Stock-based Compensation

3 Months Ended

Mar. 31, 2022

Share-based Payment Arrangement [Abstract]

Stock Incentive Plan

The Company previously maintained the 2010 Stock Incentive Plan (the “2010 Plan”) for employees, consultants, advisors and directors, as amended in March 2013, June 2014 and June 2017.

In April 2019, the Company’s board of directors adopted the 2019 Equity Incentive Plan (the “2019 Plan”) and on June 12, 2019 the stockholders approved the 2019 Plan at the Annual Meeting of Stockholders. The 2019 Plan provides similar terms as the 2010 Plan, including: (i) a provision for the grant of equity awards such as stock options and restricted stock; (ii) that the exercise price of incentive stock options cannot be less than 100% of the fair market value of the common stock on the date of the grant for participants who own less than 10% of the total combined voting power of stock of the Company and not less than 110% for participants who own more than 10% of the total combined voting power of the stock of the Company; (iii) that options and restricted stock granted under the 2019 Plan vest over periods as determined by the board of directors, which generally are equal to four years; and (iv) that options granted under the 2019 Plan expire over periods as determined by the board of directors, which generally are ten years from the date of grant. In April 2020, the board of directors adopted an amendment to the 2019 Plan to increase the total number of shares reserved under the Plan by 1,300,000 shares, among other things. This amendment was approved by stockholders at the Annual Meeting of Stockholders held on June 10, 2020. In April 2021, the board of directors adopted an additional amendment to the 2019 Plan to increase the total number of shares reserved under the Plan by 2,200,000. This amendment was approved by stockholders at the Annual Meeting of Stockholders held on June 9, 2021.

Awards may be made under the 2019 Plan for up to the sum of (i) 4,500,000 shares of common stock and (ii) such additional number of shares of common stock (up to 1,068,901 shares) as is equal to (x) the number of shares of common stock reserved for issuance under the 2010 Plan that were available for grant under the 2010 Plan immediately prior to the date the 2019 Plan was approved by the Company’s stockholders and (y) the number of shares of common stock subject to awards outstanding under the 2010 Plan, which awards expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company pursuant to a contractual repurchase right. As of March 31, 2022, there were 288,181 shares of common stock available for future issuance under the 2019 Plan and no shares of common stock available for future issuance under the 2010 Plan.

The following table summarizes stock option activity during the three months ended March 31, 2022:


	Options	Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value
Outstanding at January 1, 2022	3,156,379	$	9.45	7.55	$	5,720
Granted	2,122,976	3.68
Exercised	—	—
Forfeited	(10,043)	48.15
Outstanding at March 31, 2022	5,269,312	$	7.05	8.30	$	4,131,736
Exercisable at March 31, 2022	1,608,347	$	10.84	6.03	$	111,672

The aggregate intrinsic value is based upon the Company’s closing stock price of $5.59 on March 31, 2022.

The fair value of stock options, subject only to service or performance conditions, that are granted to employees is estimated on the date of grant using the Black-Scholes option-pricing model. The following tables summarize the assumptions used in the Black-Scholes option-pricing model in the three months ended March 31, 2022 and 2021:


	Three Months Ended March 31,
	2022	2021
Volatility factor	97.19% - 97.79%	56.17% - 102.66%
Expected term (in years)	6.25	0.25 - 6.25
Risk-free interest rates	1.69% - 2.20%	0.06% - 1.13%
Dividend yield	—	—

Based upon these assumptions, the weighted-average grant date fair value of stock options granted during the three months ended March 31, 2022 and 2021 was $2.91 and $7.03, respectively.

As of March 31, 2022, there was $15.0 million of total unrecognized stock-based compensation expense related to stock options granted to employees under the Plan. The expense is expected to be recognized over a weighted-average period of 3.32 years.

Employee Stock Purchase Plan

In February 2010, the board of directors adopted the 2010 Employee Stock Purchase Plan (the “ESPP”), as amended in March 2013 and in November 2017. In April 2021, the board of directors adopted an amendment to the 2010 ESPP Plan to increase the total number of shares reserved under the Plan by 500,000 shares, pursuant to which the Company may sell up to an aggregate of 576,400 shares of Common Stock. This amendment was approved by stockholders at the Annual Meeting of Stockholders held on June 9, 2021. The ESPP allows eligible employees to purchase common stock at a price per share equal to 85% of the lower of the fair market value of the common stock at the beginning or end of each six-month period during the term of the ESPP. As of March 31, 2022, there were 412,403 shares available for future issuance under the ESPP.

The Company did not sell any shares of common stock pursuant to the ESPP during the three months ended March 31, 2022 and March 31, 2021. The total stock-based compensation expense recorded as a result of the ESPP was $0.1 million during the three months ended March 31, 2022 and March 31, 2021, respectively.