On April 15, 2021, the Company’s Board of Directors adopted the 2021 Incentive Award Plan (the “2021 Plan”) to replace the 2011 Stock Incentive Plan (the “2011 Plan”). The 2021 Plan was approved by the Company’s stockholders at the Company’s Annual Meeting of Stockholders held on June 10, 2021. The 2021 Plan is administered by the Company’s Board of Directors and permits the Company to grant incentive and non-qualified stock options, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards.

The Company initially reserved 275,000 of its common stock for the issuance of awards under the 2021 Plan. There were 22,000 options granted during the year ended December 31, 2021 under the 2021 Plan. The weighted-average grant date fair value per share of stock options granted during the year ended December 31, 2021 was $3.68. There were 22,000 options granted during the year ended December 31, 2020. At December 31, 2021, there were 253,000 shares remaining available for grant under the 2021 Plan.

Stock options granted to non-employee directors in 2021 and 2020 vest over a one-year period, ending on the earlier of the one-year anniversary of the grant date or the day prior to the Company’s next annual meeting of stockholders after the grant date.

The fair value of stock options granted to employees during the years ended December 31, 2021 and 2020 was estimated at the date of grant using the following assumptions:

	Years Ended December 31,
	2021	2020
Risk-free interest rate	0.73%	0.2%
Expected dividend yield	0%	0%
Expected term	5.2 years	5.3 years
Expected volatility	68.48%	67.00%

The Company uses the simplified method to calculate the expected term, as it does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term of its stock options. Under this approach, the expected term is calculated to be the average of the ten-year contractual term of the option and the weighted-average vesting term of the option, taking into consideration multiple vesting tranches. The computation of expected volatility is based on the historical volatility of the Company. The risk-free interest rate is based on a treasury instrument whose term is consistent with the expected life of the stock options. Stock-based compensation expense related to employee stock options is measured using the fair value of the award at the grant date and is adjusted quarterly to reflect actual forfeitures. Stock-based compensation expense is then recognized on a straight-line basis over the vesting period, which is also the requisite service period. The Company recognized stock-based compensation expense of $0.4 million and $1.7 million during the years ended December 31, 2021 and 2020, respectively.

The following table summarizes stock option activity during the year ended December 31, 2021:

(in thousands, except per share amounts)	Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Outstanding at December 31, 2020		1,862		$	11.97		6.04	$	1,254
Granted		22		$	6.41
Exercised		(30	)	$	7.95
Forfeited		(76	)	$	20.94
Outstanding at December 31, 2021		1,778		$	11.46		5.32	$	148
Vested and expected to vest at December 31, 2021		1,778		$	11.46		5.32	$	148
Exercisable at December 31, 2021		1,767		$	11.53		5.30	$	148

The weighted-average grant date fair value of stock options granted during the years ended December 31, 2021 and 2020 was $3.68 and $1.90, respectively.

The aggregate intrinsic value was calculated as the difference between the exercise price of the stock options and the fair value of the underlying common stock. The aggregate intrinsic value of options exercised during the year ended December 31, 2021 was less than $0.1 million. There were no option exercises during the year ended December 31, 2020.

As of December 31, 2021, there was less than $0.1 million of total unrecognized stock-based compensation expense related to unvested employee stock options. The Company expects to recognize this expense over a weighted-average period of approximately 0.3 years.