Quarterly report pursuant to Section 13 or 15(d)

Stock Plans (Tables)

Stock Plans (Tables)

3 Months Ended

Mar. 31, 2022

Stock Plans

Schedule of our option activity

The following table summarizes our option activity:


							Weighted
				Weighted			Average
				Average			Remaining		Aggregate
				Exercise			Option		Intrinsic
		Options (in		Price per			Term		Value
		thousands)		share			(in years)		(in thousands)
Outstanding at December 31, 2021		682		$	12.53		8.98		$	—
Granted		310			1.18
Forfeited or expired		(2)			531.11
Outstanding at March 31, 2022		990		$	8.28		9.07		$	—
Exercisable at March 31, 2022		511		$	14.01		8.71		$	—

Schedule of the stock-based compensation expense

The following table summarizes the stock-based compensation expense recorded for awards under our stock option plans (in thousands):


		Three Months Ended
		March 31,
		2022			2021
Research and development		$	123		$	120
Selling, general and administrative			103			128
Total stock-based compensation expense		$	226		$	248

Schedule of assumptions to estimate the fair value of options


		Three Months Ended
		March 31,
		2022		2021
Weighted-average risk-free interest rate		1.47	%	0.54	%
Expected dividend payments		—		—
Expected holding period (years)⁽¹⁾		5.4		5.5
Weighted-average volatility factor⁽²⁾		113.2		113.9
Estimated forfeiture rates for options granted ⁽³⁾		5.14	%	29.6	%

(1)	Expected holding period is based on historical experience of similar awards, giving consideration to the contractual terms of the stock-based awards, vesting schedules and the expectations of future employee behavior.

(2)	Weighted average volatility is based on the historical volatility of our common stock.

(3)	Estimated forfeiture rates are based on historical data.