In June 2017, the Company’s board of directors adopted the Beam Therapeutics Inc. 2017 Stock Option and Grant Plan, or the 2017 Plan, which provided for the grant of qualified incentive stock options and nonqualified stock options, restricted stock or other awards to the Company’s employees, officers, directors, advisors, and outside consultants for the issuance or purchase of shares of the Company’s common stock. In May 2019, the 2017 Plan was amended to provide up to 8,078,681 shares of common stock for the issuance of stock options and restricted stock.

In October 2019, the Company’s board of directors adopted the Beam Therapeutics Inc. 2019 Equity Incentive Plan, or the 2019 Plan, and, following the IPO, all equity-based awards have been granted under the 2019 Plan. The 2019 Plan provides for the grant of qualified and nonqualified stock options, stock appreciation rights, restricted and unrestricted stock and stock units, performance awards, and other share-based awards to the Company’s employees, officers, directors, advisors, and outside consultants.

The maximum number of shares of the Company’s common stock that may be issued under the 2019 Plan was initially 3,700,000 shares, or the Share Pool, plus the number of shares of the Company’s common stock underlying awards under the 2017 Plan, not to exceed 5,639,818 shares, that become available again for grant under the 2017 Plan in accordance with its terms. The Share Pool will

automatically increase on January 1st of each year from 2021 to 2029 by the lesser of (i) 4.0% of the number of shares of the Company’s common stock outstanding as of the close of business on the immediately preceding December 31st and (ii) the number of shares determined by the Company’s board of directors on or prior to such date for such year.

As of September 30, 2022, the Company had 10,947,167 shares reserved including 1,703,263 shares available for future issuance pursuant to the 2019 Plan.

Stock-based compensation expense recorded as research and development and general and administrative expenses in the condensed consolidated statements of operations and other comprehensive loss is as follows (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
Research and development	$	13,859	$	7,554		38,581		17,049
General and administrative		8,350		5,414		23,241		11,019
Total stock-based compensation expense	$	22,209	$	12,968	$	61,822	$	28,068

The following table provides a summary of option activity under the Company’s equity award plans:


	Number of options			Weighted average exercise price
Outstanding at December 31, 2021		6,034,192		$	32.40
Granted		2,051,846			62.32
Exercised		(369,444	)		5.33
Forfeitures		(109,531	)		55.89
Outstanding at September 30, 2022		7,607,063			41.45
Exercisable as of September 30, 2022		3,421,139			24.52

The weighted-average grant date fair value per share of options granted in the nine months ended September 30, 2022 was $41.84. As of September 30, 2022, there was $148.5 million of unrecognized compensation expense related to unvested stock options, which is expected to be recognized over a weighted-average period of approximately 2.4 years.

The Company issues shares of restricted common stock, including both restricted stock units and restricted stock awards. Restricted common stock issued generally vests over a period of two to four years.


	Shares			Weighted- average grant date fair value
Unvested as of December 31, 2021		1,126,206		$	74.32
Issued		937,725			53.52
Vested		(379,287	)		51.00
Forfeited		(36,865	)		75.65
Unvested as of September 30, 2022		1,647,779		$	67.82

At September 30, 2022, there was approximately $98.3 million of unrecognized stock-based compensation expense related to restricted stock that is expected to vest. These costs are expected to be recognized over a weighted-average remaining vesting period of approximately 3.2 years.

In February 2020, the Company’s board of directors adopted the Beam Therapeutics Inc. 2019 Employee Stock Purchase Plan, or ESPP, which was approved by the Company’s stockholders. Pursuant to the ESPP, certain employees of the Company, excluding consultants and non-employee directors, are eligible to purchase common stock of the Company at a reduced rate during offering periods. The ESPP permits participants to purchase common stock using funds contributed through payroll deductions, subject to a calendar year limit of $25,000 and at a purchase price of 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the applicable purchase date, which will be the final trading day of the applicable purchase period. The ESPP has two annual purchase periods extending from October to March and April to September.

The Company issued 41,083 and 70,073 shares under the ESPP during the three and nine months ended September 30, 2022, respectively. There were no shares issued under the ESPP during the nine months ended September 30, 2021. As of September 30, 2022, the Company had 1,665,199 shares available for issuance under the ESPP.

Stock-based compensation recognized under the ESPP for the three and nine months ended September 30, 2022 was $0.2 million and $1.1 million, respectively. There was no stock-based compensation expense recorded under the ESPP for the three and nine months ended September 30, 2021.