Stock-Based Compensation | 6. Stock-Based Compensation 2014 Stock Option Plan On July 2, 2014, the Company’s stockholders approved the 2014 Stock Option and Incentive Plan (the “2014 Stock Option Plan”), which became effective upon the completion of the IPO. The 2014 Stock Option Plan provides for the grant of restricted stock awards, incentive stock options and non-statutory stock options. The 2014 Stock Option Plan replaced the Company’s 2011 Stock Option and Grant Plan (the “2011 Stock Option Plan”). The Company will no longer grant stock options or other awards under the 2011 Stock Option Plan. Any options or awards outstanding under the 2011 Stock Option Plan remained outstanding and effective. As of March 31, 2016, the total number of shares reserved under all equity plans is 4,981,583, and the Company had 1,401,941 shares available for future issuance under such plans. The 2014 Stock Option Plan provides for an annual increase, to be added on the first day of each fiscal year, by up to 4% of the Company’s issued and outstanding shares of common stock on the immediately preceding December 31. On January 1, 2016, 1,154,653 shares of common stock, representing 4% of the Company’s issued and outstanding shares of common stock as of December 31, 2015, were added to the 2014 Stock Option Plan. Such shares are included in the equity plan totals specified in the paragraph above. Terms of restricted stock awards and stock option agreements, including vesting requirements, are determined by the Board of Directors or the Compensation Committee of the Board of Directors, subject to the provisions of the applicable stock option plan. Options and restricted stock awards granted by the Company generally vest based on the grantee’s continued service with the Company during a specified period following grant. Awards granted to employees generally vest ratably over four years, with a 25% cliff vesting at the one year anniversary for new employee awards. All awards expire in ten years. During the three months ended March 31, 2016 and 2015, the Company granted 74,039 and 497,100 options, respectively, to employees to purchase shares of common stock that contain performance-based vesting criteria, primarily related to achievement of certain clinical and regulatory development milestones related to the Company’s product candidates. Recognition of stock-based compensation expense associated with these performance-based stock options commences when the performance condition is considered probable of achievement, using management’s best estimates. During the quarter ended June 30, 2015, the achievement of one milestone was considered probable and that milestone was achieved during the quarter ended September 30, 2015. The estimated quantity of awards expected to vest was recognized by determining the cumulative expense as of June 30, 2015 and the remaining expense was recognized over the estimated service period. This milestone represents 35% of the performance-based grants that were made during 2015. The achievement of the remaining milestones was deemed to be not probable as of March 31, 2016 and therefore no expense has been recognized related to these awards in the three months ended March 31, 2016. Stock-based compensation expense recognized during the three months ended March 31, 2016 and 2015 was as follows: Three Months Ended March 31, 2016 2015 (in thousands) Research and development $ 1,611 $ 523 General and administrative 2,103 826 $ 3,714 $ 1,349 For stock option awards, the fair value is estimated at the grant date using the Black-Scholes option-pricing model, taking into account the terms and conditions upon which options are granted. The fair value of the options is amortized on a straight-line basis for awards to employees and on a graded basis for awards to non-employees over the requisite service period of the awards. The weighted average grant date fair value per share relating to outstanding stock options granted under the Company’s stock option plans during the three months ended March 31, 2016 and 2015 was $21.87 and $38.28, respectively. The fair value of each option granted to employees and nonemployee directors during the three months ended March 31, 2016 and 2015, under the Company’s stock option plans has been calculated on the date of grant using the following weighted average assumptions: Three Months Ended March 31, 2016 2015 Expected dividend yield 0% 0% Expected volatility 79.8% 93.0% Risk free interest rate 1.40% 1.46% Expected term 6.06 years 5.89 years Expected dividend yield: Risk-free interest rate: Expected volatility: Expected term (in years): Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from estimates. The Company estimates forfeitures based on historical termination behavior. For the three months ended March 31, 2016 and 2015, forfeiture rates of 6.49% and 10.0%, respectively, were applied. For options granted to nonemployees, the expected life of the option used is ten years, which is the contractual term of each such option. All other assumptions used to calculate the grant date fair value are generally consistent with the assumptions used for options granted to employees. The table below summarizes activity related to stock options: Shares Weighted Average Exercise Price Weighted Average Remaining Life (in years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2015 3,002,809 $ 26.67 8.67 $ 96,479 Granted 636,975 31.80 Exercised (35,242 ) 2.10 Forfeited (24,900 ) 64.68 Outstanding as of March 31, 2016 3,579,642 $ 27.57 8.68 $ 38,036 Vested or expected to vest as of March 31, 2016 2,898,779 $ 26.48 8.62 $ 34,484 Exercisable as of March 31, 2016 924,772 $ 16.71 8.10 $ 16,206 As of March 31, 2016, the Company had unrecognized stock-based compensation expense related to its unvested service-based stock option awards of $39.0 million, which is expected to be recognized over the remaining weighted average vesting period of 3.1 years. The total fair value of shares vested for the three months ended March 31, 2016 and 2015 was $4.1 million and $0.4 million, respectively. In addition, the Company has 433,015 shares of outstanding unvested stock options that vest upon the achievement of certain performance criteria. Total unrecognized stock-based compensation expense related to those awards was $10.2 million at March 31, 2016. The intrinsic value of stock options exercised during the three months ended March 31, 2016 and 2015 was $1.4 million and $1.8 million, respectively. Restricted Stock Awards During the year ended December 31, 2013, the Company granted restricted stock awards to certain officers, employees, directors, and consultants of the Company. During the three months ended March 31, 2016 and 2015, the Company recorded $16,000 and $0.1 million, respectively, of stock-based compensation expense related to its restricted stock. The table below summarizes activity relating to restricted stock: Shares Outstanding as of December 31, 2015 42,781 Issued — Vested (18,060 ) Forfeited — Repurchased — Outstanding as of March 31, 2016 24,721 As of March 31, 2016, the Company had unrecognized stock-based compensation expense related to its unvested restricted stock awards of $19,000, which is expected to be recognized over the remaining weighted average vesting period of 0.33 years. During the three months ended March 31, 2016 and 2015, no shares of restricted stock were issued. Unvested shares are subject to repurchase by the Company, at the issuance price, upon the employee’s termination at the Company’s sole discretion. No shares were repurchased during the three months ended March 31, 2016 and 2015. 2014 Employee Stock Purchase Plan On July 2, 2014, the Company’s stockholders approved the 2014 Employee Stock Purchase Plan, which had been previously approved by the Board of Directors. A total of 282,000 shares of common stock were initially authorized for issuance under this plan. The 2014 Employee Stock Purchase Plan became effective upon the completion of the IPO. As of March 31, 2016, 7,159 shares have been issued under this plan. |