Prior to the pricing of the Company’s IPO on February 11, 2021, the Company granted equity awards to eligible employees, officers, directors, consultants and advisors under the 2015 Stock Incentive Plan (the “2015 Plan”) under which the Company could grant equity awards to eligible employees, officers, directors, consultants and advisors. Subsequent to the pricing of the Company’s IPO, no further awards can be made under the 2015 Plan; however, awards outstanding under the 2015 Plan continue to be governed by the 2015 Plan.

In connection with its IPO, the Company adopted the 2021 Stock Incentive Plan (the “2021 Plan”), which became effective on February 11, 2021. As of December 31, 2021, there were 1,718,093 shares of common stock authorized for issuance under the 2021 Plan. On January 1, 2022, the number of shares of common stock authorized for issuance under the 2021 Plan automatically increased by 998,079 shares. As of March 31, 2022, 1,578,184 shares were reserved for outstanding awards granted under the 2021 Plan and 1,172,500 shares remained available for issuance.

As of December 31, 2021, there were 566,037 shares of common stock authorized for issuance under the 2021 Employee Stock Purchase Plan (the “2021 ESPP”). Under the 2021 ESPP, eligible employees are able to purchase shares of common stock at a specified discount. On January 1, 2022, the number of shares of common stock authorized for issuance under the 2021 ESPP automatically increased by 249,520 shares. As of March 31, 2022, no shares have been issued under the 2021 ESPP and as such, 815,557 shares remained available for issuance under the 2021 ESPP.

A summary of the Company’s restricted stock activity and related information is as follows:


	Number of Shares of Restricted Stock Awards			Weighted Average Grant Date Fair Value
Unvested as of December 31, 2021		12,537		$	24.79
Vested		(4,573	)		22.89
Canceled/Forfeited		(18	)		15.37
Unvested as of March 31, 2022		7,946		$	25.91

The aggregate fair value of restricted stock awards that vested during the three months ended March 31, 2022 and 2021 was less than $0.1 million and $0.1 million, respectively. As of March 31, 2022, total unrecognized compensation cost related to unvested restricted stock awards was approximately $0.2 million, which is expected to be recognized over a weighted-average period of 0.5 years.

A summary of the Company’s restricted stock unit activity and related information is as follows:


	Number of Shares of Restricted Stock Units			Weighted Average Grant Date Fair Value
Unvested as of December 31, 2021		—		$	—
Granted		313,185			3.50
Vested		—			—
Canceled/Forfeited		(375	)		3.50
Unvested as of March 31, 2022		312,810		$	3.50

The Company has granted restricted stock units (“RSUs”) to certain of its employees under the 2021 Plan, as part of its equity compensation program. Pursuant to the terms of the applicable award agreements, each RSU represents the right to receive one share of the Company’s common stock. All restricted stock units granted to employees during the three months ended March 31, 2022 will vest, if at all, upon the achievement of specified development milestones associated with the Company’s DB-OTO program, provided the applicable employee remains continuously employed with the Company on the vesting date. Upon vesting, shares of the Company’s common stock will be delivered to the employee, subject to the payment of applicable withholding taxes. As of March 31, 2022, total unrecognized compensation cost related to the unvested restricted stock units was approximately $1.1 million, which will not be recognized until it becomes probable that the performance conditions will be met.

A summary of the Company’s stock option activity and related information is as follows:


	Number of Stock Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(In years)		(In thousands)
Outstanding as of December 31, 2021		3,037,463		$	5.34		8.9	$	629
Granted		790,100			3.53
Exercised		—			—
Cancelled/forfeited		(55,720	)		8.05
Outstanding as of March 31, 2022		3,771,843		$	4.92		8.8	$	—
Exercisable as of March 31, 2022		1,280,246		$	4.96		8.5	$	—
Vested and expected to vest as of March 31, 2022		3,771,843		$	4.92		8.8	$	—

As of March 31, 2022, total unrecognized compensation cost related to unvested stock options was approximately $9.8 million, which is expected to be recognized over a weighted-average period of 2.9 years. The weighted-average grant-date fair value per share of stock options granted during the three months ended March 31, 2022 and 2021 was $2.63 and $14.60, respectively.

The following table presents the components and classification of stock-based compensation expense (in thousands):


	Three Months Ended March 31,
	2022		2021
Research and development	$	384	$	271
General and administrative		458		375
Total stock-based compensation expense	$	842	$	646