7. Stock‑Based Compensation

On June 11, 2019, the Company held its 2019 Annual Meeting of Stockholders (the “Annual Meeting”). At the Annual Meeting, the Company’s stockholders approved the Company’s 2019 Equity Incentive Plan (the “2019 Plan”) and the Company’s 2019 Employee Stock Purchase Plan (the “2019 ESPP,” and together with the 2019 Plan, the “Plans”). The 2019 Plan is the successor to the Private Millendo 2012 Stock Plan and the OvaScience 2012 Stock Incentive Plan (each, as amended, the “Prior Plans”) and allows the Company to grant stock options, restricted stock unit awards and other awards at levels determined appropriate by the Company’s Board of Directors (the “Board”) or the Compensation Committee of the Board. No additional awards will be granted under either of the Prior Plans. The 2019 ESPP enables employees to purchase shares of the Company’s common stock through offerings of rights to purchase the Company’s common stock to all eligible employees. The Plans were adopted by the Board on April 29, 2019, subject to approval by the Company’s stockholders, and became effective with such stockholder approval on June 11, 2019. Outstanding awards under the Prior Plans continue to be subject to the terms and conditions of the Prior Plans.

The aggregate number of shares of our common stock initially reserved for issuance under the 2019 Plan was 2,919,872 shares. The number of shares of our common stock reserved for issuance under the 2019 Plan will automatically increase on January 1 of each year, for a period of ten years, from January 1, 2020 continuing through January 1, 2029, by 4% of the total number of shares of our common stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by the Board. The aggregate number of shares of our common stock that may be issued under the 2019 ESPP is 133,580 shares, plus the number of shares of our common stock that are automatically added on January 1st of each year, for a period of up to ten years, from January 1, 2020 continuing through January 1, 2029, by 1% of the total number of shares of our common stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by the Board.

The Company measures employee and nonemployee stock‑based awards at grant date fair value and records compensation expense on a straight‑line basis over the vesting period of the award.

The Company recorded stock‑based compensation expense in the following expense categories of its accompanying consolidated statements of operations and comprehensive loss for the three months ended September 30, 2019 and 2018 and nine months ended September 30, 2019 and 2018, respectively (in thousands):


	Three Months				Nine Months
	Ended				Ended
	September 30,				September 30,
	2019		2018		2019		2018
Research and development	$	180	$	177	$	981	$	315
General and administrative		1,016		246		2,149		444
Total	$	1,196	$	423	$	3,130	$	759

Stock options

Options issued under the 2019 Plan may have a contractual life of up to 10 years and may be exercisable in cash or as otherwise determined by the Board. Vesting generally occurs over a period of not greater than four years.

The following table summarizes the activity related to stock option grants to employees and nonemployees for the nine months ended September 30, 2019:


		Weighted		Weighted-average
		average		remaining
		exercise price		contractual
	Shares	per share		life (years)
Outstanding at December 31, 2018	1,764,287	$	26.81	8.0
Granted	1,190,501		9.82
Exercised	(97,225)		3.71
Forfeited	(269,328)		41.50
Outstanding at September 30, 2019	2,588,235	$	18.34	7.7
Vested and exercisable at September 30, 2019	992,969	$	29.61	5.2
Vested and expected to vest at September 30, 2019	2,588,235	$	18.34	7.7

As of September 30, 2019, the unrecognized compensation cost related to 1,595,266 unvested stock options expected to vest was $10.4 million. This unrecognized compensation will be recognized over an estimated weighted‑average amortization period of 3.0 years. The aggregate intrinsic value of options outstanding and options exercisable as of September 30, 2019 was $1.4 million and $1.3 million, respectively. The options granted during the three and nine months ended September 30, 2019 had an estimated weighted-average grant date fair value of $4.99 and $6.81, respectively. There were 629,720 options granted during the three and nine months ended September 30, 2018 at an estimated weighted-average fair value of $10.08. The grant date fair value of each option grant was estimated during the three and nine months ended September 30, 2019 and 2018 using the following assumptions within the Black‑Scholes option‑pricing model:


	Three Months Ended			Three Months Ended			Nine Months Ended			Nine Months Ended
	September 30,			September 30,			September 30,			September 30,
	2019			2018			2019			2018
Expected term (in years)		6.08			6.08			6.02			6.08
Expected volatility		81	%		65	%		80	%		65	%
Risk-free interest rate		1.51	%		2.78	%		2.23	%		2.78	%
Expected dividend yield		0	%		0	%		0	%		0	%

At the time of the Alizé acquisition in December 2017, Alizé had 6,219 nonemployee (BSA) warrants and 5,360 employee (BSPCE) warrants outstanding, which have weighted‑average exercise prices of €80.06 and €83.40, respectively. As of September 30, 2019, all BSA and BSPCE warrants were vested. During the three and nine months ended September 30, 2019, 710 and 1,310 BSPCE warrants were exercised resulting in the issuance of 9,601 and 17,713 shares of the Company’s common stock, respectively. In addition, during the three and nine months ended September 30, 2019, a total of 910 BSA and BSPCE warrants were forfeited. As of September 30, 2019, there were an aggregate of 126,699 shares of common stock issuable upon the exercise of the BSA and BSPCE warrants with a weighted‑average exercise price of $6.68 per share. These instruments are included in the equity attributable to noncontrolling interests.