Stockholders' Equity | 13. Stockholders’ equity: Stock-based compensation During the nine months ended September 30, 2017, a total of 908,661 options to purchase Common Stock, with an aggregate fair market value of approximately $1.8 million, were granted to Company employees. Options granted to employees have a term of 10 years from the grant date and vest ratably over a three year period. Options granted to the Company’s Board of Directors have a term of 10 years from the grant date and one-half The Company’s stock-based compensation expense is allocated between research and development and selling, general and administrative as follows: Three months ended, Nine months ended, Stock-based compensation expense September 30, September 30, September 30, September 30, Research and Development $ 0.5 $ 0.5 $ 1.3 $ 2.1 Selling, General and Administrative $ 3.7 $ 3.6 $ 8.9 $ 9.5 The fair value of each option award is estimated on the grant date using the Black-Scholes valuation model that uses assumptions for expected volatility, expected dividends, expected term, and the risk-free interest rate. Expected volatilities are based on implied volatilities from historical volatility of the Common Stock, and other factors estimated over the expected term of the options. Expected term of options granted is derived using the “simplified method” which computes expected term as the average of the sum of the vesting term plus contract term. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for the period of the expected term. The weighted average for key assumptions used in determining the fair value of options granted during the nine months ended September 30, 2017 follows: Expected price volatility 78.68% -78.77% Risk-free interest rate 1.77% -1.87% Weighted average expected life in years 6 years Dividend yield — Option activity during the nine months ended September 30, 2017 was as follows: Number of Weighted Aggregate Outstanding at January 1, 2017 3,468,991 $ 4.14 Granted in 2017 Officers and Directors 83,658 2.64 Others 825,003 1.91 Exercised (151,373 ) 2.07 Forfeitures (1,183,795 ) 5.89 Outstanding at September 30, 2017 3,042,484 $ 2.92 $ 1,466 As of September 30, 2017, options exercisable totaled 1,807,765. There was approximately $8.1 million of unrecognized compensation cost related to non-vested During the nine month ended September 31, 2017, an executive officer of the Company exercised approximately 0.15 million stock options, with net proceeds to the Company of approximately $0.3 million. Restricted stock units During the nine months ended September 30, 2017, 2,342,315 RSUs were granted to the Company’s executive officers and employees, with a fair market value of approximately $4.5 million. The fair value of restricted units is determined using quoted market prices of the Common Stock and the number of shares expected to vest. These RSUs were issued under the Company’s 2011 Equity Incentive Plan, as amended. Of the aforementioned 2017 RSU grants, 2,060,000 are one-half one-half one-half Number of Weighted Outstanding at January 1, 2017 4,584,297 $ 7.29 Granted: Executive officers 1,640,000 1.80 Directors 162,315 2.80 Employees 540,000 2.04 Vested (1,568,042 ) 2.17 Forfeitures (554,675 ) 2.28 Outstanding at September 30, 2017 4,803,895 $ 5.14 Warrants The Company has granted warrants to purchase shares of Common Stock. The fair value of each warrant grant is estimated on the grant date using the Black-Scholes valuation model that uses assumptions for expected volatility, expected dividends, expected term, and the risk-free interest rate. Expected volatilities are based on implied volatilities from historical volatility of the Common Stock, and other factors estimated over the expected term of the warrants. Expected term of warrants granted is derived using the “simplified method” which computes expected term as the average of the sum of the vesting term plus contract term. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for the period of the expected term. The weighted average for key assumptions used in determining the fair value of warrants granted during the nine months ended September 30, 2017 follows: Expected price volatility 78.39% Risk-free interest rate 1.92% Weighted average expected life in years 6 years Dividend yield — Warrant activity during the nine months ended September 30, 2017 was as follows: Number of Weighted Aggregate Outstanding at January 1, 2017 84,986 $ 3.53 Granted in 2017 1,701,583 2.38 Exercised — — Forfeitures — — Outstanding at September 30, 2017 1,786,569 $ 2.43 $ 970 |