	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
	(In thousands)				(In thousands)
Research and development	$	4,058	$	1,935	$	10,631	$	5,515
General and administrative		3,972		2,169		10,989		5,528
Total stock-based compensation	$	8,030	$	4,104	$	21,620	$	11,043

	Number of Shares			Weighted Average Grant Date Fair Value per Share
Unvested restricted common stock as of December 31, 2019		994,838		$	6.95
Vested		(579,317	)		6.95
Unvested restricted common stock as of September 30, 2020		415,521		$	6.95

As of September 30, 2020, total unrecognized stock-based compensation related to unvested restricted common stock was $2.1 million, which the Company expects to recognize over a remaining weighted-average period of 1.0 years.

On February 6, 2019, the Company adopted the 2019 Equity Incentive Plan (2019 Plan) under which the Board may issue incentive stock options, nonstatutory stock options, restricted stock, restricted stock units, stock appreciation rights, performance units, and performance shares to the Company’s employees, directors, and consultants. The Company initially reserved for issuance 7,688,156 shares of common stock pursuant to the 2019 Plan. The Company’s 2017 Stock Option and Grant Plan (2017 Plan) was terminated; however, shares subject to awards granted under it will continue to be governed by the 2017 Plan. Shares reserved for issuance but not issued pursuant to, or not subject to, awards granted under the 2017 Plan were added to the available shares in the 2019 Plan. Shares subject to awards granted under the 2017 Plan that are repurchased by, or forfeited to, the Company will also be reserved for issuance under the 2019 Plan. On January 1, 2020, the Company added 3,452,643 shares to the shares reserved for issuance. As of September 30, 2020, the Company had reserved 15,618,644 shares of common stock for issuance under the 2019 Plan, of which 5,585,374 shares were available for issuance.

Activity for the options to purchase common stock shown below (in thousands, except share and per share amounts):

	Number of Options			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (In years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2019		8,442,824		$	12.79
Granted		2,536,087			21.42
Exercised		(583,591	)		9.77
Forfeited		(362,050	)		16.53
Outstanding as of September 30, 2020		10,033,270		$	15.01		8.7	$	6,402
Exercisable as of September 30, 2020		2,834,348		$	12.22		8.3	$	3,017
Vested and expected to vest as of September 30, 2020		10,033,270		$	15.01		8.7	$	6,402

The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying stock options and the fair value of the Company’s common stock for stock options that were in-the-money. As of September 30, 2020, total unrecognized stock-based compensation related to unvested stock options was $73.3 million, which the Company expects to recognize over a remaining weighted-average period of 2.8 years.

On February 6, 2019, the Company adopted the 2019 Employee Stock Option Plan (2019 ESPP). The 2019 ESPP will enable eligible employees of the Company to purchase shares of common stock at a discount. As of September 30, 2020, the Company has reserved for issuance 1,974,319 shares of common stock pursuant to the 2019 ESPP. Each offering period is approximately six months long. ESPP participants will purchase shares of common stock at a price per share equal to 85% of the lesser of (1) the fair market value per share of the common stock on the first trading day of the offering period or (2) the fair market value of the common stock on the purchase date.