Stock-Based Compensation

3 Months Ended

Mar. 31, 2022

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

8. Stock-Based Compensation

A summary of stock option activity under our 2011 Equity Incentive Plan (“2011 Plan”) for the three months ended March 31, 2022 is presented below (in thousands, except per share and contractual life data).

	Number of Shares			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Life (in Years)
Options outstanding as of December 31, 2021		182		$	15.68		6.59
Granted		—		$	—
Exercised		—		$	—
Forfeited or expired		(2	)	$	40.00
Options outstanding as of March 31, 2022		180		$	15.47		6.40
Options exercisable as of March 31, 2022		151		$	17.76		6.11

The estimated aggregate intrinsic value of stock options exercisable as of March 31, 2022 was $5,000. As of March 31, 2022, there was $0.1 million of total unrecognized compensation cost related to outstanding stock options that will be recognized over a weighted average period of 0.86 years.

We adopted an employee stock purchase plan in June 2015 for all eligible employees. At March 31, 2022 the available number of shares that may be issued under the plan is 77,031.

Stock-based compensation expense recognized for stock-based awards in the condensed consolidated statements of operations for the three months ended March 31, 2022 and 2021 was as follows (in thousands):

	Three Months Ended March 31,
	2022		2021
Research and development		5		5
Clinical and regulatory		3		9
General and administrative		5		5
Total	$	13	$	19