The Class B‑2 Warrant and the Milestone Warrant may be exercised by the holder, in whole or in part, upon the payment of the exercise price in cash. The Class B‑2 Warrant and the Milestone Warrant terminate upon the earliest to occur of (a) the 10-year anniversary of their issuance date or (b) a liquidation event, as defined therein.
Class C Preferred Stock
On August 11, 2014, the Company entered into a Class C Stock Purchase Agreement with certain investors.
At closing, one of these investors purchased 504,478 shares of Class C preferred stock at a price of $3.96 per share.
After the initial closing, the Company agreed to sell, and these investors each agreed to purchase, an aggregate of 551,472 additional shares of Class C preferred stock at a purchase price of $4.53 per share (the “Class C Milestone Shares”) upon certain conditions which were met in March 2015, resulting in the Class C Milestone Shares being purchased by these investors in exchange for an aggregate purchase price of $5.0 million in cash.
Class D Preferred Stock Issuance
On September 3, 2015, the Company entered into a Class D Stock Purchase Agreement with an investor pursuant to which the Company issued and sold an aggregate of 3,093,092 shares of Class D preferred stock at a price per share of $21.01 for an aggregate of $64.8 million, net of issuance costs.
Common Stock Settlement and Issuance
On December 29, 2017, the Company entered into a settlement agreement and release with a stockholder to whom the Company had issued a promissory note in 2012. Under the settlement agreement, the Company was obligated to issue 105,237 shares of common stock as of December 31, 2017 and recognized a non-cash expense of $11.6 million within general and administrative expense for the year ended December 31, 2017. The Company issued the shares in January 2018.
8. Stock-based Compensation
2014 Stock Plan (the “2014 Plan”) and 2016 Equity Incentive Plan (the “2016 Plan")
In May 2014, the Company’s Board of Directors adopted the 2014 Stock Plan (the “2014 Plan”), and in January 2016, the Company adopted the 2016 Equity Incentive Plan (the “2016 Plan” and, together with the 2014 Plan, the “Plans”). The 2016 Plan became effective on February 10, 2016, or the IPO Date. On and after the IPO Date, no additional stock awards may be granted under the 2014 Plan. The Board may amend or suspend the 2016 Plan at any time, although no such action may materially impair the rights under any then-outstanding award without the holder’s consent. The Company will obtain stockholder approval for any amendments to the 2016 Plan as required by law. No incentive stock options may be granted under the 2016 Plan after the tenth anniversary of the effective date of the 2016 Plan. Initially, the aggregate number of shares of the Company’s common stock that was available to be issued pursuant to stock awards under the 2016 Plan was 4,339,451 shares, which was the sum of (1) 2,400,000 new shares, plus (2) the number of shares reserved for issuance under the 2014 Plan on the IPO Date, plus (3) any shares subject to outstanding stock awards that would have otherwise been returned to the 2014 Plan. Additionally, the number of shares of the Company’s common stock reserved for issuance under the 2016 Plan will automatically increase on January 1 of each year, beginning on January 1, 2017 and continuing through and including January 1, 2026, by 4.0% of the total number of shares of the Company’s capital stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares determined by the Board. The maximum number of shares that may be issued pursuant to the exercise of incentive stock options under the 2016 Plan is 8,678,902 shares.
The Company has not granted stock appreciation rights to directors, officers or employees under the Plans since their inception. The Company granted 57,500 service-based restricted stock awards to several employees in August 2016 and 49,332 performance-based restricted stock units to several employees in March 2017. Options generally expire ten