Stock-Based Compensation | 6. The Plan : Our 2010 Equity Incentive Plan, as amended (the “Plan”), provides for grants of incentive and non-qualified stock options for purchase of our common stock at a price per share equal to the closing market price on the date of grant and for awards of restricted stock units and restricted stock for no consideration payable by the recipient. The number of shares reserved for issuance under the Plan may be increased annually by up to three percent of the outstanding stock of the Company and on January 1, 2016, an additional 550,000 shares were reserved for issuance under the Plan. An aggregate of 8,430,945 shares are reserved for issuance under the Plan as of March 31, 2016. All stock issuances under the Plan are made with new shares from our authorized but unissued common stock. The term of grants and awards under the Plan may not exceed ten years. Employees, non-employee directors, and consultants are eligible to participate in the Plan. For purposes of determining stock-based compensation expense, we include non-employee directors with employees; we account for consultant compensation expense separately. Option activity under the Plan is as follows: Weighted Average Options Exercise Outstanding Price Balance at December 31, 2014 4,243,425 $7.01 Granted 2,152,500 $4.50 Cancelled (232,292 ) $2.85 Exercised (251,208 ) $2.27 Balance at December 31, 2015 5,912,425 $6.46 Granted 487,500 $8.18 Exercised (5,000 ) $1.80 Balance at March 31, 2016 6,394,925 $6.60 Vesting periods of stock and unit awards and option grants are determined by the Company’s board of directors. The majority of options granted by the Company vest over four years, with 25 percent vesting on the one-year anniversary of the vesting commencement date and 75 percent vesting in equal monthly installments thereafter. A majority of those options are exercisable at any time but, if exercised, are subject to a lapsing right of repurchase by us at the exercise price until fully vested. During March 2015, we granted a total of 316,000 options that vest based on certain performance milestones of the Company. We estimated the vesting term for each performance objective on the date of grant, and on each reporting date thereafter, based on our internal timelines and operating projections. Our estimates of vesting ranged from approximately nine to 30 months, with a weighted average vesting term of 11.0 months remaining as of March 31, 2016. A total of 30 percent of these options had vested through March 31, 2016 and none had been cancelled. During July 2012, January 2013, and May 2013 we awarded 33,000 shares, 40,000 shares, and 47,500 shares, respectively, of restricted stock; 25 percent of each award vests on each annual anniversary date of the award. Through March 31, 2016, none of the restricted stock had been cancelled. During March 2015, we awarded 824,200 restricted stock units (“RSUs”) to employees. These RSUs vest based on certain performance milestones of the Company. We estimated the vesting term for each performance objective on the award date, and on each reporting date thereafter, based on our internal timelines and operating projections. Our estimates of vesting ranged from approximately 21 to 30 months, with a weighted average vesting term of 11.2 months remaining as of March 31, 2016. None of these RSUs had vested or been cancelled as of March 31, 2016. During May 2015, we awarded 160,000 RSUs to employee and non-employee directors; such RSUs vest on May 24, 2016. Each RSU entitles the recipient to one share of our common stock upon vesting. Through March 31, 2016, none of these RSUs had vested and none had been cancelled. No tax benefits arising from stock-based compensation have been recognized in the consolidated statements of operations and comprehensive loss through March 31, 2016. 6. (continued) Grants and Awards to Employees : We account for option grants, restricted stock awards, and RSU awards to employees based on their estimated fair values on the date of grant or award, with the resulting stock-based compensation recorded over the requisite service period on a straight-line basis. For the options and RSUs that vest upon performance milestones, we estimate the probability that the performance milestones will be met and record the related stock-based compensation expense. During the three months ended March 31, 2015 and 2016, we determined that two of the three performance targets for our performance-based awards were probable of being achieved and, therefore, recorded expense for those awards only. Stock-based compensation arising from employee options and awards under the Plan is as follows: Three Months Ended March 31, 2015 2016 (in thousands) Employee Stock-Based Compensation: Research and development expense $ 295 $ 364 General and administrative expense 232 791 $ 527 $ 1,155 The fair value of restricted stock and RSU awards is equal to the closing market price of our common stock on the date of award. The fair value of options granted was estimated on the date of grant using the following weighted- average assumptions: Three Months Ended March 31, 2015 2016 Risk-free interest rate 1.7% 1.6% Expected volatility of common stock 56.4% 58.4% Expected life in years 5.71 6.25 Dividend yield 0% 0% The assumed risk-free interest rate was based on the implied yield on a U.S. Treasury zero-coupon issue with a remaining term equal to the expected life of the option. The assumed volatility was calculated based on the historical market prices of a selected group of publicly traded companies considered to be our peers; we use peer group data due to the fact that we have limited historical trading data but adjusted the 2016 volatility upward by approximately three percent to allow us to move toward using our trading history, which is more volatile than our peer group. For options that vest based on passage of time, the expected option life was calculated using the simplified method under the accounting standard for stock compensation and a ten-year option expiration; we use the simplified method because we do not yet have adequate history as a public company to establish a reasonable expected life. For options that vest based on performance achievements, the expected life was calculated based on the requisite service periods estimated by management and a ten-year option expiration. The expected dividend yield of zero reflects that we have not paid cash dividends since inception and do not intend to pay cash dividends in the foreseeable future. The options granted to employees during the three months ended March 31, 2016 had a weighted average grant date fair value of $4.55. The aggregate intrinsic value of options exercised during the three months ended March 31, 2015 and 2016 was $135,000 and $34,000, respectively. 6. (continued) Stock Options to Consultants : We account for stock options granted to consultants at their fair value. Under this method, the fair value is estimated at each reporting date during the vesting period using the Black-Scholes option-pricing model. The resulting stock-based compensation expense, or income if the fair value declines in a reporting period, is recorded over the consultant’s service period. Fully vested options to purchase 7,500 shares of common stock were granted to consultants during the three months ended March 31, 2016; no options were granted to consultants during the three months ended March 31, 2015. Stock-based compensation expense arising from consultant options granted under the Plan is as follows: Three Months Ended March 31, 2015 2016 (in thousands) Consultant Stock-Based Compensation: Research and development expense $ 1 $ 40 General and administrative expense 27 — $ 28 $ 40 The fair value of the options granted to consultants during the three months ended March 31, 2016 was estimated to be $5.30 per share based on weighted-average assumptions of a risk-free interest rate of 2.02 percent, volatility of 57.4 percent, an option life of ten years, and a dividend yield of zero percent. The assumed risk-free interest rate was based on the implied yield on a U.S. Treasury zero-coupon issue with a remaining term equal to the expected life of the option. The assumed volatility was calculated from the historical market prices of a selected group of publicly traded companies considered to be our peers; we use peer group data due to the fact that we have limited historical trading data. The expected option life is the remaining term of the option. The expected dividend yield of zero reflects that we have not paid cash dividends since inception and do not intend to pay cash dividends in the foreseeable future. There were no unvested consultant options at either March 31, 2015 or March 31, 2016. |