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	Flex Pharma, Inc.
Entity Central Index Key	0001615219
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		17,972,166
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 39.7

CONSOLIDATED BALANCE SHEETS - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 19,186,036	$ 22,416,040
Marketable securities	14,129,723	38,658,933
Accounts receivable	10,385	12,181
Inventory	431,891	454,132
Prepaid expenses and other current assets	777,102	925,983
Total current assets	34,535,137	62,467,269
Property and equipment, net	331,040	556,315
Other assets	0	64,800
Restricted cash	126,595	126,595
Total assets	34,992,772	63,214,979
Current liabilities:
Accounts payable	2,004,440	1,192,183
Accrued expenses and other current liabilities	3,712,221	2,587,573
Deferred revenue	72,188	88,344
Deferred rent, current portion	58,821	21,095
Total current liabilities	5,847,670	3,889,195
Deferred rent, net of current portion	39,214	8,398
Total liabilities	5,886,884	3,897,593
Stockholders' equity:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized at December 31, 2017 and December 31, 2016; none issued or outstanding at December 31, 2017 and December 31, 2016	0	0
Common stock, $0.0001 par value; 100,000,000 shares authorized at December 31, 2017 and December 31, 2016, 17,972,166 and 17,970,590 shares issued at December 31, 2017 and December 31, 2016, respectively, and 17,797,178 and 16,773,798 shares outstanding at December 31, 2017 and December 31, 2016, respectively	1,780	1,678
Additional paid-in capital	140,184,630	135,962,935
Accumulated other comprehensive loss	(1,247)	(1,614)
Accumulated deficit	(111,079,275)	(76,645,613)
Total stockholders' equity	29,105,888	59,317,386
Total liabilities and stockholders' equity	$ 34,992,772	$ 63,214,979

CONSOLIDATED BALANCE SHEET (PARENTHETICAL) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Preferred stock, authorized (shares)	10,000,000	10,000,000
Preferred stock, issued (shares)	0	0
Preferred stock, shares outstanding (shares)	0	0
Common stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (shares)	100,000,000	100,000,000
Common stock, shares issued (shares)	17,972,166	17,970,590
Common stock, shares outstanding (shares)	17,797,178	16,773,798

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)	12 Months Ended
CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net product revenue	$ 1,260,973	$ 989,918	$ 0
Other revenue	13,526	20,745	0
Total revenue	1,274,499	1,010,663	0
Costs and expenses:
Cost of product revenue	506,530	662,747	0
Research and development	16,989,911	20,378,161	12,749,379
Selling, general and administrative	18,503,684	19,855,987	16,464,279
Total costs and expenses	36,000,125	40,896,895	29,213,658
Loss from operations	(34,725,626)	(39,886,232)	(29,213,658)
Interest income, net	291,964	393,109	72,028
Net loss	(34,433,662)	(39,493,123)	(29,141,630)
Net loss attributable to common stockholders	$ (34,433,662)	$ (39,493,123)	$ (29,141,630)
Net loss per share attributable to common stockholders - basic and diluted (in usd per share)	$ (1.99)	$ (2.43)	$ (2.08)
Weighted-average number of common shares outstanding — basic and diluted (shares)	17,260,626	16,233,985	14,032,916

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($)	12 Months Ended
CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net loss	$ (34,433,662)	$ (39,493,123)	$ (29,141,630)
Other Comprehensive gain (loss):
Unrealized gain (loss) on available-for-sale securities	367	23,040	(24,654)
Comprehensive loss	$ (34,433,295)	$ (39,470,083)	$ (29,166,284)

CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY - USD ($)	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Series A Preferred Stock	Series A Preferred Stock Preferred Stock	Series A Preferred Stock Common Stock	Series A Preferred Stock Additional Paid-In Capital	Series B Preferred Stock	Series B Preferred Stock Preferred Stock	Series B Preferred Stock Common Stock	Series B Preferred Stock Additional Paid-In Capital
Preferred stock, shares outstanding, beginning balance at Dec. 31, 2014		0						15,775,221				14,078,647
Equity, beginning balance at Dec. 31, 2014	$ (6,538,340)	$ 0	$ 221	$ 1,472,299	$ 0	$ (8,010,860)		$ 15,637,032				$ 25,394,135
Common stock, shares outstanding, beginning balance at Dec. 31, 2014			2,215,711
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of preferred stock to common stock (shares)								(15,775,221)	3,683,637			(14,078,647)	3,287,471
Conversion of preferred stock to common stock							$ 15,637,032	$ (15,637,032)	$ 368	$ 15,636,664	$ 25,394,135	$ (25,394,135)	$ 329	$ 25,393,806
Issuance of stock/IPO proceeds, net of issuance costs (shares)			5,491,191
Issuance of stock/IPO proceeds, net of issuance costs	79,860,185		$ 549	79,859,636
Vesting of restricted common stock (shares)			1,016,328
Vesting of restricted common stock	$ 0		$ 102	(102)
Issuance of common stock from option exercises (shares)	47,280		47,280
Issuance of common stock from option exercises	$ 408,321		$ 5	408,316
Stock-based compensation expense	6,597,359			6,597,359
Unrealized gain (loss) on available-for-sale securities	(24,654)				(24,654)
Net loss	(29,141,630)					(29,141,630)
Preferred stock, shares outstanding, ending balance at Dec. 31, 2015		0						0				0
Equity, ending balance at Dec. 31, 2015	92,192,408	$ 0	$ 1,574	129,367,978	(24,654)	(37,152,490)		$ 0				$ 0
Common stock, shares outstanding, ending balance at Dec. 31, 2015			15,741,618
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted common stock (shares)			1,023,664
Vesting of restricted common stock	$ 0		$ 102	(102)
Issuance of common stock from option exercises (shares)	8,516		8,516
Issuance of common stock from option exercises	$ 22,098		$ 2	22,096
Stock-based compensation expense	6,572,963			6,572,963
Unrealized gain (loss) on available-for-sale securities	23,040				23,040
Net loss	$ (39,493,123)					(39,493,123)
Preferred stock, shares outstanding, ending balance at Dec. 31, 2016	0	0						0				0
Equity, ending balance at Dec. 31, 2016	$ 59,317,386	$ 0	$ 1,678	135,962,935	(1,614)	(76,645,613)		$ 0				$ 0
Common stock, shares outstanding, ending balance at Dec. 31, 2016	16,773,798		16,773,798
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of stock/IPO proceeds, net of issuance costs (shares)	0
Vesting of restricted common stock (shares)			1,021,804
Vesting of restricted common stock	$ 0		$ 102	(102)
Issuance of common stock from option exercises (shares)	1,576		1,576
Issuance of common stock from option exercises	$ 2,632		$ 0	2,632
Stock-based compensation expense	4,219,165			4,219,165
Unrealized gain (loss) on available-for-sale securities	367				367
Net loss	$ (34,433,662)					(34,433,662)
Preferred stock, shares outstanding, ending balance at Dec. 31, 2017	0	0						0				0
Equity, ending balance at Dec. 31, 2017	$ 29,105,888	$ 0	$ 1,780	$ 140,184,630	$ (1,247)	$ (111,079,275)		$ 0				$ 0
Common stock, shares outstanding, ending balance at Dec. 31, 2017	17,797,178		17,797,178

CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($)	12 Months Ended
CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net loss	$ (34,433,662)	$ (39,493,123)	$ (29,141,630)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	324,548	277,231	49,881
Stock-based compensation expense	4,219,165	6,572,963	6,597,359
Amortization and accretion on investments	(68,139)	16,161	9,523
Other non-cash items	1,781	3,434	4,123
Changes in operating assets and liabilities:
Restricted cash	0	240	(27)
Accounts receivable	1,796	(12,181)	0
Inventory	22,241	(454,132)	0
Prepaid expenses and other current assets	148,881	(17,409)	(538,178)
Other assets	64,800	(64,800)	100,103
Accounts payable	819,357	309,437	621,393
Accrued expenses and other current liabilities	1,124,648	746,879	1,570,216
Deferred revenue	(16,156)	88,344	0
Deferred rent	68,542	(9,475)	(18,881)
Other long term liabilities	0	(15,442)	0
Net cash used in operating activities	(27,722,198)	(32,051,873)	(20,746,118)
Investing activities
Purchases of marketable securities	(32,987,697)	(38,682,081)	(39,397,769)
Proceeds from maturities and sales of marketable securities	57,585,413	26,995,324	12,398,295
Purchases of property and equipment	(113,498)	(559,378)	(265,617)
Proceeds from sales of property and equipment	5,344	5,255	0
Net cash provided by (used in) investing activities	24,489,562	(12,240,880)	(27,265,091)
Financing activities
Proceeds from initial public offering, net of offering costs	0	0	80,435,430
Proceeds from exercise of common stock	2,632	22,098	8,321
Proceeds from early exercise of common stock	0	0	400,000
Net cash provided by financing activities	2,632	22,098	80,843,751
Net (decrease) increase in cash and cash equivalents	(3,230,004)	(44,270,655)	32,832,542
Cash and cash equivalents at beginning of period	22,416,040	66,686,695	33,854,153
Cash and cash equivalents at end of period	19,186,036	22,416,040	66,686,695
Supplemental cash flow information
Property and equipment purchases included in accounts payable and accrued expense	0	7,100	106,680
IPO issuance costs paid in cash through December 31, 2014	$ 0	$ 0	$ 575,245

Organization and operations	12 Months Ended
Organization and operations	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and operations	Organization and operations The Company Flex Pharma, Inc. (the "Company") is a biotechnology company that is developing innovative and proprietary treatments for muscle cramps, spasms and spasticity associated with severe neurological conditions and exercise-associated muscle cramps. The Company's lead drug product candidate, FLX-787, is currently being studied in an exploratory Phase 2 clinical trial in Australia in patients with multiple sclerosis, or MS, and in two Phase 2 clinical trials in the United States. One Phase 2 clinical trial in the United States is in patients with motor neuron disease, or MND, primarily with amyotrophic lateral sclerosis, or ALS, who suffer from muscle cramps. FLX-787 is being developed for ALS under fast track designation which was granted by the Food and Drug Administration in July 2017. The other Phase 2 clinical trial in the United States is in patients with Charcot-Marie-Tooth disease, or CMT, who suffer from muscle cramps. In 2016, the Company launched its consumer product, HOTSHOT^®, to prevent and treat exercise-associated muscle cramps. FLX-787, HOTSHOT and the Company's other drug product candidates are based on a mechanism of action the Company describes as chemical neurostimulation. The Company believes chemical neurostimulation to be a process in which a molecule, such as FLX-787, acts topically on the surfaces of the mouth, throat, esophagus and stomach to produce a sensory signal by activating nerves in those tissues. That signal is thought to ultimately result in a beneficial effect. Specifically, the Company's product candidates activate certain receptors known as transient receptor potential ion channels in primary sensory neurons producing a signal believed to inhibit neuronal circuits and thereby reduce hyperexcitability in the neurons that fire muscles. Reduced alpha-motor neuron hyperexcitability in spinal cord circuits is thought to suppress repetitive firing of alpha-motor neurons, thereby preventing or reducing muscle cramps and spasms, and potentially reducing reflex hyperexcitability and therefore spasticity. The Company operates as two reportable segments, Consumer Operations and Drug Development. See Note 15 for additional discussion and information on the Company's reportable segments. The Company is subject to risks common to companies in the biotechnology and consumer products industries, including, but not limited to, risks of failure of pre-clinical studies and clinical trials, the need to obtain marketing approval for its drug product candidates, the need to successfully commercialize and gain market acceptance of its drug product candidates and its consumer products, dependence on key personnel, protection of proprietary technology, compliance with government regulations and development by competitors of alternative products. In February 2015, the Company sold 5,491,191 shares of common stock (inclusive of 91,191 shares of common stock sold by the Company pursuant to the exercise of an overallotment option granted to the underwriters in connection with the offering) through an underwritten initial public offering ("IPO") at a price of $16.00 per share. The aggregate net proceeds received by the Company from the offering were approximately $79,900,000, after deducting underwriting discounts and commissions and offering expenses payable by the Company of approximately $8,000,000 (See Note 2). Liquidity The Company has incurred an accumulated deficit of $111,079,275 from February 26, 2014 (inception) through December 31, 2017, and will require substantial additional capital to fund its research and development and expenses related to its consumer brand and HOTSHOT. The Company had cash, cash equivalents and marketable securities of $33,315,759 at December 31, 2017. The Company's operating plan assumes: (1) the efforts of the Company's Drug Development segment are focused on the support and completion of current clinical trials; (2) reduced spending, compared to the prior year, by the Consumer Operations segment, including reduced marketing spend; and (3) limited headcount additions and corporate expenditures. Based on the Company's implemented operating plan, the Company believes that its existing cash, cash equivalents and marketable securities will be sufficient to allow the Company to fund its current operating plan for at least 12 months from the date the financial statements are issued. Management expects the Company to incur a loss for the foreseeable future. The Company's ability to achieve profitability in the future is dependent upon the successful development, approval and commercialization of its drug product candidates, and achieving a level of revenues adequate to support the Company's cost structure. The Company may never achieve profitability, and unless and until it does, the Company will continue to need to raise additional capital. Management intends to fund future operations through additional private or public debt or equity offerings, and may seek additional capital through arrangements with collaborators or from other sources. There can be no assurances, however, that additional funding will be available on terms acceptable to the Company, or at all. If the Company is unable to raise additional capital in sufficient amounts or on acceptable terms, the Company may have to significantly delay, scale back or discontinue the development or commercialization of one or more of it’s drug product candidates or sell or license assets in the Drug Development and Consumer Operations segments.

Summary of significant accounting policies

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Summary of significant accounting policies

Basis of presentation and use of estimates

The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America ("GAAP"). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification ("ASC") and Accounting Standards Update ("ASU") of the Financial Accounting Standards Board ("FASB"). The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company's management evaluates its estimates, which include, but are not limited to, estimates related to inventory write-offs, clinical study accruals, stock-based compensation expense, and amounts of expenses during the reported period. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.

Prior to the Company's IPO, the Company utilized significant estimates and assumptions in determining the fair value of its common stock. The Company utilized various valuation methodologies in accordance with the framework of the 2004 and 2013 American Institute of Certified Public Accountants Technical Practice Aids, Valuation of Privately-Held Company Equity Securities Issued as Compensation, to estimate the fair value of its common stock. Each valuation methodology included estimates and assumptions that required the Company's judgment. These estimates and assumptions included a number of objective and subjective factors, including external market conditions affecting the biotechnology industry sector, the prices at which the Company sold shares of preferred stock, the superior rights and preferences of securities senior to the Company's common stock at the time and the likelihood of achieving a liquidity event, such as an initial public offering or a sale of the Company. Significant changes to the key assumptions used in the valuations could have resulted in different fair values of common stock at each valuation date and may have materially affected the financial statements.

Principles of consolidation

The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries: TK Pharma, Inc., a Massachusetts Securities Corporation, and Flex Innovation Group LLC, a Delaware limited liability company, which contains the Company's consumer-related operations. All significant intercompany balances and transactions have been eliminated in consolidation.

Concentration of risk

The Company outsources the manufacture of HOTSHOT to a single co-packer that produces bottled finished goods. The Company also sources certain raw materials from sole suppliers. A disruption in the supply of materials or the production of finished goods could significantly impact the Company's revenues in the future as alternative sources of raw materials and co-packing may not be available at commercially reasonable rates or within a reasonably short period of time.

Segment information

Operating segments are defined as components of an enterprise about 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 assess performance. The Company and the Company's chief operating decision maker, the Company's Chief Executive Officer, view the Company's operations and manage its business as two operating segments, Drug Development and Consumer Operations (see Note 15). The Company operates in one geographic segment, the United States.

Concentrations of credit risk and off-balance sheet risk

Cash, cash equivalents and marketable securities are financial instruments that potentially subject the Company to concentrations of credit risk. The Company's cash, cash equivalents and marketable securities are held in accounts at financial institutions that management believes are creditworthy. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. The Company has no financial instruments with off-balance sheet risk of loss.

Revenue

Revenue is comprised of net product revenue and other revenue. Net product revenue includes sales of HOTSHOT finished goods to e-commerce customers, specialty retailers and sports teams. Other revenue consists of payments made by customers for expedited shipping and handling, which the Company began offering during the third quarter of 2016. Revenue is recognized when persuasive evidence of an arrangement exists, delivery of the product has occurred, the sales price is fixed or determinable and collectibility is reasonably assured. For sales through September 30, 2016, the Company issued refunds to e-commerce customers, upon request, within 21 days of shipment. When the Company began selling HOTSHOT on a third-party e-commerce website in October 2016, the refund period and related deferral period increased, as the Company began offering refunds to e-commerce customers, upon request, within 30 days of delivery, for purchases subsequent to September 30, 2016. As the Company currently does not have adequate history to accurately estimate refunds, all e-commerce sales, and their related costs, are deferred and revenue is recognized once the refund period lapses. This deferral represents total deferred revenue presented on the Company's consolidated balance sheet. For specialty retailers and sports teams, the Company does not offer a right of return or refund and revenue is recognized at the time products are delivered to customers.

Discounts provided to customers are accounted for as a reduction of product revenue, and were approximately $278,000 and $135,000 for the years ended December 31, 2017 and December 31, 2016, respectively. There were no such discounts in 2015 as the Company had not yet launched HOTSHOT.

Net product revenue and other revenue are presented net of taxes collected from customers and remitted to governmental authorities.

The Company had no customers that represented greater than 10% of total revenue during the year ended December 31, 2017 or during the year ended December 31, 2016. All revenue was generated from sales within the United States.

Accounts receivable and allowance for doubtful accounts

Accounts receivable are stated at their carrying values, net of any allowances for doubtful accounts. Accounts receivable consist primarily of amounts due from specialty retailers and sports teams, for which collectibility is reasonably assured. Receivables are evaluated for collectibility on a regular basis and an allowance for doubtful accounts is recorded, if necessary. No allowance for doubtful accounts was deemed necessary at December 31, 2017 and December 31, 2016.

Cost of product revenue

Cost of product revenue includes the cost of raw materials utilized to produce HOTSHOT, co-packing fees, repacking fees, in-bound freight charges and warehouse and transportation costs incurred to bring HOTSHOT finished goods to salable condition. All other costs incurred after this condition is met are considered selling costs and included in selling, general and administrative expenses. Cost of product revenue also includes write-offs for inventory that has become obsolete, has a cost basis in excess of its estimated realizable value, or exceeds projected sales, as well as depreciation expense related to manufacturing equipment purchased to support production and royalty amounts payable to certain of the Company's founders on HOTSHOT sales.

Inventory

The Company launched HOTSHOT in the second quarter of 2016 and began capitalizing inventory costs associated with HOTSHOT in the first quarter of 2016, when it was determined that the inventory costs had probable future economic benefit. Inventory is stated at the lower of cost or estimated net realizable value, on a first-in, first-out ("FIFO") basis.

The Company outsources the manufacture of HOTSHOT to a co-packer. Inventory at December 31, 2017 includes raw materials available for future production runs, as well as finished goods.

The Company periodically analyzes its inventory levels and writes down inventory that has become obsolete, has a cost basis in excess of its estimated realizable value, or exceeds projected sales. Estimates of excess inventory consider factors such as inventory levels, production requirements, projected sales and the estimated shelf-lives of inventory components. Inventory write-offs are recorded as a component of cost of product revenue.

Advertising expense

Advertising expense consists of media and production costs related to print and digital advertising. All advertising is expensed as incurred. Total advertising expenses are included in selling, general and administrative and were approximately $3,566,000 and $2,936,000 for the years ended December 31, 2017 and December 31, 2016, respectively. There were no such costs in 2015 as the Company had not yet launched HOTSHOT.

Shipping and handling costs

Shipping and handling costs related to the movement of inventory to the Company's co-packer and from the co-packer to the Company's third-party warehousing and fulfillment partners is capitalized as inventory and expensed as a cost of product revenue when revenue is recognized. Shipping and handling costs to move finished goods from the Company's warehousing and third-party fulfillment partners to customer locations are included in selling, general and administrative expense in the consolidated statement of operations, and were approximately $261,000 and $170,000 for the years ended December 31, 2017 and December 31, 2016, respectively. There were no such costs in 2015 as the Company had not yet launched HOTSHOT.

Property and equipment

Property and equipment is stated at cost, less accumulated depreciation. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred, while costs of major additions and betterments are capitalized. Upon disposal, the related cost and accumulated depreciation is removed from the accounts and any resulting gain or loss is included in the results of operations. Depreciation is recorded, once assets are placed in service, using the straight-line method over the estimated useful lives of the respective assets, which are as follows:



Asset type	Estimated useful life
Computers and computer equipment	3 years
Laboratory equipment	3 years
Manufacturing equipment	3 years
Website development costs	1-2 years

Impairment of long-lived assets

The Company evaluates long-lived assets for potential impairment when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparing the book values of the assets to the expected future net undiscounted cash flows that the assets are expected to generate. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the book value of the assets exceed their fair value. The Company has not recognized any impairment losses through December 31, 2017.

Research and development expense

Research and development costs are charged to expense as incurred in performing research and development activities. The costs include employee compensation costs, clinical study costs, external consultant costs, regulatory costs and facilities and overhead costs. Facilities and overhead costs primarily include the allocation of insurance, rent, utility and office-related expenses attributable to research and development personnel. The Company records payments made to outside vendors in advance of services performed or goods being delivered for use in research and development activities as prepaid expenses, which are expensed as services are performed or goods are delivered.

Stock-based compensation expense

The Company accounts for its stock-based compensation awards to employees and directors in accordance with FASB ASC Topic 718, Compensation-Stock Compensation ("ASC 718"). ASC 718 requires all stock-based payments to employees, including grants of employee stock options, to be recognized in the statement of operations based on their grant date fair values. Compensation expense related to awards to employees with service conditions is recognized on a straight-line basis based on the grant date fair value over the associated service period of the award, which is generally the vesting term. Compensation expense related to awards to employees with performance conditions is recognized based on grant date fair value over the remaining service period when management determines that achievement of the milestone is probable. Management evaluates when the achievement of a performance-based milestone is probable based on the relative satisfaction of the performance conditions as of the reporting date. The Company accounts for stock-based compensation arrangements with non-employees based upon the fair value of the consideration received or the equity instruments issued, whichever is more reliably measurable, in accordance with the provisions of FASB ASC Topic 505-50, Equity-Based Payments to Non-Employees. The measurement date for non-employee awards is generally the date performance of services required from the non-employee is complete, resulting in periodic adjustments to stock-based compensation expense during the vesting period for changes in the fair value of the awards. Stock-based compensation costs for non-employee service awards are recognized as services are provided, which is generally the vesting period, on a straight-line basis. The unvested portion of the awards is subject to re-measurement over the vesting period.

The Company estimates the fair value of its stock options using the Black-Scholes option pricing model, which requires the input of subjective assumptions, including (a) the expected stock price volatility, (b) the expected term of the award, (c) the risk-free interest rate, (d) expected dividends and (e) the estimated fair value of the Company's common stock on the measurement date. Due to the lack of significant trading history for the Company's common stock, it has based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. When selecting these public companies on which it has based its expected stock price volatility, the Company selected companies with comparable characteristics, including enterprise value, risk profiles, position within the industry, and with historical share price information sufficient to meet the expected term of the stock-based awards. The Company computes historical volatility data using the volatility for the selected companies' shares during the equivalent period of the calculated expected term of the stock-based awards. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available. Due to the lack of Company specific historical option activity, the Company has estimated the expected term of its employee stock options using the "simplified" method, whereby, the expected term equals the arithmetic average of the vesting term and the original contractual term of the option. The expected term for non-employee awards is the remaining contractual term of the option. The risk-free interest rates are based on the U.S. Treasury securities with a maturity date commensurate with the expected term of the associated award. The Company has never paid, and does not expect to pay dividends in the foreseeable future.

Prior to adoption of ASU No. 2016-09 Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting, share-based compensation expense was recognized net of estimated forfeitures, such that expense was recognized only for share-based awards that were expected to vest. A forfeiture rate was estimated annually and revised, if necessary, in subsequent periods if actual forfeitures differed from initial estimates. Upon adoption of ASU No. 2016-09 on January 1, 2017, the Company no longer applies a forfeiture rate and instead accounts for forfeitures as they occur.

Income taxes

Income taxes are recorded in accordance with FASB ASC Topic 740, Income Taxes ("ASC 740"), which provides for deferred taxes using an asset and liability approach. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial reporting and the tax reporting basis of assets and liabilities and are measured using the enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. The Company provides a valuation allowance against net deferred tax assets unless, based upon the available evidence, it is more likely than not that the deferred tax assets will be realized. The Company has evaluated available evidence and concluded that the Company may not realize the benefit of its deferred tax assets; therefore a valuation allowance has been established for the full amount of the deferred tax assets.

The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740. 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. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. As of December 31, 2017 and December 31, 2016, the Company did not have any significant uncertain tax positions. The Company's practice is to recognize interest and/or penalties related to income tax matters in income tax expense.

Net loss per share attributable to common stockholders

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

For years ended December 31, 2017, December 31, 2016 and December 31, 2015, the Company has excluded the effects of all potentially dilutive shares from the weighted-average number of common shares outstanding as their inclusion in the computation for each period would be anti-dilutive due to the net loss per share incurred by the Company.

Comprehensive loss

Comprehensive loss is the change in equity of a company during a period from transactions and other events and circumstances, excluding transactions resulting from investments by owners and distributions to owners. Comprehensive loss includes net loss and the change in accumulated other comprehensive loss for the period. Accumulated other comprehensive loss consisted entirely of unrealized gains and losses on available-for-sale marketable securities for the years ended December 31, 2017, December 31, 2016 and December 31, 2015. See the consolidated statements of comprehensive loss for relevant disclosures.

The following tables summarize the changes in accumulated other comprehensive loss during the years ended December 31, 2017, December 31, 2016 and December 31, 2015.



Balance as of December 31, 2016	$	(1,614	)
Other comprehensive gain	367
Balance as of December 31, 2017	$	(1,247	)



Balance as of December 31, 2015	$	(24,654	)
Other comprehensive gain	23,040
Balance as of December 31, 2016	$	(1,614	)



Balance as of December 31, 2014	$	—
Other comprehensive loss	(24,654		)
Balance as of December 31, 2015	$	(24,654	)

Recent accounting pronouncements

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606). The ASU provides for a single comprehensive model for use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance. The accounting standard is effective for interim and annual periods beginning after December 15, 2016 with no early adoption permitted. In July 2015, the FASB deferred the effective date of this accounting update to annual periods beginning after December 15, 2017, along with an option to permit early adoption as of the original effective date. The Company is required to adopt the standard in the ASU using one of two acceptable methods: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU recognized at the date of initial application. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers, Principal versus Agent Considerations (Reporting Revenue Gross versus Net), clarifying the implementation guidance on principal versus agent considerations. Specifically, an entity is required to determine whether the nature of a promise is to provide the specified good or service itself (that is, the entity is a principal) or to arrange for the good or service to be provided to the customer by the other party (that is, the entity is an agent). The determination influences the timing and amount of revenue recognition. The effective date and transition requirements for ASU No. 2016-08 are the same as the effective date and transition requirements for ASU No. 2014-09.

The Company has evaluated the adoption impact of the guidance related to the Company's sales of HOTSHOT. Based on evaluation of the Company's revenue streams, the Company has determined that the timing of recognition for e-commerce sales will change by an immaterial amount, due to e-commerce refund rights. Through December 31, 2017 and prior to adoption of the new standard, since the Company does not have an adequate history to accurately estimate refunds, all e-commerce sales and related costs have been deferred and recognized once the refund period lapses. Under the new standard, the Company will estimate the amount of potential refunds and may recognize revenue related to some of these sales earlier if it is probable that a significant revenue reversal will not occur. Adoption will not have a significant impact on revenue recognition for the company's specialty retail or sports team channels, as no right of refund or return exists.

The guidance is not expected to have a material impact to the consolidated statements of operations or balance sheets in any prior or prospective reporting period. The Company has finalized its accounting policy, and has designed and implemented necessary changes to processes and controls to allow for proper recognition, presentation and disclosure upon adoption effective in the beginning of fiscal year 2018.

In July 2015, the FASB issued ASU No. 2015-11, Inventory (Topic 330). This ASU simplifies the measurement of inventory by requiring certain inventory to be measured at the lower of cost or net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The amendments in this ASU are effective for fiscal years beginning after December 15, 2016 and for interim periods therein. Subsequent measurement is unchanged for inventory measured using LIFO or the retail inventory method. The Company adopted this ASU as of March 31, 2017, which did not have a material impact on its condensed consolidated financial statements

In February 2016, the FASB issued ASU No. 2016-02, Leases. The ASU requires lessees to recognize the assets and liabilities on their balance sheet for the rights and obligations created by most leases and continue to recognize expenses on their income statements over the lease term. It will also require disclosures designed to give financial statement users information on the amount, timing, and uncertainty of cash flows arising from leases. The guidance is effective for annual reporting periods beginning after December 15, 2018, and interim periods within those years. Early adoption is permitted. While the Company is currently evaluating the effect this standard will have on its consolidated financial statements and timing of adoption, the Company expects that upon adoption, it will recognize right-of-use assets and lease liabilities and those amounts could be material. The Company is still assessing the expected impact on our consolidated statements of operations and cash flows.

In March 2016, the FASB issued ASU No. 2016-09, Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. This ASU simplifies the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. The guidance is effective for annual reporting periods beginning after December 15, 2016, and interim periods within those annual periods. The Company adopted the new standard on January 1, 2017 and has elected to account for forfeitures as they occur. The change was applied on a modified retrospective basis with a cumulative effect adjustment to increase retained earnings by approximately $2,000, as of January 1, 2017. In addition, upon adoption of the new standard, the Company has additional deferred tax assets related to tax deductions from excess tax benefits related to the exercise of stock options. As a result, the deferred tax assets associated with net operating losses increased by approximately $42,000 in the first quarter of 2017. The amounts are offset by a corresponding increase in the valuation allowance. As such, there is no net effect on the Company’s consolidated statements of operations for the twelve months ended December 31, 2017.

In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments. The update amends the guidance in ASU 230 Statement of Cash Flows, and clarifies how entities should classify certain cash receipts and cash payments on the statement of cash flows with the objective of reducing the existing diversity in practice related to eight specific cash flow issues. The amendments in this update are effective for fiscal years beginning after December 15, 2017, and interim periods within those years. Early adoption is permitted. The Company does not expect the adoption of ASU 2016-15 to have a material impact on its consolidated financial statements.

In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows, which amends ASU Topic 230. This update requires entities to show the changes in the total of cash, cash equivalents, restricted cash and restricted cash equivalents in the statement of cash flows. As a result, entities will no longer be required to present transfers between cash and cash equivalents and restricted cash and restricted cash equivalents in the statement of cash flows. When cash, cash equivalents, restricted cash and restricted cash equivalents are presented in more than one line item on the balance sheet, the new guidance requires a reconciliation of the totals in the statement of cash flows to the related captions in the balance sheet. Entities will also have to disclose the nature of their restricted cash and restricted cash equivalent balances. The guidance is effective for fiscal years beginning after December 15, 2017 and interim periods within those years. Early adoption is permitted. Entities are required to apply the guidance retrospectively. The new guidance will change the presentation of restricted cash in the Company's consolidated financial statements in the first quarter of 2018.

In May 2017, the FASB issued ASU 2017-09, Stock Compensation (Topic 718): Scope of Modification Accounting, to provide clarity and reduce diversity in practice, cost and complexity when applying the guidance in Topic 718. The guidance is effective for fiscal years beginning after December 15, 2017 and interim periods within those years. Early adoption is permitted. The Company does not expect the adoption of this guidance to have a material effect on its consolidated financial statements and related disclosures.

The Company believes that the impact of other recently issued standards that are not yet effective will not have a material effect on its consolidated financial position or results of operations upon adoption.

Initial public offering

On February 3, 2015, the Company completed its IPO, whereby the Company sold 5,491,191 shares of its common stock (inclusive of 91,191 shares of common stock sold by the Company pursuant to the exercise of an overallotment option granted to the underwriters in connection with the IPO) at a price of $16.00 per share. The shares began trading on The Nasdaq Global Market on January 29, 2015. The aggregate net proceeds received by the Company from the IPO were approximately $79,900,000, after deducting underwriting discounts and commissions and other offering expenses payable by the Company. Upon the closing of the IPO, all outstanding shares of convertible preferred stock converted into 6,971,108 shares of common stock. Additionally, the Company is now authorized to issue 100,000,000 shares of common stock.

Deferred IPO issuance costs, which primarily consisted of direct incremental legal and accounting fees related to the Company's IPO, were capitalized at December 31, 2014. Upon the closing of the IPO in February 2015, IPO issuance costs of $1,848,737, as well as underwriting discounts and commissions of $6,150,134, were offset against the IPO proceeds within additional paid-in capital.

Reverse stock split

In January 2015, the Company effected a one-for-4.2825 reverse stock split of its then issued and outstanding common stock. All share and per share amounts related to issued and outstanding common stock and outstanding options exercisable for common stock included in the Company's consolidated financial statements and notes to consolidated financial statements have been retroactively adjusted for all periods presented to reflect the reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital. The conversion ratios of the Company's convertible preferred stock have also been adjusted to reflect the reverse stock split.

Subsequent events

The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the consolidated financial statements for potential recognition or disclosure in the consolidated financial statements. Subsequent events have been evaluated through the date these consolidated financial statements were issued for potential recognition or disclosure in the consolidated financial statements (see Note 18).

Restricted cash	12 Months Ended
Restricted cash	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Restricted cash	Restricted cash As of December 31, 2017 and December 31, 2016, the Company had $126,595 of restricted cash in the form of a letter of credit. The Company maintains this letter of credit as a security deposit on the lease of its office space in Boston, Massachusetts (see Note 9).

Fair value measurements

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Fair value measurements

The Company records cash equivalents and marketable securities at fair value. ASC Topic 820, Fair Value Measurements and Disclosures established a fair value hierarchy for those instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). The hierarchy consists of three levels:

Level 1 – Unadjusted quoted prices in active markets for identical assets or liabilities.

Level 2 – Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, directly or indirectly, for substantially the full term of the asset or liability.

Level 3 – Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability in which there is little, if any, market activity for the asset or liability at the measurement date.

The following table summarizes the cash equivalents and marketable securities measured at fair value on a recurring basis as of December 31, 2017 and December 31, 2016:



	Level 1		Level 2		Level 3		Balance at December 31, 2017
Cash equivalents	$	5,046,205	$	—	$	—	$	5,046,205
Marketable securities:
U.S. government agency securities	—		8,986,259		—		8,986,259
Commercial paper	—		4,440,689		—		4,440,689
Corporate debt securities	—		702,775		—		702,775
	$	5,046,205	$	14,129,723	$	—	$	19,175,928



	Level 1		Level 2		Level 3		Balance at December 31, 2016
Cash equivalents	$	11,681,074	$	—	$	—	$	11,681,074
Marketable securities:
U.S. government agency securities	—		31,059,491		—		31,059,491
Commercial paper	—		6,081,202		—		6,081,202
Corporate debt securities	—		1,518,240		—		1,518,240
	$	11,681,074	$	38,658,933	$	—	$	50,340,007

Cash equivalents and marketable securities have been initially valued at the transaction price and subsequently valued, at the end of each reporting period, utilizing third-party pricing services or other market observable data. The pricing services utilize industry standard valuation models, including both income and market based approaches and observable market inputs to determine value. The majority of the Company's cash equivalents consist of money market funds that are valued based on publicly available quoted market prices for identical securities as of December 31, 2017. After completing its validation procedures, the Company did not adjust or override any fair value carrying amounts of as of December 31, 2017.

The carrying amounts reflected in the consolidated balance sheets for cash, accounts receivable, prepaid expenses and other current assets, accounts payable, accrued expenses and other current liabilities approximate their fair values at December 31, 2017 and 2016, due to their short-term nature.

The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of assets or liabilities between Level 1 and Level 2 during the year ended December 31, 2017 or during the year ended December 31, 2016. The Company had no financial assets or liabilities that were classified as Level 3 at any point during the year ended December 31, 2017 or during the year ended December 31, 2016.

- 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

Cash equivalents and marketable securities

12 Months Ended

Dec. 31, 2017

Cash and Cash Equivalents [Abstract]

Cash equivalents and marketable securities

The Company considers all highly liquid investments with maturities of three months or less when purchased to be cash equivalents. Cash equivalents as of December 31, 2017 and December 31, 2016 consisted of money market funds.

Marketable securities as of December 31, 2017 and December 31, 2016 consisted of corporate debt securities, commercial paper and U.S. government agency securities. Management determines the appropriate classification of the securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. The Company classifies its marketable securities as available-for-sale pursuant to ASC 320, Investments – Debt and Equity Securities. Marketable securities are recorded at fair value, with unrealized gains and losses included as a component of accumulated other comprehensive income (loss) in stockholders’ equity and a component of total comprehensive income (loss) in the consolidated statement of comprehensive income (loss), until realized. Realized gains and losses are included in investment income on a specific-identification basis. There were no realized gains on marketable securities during the year ended December 31, 2017, and there were immaterial realized gains on marketable securities during the year ended December 31, 2016.

The Company reviews marketable securities for other-than-temporary impairment whenever the fair value of a marketable security is less than the amortized cost and evidence indicates that a marketable security’s carrying amount is not recoverable within a reasonable period of time. Other-than-temporary impairments of investments are recognized in the consolidated statement of operations if the Company has experienced a credit loss, has the intent to sell the marketable security, or if it is more likely than not that the Company will be required to sell the marketable security before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and the duration of the impairment and changes in value subsequent to the end of the period.

Marketable securities at December 31, 2017 and December 31, 2016 consisted of the following:



	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
As of December 31, 2017
Current (due within 1 year):
U.S. government agency securities	$	8,987,254	$	38	$	(1,033	)	$	8,986,259
Commercial paper	4,440,689		—		—			4,440,689
Corporate debt securities	703,027		—		(252		)	702,775
Total	$	14,130,970	$	38	$	(1,285	)	$	14,129,723



	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
As of December 31, 2016
Current (due within 1 year):
U.S. government agency securities	$	31,060,710	$	2,912	$	(4,131	)	$	31,059,491
Commercial paper	6,081,202		—		—			6,081,202
Corporate debt securities	1,518,635		—		(395		)	1,518,240
Total	$	38,660,547	$	2,912	$	(4,526	)	$	38,658,933

The Company held six securities that were in an unrealized loss position at both December 31, 2017 and December 31, 2016, all of which were in a continuous loss position for less than 12 months. The aggregate fair value of securities in an unrealized loss position was $8,191,315 and $16,519,620 at December 31, 2017 and December 31, 2016, respectively. There were no individual securities that were in a significant unrealized loss position as of December 31, 2017 or December 31, 2016. The Company evaluated its securities for other-than-temporary impairment and considered the decline in market value for the securities to be primarily attributable to current economic and market conditions. The Company has the intent and ability to hold such securities until recovery. Based on this analysis, these marketable securities were not considered to be other-than-temporarily impaired as of December 31, 2017.

At December 31, 2017 and December 31, 2016, all investments held by the Company were classified as current. Investments classified as current have maturities of less than one year. Investments classified as noncurrent are those that (i) have a maturity greater than one year and (ii) management does not intend to liquidate within the next year, although these funds are available for use and therefore classified as available-for-sale.

Inventory

12 Months Ended

Dec. 31, 2017

Inventory Disclosure [Abstract]

Inventory

The Company began capitalizing inventory as of March 31, 2016, when it was determined that the inventory had a probable future economic benefit. Inventory has been recorded at cost as of December 31, 2017 and December 31, 2016. Costs capitalized at December 31, 2017 and December 31, 2016 relate to HOTSHOT finished goods, as well as raw materials available to be used for future production runs.

The following table presents inventory:



	December 31, 2017		December 31, 2016
Raw materials	$	17,411	$	19,888
Finished goods	414,480		434,244
Total inventory	$	431,891	$	454,132

In the second quarter of 2017, the Company completed a production run of HOTSHOT. From the second to fourth quarter of 2017, the Company wrote off materials purchased for production that were not expected to be used in future production runs, as well as expiring finished goods. In 2016, the Company wrote off raw materials purchased for production runs of HOTSHOT that were not expected to be used in future production runs, as well as finished goods not expected to be sold based upon projected sales, estimated product shelf life, the number of units produced and production level requirements.

Write-offs totaled approximately $42,000 and $282,000 for the years ended December 31, 2017 and December 31, 2016, respectively, and are included in cost of product revenue in the accompanying consolidated statement of operations.

The cost of product revenue related to deferred revenue is capitalized and recorded as cost of product revenue at the time the revenue is recognized.

Property and equipment, net

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property and equipment, net

Property and equipment, net consists of the following:



	December 31, 2017			December 31, 2016
Manufacturing equipment	$	421,999		$	421,999
Computers and computer equipment	311,847			276,263
Website development costs	177,886			159,836
Laboratory equipment	13,368			13,368
Capital in progress	28,823			7,863
Total property and equipment	953,923			879,329
Accumulated depreciation	(622,883		)	(323,014		)
Property and equipment, net	$	331,040		$	556,315

Capital in progress consists of assets acquired but not yet placed into service. At December 31, 2017 capital in progress consisted of computers and computer equipment, and at December 31, 2016 capital in progress consisted of computers and website development costs.

Depreciation expense was $324,548, $277,231 and $49,881 for the years ended December 31, 2017, December 31, 2016, and December 31, 2015, respectively.

Commitments and contingencies

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Commitments and contingencies

Lease commitments

On April 29, 2014, the Company leased office space in Boston, Massachusetts that was scheduled to expire on August 31, 2017. In January 2017, the Company signed a lease to extend the use of the same office space from September 1, 2017 to August 31, 2019.

Additionally, on October 21, 2014, the Company leased office space in New York, New York under an operating lease that was originally scheduled to expire on October 31, 2018. In March 2017, the Company commenced a plan to transition its consumer operations from New York to Boston. In connection with this transition, the Company terminated its New York office operating lease and was released from any further obligations in July 2017.

As of December 31, 2017, the minimum future lease payments under the Company's Boston operating lease was as follows:



2018	$	466,593
2019	311,062
Total minimum lease payments	$	777,655

Rent expense is being recognized on a straight-line basis. The Company recorded approximately $522,000, $337,000 and $253,000 of rent expense for the twelve months ended December 31, 2017, December 31, 2016 and December 31, 2015, respectively.

Royalty agreement

In March 2014, the Company entered into a royalty agreement with certain of its founders. Under the agreement, the Company agreed to pay the founders an aggregate royalty of 2% of gross sales of the Company's products in perpetuity. The Company began incurring royalty expense upon commencement of HOTSHOT sales during the second quarter of 2016. The Company recorded approximately $25,000 and $20,000 of royalty expense during the twelve months ended December 31, 2017 and December 31, 2016, respectively. Royalty amounts owed to the founders as of December 31, 2017 and December 31, 2016 were approximately $3,000 and $4,000. No royalty amounts were owed to the founders as of December 31, 2015.

Litigation

The Company is not a party to any litigation and does not have contingency reserves established for any litigation liabilities as of December 31, 2017.

Convertible preferred stock	12 Months Ended
Convertible preferred stock	Dec. 31, 2017
Equity [Abstract]
Convertible preferred stock	Convertible preferred stock As of December 31, 2014, the Company had authorized 16,000,000 shares of Series A convertible preferred stock ("Series A Preferred Stock"), $0.0001 par value per share, for issuance. During March, April and May 2014, the Company issued an aggregate of 15,775,221 shares of Series A Preferred Stock for $1.00 per share, resulting in net proceeds to the Company of $15,637,032, which was also the carrying value of the Series A Preferred Stock as of December 31, 2014. As of December 31, 2014, the Company had authorized 14,500,000 shares of Series B convertible preferred stock ("Series B Preferred Stock"), $0.0001 par value per share, for issuance. From July to October 2014, the Company issued an aggregate of 14,078,647 shares of Series B Preferred Stock for $1.81 per share, resulting in net proceeds to the Company of $25,394,135, which was also the carrying value of the Series B Preferred Stock as of December 31, 2014. In conjunction with the Company's IPO in February 2015, all shares of the Series A and Series B Preferred Stock converted into common stock. As of December 31, 2017, there were no shares of Series A convertible preferred stock or Series B convertible preferred stock authorized. On February 3, 2015, the Company filed an amended and restated certificate of incorporation (the “Restated Certificate”) with the Secretary of State of the State of Delaware in connection with the closing of the Company’s IPO. As of December 31, 2017, under the Restated Certificate, the Company is authorized to issue 10,000,000 shares of preferred stock ("Preferred Stock") with a par value of $0.0001 per share. The Company has not issued any shares of Preferred Stock as of December 31, 2017.

Common stock

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Common stock

As of December 31, 2017, the Company had authorized 100,000,000 shares of common stock, $0.0001 par value per share. Each share of common stock is entitled to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when declared by the board of directors. The Company does not intend to declare dividends for the foreseeable future.

Restricted common stock to founders

In March 2014, the Company sold 4,553,415 shares of restricted common stock to the founders of the Company ("recipients"), for $0.0004 per share, for total proceeds of $1,950. In April 2014, based upon anti-dilution provisions granted to the founders, an additional 867,314 shares of restricted common stock were sold to the same founders, after which the anti-dilution provisions were terminated. The restricted common stock vested 25% upon issuance, and the remaining 75% vests ratably over four years, during which time the Company has the right to repurchase the unvested shares held by a recipient if the relationship between such recipient and the Company ceases. If the relationship terminates, the Company has 90 days to repurchase unvested shares at $0.0004. Such shares are not accounted for as outstanding until they vest. There were 5,251,075 shares of restricted common stock outstanding as of December 31, 2017. Unvested restricted common stock awards to non-employees are re-measured at each vest date and each financial reporting date.

The following is a summary of restricted common stock activity:



	Number of Shares		Weighted-Average Grant Date Fair Value
Unvested at December 31, 2016	1,185,958		$	0.10
Issued	—		—
Vested	(1,016,304	)	0.10
Forfeited	—		—
Unvested at December 31, 2017	169,654		$	0.10

The total fair value of shares vested during the twelve months ended 2017, 2016 and 2015 was approximately $3,840,000, $9,646,000 and $15,616,000 respectively.

Restricted common stock to consultants

There were no shares of restricted common stock granted to non-employee consultants and advisors during 2017 or 2015. During 2016, the Company granted a total of 18,194 of shares of restricted common stock to non-employee consultants and advisors. Such shares are not accounted for as outstanding until they vest. There were 12,860 shares of restricted common stock issued to consultants outstanding as of December 31, 2017. Unvested restricted common stock awards to non-employees are re-measured at each vest date and each financial reporting date.

The following is a summary of restricted common stock activity:



	Number of Shares		Weighted-Average Grant Date Fair Value
Unvested at December 31, 2016	10,834		$	9.72
Issued	—		—
Vested	(5,500	)	8.95
Forfeited	—		—
Unvested at December 31, 2017	5,334		$	10.51

The total fair value of shares vested during the twelve months ended 2017 and 2016 was approximately $22,000 and $71,000, respectively. No shares were issued to consultants during the twelve months ended December 31, 2015.

Employee stock purchase plan

In 2015, the Company's Board of Directors adopted, and the Company's stockholders approved, the 2015 Employee Stock Purchase Plan (the "ESPP"). As of the December 31, 2017, no shares of common stock have been purchased under the ESPP.

Shares reserved for future issuance

The Company has reserved the following number of shares of common stock for future issuance:



	As of December 31,
	2017	2016
Stock-based compensation awards	3,439,820	2,722,573
Vesting of restricted common stock	174,988	1,196,792
Employee stock purchase plan	534,274	354,569
Total	4,149,082	4,273,934

Stock-based compensation

12 Months Ended

Dec. 31, 2017

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

Stock-based compensation

In March 2014, the Company adopted the Flex Pharma, Inc. 2014 Equity Incentive Plan (the "2014 Plan"), under which it had the ability to grant incentive stock options ("ISOs"), non-qualified stock options, restricted stock awards, restricted stock units and stock appreciation rights to purchase up to 116,754 shares of common stock. In April 2014, the Company amended the 2014 Plan to reserve for the issuance of up to 1,451,087 shares of common stock pursuant to equity awards. In September 2014, the Company further amended the 2014 Plan to reserve for the issuance of up to 2,070,200 shares of common stock pursuant to equity awards. Terms of stock award agreements, including vesting requirements, were determined by the board of directors, subject to the provisions of the 2014 Plan. For options granted under the 2014 Plan, the exercise price equaled the fair market value of the common stock as determined by the board of directors on the date of grant. No further awards will be granted under the 2014 Plan.

In January 2015, the Company's board of directors adopted, and the Company's stockholders approved, the 2015 Equity Incentive Plan (the "2015 Plan"), which became effective immediately prior to the closing of the Company's IPO. The 2015 Plan provides for the grant of ISOs, nonstatutory stock options, restricted stock awards, restricted stock units, stock appreciation rights, performance-based stock awards and other stock-based awards. Additionally, the 2015 Plan provides for the grant of performance-based cash awards. ISOs may be granted only to the Company's employees. All other awards may be granted to the Company's employees, including officers, and to non-employee directors and consultants. As of December 31, 2017, there were 859,329 shares remaining available for the grant of stock awards under the 2015 Plan.

There were no stock options issued to non-employee consultants or members of the Scientific Advisory Board during 2017. During 2016 and 2015, the Company granted a total of 14,670 and 10,507, respectively, of stock options to non-employee consultants and members of its Scientific Advisory Board. The options generally vest over a four-year period, and have a contractual term of ten years. The total stock-based compensation expense related to all non-employee stock options for the year ended December 31, 2017, December 31, 2016 and December 31, 2015 was approximately $201,000, $370,000 and $517,000, respectively.

The Company has awarded stock options to its employees, directors, advisors and consultants, pursuant to the plans described above. Stock options subsequent to the completion of the Company's IPO are granted with an exercise price equal to the closing market price of the Company's common stock on the date of grant. Stock options generally vest over one to four years and have a contractual term of ten years. Stock options are valued using the Black-Scholes option pricing model and compensation cost is recognized based on the resulting value over the service period. Unvested awards to non-employees are re-measured at each vest date and at each financial reporting date. The following table summarizes stock option activity for employees and non-employees for the twelve months ended December 31, 2017:



	Shares		Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at December 31, 2016	2,156,250		$	8.66	7.94	$	1,605,684
Granted	1,059,500		4.20
Exercised	(1,576	)	1.67
Forfeited	(418,642	)	8.87
Expired	(215,041	)	10.51
Outstanding at December 31, 2017	2,580,491		$	6.65	7.55	$	803,600
Exercisable at December 31, 2017	1,404,844		$	7.21	6.56	$	692,232
Vested or expected to vest at December 31, 2017	2,580,491		$	6.65	7.55	$	803,600

During 2017, 2016 and 2015, the Company granted stock options to purchase an aggregate of 1,059,500, 763,320, and 994,748 shares of its common stock, respectively. The weighted-average grant date fair value of option awards granted during 2017, 2016 and 2015 were $2.80, $6.35, and $8.55, respectively.

The number of stock options exercised during 2017, 2016 and 2015 were 1,576, 8,516, and 47,280, respectively. The weighted-average exercise price of options exercised during 2017, 2016 and 2015 was $1.67, $2.59, and $8.63, respectively. The total intrinsic value of options exercised during 2017, 2016 and 2015 was $2,606, $64,302, and $149,386, respectively. The intrinsic value is calculated as the difference between the fair value of the Company's common stock and the exercise price of the options at the date of exercise.

The Company estimates the fair value of each stock option award on the grant date using the Black-Scholes option-pricing model based on the following assumptions regarding the fair value of the underlying Common Stock on each measurement date:



	Year Ended December 31, 2017		Year Ended December 31, 2016		Year Ended December 31, 2015
Expected volatility	73.87% to 81.04%		71.01% to 74.20%		72.98% to 74.94%
Risk-free interest rate	1.83% to 2.40%		1.23% to 2.40%		1.62% to 2.49%
Expected term	5.3 - 9.5 years		5.3 - 10 years		5.3 - 10 years
Expected dividend yield	0	%	0	%	0	%

Total stock-based compensation expense recognized for employee and non-employee restricted common stock, and stock options granted to employees and non-employees is included in the Company's consolidated statements of operations and comprehensive loss as follows:



	Year Ended December 31, 2017		Year Ended December 31, 2016		Year Ended December 31, 2015
Research and development	$	1,545,737	$	2,435,565	$	3,192,063
Selling, general and administrative	2,673,428		4,137,398		3,405,296
Total	$	4,219,165	$	6,572,963	$	6,597,359

Selling, general and administrative expense for the year ended December 31, 2016 included $285,000 related to stock options that were modified in connection with an employee termination agreement.

As of December 31, 2017, there was approximately $4,533,000 of total unrecognized compensation cost related to unvested equity awards. Total unrecognized compensation cost will be adjusted for the re-measurement of non-employee awards as well as future changes in employee and non-employee forfeitures, if any. The Company expects to recognize that cost over a remaining weighted-average period of 2.26 years.

Income taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income taxes

For the years ended December 31, 2017, December 31, 2016 and December 31, 2015, the Company did not record a current or deferred income tax provision or benefit. The Company's losses before income taxes for the periods presented consisted solely of domestic losses.

On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act tax reform legislation. This legislation makes significant changes in U.S. tax law including a reduction in the corporate tax rates, changes to net operating loss carryforwards and carrybacks, and a repeal of the corporate alternative minimum tax. The legislation reduced the U.S. corporate tax rate from the current rate of 35% to 21%. As a result of the enacted law, the Company was required to revalue deferred tax assets and liabilities at the enacted rate. This revaluation resulted in a decrease in net deferred tax assets of $12,600,000 and a corresponding reduction in the valuation allowance against these assets. There is no impact to income tax expense. The other provisions of the Tax Cuts and Jobs Act did not have a material impact on the 2017 consolidated financial statements.

On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118, or SAB 118, to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed, including computations, in reasonable detail to complete the accounting for certain income tax effects of the Tax Reform Act. The Company has recognized the provisional tax impacts related to the revaluation of the deferred tax assets and liabilities and included these amounts in its consolidated financial statements for the year ended December 31, 2017. The ultimate impact may differ from these provisional amounts due to, among other things, additional analysis, changes in interpretations and assumptions the Company has made, additional regulatory guidance that may be issued, and actions the Company may take as a result of the Tax Reform Act. The accounting is expected to be complete when the 2017 U.S. corporate income tax return is filed in 2018.

The following table presents a reconciliation of income tax expense (benefit) computed at the statutory federal income tax rate to the effective income tax rate as reflected in the consolidated financial statements:



	Year Ended December 31, 2017		Year Ended December 31, 2016		Year Ended December 31, 2015
Federal income tax expense at statutory rate	35.0	%	35.0	%	35.0	%
State income tax, net of federal benefit	5.0	%	5.0	%	3.4	%
Permanent differences	(0.7	)%	0.0	%	(0.2	)%
Stock-based compensation	(1.9	)%	(2.6	)%	(6.3	)%
Research credits	2.2	%	1.9	%	1.8	%
Other, net	(1.3	)%	(0.1	)%	0.4	%
Payroll Tax Credit Election	(0.7	)%	0.0	%	0.0	%
Change in valuation allowance	(1.1	)%	(39.2	)%	(34.1	)%
Deferred rate change	(36.5	)%	0.0	%	0.0	%
Effective tax rate	0.0	%	0.0	%	0.0	%

Deferred income tax assets and liabilities are determined based upon temporary differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse.

The following table presents the significant components of the Company's deferred tax assets and liabilities:



	December 31, 2017			December 31, 2016
Deferred tax assets:
U.S. and state net operating loss carryforwards	$	24,744,841		$	24,322,172
Accruals and other temporary differences	202,301			529,462
Amortization	35,783			32,171
Stock-based compensation	1,591,131			1,847,441
Tax credit carryforward	1,964,189			1,423,292
Total deferred tax assets	28,538,245			28,154,538
Less valuation allowance	(28,533,755		)	(28,127,611		)
Deferred tax assets	4,490			26,927
Deferred tax liabilities:
Stock-based compensation	(4,490		)	(23,316		)
Depreciation	—			(3,611		)
Accruals and other temporary differences	—			—
Deferred tax liabilities	(4,490		)	(26,927		)
Net deferred tax assets	$	—		$	—

As of December 31, 2017, the Company has U.S. federal net operating loss carryforwards of approximately $91,200,000 and U.S. state net operating loss carryforwards of approximately $90,400,000 ($7,100,000 tax affected), which are available to reduce future taxable income. The Company also had federal research and development tax credit carryforwards of approximately $1,600,000 and state research and development tax credit carryforwards of approximately $428,000, which may be used to offset future tax liabilities.

The Company adopted ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting, for the quarter ended March 31, 2017. As a result of adoption, the deferred tax assets associated net operating losses increased by approximately $42,000. These amounts were offset by a corresponding increase in the valuation allowance. The adoption of ASU 2016-09 had no impact to the Company’s consolidated statement of operations, balance sheet, or retained earnings.

The Company's federal and state operating loss carryforwards and tax credit carryforwards will expire at various dates through 2037. Under the provisions of the Internal Revenue Code, the net operating loss and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service and state tax authorities. Net operating loss and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50 percent, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. The amount of the annual limitation is determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. The Company has completed financings since its inception which may have resulted in a change in control as defined by Sections 382 and 383 of the Internal Revenue Code, or could result in a change in control in the future. The Company has not conducted an assessment to determine whether there may have been a Section 382 or 383 ownership changes.

ASC 740 requires 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 considerations of all the evidence, both positive and negative, the Company continues to maintain a valuation allowance for the full amount of the 2017 deferred tax asset because it is more likely than not that the deferred tax asset will not be realized. The valuation allowance increased by approximately $406,000 from December 31, 2016 to December 31, 2017, primarily due to an increase in net operating losses.

The Company has no unrecognized tax benefits. Interest and penalty charges, if any, related to uncertain tax positions would be classified as income tax expenses in the accompanying consolidated statement of operations. At December 31, 2017 and 2016, the Company had no accrued interest or penalties related to uncertain tax positions.

Under the Protecting Americans from Tax Hikes Act, enacted in December 2015, certain qualified small businesses may elect to apply up to $250,000 of its federal research and development tax credit against the Social Security portion of its payroll tax liability. The Company elected the $250,000 credit on its 2016 tax return and utilized approximately $22,000 of the credit as a decrease to its payroll tax expense in 2017.

Net loss per share

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Net loss per share

Because the Company has reported net losses for the periods presented, diluted net loss per common share is the same as basic net loss per common share.

The following potentially dilutive securities outstanding, prior to the use of the treasury stock method or if-converted method, have been excluded from the computation of diluted weighted-average shares outstanding for the periods indicated, because including them would have had an anti-dilutive impact:



	Year Ended December 31, 2017	Year Ended December 31, 2016	Year Ended December 31, 2015
Options to purchase common stock	2,580,491	2,156,250	1,824,973
Unvested restricted common stock	174,988	1,196,792	2,202,262
Total	2,755,479	3,353,042	4,027,235

Segment Information

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Segment Information

Effective as of the second quarter of 2016 and in connection with the launch of HOTSHOT, the Company operates as two reportable segments:


•	The Consumer Operations segment, which reflects the total revenue and costs and expenses related to HOTSHOT and the Company's consumer operations.


•	The Drug Development segment, which reflects the costs and expenses related to the Company's efforts to develop innovative and proprietary drug products to treat muscle cramps, spasms and spasticity associated with severe neurological conditions.

The Company discloses information about its reportable segments based on the way that the Company's Chief Operating Decision Maker, who the Company has identified as the Chief Executive Officer, and management, organizes segments within the Company for making operating decisions and assessing financial performance. The Company evaluates the performance of its reportable segments based on revenue and operating income or loss. The accounting policies of the segments are the same as those described herein as well as those described in Note 2. Corporate and unallocated amounts that do not relate to a reportable segment have been allocated to "Corporate". No asset information has been provided for the Company's reportable segments as management does not measure or allocate such assets on a reportable segment basis.

Information for the Company's reportable segments for the years ended December 31, 2017, December 31, 2016, and December 31, 2015 are as follows:



Year Ended December 31, 2017	Consumer Operations		Drug Development	Corporate	Consolidated
Total revenue	$	1,274,499	—	—	$	1,274,499
Loss from operations	$	8,877,330	16,715,752	9,132,544	$	34,725,626
Interest income, net	$	—	—	291,964	$	291,964



Year Ended December 31, 2016	Consumer Operations		Drug Development	Corporate	Consolidated
Total revenue	$	1,010,663	—	—	$	1,010,663
Loss from operations	$	10,023,137	19,620,338	10,242,757	$	39,886,232
Interest income, net	$	—	—	393,109	$	393,109



Year Ended December 31, 2015	Consumer Operations		Drug Development	Corporate	Consolidated
Total revenue	$	—	—	—	$	—
Loss from operations	$	7,892,584	12,224,692	9,096,382	$	29,213,658
Interest income, net	$	—	—	72,028	$	72,028

Related parties	12 Months Ended
Related parties	Dec. 31, 2017
Related Party Transactions [Abstract]
Related parties	Related parties Royalty agreement In 2014, the Company entered into a royalty agreement with certain of the Company's founders under which these founders are paid a royalty of 2%, in the aggregate, of gross sales of any product sold by the Company or by any of the Company's licensees for use in the treatment of any neuromuscular disorder, and that uses, incorporates or embodies, or is made using, any of the Company's intellectual property, including any know-how. Upon the launch of HOTSHOT in the second quarter of 2016, the Company's founders began earning royalties under this agreement. Royalty amounts earned by the founders during the years ended December 31, 2017 and December 31, 2016 totaled approximately $25,000 and $20,000, respectively, including approximately $3,000 and$4,000 not yet paid as of year end, respectively. There were no such amounts earned during the year ended December 31, 2015. Royalty expense is recorded in cost of product revenue in the consolidated statement of operations. License agreement For the period from May 2014 through July 2016, the Company licensed a portion of its office space to ECLDS, LLC, which was controlled by the Company's former Chief Executive Officer. In October 2015, the license agreement was assigned by ECLDS, LLC to a third party, that was not owned by the Company's former Chief Executive Officer, but for which a business relationship existed. In July 2016, the license agreement terminated. Under the terms of the license, the entity charged the same rental rate as that was charged to the Company. During the years ended December 31, 2016 and December 31, 2015, the Company received approximately $32,000, and $61,000, respectively, in license fees from the aforementioned related party, and such amounts received have been recorded as a reduction to rent expense.

Quarterly financial information (unaudited)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Quarterly financial information (unaudited)



	First Quarter Ended March 31, 2017			Second Quarter Ended June 30, 2017			Third Quarter Ended September 30, 2017			Fourth Quarter Ended December 31, 2017
Net product revenue	$	240,292		$	330,688		$	407,241		$	282,752
Other revenue	2,255			4,835			6,360			76
Total revenue	242,547			335,523			413,601			282,828
Costs and expenses:
Cost of product revenue	79,106			145,325			148,756			133,343
Research and development	3,914,974			4,076,220			4,739,360			4,259,357
Selling, general and administrative	4,594,716			4,990,943			4,934,937			3,983,088
Total costs and expenses	8,588,796			9,212,488			9,823,053			8,375,788
Loss from operations	(8,346,249		)	(8,876,965		)	(9,409,452		)	(8,092,960		)
Interest income, net	77,854			72,342			77,339			64,429
Net loss	$	(8,268,395	)	$	(8,804,623	)	$	(9,332,113	)	$	(8,028,531	)
Net loss per share attributable to common stockholders — basic and diluted	$	(0.49	)	$	(0.51	)	$	(0.54	)	$	(0.46	)
Weighted-average number of common shares outstanding — basic and diluted	16,873,512			17,130,264			17,386,249			17,642,646



	First Quarter Ended March 31, 2016			Second Quarter Ended June 30, 2016			Third Quarter Ended September 30, 2016			Fourth Quarter Ended December 31, 2016
Net product revenue	$	—		$	112,685		$	586,134		$	291,099
Other revenue	—			—			12,940			7,805
Total revenue	—			112,685			599,074			298,904
Costs and expenses:
Cost of product revenue	197,020			110,931			221,090			133,706
Research and development	4,387,079			6,094,921			5,665,357			4,230,804
Selling, general and administrative	5,111,695			5,377,784			5,447,847			3,918,661
Total costs and expenses	9,695,794			11,583,636			11,334,294			8,283,171
Loss from operations	(9,695,794		)	(11,470,951		)	(10,735,220		)	(7,984,267		)
Interest income, net	103,333			107,818			97,726			84,232
Net loss	$	(9,592,461	)	$	(11,363,133	)	$	(10,637,494	)	$	(7,900,035	)
Net loss per share attributable to common stockholders — basic and diluted	$	(0.61	)	$	(0.71	)	$	(0.65	)	$	(0.48	)
Weighted-average number of common shares outstanding — basic and diluted	15,843,532			16,105,555			16,361,617			16,619,596

Summary of significant accounting policies (Policies)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Basis of presentation

Use of estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company's management evaluates its estimates, which include, but are not limited to, estimates related to inventory write-offs, clinical study accruals, stock-based compensation expense, and amounts of expenses during the reported period. The Company bases its estimates on historical experience and other market-specific or other relevant assumptions that it believes to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.

Principles of consolidation

Concentrations of risk, Concentrations of credit risk and off-balance sheet risk

Concentrations of credit risk and off-balance sheet risk

Concentration of risk

Segment information

Revenue

Net product revenue and other revenue are presented net of taxes collected from customers and remitted to governmental authorities.

Revenue

Revenue, discounts

Accounts receivable and allowance for doubtful accounts

Cost of product revenue

Inventory

The Company outsources the manufacture of HOTSHOT to a co-packer. Inventory at December 31, 2017 includes raw materials available for future production runs, as well as finished goods.

Advertising expense

Advertising expense consists of media and production costs related to print and digital advertising. All advertising is expensed as incurred.

Shipping and handling costs

Property and equipment



Asset type	Estimated useful life
Computers and computer equipment	3 years
Laboratory equipment	3 years
Manufacturing equipment	3 years
Website development costs	1-2 years

Impairment of long-lived assets

Research and development expenses

Research and development expense

Stock-based compensation expense

Income taxes

Net loss per share attributable to common stockholders

Comprehensive loss

Recent accounting pronouncements

Subsequent events

Fair value measurements

Level 1 – Unadjusted quoted prices in active markets for identical assets or liabilities.

Summary of significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Depreciation over estimated useful life

Depreciation is recorded, once assets are placed in service, using the straight-line method over the estimated useful lives of the respective assets, which are as follows:



Asset type	Estimated useful life
Computers and computer equipment	3 years
Laboratory equipment	3 years
Manufacturing equipment	3 years
Website development costs	1-2 years

Property and equipment, net consists of the following:



	December 31, 2017			December 31, 2016
Manufacturing equipment	$	421,999		$	421,999
Computers and computer equipment	311,847			276,263
Website development costs	177,886			159,836
Laboratory equipment	13,368			13,368
Capital in progress	28,823			7,863
Total property and equipment	953,923			879,329
Accumulated depreciation	(622,883		)	(323,014		)
Property and equipment, net	$	331,040		$	556,315

Reclassification out of Accumulated Other Comprehensive Income

The following tables summarize the changes in accumulated other comprehensive loss during the years ended December 31, 2017, December 31, 2016 and December 31, 2015.



Balance as of December 31, 2016	$	(1,614	)
Other comprehensive gain	367
Balance as of December 31, 2017	$	(1,247	)



Balance as of December 31, 2015	$	(24,654	)
Other comprehensive gain	23,040
Balance as of December 31, 2016	$	(1,614	)



Balance as of December 31, 2014	$	—
Other comprehensive loss	(24,654		)
Balance as of December 31, 2015	$	(24,654	)

Fair value measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Summary of Cash Equivalents and Marketable Securities Measured at Fair Value on a Recurring Basis

The following table summarizes the cash equivalents and marketable securities measured at fair value on a recurring basis as of December 31, 2017 and December 31, 2016:



	Level 1		Level 2		Level 3		Balance at December 31, 2017
Cash equivalents	$	5,046,205	$	—	$	—	$	5,046,205
Marketable securities:
U.S. government agency securities	—		8,986,259		—		8,986,259
Commercial paper	—		4,440,689		—		4,440,689
Corporate debt securities	—		702,775		—		702,775
	$	5,046,205	$	14,129,723	$	—	$	19,175,928



	Level 1		Level 2		Level 3		Balance at December 31, 2016
Cash equivalents	$	11,681,074	$	—	$	—	$	11,681,074
Marketable securities:
U.S. government agency securities	—		31,059,491		—		31,059,491
Commercial paper	—		6,081,202		—		6,081,202
Corporate debt securities	—		1,518,240		—		1,518,240
	$	11,681,074	$	38,658,933	$	—	$	50,340,007

Cash equivalents and marketable securities (Tables)

12 Months Ended

Dec. 31, 2017

Cash and Cash Equivalents [Abstract]

Schedule of Marketable Securities

Marketable securities at December 31, 2017 and December 31, 2016 consisted of the following:



	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
As of December 31, 2017
Current (due within 1 year):
U.S. government agency securities	$	8,987,254	$	38	$	(1,033	)	$	8,986,259
Commercial paper	4,440,689		—		—			4,440,689
Corporate debt securities	703,027		—		(252		)	702,775
Total	$	14,130,970	$	38	$	(1,285	)	$	14,129,723



	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
As of December 31, 2016
Current (due within 1 year):
U.S. government agency securities	$	31,060,710	$	2,912	$	(4,131	)	$	31,059,491
Commercial paper	6,081,202		—		—			6,081,202
Corporate debt securities	1,518,635		—		(395		)	1,518,240
Total	$	38,660,547	$	2,912	$	(4,526	)	$	38,658,933

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Inventory (Tables)

12 Months Ended

Dec. 31, 2017

Inventory Disclosure [Abstract]

Schedule of Inventory, Net

The following table presents inventory:



	December 31, 2017		December 31, 2016
Raw materials	$	17,411	$	19,888
Finished goods	414,480		434,244
Total inventory	$	431,891	$	454,132

Property and equipment, net (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property and equipment, net

Depreciation is recorded, once assets are placed in service, using the straight-line method over the estimated useful lives of the respective assets, which are as follows:



Asset type	Estimated useful life
Computers and computer equipment	3 years
Laboratory equipment	3 years
Manufacturing equipment	3 years
Website development costs	1-2 years

Property and equipment, net consists of the following:



	December 31, 2017			December 31, 2016
Manufacturing equipment	$	421,999		$	421,999
Computers and computer equipment	311,847			276,263
Website development costs	177,886			159,836
Laboratory equipment	13,368			13,368
Capital in progress	28,823			7,863
Total property and equipment	953,923			879,329
Accumulated depreciation	(622,883		)	(323,014		)
Property and equipment, net	$	331,040		$	556,315

Accrued expenses and other current liabilities (Tables)

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

Accrued expenses

Accrued expenses and other current liabilities consist of the following:



	December 31, 2017		December 31, 2016
Research and development costs	$	2,502,400	$	938,665
Payroll and employee-related costs	874,246		1,453,665
Professional fees	227,980		153,219
Consumer product-related costs	107,595		42,024
Total	$	3,712,221	$	2,587,573

Other current liabilities

Accrued expenses and other current liabilities consist of the following:



	December 31, 2017		December 31, 2016
Research and development costs	$	2,502,400	$	938,665
Payroll and employee-related costs	874,246		1,453,665
Professional fees	227,980		153,219
Consumer product-related costs	107,595		42,024
Total	$	3,712,221	$	2,587,573

Common stock (Tables)

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Restricted common stock activity

The following is a summary of restricted common stock activity:



	Number of Shares		Weighted-Average Grant Date Fair Value
Unvested at December 31, 2016	1,185,958		$	0.10
Issued	—		—
Vested	(1,016,304	)	0.10
Forfeited	—		—
Unvested at December 31, 2017	169,654		$	0.10

The following is a summary of restricted common stock activity:



	Number of Shares		Weighted-Average Grant Date Fair Value
Unvested at December 31, 2016	10,834		$	9.72
Issued	—		—
Vested	(5,500	)	8.95
Forfeited	—		—
Unvested at December 31, 2017	5,334		$	10.51

Shares reserved for future issuance

The Company has reserved the following number of shares of common stock for future issuance:



	As of December 31,
	2017	2016
Stock-based compensation awards	3,439,820	2,722,573
Vesting of restricted common stock	174,988	1,196,792
Employee stock purchase plan	534,274	354,569
Total	4,149,082	4,273,934

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

+ References

Reference 1: 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 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=65877616&loc=d3e177068-122764

Reference 3: 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(d))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 4: 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(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21553-112644

Reference 7: 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 8: 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(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65888546&loc=d3e21300-112643

Reference 10: 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(27))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 11: 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

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21484-112644

Reference 13: 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 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21488-112644

+ Details

Stock-based compensation (Tables)

12 Months Ended

Dec. 31, 2017

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

Summary of stock option activity

The following table summarizes stock option activity for employees and non-employees for the twelve months ended December 31, 2017:



	Shares		Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at December 31, 2016	2,156,250		$	8.66	7.94	$	1,605,684
Granted	1,059,500		4.20
Exercised	(1,576	)	1.67
Forfeited	(418,642	)	8.87
Expired	(215,041	)	10.51
Outstanding at December 31, 2017	2,580,491		$	6.65	7.55	$	803,600
Exercisable at December 31, 2017	1,404,844		$	7.21	6.56	$	692,232
Vested or expected to vest at December 31, 2017	2,580,491		$	6.65	7.55	$	803,600

Schedule of fair value assumptions



	Year Ended December 31, 2017		Year Ended December 31, 2016		Year Ended December 31, 2015
Expected volatility	73.87% to 81.04%		71.01% to 74.20%		72.98% to 74.94%
Risk-free interest rate	1.83% to 2.40%		1.23% to 2.40%		1.62% to 2.49%
Expected term	5.3 - 9.5 years		5.3 - 10 years		5.3 - 10 years
Expected dividend yield	0	%	0	%	0	%

Summary of stock-based compensation expense



	Year Ended December 31, 2017		Year Ended December 31, 2016		Year Ended December 31, 2015
Research and development	$	1,545,737	$	2,435,565	$	3,192,063
Selling, general and administrative	2,673,428		4,137,398		3,405,296
Total	$	4,219,165	$	6,572,963	$	6,597,359

Income taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of effective income tax rate reconciliation



	Year Ended December 31, 2017		Year Ended December 31, 2016		Year Ended December 31, 2015
Federal income tax expense at statutory rate	35.0	%	35.0	%	35.0	%
State income tax, net of federal benefit	5.0	%	5.0	%	3.4	%
Permanent differences	(0.7	)%	0.0	%	(0.2	)%
Stock-based compensation	(1.9	)%	(2.6	)%	(6.3	)%
Research credits	2.2	%	1.9	%	1.8	%
Other, net	(1.3	)%	(0.1	)%	0.4	%
Payroll Tax Credit Election	(0.7	)%	0.0	%	0.0	%
Change in valuation allowance	(1.1	)%	(39.2	)%	(34.1	)%
Deferred rate change	(36.5	)%	0.0	%	0.0	%
Effective tax rate	0.0	%	0.0	%	0.0	%

Schedule of deferred tax assets and liabilities

The following table presents the significant components of the Company's deferred tax assets and liabilities:



	December 31, 2017			December 31, 2016
Deferred tax assets:
U.S. and state net operating loss carryforwards	$	24,744,841		$	24,322,172
Accruals and other temporary differences	202,301			529,462
Amortization	35,783			32,171
Stock-based compensation	1,591,131			1,847,441
Tax credit carryforward	1,964,189			1,423,292
Total deferred tax assets	28,538,245			28,154,538
Less valuation allowance	(28,533,755		)	(28,127,611		)
Deferred tax assets	4,490			26,927
Deferred tax liabilities:
Stock-based compensation	(4,490		)	(23,316		)
Depreciation	—			(3,611		)
Accruals and other temporary differences	—			—
Deferred tax liabilities	(4,490		)	(26,927		)
Net deferred tax assets	$	—		$	—

Net loss per share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Schedule of antidilutive securities excluded from computation of earnings per share



	Year Ended December 31, 2017	Year Ended December 31, 2016	Year Ended December 31, 2015
Options to purchase common stock	2,580,491	2,156,250	1,824,973
Unvested restricted common stock	174,988	1,196,792	2,202,262
Total	2,755,479	3,353,042	4,027,235

Segment Information (Tables)

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Schedule of Segment Reporting Information

Information for the Company's reportable segments for the years ended December 31, 2017, December 31, 2016, and December 31, 2015 are as follows:



Year Ended December 31, 2017	Consumer Operations		Drug Development	Corporate	Consolidated
Total revenue	$	1,274,499	—	—	$	1,274,499
Loss from operations	$	8,877,330	16,715,752	9,132,544	$	34,725,626
Interest income, net	$	—	—	291,964	$	291,964



Year Ended December 31, 2016	Consumer Operations		Drug Development	Corporate	Consolidated
Total revenue	$	1,010,663	—	—	$	1,010,663
Loss from operations	$	10,023,137	19,620,338	10,242,757	$	39,886,232
Interest income, net	$	—	—	393,109	$	393,109



Year Ended December 31, 2015	Consumer Operations		Drug Development	Corporate	Consolidated
Total revenue	$	—	—	—	$	—
Loss from operations	$	7,892,584	12,224,692	9,096,382	$	29,213,658
Interest income, net	$	—	—	72,028	$	72,028

Quarterly financial information (unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Schedule of quarterly financial information



	First Quarter Ended March 31, 2017			Second Quarter Ended June 30, 2017			Third Quarter Ended September 30, 2017			Fourth Quarter Ended December 31, 2017
Net product revenue	$	240,292		$	330,688		$	407,241		$	282,752
Other revenue	2,255			4,835			6,360			76
Total revenue	242,547			335,523			413,601			282,828
Costs and expenses:
Cost of product revenue	79,106			145,325			148,756			133,343
Research and development	3,914,974			4,076,220			4,739,360			4,259,357
Selling, general and administrative	4,594,716			4,990,943			4,934,937			3,983,088
Total costs and expenses	8,588,796			9,212,488			9,823,053			8,375,788
Loss from operations	(8,346,249		)	(8,876,965		)	(9,409,452		)	(8,092,960		)
Interest income, net	77,854			72,342			77,339			64,429
Net loss	$	(8,268,395	)	$	(8,804,623	)	$	(9,332,113	)	$	(8,028,531	)
Net loss per share attributable to common stockholders — basic and diluted	$	(0.49	)	$	(0.51	)	$	(0.54	)	$	(0.46	)
Weighted-average number of common shares outstanding — basic and diluted	16,873,512			17,130,264			17,386,249			17,642,646



	First Quarter Ended March 31, 2016			Second Quarter Ended June 30, 2016			Third Quarter Ended September 30, 2016			Fourth Quarter Ended December 31, 2016
Net product revenue	$	—		$	112,685		$	586,134		$	291,099
Other revenue	—			—			12,940			7,805
Total revenue	—			112,685			599,074			298,904
Costs and expenses:
Cost of product revenue	197,020			110,931			221,090			133,706
Research and development	4,387,079			6,094,921			5,665,357			4,230,804
Selling, general and administrative	5,111,695			5,377,784			5,447,847			3,918,661
Total costs and expenses	9,695,794			11,583,636			11,334,294			8,283,171
Loss from operations	(9,695,794		)	(11,470,951		)	(10,735,220		)	(7,984,267		)
Interest income, net	103,333			107,818			97,726			84,232
Net loss	$	(9,592,461	)	$	(11,363,133	)	$	(10,637,494	)	$	(7,900,035	)
Net loss per share attributable to common stockholders — basic and diluted	$	(0.61	)	$	(0.71	)	$	(0.65	)	$	(0.48	)
Weighted-average number of common shares outstanding — basic and diluted	15,843,532			16,105,555			16,361,617			16,619,596

Organization and operations (Details)		1 Months Ended	12 Months Ended
Organization and operations (Details)	Feb. 03, 2015 USD ($) $ / shares shares	Feb. 28, 2015 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) segment shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments \| segment			2
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued \| shares			0
Proceeds from initial public offering, net of offering costs	$ 79,900,000	$ 79,900,000	$ 0	$ 0	$ 80,435,430
Payments of stock issuance costs		$ 8,000,000
Accumulated deficit			111,079,275	$ 76,645,613
Cash, cash equivalents, and marketable securities			$ 33,315,759
IPO
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued \| shares	5,491,191	5,491,191
Common stock, price per share (in usd per share) \| $ / shares	$ 16.00	$ 16.00
Over-Allotment Option
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued \| shares	91,191	91,191

Summary of significant accounting policies - Narrative (Details)		1 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended			15 Months Ended
	Feb. 03, 2015 USD ($) $ / shares shares	Feb. 28, 2015 USD ($) $ / shares shares	Jan. 31, 2015	Mar. 31, 2017 USD ($)	Sep. 30, 2016	Dec. 31, 2017 USD ($) segment shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($) shares	Jan. 01, 2017 USD ($)
Entity Location [Line Items]
Number of operating segments \| segment						2
Revenue recognition, refund period					21 days				30 days
Sale discounts						$ 278,000	$ 135,000	$ 0
Advertising expenses						3,566,000	2,936,000	0
Shipping and handling costs						261,000	170,000	0
Deferred tax assets						$ 0	0		$ 0
Common stock, shares issued \| shares						0
IPO proceeds, net of issuance costs	$ 79,900,000	$ 79,900,000				$ 0	$ 0	$ 80,435,430
Common stock, number of shares issued from conversion of preferred stock (shares) \| shares	6,971,108
Common stock, shares authorized (shares) \| shares						100,000,000	100,000,000		100,000,000
IPO issuance costs	$ 1,848,737
IPO underwriting discounts and commissions	$ 6,150,134
Reverse stock split conversion ratio			0.2335
IPO
Entity Location [Line Items]
Common stock, shares issued \| shares	5,491,191	5,491,191
Common stock, price per share (in usd per share) \| $ / shares	$ 16.00	$ 16.00
Over-Allotment Option
Entity Location [Line Items]
Common stock, shares issued \| shares	91,191	91,191
United States
Entity Location [Line Items]
Number of geographic segments \| segment						1
Retained Earnings \| Accounting Standards Update 2016-09
Entity Location [Line Items]
Increase to retained earnings due to new accounting principle										$ 2,000
U.S. Federal and State
Entity Location [Line Items]
Operating loss carryforwards that will increase additional paid in capital if used to reduce income taxes payable				$ 42,000

Summary of significant accounting policies - Depreciation Over Estimated Useful Life (Details)	12 Months Ended
	Dec. 31, 2017
Computers and computer equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Minimum \| Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	1 year
Maximum \| Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated useful life	2 years

Summary of significant accounting policies - Summary of changes in accumulated other comprehensive loss (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Equity, beginning balance	$ 59,317,386	$ 92,192,408	$ (6,538,340)
Other comprehensive gain (loss)	367	23,040	(24,654)
Equity, ending balance	29,105,888	59,317,386	92,192,408
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Equity, beginning balance	(1,614)	(24,654)	0
Equity, ending balance	$ (1,247)	$ (1,614)	$ (24,654)

Restricted cash (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 126,595	$ 126,595
Letter of Credit
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 126,595	$ 126,595

Fair value measurements (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Marketable securities:
Marketable securities	$ 14,129,723	$ 38,658,933
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	5,046,205	11,681,074
Marketable securities:
Total assets	19,175,928	50,340,007
Fair Value, Measurements, Recurring \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	5,046,205	11,681,074
Marketable securities:
Total assets	5,046,205	11,681,074
Fair Value, Measurements, Recurring \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Marketable securities:
Total assets	14,129,723	38,658,933
Fair Value, Measurements, Recurring \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Marketable securities:
Total assets	0	0
Fair Value, Measurements, Recurring \| U.S. government agency securities
Marketable securities:
Marketable securities	8,986,259	31,059,491
Fair Value, Measurements, Recurring \| U.S. government agency securities \| Level 1
Marketable securities:
Marketable securities	0	0
Fair Value, Measurements, Recurring \| U.S. government agency securities \| Level 2
Marketable securities:
Marketable securities	8,986,259	31,059,491
Fair Value, Measurements, Recurring \| U.S. government agency securities \| Level 3
Marketable securities:
Marketable securities	0	0
Fair Value, Measurements, Recurring \| Commercial paper
Marketable securities:
Marketable securities	4,440,689	6,081,202
Fair Value, Measurements, Recurring \| Commercial paper \| Level 1
Marketable securities:
Marketable securities	0	0
Fair Value, Measurements, Recurring \| Commercial paper \| Level 2
Marketable securities:
Marketable securities	4,440,689	6,081,202
Fair Value, Measurements, Recurring \| Commercial paper \| Level 3
Marketable securities:
Marketable securities	0	0
Fair Value, Measurements, Recurring \| Corporate debt securities
Marketable securities:
Marketable securities	702,775	1,518,240
Fair Value, Measurements, Recurring \| Corporate debt securities \| Level 1
Marketable securities:
Marketable securities	0	0
Fair Value, Measurements, Recurring \| Corporate debt securities \| Level 2
Marketable securities:
Marketable securities	702,775	1,518,240
Fair Value, Measurements, Recurring \| Corporate debt securities \| Level 3
Marketable securities:
Marketable securities	$ 0	$ 0

Cash equivalents and marketable securities (Details)	12 Months Ended
Cash equivalents and marketable securities (Details)	Dec. 31, 2017 USD ($) security	Dec. 31, 2016 USD ($) security
Cash and Cash Equivalents [Abstract]
Realized gains on marketable securities	$ 0	$ 0
Marketable securities:
Amortized Cost	14,130,970	38,660,547
Unrealized Gains	38	2,912
Unrealized Losses	(1,285)	(4,526)
Fair Value	$ 14,129,723	$ 38,658,933
Number of debt securities held \| security	6	6
Aggregate fair value of debt securities in an unrealized loss position	$ 8,191,315	$ 16,519,620
Current Assets \| U.S. government agency securities
Marketable securities:
Amortized Cost	8,987,254	31,060,710
Unrealized Gains	38	2,912
Unrealized Losses	(1,033)	(4,131)
Fair Value	8,986,259	31,059,491
Current Assets \| Commercial paper
Marketable securities:
Amortized Cost	4,440,689	6,081,202
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	4,440,689	6,081,202
Current Assets \| Corporate debt securities
Marketable securities:
Amortized Cost	703,027	1,518,635
Unrealized Gains	0	0
Unrealized Losses	(252)	(395)
Fair Value	$ 702,775	$ 1,518,240

Inventory (Details) - USD ($)	12 Months Ended
Inventory (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Raw materials	$ 17,411	$ 19,888
Finished goods	414,480	434,244
Total inventory	431,891	454,132
Write-off of inventory	$ 42,000	$ 282,000

Property and equipment, net (Details) - USD ($)	12 Months Ended
Property and equipment, net (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 953,923	$ 879,329
Accumulated depreciation	(622,883)	(323,014)
Property and equipment, net	331,040	556,315
Depreciation expense	324,548	277,231	$ 49,881
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	421,999	421,999
Computers and computer equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	311,847	276,263
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	177,886	159,836
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	13,368	13,368
Capital in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 28,823	$ 7,863

Accrued expenses and other current liabilities (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Research and development costs	$ 2,502,400	$ 938,665
Payroll and employee-related costs	874,246	1,453,665
Professional fees	227,980	153,219
Consumer product-related costs	107,595	42,024
Total	$ 3,712,221	$ 2,587,573

Commitments and contingencies - Minimum future lease payments (Details)	Dec. 31, 2017 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2018	$ 466,593
2019	311,062
Total minimum lease payments	$ 777,655

Commitments and contingencies - Narrative (Details) - USD ($)	1 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Rent expense		$ 522,000	$ 337,000	$ 253,000
Percent of gross sales due to related parties	2.00%				2.00%
Royalty expense		25,000	20,000	0
Royalties payable		$ 3,000	$ 4,000	$ 0

Convertible preferred stock (Details) - USD ($)	3 Months Ended	4 Months Ended	12 Months Ended
Convertible preferred stock (Details) - USD ($)	May 31, 2014	Oct. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Class of Stock [Line Items]
Preferred stock, authorized (shares)			10,000,000	10,000,000
Preferred stock, par value (in usd per share)			$ 0.0001	$ 0.0001
Issuance of stock/IPO proceeds, net of issuance costs (shares)			0
Preferred stock, carrying value			$ 0	$ 0
Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, authorized (shares)					16,000,000
Preferred stock, par value (in usd per share)					$ 0.0001
Issuance of stock/IPO proceeds, net of issuance costs (shares)	15,775,221
Preferred stock, carrying value				15,637,032
Convertible preferred stock, automatic conversion, minimum share price (in usd per share)	$ 1.00
Net proceeds from issuance of convertible preferred stock	$ 15,637,032
Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, authorized (shares)			0		14,500,000
Preferred stock, par value (in usd per share)					$ 0.0001
Issuance of stock/IPO proceeds, net of issuance costs (shares)		14,078,647
Preferred stock, carrying value				$ 25,394,135
Convertible preferred stock, automatic conversion, minimum share price (in usd per share)		$ 1.81
Net proceeds from issuance of convertible preferred stock		$ 25,394,135

Common stock - Narrative (Details)	1 Months Ended		12 Months Ended
Common stock - Narrative (Details)	Apr. 30, 2014 shares	Mar. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) vote $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) shares
Class of Stock [Line Items]
Common stock, shares authorized (shares)			100,000,000	100,000,000
Common stock, par value (in usd per share) \| $ / shares			$ 0.0001	$ 0.0001
Common stock, number of votes per share \| vote			1
Restricted common stock, shares sold			0
Stock issued under Employee Stock Purchase Plan			0
Unvested restricted common stock
Class of Stock [Line Items]
Restricted common stock, shares sold	867,314	4,553,415
Restricted common stock, price per share (in usd per share) \| $ / shares		$ 0.0004
Proceeds from sale of restricted common stock to founders \| $		$ 1,950
Restricted common stock, repurchase period			90 days
Restricted common stock, repurchase price \| $ / shares			$ 0.0004
Restricted common stock, shares outstanding			5,251,075
Restricted common stock, fair value of shares vested \| $			$ 3,840,000	$ 9,646,000	$ 15,616,000
Issued, number of shares (shares)			0
Unvested restricted common stock \| Vests upon issuance
Class of Stock [Line Items]
Restricted common stock, percent vested			25.00%
Unvested restricted common stock \| Vests ratably over four years
Class of Stock [Line Items]
Restricted common stock, percent vested			75.00%
Restricted common stock, vesting period			4 years
Non-employee Consultants and Advisers \| Unvested restricted common stock
Class of Stock [Line Items]
Restricted common stock, shares outstanding			12,860
Restricted common stock, fair value of shares vested \| $			$ 22,000	$ 71,000
Issued, number of shares (shares)			0	18,194	0

Common stock - Restricted common stock activity (Details) - Unvested restricted common stock - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance, non-vested, number of shares (shares)	1,185,958
Issued, number of shares (shares)	0
Vested, number of shares (shares)	(1,016,304)
Forfeited, number of shares (shares)	0
Ending balance, non-vested, number of shares (shares)	169,654	1,185,958
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning balance, non-vested, weighted average grant date fair value (in usd per share)	$ 0.10
Issued, weighted average grant date fair value (in usd per share)	0.00
Vested, weighted average grant date fair value (in usd per share)	0.10
Forfeited, weighted average grant date fair value (in usd per share)	0.00
Ending balance, non-vested, weighted average grant date fair value (in usd per share)	$ 0.10	$ 0.10
Non-employee Consultants and Advisers
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance, non-vested, number of shares (shares)	10,834
Issued, number of shares (shares)	0	18,194	0
Vested, number of shares (shares)	(5,500)
Forfeited, number of shares (shares)	0
Ending balance, non-vested, number of shares (shares)	5,334	10,834
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning balance, non-vested, weighted average grant date fair value (in usd per share)	$ 9.72
Issued, weighted average grant date fair value (in usd per share)	0.00
Vested, weighted average grant date fair value (in usd per share)	8.95
Forfeited, weighted average grant date fair value (in usd per share)	0.00
Ending balance, non-vested, weighted average grant date fair value (in usd per share)	$ 10.51	$ 9.72

Common stock - Shares reserved for future issuance (Details) - shares	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Stock-based compensation awards	3,439,820	2,722,573
Employee stock purchase plan	534,274	354,569
Total	4,149,082	4,273,934
Unvested restricted common stock
Class of Stock [Line Items]
Vesting of restricted common stock	174,988	1,196,792

Stock-based compensation - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2014	Apr. 30, 2014	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 4,219,165	$ 6,572,963	$ 6,597,359
Shares granted (shares)	1,059,500	763,320	994,748
Shares granted, weighted-average grant date fair value (in usd per share)	$ 2.80	$ 6.35	$ 8.55
Shares exercised (shares)	1,576	8,516	47,280
Shares exercised, weighted average exercise price (in usd per share)	$ 1.67	$ 2.59	$ 8.63
Stock options exercised, intrinsic value	$ 2,606	$ 64,302	$ 149,386
Unrecognized compensation cost	$ 4,533,000
Unrecognized compensation cost, recognition period	2 years 3 months 4 days
Non-employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted to non-employee consultants and members of the Scientific Advisory Board (shares)	0	14,670	10,507
Stock options, vesting period	4 years
Stock options, contractual term	10 years
Stock-based compensation expense	$ 201,000	$ 370,000	$ 517,000
Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, contractual term	10 years
Options to purchase common stock \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, vesting period	1 year
Options to purchase common stock \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, vesting period	4 years
Flex Pharma, Inc. 2014 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized (shares)				2,070,200	1,451,087	116,754
Shares remaining available for grant of stock awards (shares)	859,329
Selling, General and Administrative Expenses [Member] \| Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 285,000

Stock-based compensation - Summary of stock option activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shares
Shares outstanding, beginning balance (shares)	2,156,250
Shares granted (shares)	1,059,500	763,320	994,748
Shares exercised (shares)	(1,576)	(8,516)	(47,280)
Shares forfeited (shares)	(418,642)
Shares expired (shares)	(215,041)
Shares outstanding, ending balance (shares)	2,580,491	2,156,250
Shares exercisable (shares)	1,404,844
Shares vested or expected to vest (shares)	2,580,491
Weighted-Average Exercise Price
Shares outstanding, beginning balance, weighted average exercise price (in usd per share)	$ 8.66
Shares granted, weighted average exercise price (in usd per share)	4.20
Shares exercised, weighted average exercise price (in usd per share)	1.67	$ 2.59	$ 8.63
Shares forfeited, weighted average exercise price (in usd per share)	8.87
Shares expired, weighted average exercise price (in usd per share)	10.51
Shares outstanding, ending balance, weighted average exercise price (in usd per share)	6.65	$ 8.66
Shares exercisable, weighted average exercise price (in usd per share)	7.21
Shares vested or expected to vest, weighted average exercise price (in usd per share)	$ 6.65
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding, weighted average remaining contractual term	7 years 6 months 18 days	7 years 11 months 9 days
Exercisable, weighted average remaining contractual term	6 years 6 months 22 days
Vested or expected to vest, weighted average remaining contractual term	7 years 6 months 18 days
Outstanding, aggregate intrinsic value	$ 803,600	$ 1,605,684
Exercisable, aggregate intrinsic value	692,232
Vested or expected to vest, aggregate intrinsic value	$ 803,600

Stock-based compensation - Schedule of fair value assumptions (Details) - Options to purchase common stock	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum (as a percent)	1.83%	1.23%	1.62%
Risk-free interest rate, maximum (as a percent)	2.40%	2.40%	2.49%
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility (as a percent)	73.87%	71.01%	72.98%
Expected term (in years)	5 years 3 months 18 days	5 years 3 months 18 days	5 years 3 months 18 days
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility (as a percent)	81.04%	74.20%	74.94%
Expected term (in years)	9 years 6 months	10 years	10 years

Stock-based compensation - Summary of stock-based compensation expense (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share-Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 4,219,165	$ 6,572,963	$ 6,597,359
Research and development
Employee Service Share-Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,545,737	2,435,565	3,192,063
Selling, general and administrative
Employee Service Share-Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,673,428	$ 4,137,398	$ 3,405,296

Income taxes - Schedule of effective income tax rate reconciliation (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal income tax expense at statutory rate	35.00%	35.00%	35.00%
State income tax, net of federal benefit	5.00%	5.00%	3.40%
Permanent differences	(0.70%)	0.00%	(0.20%)
Stock-based compensation	(1.90%)	(2.60%)	(6.30%)
Research credits	2.20%	1.90%	1.80%
Other, net	(1.30%)	(0.10%)	0.40%
Payroll Tax Credit Election	(0.70%)	0.00%	0.00%
Change in valuation allowance	(1.10%)	(39.20%)	(34.10%)
Deferred rate change	(36.50%)	0.00%	0.00%
Effective tax rate	0.00%	0.00%	0.00%

Income taxes - Schedule of deferred tax assets and liabilities (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
U.S. and state net operating loss carryforwards	$ 24,744,841	$ 24,322,172
Accruals and other temporary differences	202,301	529,462
Amortization	35,783	32,171
Stock-based compensation	1,591,131	1,847,441
Tax credit carryforward	1,964,189	1,423,292
Total deferred tax assets	28,538,245	28,154,538
Less valuation allowance	(28,533,755)	(28,127,611)
Deferred tax assets	4,490	26,927
Deferred tax liabilities:
Stock-based compensation	(4,490)	(23,316)
Depreciation	0	(3,611)
Accruals and other temporary differences	0	0
Deferred tax liabilities	(4,490)	(26,927)
Net deferred tax assets	$ 0	$ 0

Income taxes - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
Income taxes - Narrative (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Decrease in net deferred tax asset		$ 12,600,000
Net impact to income tax expense		0
Income Taxes [Line Items]
Increase (decrease) in valuation allowance		406,000
Payroll tax credit		22,000
U.S. Federal
Income Taxes [Line Items]
Net operating loss carryforward		91,200,000
Research and development tax credit carryforwards		1,600,000
U.S. State
Income Taxes [Line Items]
Net operating loss carryforward		90,400,000
Operating loss carryforward tax affected		7,100,000
Research and development tax credit carryforwards		$ 428,000
U.S. Federal and State
Income Taxes [Line Items]
Operating loss carryforwards that will increase additional paid in capital if used to reduce income taxes payable	$ 42,000

Net loss per share (Details) - shares	12 Months Ended
Net loss per share (Details) - shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	2,755,479	3,353,042	4,027,235
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	2,580,491	2,156,250	1,824,973
Unvested restricted common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	174,988	1,196,792	2,202,262

Segment Information (Details)	3 Months Ended								12 Months Ended
Segment Information (Details)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| segment									2
Segment Reporting Information [Line Items]
Total revenue	$ 282,828	$ 413,601	$ 335,523	$ 242,547	$ 298,904	$ 599,074	$ 112,685	$ 0	$ 1,274,499	$ 1,010,663	$ 0
Loss from operations	8,092,960	9,409,452	8,876,965	8,346,249	7,984,267	10,735,220	11,470,951	9,695,794	34,725,626	39,886,232	29,213,658
Interest income, net	$ 64,429	$ 77,339	$ 72,342	$ 77,854	$ 84,232	$ 97,726	$ 107,818	$ 103,333	291,964	393,109	72,028
Operating Segments \| Consumer Operations
Segment Reporting Information [Line Items]
Total revenue									1,274,499	1,010,663	0
Loss from operations									8,877,330	10,023,137	7,892,584
Interest income, net									0	0	0
Operating Segments \| Drug Development
Segment Reporting Information [Line Items]
Total revenue									0	0	0
Loss from operations									16,715,752	19,620,338	12,224,692
Interest income, net									0	0	0
Corporate
Segment Reporting Information [Line Items]
Total revenue									0	0	0
Loss from operations									9,132,544	10,242,757	9,096,382
Interest income, net									$ 291,964	$ 393,109	$ 72,028

Related parties (Details) - USD ($)	1 Months Ended	12 Months Ended
Related parties (Details) - USD ($)	Mar. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Percent of gross sales due to related parties	2.00%				2.00%
Royalty expense		$ 25,000	$ 20,000	$ 0
Royalties payable		$ 3,000	4,000	0
Affiliated Entity
Related Party Transaction [Line Items]
License fees received			$ 32,000	$ 61,000

Quarterly financial information (unaudited) (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
Quarterly Financial Information Disclosure [Abstract]
Net product revenue	$ 282,752	$ 407,241	$ 330,688	$ 240,292	$ 291,099	$ 586,134	$ 112,685	$ 0	$ 1,260,973	$ 989,918	$ 0
Other revenue	76	6,360	4,835	2,255	7,805	12,940	0	0	13,526	20,745	0
Total revenue	282,828	413,601	335,523	242,547	298,904	599,074	112,685	0	1,274,499	1,010,663	0
Costs and expenses:
Cost of product revenue	133,343	148,756	145,325	79,106	133,706	221,090	110,931	197,020	506,530	662,747	0
Research and development	4,259,357	4,739,360	4,076,220	3,914,974	4,230,804	5,665,357	6,094,921	4,387,079	16,989,911	20,378,161	12,749,379
Selling, general and administrative	3,983,088	4,934,937	4,990,943	4,594,716	3,918,661	5,447,847	5,377,784	5,111,695	18,503,684	19,855,987	16,464,279
Total costs and expenses	8,375,788	9,823,053	9,212,488	8,588,796	8,283,171	11,334,294	11,583,636	9,695,794	36,000,125	40,896,895	29,213,658
Loss from operations	(8,092,960)	(9,409,452)	(8,876,965)	(8,346,249)	(7,984,267)	(10,735,220)	(11,470,951)	(9,695,794)	(34,725,626)	(39,886,232)	(29,213,658)
Interest income, net	64,429	77,339	72,342	77,854	84,232	97,726	107,818	103,333	291,964	393,109	72,028
Net loss	$ (8,028,531)	$ (9,332,113)	$ (8,804,623)	$ (8,268,395)	$ (7,900,035)	$ (10,637,494)	$ (11,363,133)	$ (9,592,461)	$ (34,433,662)	$ (39,493,123)	$ (29,141,630)
Net loss per share attributable to common stockholders - basic and diluted (in usd per share)	$ (0.46)	$ (0.54)	$ (0.51)	$ (0.49)	$ (0.48)	$ (0.65)	$ (0.71)	$ (0.61)	$ (1.99)	$ (2.43)	$ (2.08)
Weighted-average number of common shares outstanding — basic and diluted (shares)	17,642,646	17,386,249	17,130,264	16,873,512	16,619,596	16,361,617	16,105,555	15,843,532	17,260,626	16,233,985	14,032,916

CONSOLIDATED STATEMENT OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (PARENTHETICAL)	12 Months Ended
	Dec. 31, 2015 USD ($)
Statement of Stockholders' Equity [Abstract]
Issuance costs	$ 7,998,871

Subsequent events	12 Months Ended
Subsequent events	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent events	Subsequent events The Company has completed an evaluation of all subsequent events after the balance sheet date of December 31, 2017 through the date these consolidated financial statements were issued. The Company concluded that no subsequent events have occurred that require disclosure.