Quarterly report pursuant to Section 13 or 15(d)

Stock Option and Incentive Plans

Stock Option and Incentive Plans
6 Months Ended
Jun. 30, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
Stock Option and Incentive Plans
10. Stock Option and Incentive Plans
Amended and Restated 2008 Equity Incentive Plan
In July 2008, the Company adopted the 2008 Equity Incentive Plan (the “Plan”). On February 26, 2013, the board of directors approved an amended and restated plan (the “Amended Plan”) under which the number of shares of common stock available for issuance was 1,571,428. For new awards, the period that vested awards would remain exercisable upon termination of service was reduced from ten years to two years. The board of directors also increased the number of shares of common stock available under the Company’s Amended Plan on February 24, 2014 and April 29, 2014 to 1,857,142 and 2,357,142, respectively.
As of the closing of the Company’s IPO, there were no further grants made under the Amended Plan.
2014 Omnibus Incentive Plan
In April 2014, the Company’s board of directors adopted the 2014 Omnibus Incentive Plan (the “2014 Plan”). The 2014 Plan was approved by the Company’s stockholders on July 3, 2014. The 2014 Plan allows for the granting of incentive and
stock options, restricted stock and stock unit awards, stock appreciation rights and other performance-based awards to the Company’s employees, members of the board of directors and consultants of the Company. On July 28, 2014, the effective date of the 2014 Plan, the number of shares of common stock reserved pursuant to the 2014 Plan was 571,429. The 2014 Plan provides for an annual increase, to be added on the first day of each fiscal year, beginning with the fiscal year ended December 31, 2015 and ending on January 1, 2024, equal to the lesser of (i) 4% of the outstanding shares of common stock on December 31 immediately preceding such date or (ii) an amount determined by the Company’s board of directors. Consistent with the provision for annual increases, an additional 9,696,859 shares of common stock have been made available for issuance under the 2014 Plan.
The Company recognized compensation expense for share-based compensation based on the fair value of the underlying instrument. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. A summary of stock option activity for the six months ended June 30, 2019, is summarized as follows:
Number of









(in years)


Options outstanding at December 31, 2018
    7,187,885     $ 3.17                  
    5,505,000       0.40                  
    —         —                    
    (192,266     2.92                  
    (135,625     1.22                  
Options outstanding at June 30, 2019
    12,364,994       1.96       7.67     $ 585,100  
Vested and exercisable at June 30, 2019
    5,540,325       3.49       5.63     $ 29,138  
The fair value of each option grant is estimated on the date of the grant using the Black-Scholes option-pricing model. The weighted average grant date fair value of options granted during the three months ended June 30, 2019 and 2018 was $0.41, and $1.63, respectively, and the 
six months ended June 30, 2019 and 2018 was 
$0.40 and $1.45, respectively. Total compensation expense recognized amounted to $369,927 and $416,133 
for the three months ended June 30, 2019 and 2018, respectively, and
 $693,701 and $853,814 for the six months ended June 30, 2019 and 2018, respectively. As of June 30, 2019, the total remaining unrecognized compensation cost related to unvested stock options was approximately $3.2 million which will be recognized over a weighted average period of approximately 2.83 years.
The following assumptions were used to compute the fair value of stock options granted during the period:
Three Months Ended

June 30,
Six Months Ended

June 30,
Risk free interest rate
    2.28     2.81     2.37     2.57
Expected dividend yield
          —               —    
Expected term (in years)
    6.09       5.40       6.08       6.02  
Expected volatility
    90.0     82.5     89.7     82.3
Expected volatility—
The Company
based the expected volatility on the historical volatility of its own common shares.
Expected term—
The Company based expected term on the midpoint of the vesting period and the contractual term of each respective option grant.
Risk-free interest rate
—The Company estimated the risk-free interest rate in reference to yield on U.S. Treasury securities with a maturity date commensurate with the expected term of the associated award.
Expected dividend yield—
The Company estimated the expected dividend yield based on consideration of its historical dividend experience and future dividend expectations. The Company has not historically declared or paid dividends to common stockholders. Moreover, it does not intend to pay dividends in the future, but instead expects to retain any earnings to invest in its continued growth.