in capital upon the closing of the IPO. Immediately prior to the close of the Company’s IPO, the following inputs were used for the warrant liability:


	Immediately prior to close of IPO

Expected volatility based on comparable public companies		70	%
Estimated fair value of the common stock	$	9.20
Remaining contractual term		4 years

(2) Prior to the amendment of the Company’s outstanding convertible notes in September 2015, the Company considered its convertible note related embedded derivative liabilities as Level 3 financial instruments. The fair value of the embedded derivative liabilities related to the Company’s outstanding convertible notes was estimated on the grant date and at each reporting period using a probability weighted estimated returns method, which incorporated the “with‑and‑without” method to bifurcate the embedded derivatives. The amendment was deemed to be a substantive change and resulted in extinguishment accounting, which included the extinguishment of the embedded derivative liabilities. The Company used three different exit scenarios in valuing the embedded derivative liabilities: an initial public offering, a private equity financing, and a liquidation. A Monte Carlo simulation was run for the exit scenario immediately prior to the effective date of the note amendment, with the following inputs:


	Immediately prior to
	note amendment

Expected volatility based on comparable public companies	70	%
Estimated time to liquidity	0.1 - 0.2 years

(3) The change in the fair values of the warrant and embedded derivative liabilities are recorded in the statements of operations.

- Definition

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

+ References + Details

Net Loss per Common Share

12 Months Ended

Dec. 31, 2017

Net Loss per Common Share

Net Loss per Common Share

Note 4.Net Loss per Common Share

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


	Year ended December 31,
	2017		2016		2015

Basic and diluted net loss per common share:
Net loss	$	(28,943,392)	$	(27,201,653)	$	(12,210,579)
Weighted average common shares outstanding—basic and diluted		22,764,606		19,150,690		11,945,318
Net loss per common share—basic and diluted	$	(1.27)	$	(1.42)	$	(1.02)

The following potentially dilutive securities outstanding at December 31, 2017, 2016, and 2015 have been excluded from the computation of diluted weighted average shares outstanding, as they would be anti‑dilutive:


	December 31,
	2017	2016	2015

Stock options	2,315,638	1,772,050	998,198
Warrants	2,099,149	337,696	272,468
	4,414,787	2,109,746	1,270,666

Convertible Notes	12 Months Ended
Convertible Notes	Dec. 31, 2017
Debt Disclosure [Abstract]
Convertible Notes	Note 6.Convertible Notes During March 2013, the Company issued a total of $211,000 in convertible notes (“March 2013 Notes”) to several investors. The March 2013 Notes accrued interest at an annual rate of 8.0% and were due and payable one year from the date of issuance. The principal and accrued interest were convertible into shares of the Company’s common stock at the option of the holder, upon the occurrence of a qualified financing, as defined in the March 2013 Notes, immediately prior to the closing of a change in control event, or on the maturity date. In March 2014, all outstanding March 2013 Notes and related accrued interest converted into 175,228 shares of common stock at a conversion price of $1.30 per share. During the period from June through October 2013, the Company issued a total of $3,904,000 in convertible notes to several investors (“June 2013 Notes”). The June 2013 Notes accrued interest at an annual rate of 8.0% and were due and payable one year from the date of issuance. The principal and accrued interest were convertible into shares of the Company’s common stock at the option of the holder, or upon the occurrence of a qualified financing, as defined in the June 2013 Notes, in which the conversion price would be equal to the lesser of (i) 90% of the lowest price per share at which the Company’s shares of equity securities were sold or (ii) $1.30, as adjusted for capitalization change. The Company recorded an initial discount on the June 2013 Notes of $339,735 for fees paid directly to the placement agent. In June 2014, the Company and the holders of the June 2013 Notes amended the June 2013 Notes pursuant to which the June 2013 Notes and any accrued and unpaid interest would convert into shares of the Company’s common stock on the due date at a conversion price of $1.30 (see further discussions in “—Accounting Analysis” below). In accordance with this amendment, during the period from June 2014 through October 2014, all of the outstanding balance of the June 2013 Notes and accrued and unpaid interest converted into 3,242,344 shares of common stock. During the period from September 2014 through November 2014, the Company issued a total of $4,140,000 in convertible notes to several investors (“September 2014 Notes”). The September 2014 Notes accrued interest at an annual rate of 8.0% and were due and payable ten years from the date of issuance. The principal and accrued interest were convertible into shares of the Company’s common stock upon the occurrence of a qualified financing, as defined in the September 2014 Notes, in which the conversion price would be equal to the lesser of (i) 75% of the lowest price per share at which the Company's shares of equity securities are sold (see further discussions in “—Accounting Analysis” below), or (ii) $5.40, as adjusted for capitalization change. The Company’s IPO in November 2015 met the definition of a qualified financing, and upon the close of the IPO all of the outstanding balance of the September 2014 Notes and accrued and unpaid interest converted into 836,202 shares of common stock. During the period from December 2014 through January 2015, the Company issued a total of $1,570,000 in convertible notes to several investors (“December 2014 Notes”). The December 2014 Notes accrued interest at an annual rate of 8.0% and were due and payable ten years from the date of issuance. The principal and accrued interest were convertible into shares of the Company’s common stock upon the occurrence of a qualified financing, as defined in the December 2014 Notes, in which the conversion price would be equal to the lesser of (i) 75% of the lowest price per share at which the Company's shares of equity securities are sold (see further discussions in “—Accounting Analysis” below), or (ii) $5.94, as adjusted for capitalization change. The Company’s IPO in November 2015 met the definition of a qualified financing, and upon the close of the IPO all of the outstanding balance of the December 2014 Notes and accrued and unpaid interest converted into 283,131 shares of common stock. During the period from May 2015 through July 2015, the Company issued a total of $7,166,469 in convertible notes (“2015 Notes”). The 2015 Notes accrued interest at an annual rate of 8.0% and were due and payable ten years from the date of issuance. The principal and accrued interest were convertible into shares of the Company’s common stock upon the occurrence of a qualified financing, as defined in the 2015 Notes, in which the conversion price would be equal to the lesser of (i) 75% of the lowest price per share at which the Company's shares of equity securities are sold (see further discussions in “—Accounting Analysis” below), or (ii) $5.94, as adjusted for capitalization change. The Company’s IPO in November 2015 met the definition of a qualified financing, and upon the close of the IPO all of the outstanding balance of the 2015 Notes and accrued and unpaid interest converted into 1,255,273 shares of common stock. In September 2015, the Company and the holders of its outstanding convertible notes amended the terms of the September 2014 Notes, December 2014 Notes, and 2015 Notes to provide that the principal and any accrued and unpaid interest would automatically convert into shares of the Company’s common stock upon the occurrence of an equity financing of at least $2.0 million in gross aggregate cash proceeds at a conversion price equal to the applicable fixed conversion price for the notes; provided, however, if the lowest price per share at which the shares of equity securities were sold in such equity financing is less than the applicable fixed conversion price, then the note conversion price would equal 75% of the lowest price per share at which the shares of equity securities are sold (see further discussions in “—Accounting Analysis” below). Accounting Analysis The June 2014 amendment of the June 2013 Notes, pursuant to which the June 2013 Notes plus any accrued and unpaid interest automatically converted into shares of the Company’s common stock on the due date, was considered substantive. As such, the June 2013 Notes were considered extinguished, and the amended notes were recorded at fair value. The difference between the fair value of the amended notes of $6,691,000, which was measured using the backsolve method, and the carrying value of the extinguished notes of $3,820,097 was recorded as a loss on extinguishment of debt in the Company’s consolidated financial statements. The difference between the fair value and the face value of the amended notes was recorded as a premium to the notes and amortized over the remaining life of the notes. The amortization of the premium is included in interest and amortization of debt discount/premium (expense) income in the consolidated statements of operations. The September 2014 Notes, December 2014 Notes, and 2015 Notes each included a redemption provision, which is an embedded derivative. These embedded derivatives required bifurcation from the host debt instrument. The Company aggregated these bifurcated features and reflected the values of these embedded derivatives in the account “embedded derivative liabilities” that was re‑measured at each reporting period and any changes in fair value was recognized in the consolidated statements of operations. See Note 3, “Fair Value Measurements.” The September 2015 amendment to the September 2014 Notes, December 2014 Notes, and 2015 Notes amended the conversion provision, which was considered substantive. As such, the September 2014 Notes, December 2014 Notes, and 2015 Notes were considered extinguished, and the amended notes were recorded at fair value. The difference between the fair value of the amended notes of $15,146,410 and the carrying value of the extinguished notes of $12,701,894 was recorded as a loss on extinguishment of debt in the Company’s consolidated financial statements. No convertible notes were outstanding as of December 31, 2017, 2016 and 2015.

Loan and Security Agreement

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Loan and Security Agreement

Note 7.Loan and Security Agreement

In November 2016, the Company entered into a $20.0 million Term Loan Agreement (“Term Loan”) with SVB. The three-tranche Term Loan consists of an initial $10.0 million tranche triggered upon closing, with the remaining $10.0 million available to be drawn in two $5.0 million tranches, at the Company’s option, subject to the achievement of certain clinical and financial milestones.

The loan bears interest at an annual rate equal to 4.50% plus the prime rate, which is the greater of 3.50% or the Wall Street Journal prime rate, and is payable monthly. It matures in November 2020 and has an interest-only payment period until December 1,2017, which may be extended to May 2018 upon the drawing of the second tranche. Following the interest only payment period, the Company will begin making monthly payments of principal and interest until the maturity date. Principal payments coming due within twelve months have been classified as current liabilities in the accompanying balance sheet. In addition, the Company is required to pay a final payment fee of 8.5% of the principal amount extended on the date of repayment of the Term Loan, which is being accreted and amortized into interest expense using the effective interest rate method over the term of the loan. Because the Company did not achieve the conditional criteria to access the second and third term advances before the specified dates, the $10.0 million in additional term loan advances expired and the Company began to repay principal in December 2017.

The Company may prepay all, but not less than all, of the Term Loan subject to a prepayment premium of 3.0% of the outstanding principal if prepaid within two years of the effective date of the loan, 2.0% of the outstanding principal if prepaid during the third year of the loan, and 1.0% of the outstanding principal if prepaid after the third year. The Term Loan is collateralized by a security interest in all of the Company’s assets except intellectual property. The Company’s intellectual property is subject to a negative pledge.

Interest expense was $869,678 and $116,736 and amortization of the final payment was $346,978 and $49,781 for the years ended December 31, 2017 and 2016, respectively.

Long-term debt and unamortized debt discount balances are as follows:


	December 31,
	2017

Long-term debt	$	9,722,222
Less debt discount, net of current portion		274,116
Long-term debt, net of debt discount		9,996,338
Less current portion of long-term debt		(3,333,333)
Loan payable, long-term	$	6,663,005
Current portion of long-term debt		3,333,333
Current portion of debt discount		(63,987)
Loan payable, current portion	$	3,269,346

In connection with the Term Loan, SVB and Life Science Loans, LLC (“the lenders”) received warrants to purchase an aggregate 65,228 shares of the Company’s common stock at an exercise price of $7.41 per share, which are exercisable for seven years from the date of issuance.

The proceeds of $10.0 million were allocated based on the relative fair values of the debt instrument and the warrant instrument. The fair value of the warrants and the closing costs were recorded as debt discounts and are being amortized using the effective interest rate method over the term of the loan. Amortization of the debt discount was $123,543 and $19,149 for the years ended December 31, 2017 and 2016, respectively.

Scheduled principal payments on outstanding debt, as of December 31, 2017, are as follows:


2018	$	3,333,333
2019		3,333,333
2020		3,055,556
	$	9,722,222

Stockholders' Equity

12 Months Ended

Dec. 31, 2017

Stockholders? Equity

Stockholders? Equity

Note 8. Stockholders’ Equity

Capital Structure

As of December 31, 2014, the Company was authorized to issue 14,689,000 shares of common stock at $0.0001 par value per share. In April 2015, the Company’s board of directors and stockholders approved an increase of the Company’s authorized shares of common stock to 22,033,500 shares. In connection with the close of the Company’s IPO on November 24, 2015, the Company’s stockholders approved an amended and restated certificate of incorporation increasing the number of authorized shares of common stock to 150,000,000 and the number of authorized shares of preferred stock to 10,000,000, par value $0.0001 per share.

In November 2015, the Company completed its IPO, whereby it sold 5,666,667 shares of common stock at a public offering price of $9.00 per share. The Company received gross proceeds of approximately $51.0 million and net proceeds of approximately $45.5 million, after deducting underwriting discounts and commissions and offering-related transaction costs.

In March 2017, the Company completed an underwritten public offering, whereby it sold 4,304,813 shares of common stock at a public offering price of $3.74 per share. The Company received gross proceeds of approximately $16.1 million and net proceeds of approximately $14.8 million, net of underwriting discounts and offering expenses.

In October 2017, the Company entered into the Sales Agreement with Leerink , pursuant to which the Company may sell up to $30 million in shares of its common stock from time to time through Leerink, acting as its sales agent, in one or more at-the-market offerings. Leerink is entitled to receive a commission of 3.0% of the gross proceeds for any shares sold under the Sales Agreement. Gross sales of $0.1 million were made under the Sales Agreement during the year ended December 31, 2017.

In December 2017, the Company completed the Registered Direct Offering, whereby it sold an aggregate of $9.5 million worth of units (“Units”) at a purchase price of $5.325 per Unit with each Unit consisting of (i) one share of the Company’s common stock, and (ii) a Common Warrant at an exercise price equal to $5.25 per share. The Company sold an aggregate of 1,783,587 Units for gross proceeds of approximately $9.5 million and net proceeds of approximately $8.8 million, net of underwriting discounts and offering expenses. Additionally, the Company issued 107,015 Placement Agent Warrants. The Company incurred issuance costs associated with the Units offering of $745,856, which included $81,000 related to issuance of 107,015 Placement Agent Warrants, of which, $583,768 was allocated to the common stock sold and was recorded as a reduction to equity. The remaining amount was allocated to the Common Warrants and was expensed. The Placement Agent Warrants have the same terms as the Common Warrants, except for the exercise price of $6.6562 per share.

Each of the warrants issued in December 2017, in connection with the Registered Direct Offering are liabilities pursuant to ASC 815 as registered common stock warrants that require the issuance of registered shares upon exercise and do not expressly preclude an implied right to cash settlement are accounted for as derivative liabilities. The Company classifies these derivative warrant liabilities on the consolidated balance sheet as a current liability. The initial fair value of the Common Warrants and Placement Agent Warrants was estimated to be approximately $2,145,000 and was deducted from the gross proceeds of the Unit offering with the residual amount recorded to equity.

The holders of shares of common stock are entitled to one vote for each share of common stock held at all meetings of stockholders and written actions in lieu of meetings. The holders of shares of common stock are entitled to receive dividends, if and when declared by the board of directors.

Shelf Registration Statement

On December 1, 2016, the Company filed a shelf registration statement with the Securities and Exchange Commission (“SEC”) for the issuance of common stock, preferred stock, warrants, rights, debt securities and units up to an aggregate amount of $150.0 million, which the Company refers to as the 2016 Shelf Registration Statement. On December 16, 2016, the 2016 Shelf Registration Statement was declared effective by the SEC. The Company completed an offering of common stock in March 2017, entered into a sales agreement in October 2017 pursuant to which the Company may sell shares of its common stock from time to time in an at-the-market offering and sold shares of its common stock and warrants (as described above) in the Registered Direct Offering priced at the market in December 2017 utilizing the 2016 Shelf Registration Statement. In the future, the Company may also periodically offer one or more of these securities in amounts, prices and terms to be announced when and if the securities are offered. At the time any of the securities covered by the 2016 Shelf Registration Statement are offered for sale, a prospectus supplement will be prepared and filed with the SEC containing specific information about the terms of any such offering.

Equity Incentive Plans

The Company had granted stock options under its 2013 Equity Compensation Plan (the "2013 Plan"), which was adopted for employees and consultants for the purpose of advancing the interests of the Company's stockholders by enhancing its ability to attract, retain and motivate persons who are expected to make important contributions to the Company. In November 2015, the 2015 Omnibus Incentive Compensation Plan (the “2015 Plan”) was adopted by the Company’s stockholders. The 2015 Plan is the successor to the Company's 2013 Plan. In conjunction with the adoption of the 2015 Plan, no additional grants were made from the 2013 Plan and options from the 2013 Plan remain outstanding. As of December 31, 2017, there were 2,852,551 shares available for future grant under the 2015 Plan.

Stock Options

The following table summarizes stock option activity as of December 31, 2017:


				Weighted
		Weighted		average	Aggregate
	Number	average		contractual	intrinsic
	of shares	exercise price		term	value
Outstanding at December 31, 2016	1,772,050	$	5.74
Granted	847,510		5.24
Exercised	(88,922)		3.56
Forfeited	(101,497)		6.69
Expired	(113,503)		6.30
Outstanding at December 31, 2017	2,315,638	$	5.57	8.2	$	2,385,761
Vested and expected to vest at December 31, 2017	2,309,469	$	5.58	8.2	$	2,359,235
Exercisable at December 31, 2017	1,190,135	$	4.78	7.5	$	2,042,324

The fair value of each stock option grant is estimated on the date of grant using the Black‑Scholes option pricing model. The Company periodically remeasures the fair value of stock‑based awards issued to non‑employees and records the expense over the requisite service period. The expected term of the Company’s stock options has been determined utilizing the “simplified” method as described in the SEC’s Staff Accounting Bulletin No. 107 relating to stock‑based compensation. The simplified method was chosen because the Company has limited historical option exercise experience due to its short operating history. The risk‑free interest rate is based on the U.S. Treasury yield in effect at the time of grant for a period approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future. Expected volatility is based on historical volatilities of similar entities within the Company’s industry which were commensurate with the Company’s expected term assumption. The relevant data used to determine the value of the stock option grants for the years ended December 31, 2017, 2016 and 2015 is as follows:


Black-Scholes option valuation assumptions	2017				2016				2015

Risk-free interest rates	1.6	-	2.2	%	0.9	-	2.0	%	0.7	-	1.9	%
Dividend yield		—				—				—
Volatility	73	-	77	%	69	-	75	%	67	-	71	%
Weighted average expected term	3.50	-	6.12	years	3.25	-	6.25	years	2.5	-	6	years

The weighted average valuation date fair value of options granted was $3.06, $5.13, and $4.21 per option for the years ended December 31, 2017, 2016 and 2015, respectively. As of December 31, 2017, there was $4.1 million of total unrecognized compensation cost related to non‑vested stock options which is expected to be recognized over a weighted average period of 2.7 years. These amounts do not include 47,153 options outstanding as of December 31, 2017, which are performance‑based and vest upon the achievement of certain corporate milestones. Stock‑based compensation will be measured and recorded if and when it is probable that the milestone will occur.

Stock‑based compensation expense recognized for the years ended December 31, 2017, 2016 and 2015 was as follows:



	2017		2016		2015
Research and development	$	613,629	$	1,115,626	$	622,901
General and administrative		1,458,581		915,792		180,378
	$	2,072,210	$	2,031,418	$	803,279

Performance‑Based Awards

During the year ended December 31, 2017, the Company issued 20,650 performance-based awards, with a weighted average exercise price of $5.70, to employees that vest upon completion of certain clinical events. The Company issued no performance-based awards during the year ended December 31, 2016. During the year ended December 31, 2015, the Company issued 81,346 options with a weighted average exercise price of $6.47, to employees and non‑employees that vest upon the completion of certain clinical and corporate events. For awards granted to employees with performance conditions, no expense will be recognized, and no measurement date can occur, until the occurrence of the event is probable. For awards granted to non‑employees, the Company will recognize the lowest aggregate amount within the range of potential values as expense until the measurement date is established. For the years ended December 31, 2017, 2016, and 2015, the Company recognized $59,424, $604,866, and $283,394, respectively, as expense related to performance‑based awards.

Warrants

12 Months Ended

Dec. 31, 2017

Warrants

Warrants

Note 9. Warrants

As of December 31, 2017, the Company had outstanding warrants to purchase 2,099,149 shares of common stock. The following table summarizes warrant activity as of December 31, 2017, 2016 and 2015:


		Weighted
		average
	Warrants	exercise price
Outstanding at December 31, 2014	230,409	$	1.30
Issued	42,059		5.94
Outstanding at December 31, 2015	272,468		2.02
Issued	65,228		7.41
Outstanding at December 31, 2016	337,696		3.06
Issued	1,890,602		5.33
Exercised	(129,149)		1.30
Outstanding at December 31, 2017	2,099,149	$	5.21

In connection with the the Registered Direct Offering, the Company issued Common Warrants and Placement Agent Warrants to purchase 1,783,587 shares and 107,015 shares of common stock, respectively, with an exercise price of $5.25 per share and $6.6562 per share, respectively, which are exercisable from the date of issuance until December 11, 2018. The Common Warrants and Placement Agent Warrants were classified as warrant liabilitity. See Note 3, “Fair Value Measurements”, for the fair value calculations of the warrant liability.

In connection with the Company’s debt financing which was completed on November 9, 2016, the Company issued warrants to purchase 65,228 shares of common stock with an exercise price of $7.41 per share, which are exercisable upon issuance. The warrants were classified as a component of stockholders' equity.

On November 3, 2014, the Company issued warrants to purchase 42,059 shares of common stock with an exercise price of $5.94 per share to the placement agent in connection with the issuance of the September 2014 Notes, which were exercisable upon issuance. The warrants were initially classified as a liability in the consolidated financial statements, as upon a qualified financing, as defined in the September 2014 Notes, the warrant price would automatically adjust to a 10% premium to the conversion price of the September 2014 Notes in such mandatory conversion. The initial fair value of the warrant liability was $79,129 which was recorded as a discount to the notes and amortized over the term of the original September 2014 Notes. Upon the note amendment that occurred in September 2015, the discount was included in the carrying amount in the calculation of a loss on extinguishment. In connection with the automatic conversion of the September 2014 Notes upon the close of the Company’s IPO in November 2015, the warrant liability was reclassified to equity. See Note 3, “Fair Value Measurements”, for the fair value calculations of the warrant liability.

On October 29, 2013, the Company issued warrants to purchase 230,409 shares of common stock with an exercise price of $1.30 per share to the placement agent in connection with the June 2013 Notes, which were exercisable upon issuance. The warrants were classified as a component of stockholders’ equity.

The value of the warrants issued in 2016 of $264,365 was determined using the Black-Scholes option-pricing model with the following assumptions:


Black-Scholes option valuation assumptions	2016
Risk-free interest rate	1.8	%
Dividend yield	—
Volatility	73	%
Weighted average contractual term	7 years

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Taxes

Income Taxes

Note 12. Income Taxes

As of December 31, 2017, the Company had U.S. net operating loss (“NOL”) carryforwards of $61 million, which will expire beginning in 2033. The NOL carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. NOL carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders, as defined under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended, as well as similar state tax provisions. This could limit the amount of NOLs that the Company can utilize annually to offset future taxable income or tax liabilities.

The components of the Company’s deferred tax assets are as follows:


	December 31, 2017		December 31, 2016
Deferred tax assets:
Net federal operating loss carryforward	$	12,844,032	$	12,747,837
Net foreign operating loss carryforward		49,846		23,293
Net state operating loss carryforward		7,981,812		4,068,086
Non-cash compensation		1,719,315		1,450,620
Research and development credits		5,713,709		3,491,251
Deferred finance costs		44,042		—
Fixed Assets		2,597		—
Accrued expenses		472,004		308,007
Deferred tax asset, excluding valuation allowance		28,827,357		22,089,094
Fixed Assets		—		(19,985)
Less valuation allowance		(28,827,357)		(22,069,109)
Net deferred tax assets	$	—	$	—

The Company records a valuation allowance to reduce the deferred tax assets reported if, based on the weight of available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. After consideration of all the evidence, both positive and negative, the Company has recorded a full valuation allowance against its deferred tax assets at December 31, 2017 and 2016 because the Company’s management has determined that it is more likely than not that these assets will not be realized. The valuation allowance for deferred tax assets was $7,756,147 as of December 31, 2015.

A reconciliation of income tax expense (benefit) at the statutory federal income tax rate and income taxes as reflected in the consolidated financial statements is as follows:


	December 31, 2017		December 31, 2016
U.S. federal statutory income tax rate	34.0	%	34.0	%
State taxes, net of federal benefit	10.0		9.4
Permanent differences	(2.9)		(3.7)
Tax credit	7.7		12.8
US Federal tax rate change - tax reform	(25.4)		—
Change in valuation allowance	(23.4)		(52.5)
Other	—		—
Effective tax rate	—	%	—	%

The Company is not currently under examination at the federal or state levels and as of the date of the consolidated financial statements there were no known assessments.

Impact of U.S. Tax Reform

On December 22, 2017, the U.S. President signed the Tax Cuts and Jobs Act (the “Act”) into law. Effective January 1, 2018, among other changes, the Act (1) reduces the Company’s U.S. federal corporate tax rate from 34 percent to 21 percent, (2) changes the rules relating to net operating loss ("NOL") carryforwards and carrybacks, (3) eliminates the corporate alternative minimum tax ("AMT") and changes how existing AMT credits can be realized; and (4) requires companies to pay a one-time transition tax on certain unrepatriated earnings of foreign subsidiaries. The impact on the Company's financial statements for the period ended December 31, 2017 is immaterial, primarily because the Company has a valuation allowance on deferred tax assets in the U.S. In addition, the Act makes the AMT credit refundable in tax years beginning after 2017.

The SEC staff issued Staff Accounting Bulletin ("SAB") 118, which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provides a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under Accounting Standards Codification (ASC) 740. In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the Tax Act for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for certain income tax effects of the Tax Act is incomplete but it is able to determine a reasonable estimate, it must record a provisional estimate in the financial statements. If a company cannot determine a provisional estimate to be included in the financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the Tax Act.

The Tax Act did not have a material impact on our financial statements since our deferred temporary differences in the United States are fully offset by a valuation allowance and we do not have any significant off shore earnings from which to record the mandatory transition tax.

Quarterly Consolidated Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2017

Quarterly Consolidated Financial Data (Unaudited)

Quarterly Consolidated Financial Data (Unaudited)

Note 14. Quarterly Consolidated Financial Data (Unaudited)


	2017
	Mar. 31		June 30		Sept. 30		Dec. 31

Total operating expenses	$	7,672,033	$	6,750,738	$	6,297,416	$	6,444,120
Net loss	$	(7,995,039)	$	(7,084,316)	$	(6,433,536)	$	(7,430,501)
Net loss per common share, basic and diluted (1)	$	(0.41)	$	(0.30)	$	(0.27)	$	(0.31)

	2016
	Mar. 31		June 30		Sept. 30		Dec. 31

Total operating expenses	$	5,882,865	$	6,827,280	$	7,207,803	$	7,625,560
Net loss	$	(5,865,941)	$	(6,812,190)	$	(7,194,584)	$	(7,328,938)
Net loss per common share, basic and diluted (1)	$	(0.31)	$	(0.36)	$	(0.38)	$	(0.38)

(1)

Basic and diluted net loss per common share is computed independently for each of the quarters presented. Therefore, the sum of all quarterly basic and fully diluted net loss per common share may not equal the annual basic and diluted net loss per common share.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2017
Summary of Significant Accounting Policies
Significant Risks and Uncertainties	Significant Risks and Uncertainties The Company’s operations are subject to a number of factors that can affect its operating results and financial condition. Such factors include, but are not limited to: the results of clinical testing and trial activities of the Company’s product candidates; the Company’s ability to obtain regulatory approval to market its products, if approved; competition from products manufactured and sold or being developed by other companies; the price of, and demand for, Company products, if approved; the Company’s ability to negotiate favorable licensing or other manufacturing and marketing agreements for its products, if approved; and the Company’s ability to raise additional financing. If the Company does not successfully commercialize any of its product candidates, it will be unable to generate recurring product revenue or achieve and maintain profitability.
Use of Estimates	Use of Estimates Management considers many factors in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes and management must select an amount that falls within that range of reasonable estimates. This process may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements if these results differ from historical experience, or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. In preparing these financial statements, management used significant estimates in the following areas, among others: stock‑based compensation expense; the determination of the fair value of the warrant and embedded derivative liabilities; the accounting for research and development costs; and the recoverability of the Company’s net deferred tax assets and related valuation allowance. Prior to being a public company, the Company utilized significant estimates and assumptions in determining the fair value of its common stock. The Company granted stock options at exercise prices not less than the fair market value of its common stock as determined by the board of directors, with input from management. The board of directors determined the estimated fair value of the Company’s common stock based on a number of objective and subjective factors, including external market conditions affecting the biotechnology industry, the prices at which the Company issued convertible notes, and the likelihood of achieving a liquidity event, such as an IPO or sale of the Company.
Foreign Currency Translation	Foreign Currency Translation Expenses denominated in foreign currency are translated into U.S. dollars at the exchange rate on the date the expense is incurred. Assets and liabilities of foreign operations are translated at period-end exchange rates. The effect of exchange rate fluctuations on translating foreign currency into U.S. dollars is included in the Statements of Operations and is not material to the Company’s financial statements.
Segment and Geographic Information	Segment and Geographic Information Operating segments are defined as components of an enterprise for which separate discrete information is available for evaluation by the chief operating decision maker or decision making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business as one operating segment, which is the business of developing novel therapies for the management of CNS disorders.
Cash Equivalents	Cash Equivalents The Company considers all highly liquid investments that have maturities of three months or less when acquired to be cash equivalents. Cash equivalents are valued at cost, which approximates their fair value. There were no cash equivalents at December 31, 2017 and 2016.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash. The Company maintains its cash at financial institutions, which at times, exceed federally insured limits. At December 31, 2017, the majority of the Company’s cash was held by one financial institution and the amount on deposit was in excess of Federal Deposit Insurance Corporation insurance limits. The Company has not recognized any losses from credit risks on such accounts since inception. The Company believes it is not exposed to significant credit risk on cash.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Assets and liabilities that are measured at fair value are reported using a three‑level fair value hierarchy that prioritizes the inputs used to measure fair value. This hierarchy maximizes the use of observable inputs and minimizes the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows: Level 1—Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Inputs other than quoted prices in active markets that are observable for the asset or liability, either directly or indirectly. Level 3—Inputs that are unobservable for the asset or liability. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts reported in the accompanying consolidated financial statements for accounts payable and accrued expenses approximate their respective fair values due to their short‑term maturities. The fair value of the warrant and embedded derivative liabilities are discussed in Note 3, “Fair Value Measurements.”
Debt Issuance Costs	Debt Issuance Costs The Company incurred third‑party costs in connection with the Company’s convertible notes and term loan as described in Note 6 and Note 7, respectively. These costs are classified on the consolidated balance sheet as a direct deduction from the debt liability. The Company amortizes these costs over the term of its debt agreements as interest expense in the consolidated statement of operations.
Equipment	Equipment Equipment consists primarily of computer equipment and is recorded at cost. Equipment is depreciated on a straight‑line basis over its estimated useful life, which the Company estimates to be three years. When equipment is sold or otherwise disposed of, the cost and related accumulated depreciation are removed from the accounts and the resulting gain or loss is included in operating expenses.
Research and Development Costs	Research and Development Costs Research and development expenses primarily consist of costs incurred in performing research and development activities, including preclinical studies, clinical trials, manufacturing costs, employee salaries and benefits, stock‑based compensation expense, contract services, including external research and development expenses incurred under arrangements with third parties, such as contract research organizations (“CROs”), facilities costs, overhead costs, depreciation, and other related costs. Generally, research and development costs are expensed as incurred. Nonrefundable advance payments for goods or services that will be used or rendered for future research and development activities are deferred and amortized over the period that the goods are delivered or the related services are performed, subject to an assessment of recoverability. The Company makes estimates of costs incurred in relation to external CROs, and clinical site costs. The Company analyzes the progress of clinical trials, including levels of patient enrollment, invoices received and contracted costs when evaluating the adequacy of the amount expensed and the related prepaid asset and accrued liability. Significant judgments and estimates must be made and used in determining the accrued balance and expense in any accounting period. The Company reviews and accrues CRO expenses and clinical trial study expenses based on work performed and relies upon estimates of those costs applicable to the stage of completion of a study. Accrued CRO costs are subject to revisions as such trials progress to completion. Revisions are charged to expense in the period in which the facts that give rise to the revision become known. With respect to clinical site costs, the financial terms of these agreements are subject to negotiation and vary from contract to contract. Payments under these contracts may be uneven, and depend on factors such as the achievement of certain events, the successful recruitment of patients, the completion of portions of the clinical trial or similar conditions. The objective of our policy is to match the recording of expenses in our financial statements to the actual services received and efforts expended. As such, expense accruals related to clinical site costs are recognized based on our estimate of the degree of completion of the event or events specified in the specific clinical study or trial contract.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Under this method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to the differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases, operating losses, and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Valuation allowances are provided if, based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not to be sustained upon examination based on the technical merits of the position as well as consideration of the available facts and circumstances. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. As of December 31, 2017, the Company does not believe any material uncertain tax positions are present. In the event the Company determines that accrual of interest or penalties are necessary in the future, the amount will be presented as a component of income tax expense.
Stock Based Compensation	Stock‑Based Compensation For stock options issued to employees and members of the Company’s board of directors for their services, the Company estimates the grant date fair value of each option using the Black‑Scholes option pricing model. The Black-Scholes model takes into account the expected volatility of the Company’s common stock, the risk-free interest rate, the estimated life of the option, the closing market price of the Company’s common stock and the exercise price. The estimates utilized in the Black-Scholes calculation involve inherent uncertainties and the application of management judgment. In addition, the Company recognizes expense for equity awards expected to vest and accounts for forfeitures as they occur. For awards subject to service-based vesting conditions, the Company recognizes stock-based compensation expense on a straight-line basis over the requisite service period, which is generally the vesting term. For awards subject to performance-based vesting conditions, the Company recognizes stock-based compensation expense using the accelerated attribution method when it is probable that the performance condition will be achieved. The expense related to the stock-based compensation is recorded within the financial statement line item the grantee’s cash compensation is recorded in. For stock‑based payments issued to non‑employees, compensation expense is determined at the “measurement date,” which is the earlier of (i) the date at which a commitment for performance by the counterparty to earn the equity instrument is reached or (ii) the date at which the counterparty’s performance is complete. The expense is recognized over the vesting period of the award. Until the measurement date is reached, the total amount of compensation expense remains uncertain. The Company records compensation expense based on the fair value of the award at the reporting date. The awards to non‑employees are then revalued, or the total compensation is recalculated based on the then‑current fair value, at each subsequent reporting date.
Tax Credit	Tax Credit The tax credit represents the receipt of the New York City Biotechnology Tax Credit, or NYC Biotech credit, and receipt by Axsome Therapeutics Australia PTY, LTD, our Australian subsidiary, of the Australia Tax Incentive Credit, related to our research and development expenses incurred for our product candidates. These expenses were incurred in prior periods and therefore the grant income was recorded when the funds were received.
Basic and Diluted Net Loss per Common Share	Basic and Diluted Net Loss per Common Share Basic net loss per share of common stock is computed by dividing net loss by the weighted average number of shares of common stock outstanding during the period. Diluted net loss per share of common stock includes the effect, if any, from the potential exercise or conversion of securities, such as convertible notes, warrants, and stock options, which would result in the issuance of incremental shares of common stock. As the impact of these items is anti‑dilutive during periods of net loss, there was no difference between basic and diluted net loss per share of common stock for the years ended December 31, 2017, 2016, and 2015.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842), which supersedes FASB Topic 840, Leases (Topic 840) and provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than twelve months regardless of classification. Leases with a term of twelve months or less will be accounted for similarly to existing guidance for operating leases. The standard will be effective for annual and interim periods beginning after December 15, 2018, with early adoption permitted upon issuance. The Company is currently evaluating the potential impact of the new guidance. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) – Classification of Certain Cash Receipts and Cash Payments, which is guidance to address diversity in practice with respect to how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The updated guidance addresses eight specific cash flow issues with the objective of reducing the existing diversity that occurs in practice. The guidance is effective for annual and interim periods beginning after December 15, 2017. The Company will adopt this guidance effective January 1, 2018 and the adoption of the guidance is not anticipated to have a material impact on the Company’s financial statements. In May 2017, the FASB issued No. ASU 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting. ASU 2017-09 provides clarity and reduces both (1) diversity in practice and (2) cost and complexity when applying the guidance in Topic 718, to a change to the terms or conditions of a share-based payment award. The amendments in ASU 2017-09 should be applied prospectively to an award modified on or after the adoption date. This ASU is effective for fiscal years beginning after December 15, 2017, including interim periods within those years. The Company will adopt this guidance effective January 1, 2018 and the adoption of the guidance is not anticipated to have a material impact on the Company’s financial statements.

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Summary of changes in the fair value of Level 3 liabilities



December 31, 2017	Beginning of period		Issuances		Change in fair value (3)		Extinguishments		End of period
Warrant liability	$	—	$	2,145,000	$	646,000	$	—	$	2,791,000
Embedded derivative liabilities		—		—		—		—		—
Total	$	—	$	2,145,000	$	646,000	$	—	$	2,791,000

December 31, 2016	Beginning of period		Issuances		Change in fair value (3)		Extinguishments		End of period
Warrant liability	$	—	$	—	$	—	$	—	$	—
Embedded derivative liabilities		—		—		—		—		—
Total	$	—	$	—	$	—	$	—	$	—


December 31, 2015	Beginning of period		Issuances		Change in fair value (3)		Extinguishments		End of period
Warrant liability (1)	$	136,235	$	—	$	108,539	$	(244,774)	$	—
Embedded derivative liabilities (2)		496,400		871,000		(274,800)		(1,092,600)		—
Total	$	632,635	$	871,000	$	(166,261)	$	(1,337,374)	$	—

Warrants

Summary of liability fair value inputs


	Immediately prior to close of IPO

Expected volatility based on comparable public companies		70	%
Estimated fair value of the common stock	$	9.20
Remaining contractual term		4 years

Derivative Liabilities

Summary of liability fair value inputs


	Immediately prior to
	note amendment

Expected volatility based on comparable public companies	70	%
Estimated time to liquidity	0.1 - 0.2 years

Net Loss per Common Share (Tables)

12 Months Ended

Dec. 31, 2017

Net Loss per Common Share

Computation of basic and diluted net loss per common share


	Year ended December 31,
	2017		2016		2015

Basic and diluted net loss per common share:
Net loss	$	(28,943,392)	$	(27,201,653)	$	(12,210,579)
Weighted average common shares outstanding—basic and diluted		22,764,606		19,150,690		11,945,318
Net loss per common share—basic and diluted	$	(1.27)	$	(1.42)	$	(1.02)

Schedule of potentially dilutive securities


	December 31,
	2017	2016	2015

Stock options	2,315,638	1,772,050	998,198
Warrants	2,099,149	337,696	272,468
	4,414,787	2,109,746	1,270,666

Loan and Security Agreement (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Schedule of long-term debt and unamortized debt discount balances


	December 31,
	2017

Long-term debt	$	9,722,222
Less debt discount, net of current portion		274,116
Long-term debt, net of debt discount		9,996,338
Less current portion of long-term debt		(3,333,333)
Loan payable, long-term	$	6,663,005
Current portion of long-term debt		3,333,333
Current portion of debt discount		(63,987)
Loan payable, current portion	$	3,269,346

Schedule of principal payments


2018	$	3,333,333
2019		3,333,333
2020		3,055,556
	$	9,722,222

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21475-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21538-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21521-112644

+ Details

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

Stockholders? Equity

Schedule of stock option activity


				Weighted
		Weighted		average	Aggregate
	Number	average		contractual	intrinsic
	of shares	exercise price		term	value
Outstanding at December 31, 2016	1,772,050	$	5.74
Granted	847,510		5.24
Exercised	(88,922)		3.56
Forfeited	(101,497)		6.69
Expired	(113,503)		6.30
Outstanding at December 31, 2017	2,315,638	$	5.57	8.2	$	2,385,761
Vested and expected to vest at December 31, 2017	2,309,469	$	5.58	8.2	$	2,359,235
Exercisable at December 31, 2017	1,190,135	$	4.78	7.5	$	2,042,324

Summary of Black-Scholes option valuation assumptions


Black-Scholes option valuation assumptions	2017				2016				2015

Risk-free interest rates	1.6	-	2.2	%	0.9	-	2.0	%	0.7	-	1.9	%
Dividend yield		—				—				—
Volatility	73	-	77	%	69	-	75	%	67	-	71	%
Weighted average expected term	3.50	-	6.12	years	3.25	-	6.25	years	2.5	-	6	years

Schedule of stock-based compensation expense



	2017		2016		2015
Research and development	$	613,629	$	1,115,626	$	622,901
General and administrative		1,458,581		915,792		180,378
	$	2,072,210	$	2,031,418	$	803,279

Warrants (Tables)

12 Months Ended

Dec. 31, 2017

Warrants

Schedule of warrant activity


		Weighted
		average
	Warrants	exercise price
Outstanding at December 31, 2014	230,409	$	1.30
Issued	42,059		5.94
Outstanding at December 31, 2015	272,468		2.02
Issued	65,228		7.41
Outstanding at December 31, 2016	337,696		3.06
Issued	1,890,602		5.33
Exercised	(129,149)		1.30
Outstanding at December 31, 2017	2,099,149	$	5.21

Summary of equity instruments fair value inputs


Black-Scholes option valuation assumptions	2016
Risk-free interest rate	1.8	%
Dividend yield	—
Volatility	73	%
Weighted average contractual term	7 years

- 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

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Taxes

Schedule of components of deferred tax assets


	December 31, 2017		December 31, 2016
Deferred tax assets:
Net federal operating loss carryforward	$	12,844,032	$	12,747,837
Net foreign operating loss carryforward		49,846		23,293
Net state operating loss carryforward		7,981,812		4,068,086
Non-cash compensation		1,719,315		1,450,620
Research and development credits		5,713,709		3,491,251
Deferred finance costs		44,042		—
Fixed Assets		2,597		—
Accrued expenses		472,004		308,007
Deferred tax asset, excluding valuation allowance		28,827,357		22,089,094
Fixed Assets		—		(19,985)
Less valuation allowance		(28,827,357)		(22,069,109)
Net deferred tax assets	$	—	$	—

Schedule of income tax rate reconciliation


	December 31, 2017		December 31, 2016
U.S. federal statutory income tax rate	34.0	%	34.0	%
State taxes, net of federal benefit	10.0		9.4
Permanent differences	(2.9)		(3.7)
Tax credit	7.7		12.8
US Federal tax rate change - tax reform	(25.4)		—
Change in valuation allowance	(23.4)		(52.5)
Other	—		—
Effective tax rate	—	%	—	%

Quarterly Consolidated Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Consolidated Financial Data (Unaudited)

Summary of quarterly consolidated financial data


	2017
	Mar. 31		June 30		Sept. 30		Dec. 31

Total operating expenses	$	7,672,033	$	6,750,738	$	6,297,416	$	6,444,120
Net loss	$	(7,995,039)	$	(7,084,316)	$	(6,433,536)	$	(7,430,501)
Net loss per common share, basic and diluted (1)	$	(0.41)	$	(0.30)	$	(0.27)	$	(0.31)

	2016
	Mar. 31		June 30		Sept. 30		Dec. 31

Total operating expenses	$	5,882,865	$	6,827,280	$	7,207,803	$	7,625,560
Net loss	$	(5,865,941)	$	(6,812,190)	$	(7,194,584)	$	(7,328,938)
Net loss per common share, basic and diluted (1)	$	(0.31)	$	(0.36)	$	(0.38)	$	(0.38)

Nature of Business and Basis of Presentation - Liquidity and Capital Resources (Details) - USD ($)	1 Months Ended				3 Months Ended	12 Months Ended
	Dec. 31, 2017	Oct. 31, 2017	Mar. 31, 2017	Nov. 30, 2015	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2015	Dec. 31, 2016	Nov. 30, 2016	Dec. 31, 2014
Accumulated deficit	$ 76,584,843					$ 76,584,843		$ 47,641,451
Shares issued	1,783,587		4,304,813		4,304,813
Share price	$ 5.325		$ 3.74		$ 3.74	$ 5.325
Proceeds from issuance of initial public offering, net							$ 45,549,121
Gross proceeds from issuance of common stock	$ 9,500,000				$ 16,100,000
Proceeds from issuance of common stock, net	8,800,000		$ 14,800,000		$ 14,800,000	$ 23,677,341
Common stock sales agreement, authorized amount		$ 30,000,000
Common stock sales agreement, commission percentage		3.00%
Common stock sales agreement, gross sales						100,000
Cash	$ 34,021,123					$ 34,021,123	$ 48,036,260	$ 36,618,497		$ 2,617,815
IPO
Shares issued				5,666,667
Share price				$ 9.00
Gross proceeds from initial public offering				$ 51,000,000
Proceeds from issuance of initial public offering, net				$ 45,500,000
Term Loan
Maximum loan amount									$ 20,000,000
Term Loan, Tranche One, triggered upon closing
Loan amount									$ 10,000,000

Fair Value Measurements - Recurring Basis (Details) - USD ($)					12 Months Ended
	Dec. 31, 2017	Dec. 04, 2017	Aug. 31, 2015	Nov. 23, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants issued					1,890,602	65,228	42,059
Exercise price of warrants (in dollars per share)	$ 5.21				$ 5.21	$ 3.06	$ 2.02			$ 1.30
Fair value	$ 2,145,000				$ 2,145,000
Share Price	$ 5.325				$ 5.325			$ 3.74	$ 3.74
Risk-free interest rates						1.80%
Expected volatility rate				70.00%		73.00%
10% share price increase
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Increase (decrease) in warrant liability					$ 700,000
10% share price decrease
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Increase (decrease) in warrant liability					(700,000)
10% expected volatility increase
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Increase (decrease) in warrant liability					200,000
10% expected volatility decrease
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Increase (decrease) in warrant liability					(200,000)
Common warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants issued		1,783,587
Exercise price of warrants (in dollars per share)		$ 5.25
Fair value	$ 2,683,000	$ 2,064,000			$ 2,683,000
Share Price	$ 5.60	$ 5.00			$ 5.60
Risk-free interest rates	1.76%	1.66%
Expected volatility rate	62.00%	61.00%
Placement agent warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants issued		107,015
Exercise price of warrants (in dollars per share)		$ 6.6562
Fair value	$ 108,000	$ 81,000			$ 108,000
Share Price	$ 5.60	$ 5.00			$ 5.60
Risk-free interest rates	1.76%	1.66%
Expected volatility rate	62.00%	61.00%
Warrant liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Expected volatility rate				9.20%
Embedded derivative liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Expected volatility rate			70.00%

Loan and Security Agreement - Additional Information (Details)	1 Months Ended	12 Months Ended
	Nov. 30, 2016 USD ($) tranche	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Amortization of debt issuance costs				$ 7,757
Term Loan
Maximum loan amount	$ 20,000,000
Number of loan tranches \| tranche	3
Base interest rate	4.50%
Interest rate spread	3.50%
Final payment fee, percent of principal	8.50%
Prepayment premium, percent of principal, if prepaid within two years	3.00%
Prepayment premium, condition one, term	2 years
Prepayment premium, percent of principal, if prepaid during the third year	2.00%
Prepayment premium, percent of principal, if prepaid after the third year	1.00%
Interest expense		$ 869,678	$ 116,736
Amortization of debt issuance costs		$ 346,978	$ 49,781
Term Loan, Tranche One, triggered upon closing
Loan amount	$ 10,000,000
Term Loan, Tranches Two and Three
Maximum loan amount	$ 10,000,000
Number of loan tranches \| tranche	2
Term Loan, Tranche Two
Maximum loan amount	$ 5,000,000
Term Loan, Tranche Three
Maximum loan amount	$ 5,000,000

Stockholders' Equity - Capital Structure (Details)	1 Months Ended				3 Months Ended	12 Months Ended
Stockholders' Equity - Capital Structure (Details)	Dec. 31, 2017 USD ($) $ / shares shares	Oct. 31, 2017 USD ($)	Mar. 31, 2017 USD ($) $ / shares shares	Nov. 30, 2015 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) Vote / shares $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($)	Dec. 04, 2017 USD ($) $ / shares	Dec. 01, 2016 USD ($)	Nov. 24, 2015 $ / shares shares	Oct. 30, 2015 shares	Apr. 30, 2015 shares	Dec. 31, 2014 $ / shares shares
Subsidiary, Sale of Stock [Line Items]
Common stock, shares authorized \| shares	150,000,000					150,000,000	150,000,000				150,000,000	25,000,000	22,033,500	14,689,000
Common stock, par value \| $ / shares	$ 0.0001					$ 0.0001	$ 0.0001				$ 0.0001			$ 0.0001
Preferred stock, shares authorized \| shares	10,000,000					10,000,000	10,000,000				10,000,000
Preferred stock, par value \| $ / shares	$ 0.0001					$ 0.0001	$ 0.0001				$ 0.0001
Shares issued \| shares	1,783,587		4,304,813		4,304,813
Share Price \| $ / shares	$ 5.325		$ 3.74		$ 3.74	$ 5.325
Issuance costs	$ 745,856
Fair Value Of Warrants	2,145,000					$ 2,145,000
Proceeds from issuance of common stock, gross	9,500,000		$ 16,100,000				$ 33,030	$ 45,506,501
Proceeds from issuance of common stock, net	8,800,000
Procceds from issuance of common stock upon financing, net	$ 8,800,000		$ 14,800,000		$ 14,800,000	23,677,341
Proceeds from issuance of initial public offering, net								$ 45,549,121
Common stock sales agreement, authorized amount		$ 30,000,000
Common stock sales agreement, commission percentage		3.00%
Common stock sales agreement, gross sales						$ 100,000
Common stock, voting right per share \| Vote / shares						1
Shelf Registration Statement, maximum aggregate amount issuable										$ 150,000,000
IPO
Subsidiary, Sale of Stock [Line Items]
Shares issued \| shares				5,666,667
Share Price \| $ / shares				$ 9.00
Gross proceeds from initial public offering				$ 51,000,000
Proceeds from issuance of initial public offering, net				$ 45,500,000
Common warrants
Subsidiary, Sale of Stock [Line Items]
Share Price \| $ / shares	$ 5.60					$ 5.60			$ 5.00
Exercise price \| $ / shares	$ 5.25					$ 5.25
Fair Value Of Warrants	$ 2,683,000					$ 2,683,000			$ 2,064,000
Placement agent warrants
Subsidiary, Sale of Stock [Line Items]
Shares issued \| shares	107,015
Share Price \| $ / shares	$ 5.60					$ 5.60			$ 5.00
Exercise price \| $ / shares	$ 6.6562					$ 6.6562
Issuance costs	$ 81,000
Fair Value Of Warrants	108,000					$ 108,000			$ 81,000
Procceds from issuance of common stock upon financing, net	$ 583,768

Stockholders' Equity - Stock Option Activity (Details)	12 Months Ended
Stockholders' Equity - Stock Option Activity (Details)	Dec. 31, 2017 USD ($) $ / shares shares
Number of shares
Beginning balance outstanding (in shares) \| shares	1,772,050
Granted (in shares) \| shares	847,510
Exercised (in shares) \| shares	(88,922)
Forfeited (in shares) \| shares	(101,497)
Expired (in shares) \| shares	(113,503)
Ending balance outstanding (in shares) \| shares	2,315,638
Vested and expected to vest (in shares) \| shares	2,309,469
Exercisable (in shares) \| shares	1,190,135
Weighted average exercise price
Beginning balance outstanding (in dollars per share) \| $ / shares	$ 5.74
Granted (in dollars per share) \| $ / shares	5.24
Exercised (in dollars per share) \| $ / shares	3.56
Forfeited (in dollars per share) \| $ / shares	6.69
Expired (in dollars per share) \| $ / shares	6.30
Ending balance outstanding (in dollars per share) \| $ / shares	5.57
Vested and expected to vest (in dollars per share) \| $ / shares	5.58
Exercisable (in dollars per share) \| $ / shares	$ 4.78
Weighted average contractual term
Outstanding (in years)	8 years 2 months 12 days
Vested and expected to vest (in years)	8 years 2 months 12 days
Exercisable (in years)	7 years 6 months
Aggregate intrinsic value
Outstanding (in dollars) \| $	$ 2,385,761
Vested and expected to vest (in dollars) \| $	2,359,235
Exercisable (in dollars) \| $	$ 2,042,324

Warrants - Background Information (Details) - USD ($)				12 Months Ended
Warrants - Background Information (Details) - USD ($)	Dec. 04, 2017	Nov. 03, 2014	Oct. 29, 2013	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 30, 2016	Nov. 09, 2016
Warrants
Warrants outstanding beginning balance				337,696	272,468	230,409
Warrants issued				1,890,602	65,228	42,059
Warrants exercised				(129,149)
Warrants outstanding ending balance				2,099,149	337,696	272,468
Weighted average exercise price
Beginning balance (in dollars per share)				$ 3.06	$ 2.02	$ 1.30
Issued (in dollars per share)				5.33	7.41	5.94
Exercised (in dollars per share)				1.30
Ending balance (in dollars per share)				$ 5.21	$ 3.06	$ 2.02
Value of warrants issued					$ 264,365
Common warrants
Warrants
Warrants issued	1,783,587
Weighted average exercise price
Ending balance (in dollars per share)	$ 5.25
Placement agent warrants
Warrants
Warrants issued	107,015
Weighted average exercise price
Ending balance (in dollars per share)	$ 6.6562
Term Loan
Weighted average exercise price
Common stock to be issued if warrants are exercised (in shares)							65,228	65,228
June 2013 Notes
Weighted average exercise price
Exercised (in dollars per share)			$ 1.30
Common stock to be issued if warrants are exercised (in shares)			230,409
September 2014 Notes
Weighted average exercise price
Ending balance (in dollars per share)		$ 5.94
Common stock to be issued if warrants are exercised (in shares)		42,059
Fair value of warrant recorded as a debt discount		$ 79,129
Mandatory conversion, warrant price premium as a percent of the conversion price		10.00%

Income Taxes - Components of Deferred Tax Asset (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets
Net federal operating loss carryforwards	$ 12,844,032	$ 12,747,837
Net foreign operating loss carryforwards	49,846	23,293
Net state operating loss carryforwards	7,981,812	4,068,086
Non-cash compensation	1,719,315	1,450,620
Research and development credits	5,713,709	3,491,251
Deferred finance costs	44,042
Fixed assets	2,597
Accrued expenses	472,004	308,007
Deferred tax asset, excluding valuation allowance	28,827,357	22,089,094
Fixed Assets		(19,985)
Less valuation allowance	$ (28,827,357)	$ (22,069,109)	$ (7,756,147)

Related-Party Transactions - Loan Payable (Details)	1 Months Ended				3 Months Ended	12 Months Ended
Related-Party Transactions - Loan Payable (Details)	Dec. 31, 2017 shares	Mar. 31, 2017 shares	Dec. 31, 2014 USD ($)	Jan. 31, 2012 shares	Jun. 30, 2017 shares	Dec. 31, 2017 item	Dec. 31, 2015 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 item
Related Party Transaction [Line Items]
Payment of loan from related party							$ 41,469
Shares issued \| shares	1,783,587	4,304,813			4,304,813
Dr. Tabuteau
Related Party Transaction [Line Items]
Ownership of outstanding common shares, percent	5.00%					5.00%
Dr. Tabuteau \| Loan payable
Related Party Transaction [Line Items]
Outstanding payable							$ 41,469	$ 62,469
Interest payable								$ 0
Payment of loan from related party			$ 21,000
Antecip
Related Party Transaction [Line Items]
Shares issued \| shares				7,344,500
License Agreements \| Antecip
Related Party Transaction [Line Items]
Number of exclusive license agreements \| item						3			3

License Agreements	12 Months Ended
License Agreements	Dec. 31, 2017
License Agreements.
License Agreements	Note 10. License Agreements In 2012, the Company entered into three exclusive license agreements with Antecip Bioventures II LLC, or Antecip, an entity owned by Axsome’s Chief Executive Officer and Chairman of the Board, Herriot Tabuteau, M.D., in which it was granted exclusive licenses to develop, manufacture, and commercialize Antecip’s patents and applications related to the development of AXS‑02, AXS‑05, and AXS‑04, a product candidate that is currently in early stage development, anywhere in the world for veterinary and human therapeutic and diagnostic use. Pursuant to the agreements, the Company is required to use commercially reasonable efforts to develop, obtain regulatory approval for and commercialize AXS‑02, AXS‑05, and AXS‑04. Under the terms of the agreements, the Company is required to pay to Antecip a royalty equal to 4.5% for AXS‑02, 3.0% for AXS‑05, and 1.5% for AXS‑04, of net sales of products containing the licensed technology by the Company, its affiliates, or permitted sublicensees. These royalty payments are subject to reduction by an amount up to 50.0% of any required payments to third parties. Unless earlier terminated by a party for cause or by the Company for convenience, the agreements shall remain in effect on a product‑by‑product and country‑by‑country basis until the later to occur of (i) the applicable product is no longer covered by a valid claim in that country or (ii) 10 years from the first commercial sale of the applicable product in that country. Upon expiration of the agreements with respect to a product in a country, the Company’s license grant for that product in that country will become a fully paid‑up, royalty‑free, perpetual non‑exclusive license. If Antecip terminates any of the agreements for cause, or if the Company exercises its right to terminate any of the agreements for convenience, the rights granted to the Company under such terminated agreement will revert to Antecip. To date, the Company has not been required to make any payments to Antecip under any of the license agreements.

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2017
Commitments and Contingencies
Commitments and Contingencies	Note 11. Commitments and Contingencies Operating Leases The Company’s offices are located in New York, New York. The Company is not currently under a lease agreement. Rent expense incurred during the years ended December 31, 2017, 2016 and 2015 was $307,557, $254,170, and $127,559.

Related-Party Transactions	12 Months Ended
Related-Party Transactions	Dec. 31, 2017
Related-Party Transactions
Related-Party Transactions	Note 13. Related Party Transactions From March 2013 through June 2015, members of the Company’s board of directors, officers, and some family members participated in the Company’s issuance of convertible notes for a total investment of $3,371,469. The terms of these convertible notes were identical to the terms of the convertible notes issued to unrelated third parties. As of December 31, 2015, the entire principal plus interest under these convertible notes issued to these related parties have converted into 696,221 shares of the Company’s common stock. In April 2012, the Company entered into a three‑year consulting agreement with Mark Coleman, M.D., a member of its board of directors since December 2014, which was subsequently amended in June 2014, to engage Dr. Coleman to provide certain consulting services in connection with the Company’s development of pharmaceutical and other therapeutic product candidates. The consulting agreement provided the Company with the ability to compensate Dr. Coleman in cash or options. In March 2013, the Company issued to Dr. Coleman an option grant to purchase 20,997 shares of the Company’s common stock with an exercise price of $1.30 per share that vested immediately; in June 2014, the Company issued to Dr. Coleman an option grant to purchase 76,904 shares of the Company’s common stock with an exercise price of $1.30 per share which were subject to certain performance‑based vesting restrictions, of which the grant was forfeited in December 2015; and in June 2015, the Company issued to Dr. Coleman an option grant to purchase 33,410 shares of the Company’s common stock with an exercise price of $5.94 per share that vested immediately. The Company recorded stock‑based compensation expense of $99,234 during the year ended December 31, 2015 related to these option grants. No further expense will be incurred related to these grants. In 2013, the Company had an outstanding loan payable to its Chief Executive Officer and Chairman of the Board in the amount of $62,469 pertaining to payment of startup costs of the Company. The loan carried no interest payable and was payable on demand. In December 2014, the Company satisfied a portion of the loan payable with a cash payment of $21,000, leaving a balance at December 31, 2014 of $41,469. In June 2015, the Company paid the remaining balance of the loan obligation, which Dr. Tabuteau then reinvested into the Company by purchasing an equivalent amount of convertible notes issued by the Company. From the Company’s inception, Herriot Tabuteau, M.D. has been the Company’s founder, Chief Executive Officer, Chairman of the Company’s board of directors, and the beneficial owner of more than 5% of the outstanding shares of the Company’s common stock. In connection with the formation of the Company, in January 2012, the Company issued to Antecip Capital LLC, an entity controlled by Dr. Tabuteau, an aggregate of 7,344,500 shares of the Company’s common stock for nominal consideration. The Company is a party to three exclusive license agreements with Antecip Bioventures II LLC, an entity owned by Dr. Tabuteau. See Note 10 for further information regarding the license agreements.

Summary of Significant Accounting Policies (Details)	12 Months Ended
Summary of Significant Accounting Policies (Details)	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 segment	Dec. 31, 2015 segment
Segment and Geographic Information
Number of operating segments \| segment	1	1	1
Cash Equivalents
Cash Equivalents \| $	$ 0

Accrued Expenses (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Accrued Expenses
Research and development	$ 1,642,154	$ 1,693,748
Accrued compensation	704,556	539,290
Other	332,824	587,339
Accounts Payable and Other Accrued Liabilities, Current	$ 2,679,534	$ 2,820,377

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	25,492,992	19,158,417
Common stock, shares outstanding	25,492,992	19,149,417

Nature of Business and Basis of Presentation - Amendment to Certificate of Incorporation (Details)	Oct. 30, 2015 shares	Dec. 31, 2017 item $ / shares shares	Dec. 31, 2016 $ / shares shares	Nov. 24, 2015 $ / shares shares	Apr. 30, 2015 shares	Dec. 31, 2014 $ / shares shares
Nature of Business and Basis of Presentation
Number of late-stage candidates in Company's product candidate portfolio \| item		5
Common stock, shares authorized \| shares	25,000,000	150,000,000	150,000,000	150,000,000	22,033,500	14,689,000
Stock split ratio	7.3445
Preferred stock, shares authorized \| shares		10,000,000	10,000,000	10,000,000
Common stock, par value \| $ / shares		$ 0.0001	$ 0.0001	$ 0.0001		$ 0.0001
Preferred stock, par value \| $ / shares		$ 0.0001	$ 0.0001	$ 0.0001

Fair Value Measurements - Changes in Fair Value of Level 3 Liabilities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning of period		$ 632,635
Issuances	$ 2,145,000	871,000
Change in fair value	646,000	(166,261)
End of period	2,791,000	1,337,374
Warrant liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning of period		136,235
Issuances	2,145,000
Change in fair value	646,000	108,539
End of period	$ 2,791,000	244,774
Embedded derivative liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning of period		496,400
Issuances		871,000
Change in fair value		(274,800)
End of period		$ 1,092,600

Net Loss per Common Share - Computation of Basic and Diluted Net Loss per Common Share (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Basic and diluted net loss per common share:
Net loss	$ (7,430,501)	$ (6,433,536)	$ (7,084,316)	$ (7,995,039)	$ (7,328,938)	$ (7,194,584)	$ (6,812,190)	$ (5,865,941)	$ (28,943,392)	$ (27,201,653)	$ (12,210,579)
Weighted average common shares outstanding, basic and diluted									22,764,606	19,150,690	11,945,318
Net loss per common share, basic and diluted	$ (0.31)	$ (0.27)	$ (0.30)	$ (0.41)	$ (0.38)	$ (0.38)	$ (0.36)	$ (0.31)	$ (1.27)	$ (1.42)	$ (1.02)

Convertible Notes - Short-term (Details) - Notes payable - USD ($)	1 Months Ended		5 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Oct. 31, 2014	Oct. 31, 2013
Loan amount		$ 211,000		$ 3,904,000
Base interest rate		8.00%		8.00%
Debt term		1 year		1 year
Shares issued in conversion of outstanding convertible notes	175,228		3,242,344
Conversion price per share	$ 1.30			$ 1.30
Conversion price, percent of price per share of equity securities				90.00%
Initial discount				$ 339,735

Convertible Notes - Long-term (Details) - USD ($)	1 Months Ended		2 Months Ended	3 Months Ended		12 Months Ended
Convertible Notes - Long-term (Details) - USD ($)	Nov. 30, 2015	Sep. 30, 2015	Jan. 31, 2015	Jul. 31, 2015	Nov. 30, 2014	Dec. 31, 2015
Shares issued upon conversion, value						$ 15,302,861
Notes payable
Conversion price, percent of price per share of equity securities		75.00%
Equity financing, gross aggregate cash proceeds, conversion trigger		$ 2,000,000
September 2014 Notes
Loan amount					$ 4,140,000
Base interest rate					8.00%
Debt term					10 years
Shares issued upon conversion, value	$ 836,202
Conversion price per share					$ 5.40
Conversion price, percent of price per share of equity securities					75.00%
December 2014 Notes
Loan amount			$ 1,570,000
Base interest rate			8.00%
Debt term			10 years
Shares issued upon conversion, value	283,131
Conversion price per share			$ 5.94
Conversion price, percent of price per share of equity securities			75.00%
2015 Notes
Loan amount				$ 7,166,469
Base interest rate				8.00%
Debt term				10 years
Shares issued upon conversion, value	$ 1,255,273
Conversion price per share				$ 5.94
Conversion price, percent of price per share of equity securities				75.00%

Convertible Notes - Accounting Analysis (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2014
Outstanding Convertible Notes Payable	$ 0	$ 0	$ 0
Notes payable
Fair value				$ 15,146,410
Carrying value				$ 12,701,894
Notes payable
Fair value					$ 6,691,000
Carrying value					$ 3,820,097

Loan and Security Agreement - Long-term Debt and Unamortized Debt Discount (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Long-term debt	$ 9,722,222
Less debt discount, net of current portion	(274,116)
Long-term debt, net of debt discount	9,996,338
Less current portion of long-term debt	(3,333,333)
Loan payable, long-term	6,663,005	$ 9,470,445
Current portion of long-term debt	3,333,333
Current portion of debt discount	(63,987)
Loan payable, current portion	$ 3,269,346	$ 269,162

Loan and Security Agreement - Schedule of Principal Payments (Details)	Dec. 31, 2017 USD ($)
Debt Disclosure [Abstract]
2018	$ 3,333,333
2019	3,333,333
2020	3,055,556
Total	$ 9,722,222

Stockholders' Equity - Equity Incentive Plans (Details)	Dec. 31, 2017 shares
2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant	0
2015 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant	2,852,551

Warrants - Fair Value Valuation Assumptions (Details)		12 Months Ended
Warrants - Fair Value Valuation Assumptions (Details)	Nov. 23, 2014	Dec. 31, 2017	Dec. 31, 2016
Warrants
Risk-free interest rates			1.80%
Volatility	70.00%		73.00%
Weighted average contractual term	4 years	7 years

License Agreements (Details) - Antecip - License Agreements - item	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2012
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of exclusive license agreements	3	3
License agreement royalty, maximum reduction percent as a result of required third party payments		50.00%
License agreement term, from first commercial sale		10 years
AXS-02
Research and Development Arrangement, Contract to Perform for Others [Line Items]
License agreement royalty as a percent of net sales		4.50%
AXS-05
Research and Development Arrangement, Contract to Perform for Others [Line Items]
License agreement royalty as a percent of net sales		3.00%
AXS-04
Research and Development Arrangement, Contract to Perform for Others [Line Items]
License agreement royalty as a percent of net sales		1.50%

Commitments and Contingencies (Details) - USD ($)	12 Months Ended
Commitments and Contingencies (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies
Rent expense	$ 307,557	$ 254,170	$ 127,559

Income Taxes - Reconciliation of Income Tax Expense (Benefit) (Details)		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of income tax expense (benefit)
U.S. federal statutory income tax rate		34.00%	34.00%
State taxes, net of federal benefit		10.00%	9.40%
Permanent differences		(2.90%)	(3.70%)
Tax credits		7.70%	12.80%
US federal tax rate change- tax reform		(25.40%)
Change in valuation allowance		(23.40%)	(52.50%)
Forecast
Reconciliation of income tax expense (benefit)
U.S. federal statutory income tax rate	21.00%

Related-Party Transactions - Convertible Notes (Details) - Notes payable - USD ($)	12 Months Ended	28 Months Ended
	Dec. 31, 2016	Jun. 30, 2015
Debt Conversion [Line Items]
Investment from issuance of convertible notes		$ 3,371,469
Shares of common stock, converted from notes payable	696,221