Stock-Based Compensation
Calyxt, Inc. Equity Incentive Plans
We adopted the Calyxt, Inc. Equity Incentive Plan, or the Initial Plan, which allows for the grant of stock options to attract and retain highly qualified employees. In June 2017, we also adopted an omnibus incentive plan, or the Omnibus Plan, under which we have granted stock options and restricted stock units to certain of our employees, nonemployees, and certain employees and nonemployees of Cellectis.
The options granted under the Initial Plan and the Omnibus Plan, which were only eligible for exercise following the completion of the IPO on July 25, 2017, have an exercise price equal to the estimated fair value of the stock at the grant date for the Omnibus Plan and the grant date for the Initial Plan, respectively.
The Company recognized stock-based compensation expense of $2.3 million and $443 thousand for stock options granted under the plans for the three-month period ended June 30, 2018 and 2017, respectively. The Company recognized stock-based compensation expense of $2.2 million and $443 thousand for stock options granted under the plans for thesix-month period ended June 30, 2018 and 2017, respectively.
For accounting purposes, we treat stock-based compensation awards granted to employees of Cellectis as deemed dividends to Cellectis, which we record quarterly. We recorded $663 thousand and $1.4 million and $69 thousand and $69 thousand in deemed dividends to Cellectis in the three and six months ended June 30, 2018, and 2017, respectively, for such restricted stock units and stock options granted to employees of Cellectis.
At June 30, 2018, we had 3,383,258 stock options outstanding, of which 1,361,055 are vested. At June 30, 2018, the total unrecognized stock-based compensation expense related tonon-vested stock options is approximately $3.7 million, which we expect to recognize over a weighted-average period of 4.2 years.
As of June 30, 2018, we had 1,485,326 shares of common stock issuable upon the exercise of outstanding stock options under the Initial Plan, 1,897,932 shares of common stock issuable upon the exercise of stock options under the Omnibus Plan and restricted stock units with respect to 1,043,581 shares of common stock outstanding under the Omnibus Plan. Of that total, 1,361,055 stock options and restricted stock units were fully vested as of June 30, 2018 or will vest within 60 days of quarter’s end.
Equity instruments issued tonon-employees include RSUs and options to purchase shares of the Company’s common stock. These RSUs and options vest over a certain period during which services are provided. The Company expenses the fair market value of the awards over the period in which the related services are received. Unvested awards arere-measured to fair value until they vest.
At June 30, 2018, we had 1,043,581 restricted stock units outstanding and unvested. As of June 30, 2018, we had approximately $4.6 million of unrecognized stock-based compensation expense related to restricted stock units that we expect to recognize over a weighted-average period of 4.6 years.
The fair value of each stock option is estimated using the Black- Scholes option pricing model at each measurement date. The fair value of stock options under the Black-Scholes model requires management to make assumptions regarding projected employee stock option exercise behaviors, risk-free interest rates, volatility of the stock price, and expected dividends. The awards currently outstanding were granted with vesting terms between two and six years. Certain awards contain a 25% acceleration vesting clause, which was triggered in connection with our IPO. In addition, certain awards contain a provision for 100% accelerated vesting in the event of (a) the termination of employment without cause or (b) the resignation of the employee for good reason within twelve months following a triggering event as defined in the Initial Plan.
We have not historically paid dividends to our stockholders, and we currently do not anticipate paying any dividends in the foreseeable future. As a result, we assumed a dividend yield of 0%. The risk-free interest rate is based upon the rates of U.S. Treasury bills with a term that approximates the expected life of the option. We use the simplified method, or the lattice method when appropriate, to reasonably estimate the expected life of our option awards. Expected volatility is based upon the volatility of comparable public companies.
Cellectis Awards
Cellectis has granted stock options to our employees from time to time. Compensation costs related to the grant of the Cellectis awards to our employees have been recognized in our statements of operations with a corresponding credit to stockholders’ equity, representing Cellectis’ capital contribution. The fair value of each stock option is estimated at the grant date using the Black-Scholes
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