Share-Based Compensation | 8. Share‑Based Compensation Share-based compensation expense was included in general and administrative and research and development expenses as follows in the accompanying condensed statements of comprehensive loss (in thousands): Three Months Ended March 31, 2018 2017 General and administrative $ 711 $ 569 Research and development 309 267 Total share-based compensation $ 1,020 $ 836 Restricted Stock Awards During the three months ended March 31, 2018 and 2017, the Company did not grant any restricted stock awards (RSAs). The RSAs previously granted were subject to various vesting schedules and generally vested ratably over a six to 24 month period coinciding with their respective service periods. During the three months ended March 31, 2018 and 2017, zero and 4,009 RSAs vested, respectively. No RSAs were forfeited during the three months ended March 31, 2018 or 2017. Stock Options In April 2015, the Company adopted a 2015 Equity Incentive Plan (the 2015 Plan) under which 320,615 shares of the Company’s common stock were reserved for issuance to employees, directors and consultants. The 2015 Plan permits the grant of incentive and non‑statutory stock options, appreciation rights, restricted stock, restricted stock units, performance stock and cash awards, and other stock‑based awards. Amended and Restated 2015 Equity Incentive Plan In April 2016, the Company’s board of directors approved the Company’s amended and restated 2015 Plan (the A&R 2015 Plan). The Company’s stockholders also approved the A&R 2015 Plan in April 2016 and the A&R 2015 Plan became effective immediately upon the execution and delivery of the underwriting agreement related to the IPO. The A&R 2015 Plan provides for the grant of stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance-based stock awards and other forms of equity awards, as well as performance cash awards. The Company initially reserved 2,400,000 shares of common stock for issuance under the A&R 2015 Plan. Under the A&R 2015 Plan, the number of shares of common stock reserved for issuance thereunder automatically increases on January 1st of each year, for a period of 10 years commencing on January 1, 2017 and ending on (and including) January 1, 2026, to an amount equal to 20% of the Company’s fully-diluted shares as of December 31st of the preceding calendar year. Notwithstanding the foregoing, the Company’s board of directors may act prior to January 1st of a given year to provide that there will be no January 1st increase in the shares reserved for such year, or that the increase in shares reserved for such year will be less than would have otherwise been allowed under the provision. Effective January 1, 2018, 415,077 shares were added to the A&R 2015 Plan under the share reserve provision for a total share reserve of 2,815,077 shares as of March 31, 2018. Inducement Plan In September 2016, the Company’s board of directors approved the Company’s Inducement Plan (the Inducement Plan). The Company initially reserved 300,000 shares of its common stock to be used exclusively for grants of awards to individuals who were not previously employees or directors of the Company, as an inducement material to the individual’s entry into employment with the Company within the meaning of Rule 5635(c)(4) of the NASDAQ Listing Rules. The Plan was approved by the Company’s board of directors without stockholder approval pursuant to Rule 5635(c)(4), and the terms and conditions of the Plan are substantially similar to the Company’s stockholder-approved A&R 2015 Plan. 2016 Employee Stock Purchase Plan In April 2016, the Company’s board of directors approved the 2016 Employee Stock Purchase Plan (the ESPP) in order to enable eligible employees to purchase shares of the Company’s common stock at a discount following the effective date of the IPO. The Company’s stockholders also approved the ESPP in April 2016 and the ESPP became effective immediately upon the execution and delivery of the underwriting agreement related to the IPO. The Company initially reserved 150,000 shares of common stock for issuance under the ESPP. As of March 31, 2018, no shares were purchased under the ESPP. During the three months ended March 31, 2018 and 2017, the Company granted an aggregate of 472,000 and 123,500 stock options, respectively, under the A&R 2015 Plan and the Inducement Plan to its officers, directors, employees and consultants, generally vesting over a four-year period with a weighted average grant date fair value of $10.18 and $6.32 per share, respectively. The Company measures the fair value of stock options with service‑based and performance‑based vesting criteria to employees, consultants and directors on the date of grant using the Black‑Scholes option pricing model. The fair value of equity instruments issued to non‑employees is re‑measured as the award vests. The Company does not have history to support a calculation of volatility and expected term. As such, the Company has used a weighted‑average volatility considering the volatilities of several guideline companies. For purposes of identifying similar entities, the Company considered characteristics such as industry, length of trading history, and stage of life cycle. The assumed dividend yield was based on the Company’s expectation of not paying dividends in the foreseeable future. The average expected life of the options was determined based on the mid‑point between the vesting date and the end of the contractual term according to the “simplified method” as described in Staff Accounting Bulletin 110. The risk‑free interest rate is determined by reference to implied yields available from U.S. Treasury securities with a remaining term equal to the expected life assumed at the date of grant. The Company records forfeitures when they occur. The weighted‑average assumptions used in the Black‑Scholes option‑pricing model are as follows: Three Months Ended March 31, 2018 2017 Expected stock price volatility 66.5 % 65.1 % Expected life of options (years) 5.8 6.1 Expected dividend yield 0 % 0 % Risk free interest rate 2.5 % 2.1 % During the three months ended March 31, 2018 and 2017, 180,348 and 136,353 stock options vested, respectively, and 3,500 and 3,250 were forfeited, respectively. As of March 31, 2018, 2,926,227 stock options were outstanding, and 158,906 shares in the aggregate were available for future issuance under the A&R 2015 and Inducement Plans. Unrecognized share‑based compensation cost for stock options issued under the A&R 2015 Plan and the Inducement Plan was $8.8 million as of March 31, 2018. The non‑employee portion of the unrecognized compensation cost was estimated utilizing the Company’s fair market value for its common stock as of March 31, 2018. The unrecognized share‑based expense is expected to be recognized over a weighted average period of 2.3 years for the stock options. There was no remaining unrecognized stock-based compensation related to the RSAs as of March 31, 2018. |