The Company has three equity incentive compensation plans: the 2006 Plan, the 2015 Plan and the 2021 Plan.

The 2006 Plan was originally adopted by the Board and approved by the Company’s stockholders in 2006. The 2006 Plan was terminated in 2015 in connection with the adoption of the 2015 Plan and as a result no new awards may be issued under the 2006 Plan. However, the 2006 Plan will continue to govern the terms and conditions of the outstanding awards previously granted under the 2006 Plan.

The 2015 Plan was originally adopted by the Board and approved by the Company’s stockholders in 2015. The 2015 Plan was most recently amended in March 2021. In July 2021, upon completion of the IPO, the 2015 Plan terminated immediately prior to effectiveness of the 2021 Plan with respect to the grant of future awards. However, the 2015 Plan will continue to govern the terms and conditions of the outstanding awards previously granted under the 2015 Plan.

On July 28, 2021, the 2021 Plan was adopted and approved by the Board and stockholders prior to the IPO and became effective on the business day immediately prior to the effective date of the Company’s IPO registration statement. The 2021 Plan provides for the grant of incentive stock options to employees and any subsidiary corporations’ employees, and for the grant of nonstatutory stock options, stock appreciation rights, restricted stock, restricted stock units (“RSUs”), and performance awards to employees, directors, and consultants and subsidiary corporations’ employees and consultants. The number of shares of the Company’s common stock originally available for issuance under the 2021 Plan was equal to 2,420,135 shares of common stock plus any shares subject to awards granted under the 2015 Plan and the 2006 Plan that, after the effectiveness of the 2021 Plan, expire or otherwise terminate without having been exercised in full, are tendered to or withheld by the Company for payment of an exercise price or for tax withholding obligations, or are forfeited to or repurchased by the Company due to failure to vest, with the maximum number of shares to be added to the 2021 Plan from the 2015 Plan and 2006 Plan equal to 4,569,530 shares of common stock.

The number of common shares reserved for issuance under the 2021 Plan will be increased automatically on the first day of each fiscal year beginning with the 2022 fiscal year and ending on the ten year anniversary of the date the Board approved the 2021 Plan, by a number equal to the least of: (i) 7,260,406 shares of our common stock; (ii) 4% of the outstanding shares of our common stock on the last day of the immediately preceding fiscal year; or (iii) such lesser number of shares of our common stock as the administrator may determine. The 2021 Plan is administered by the Board. On January 1, 2022, the number of shares available under the 2021 Plan increased by 1,094,670 shares of common stock pursuant to this feature. On January 1, 2023, the number of shares available under the 2021 Plan further increased by 1,130,735 shares of common stock pursuant to this feature. As of September 30, 2023, the number of shares of the Company’s common stock available for future issuance under the 2021 Plan was equal to 416,652 shares of common stock.

On July 28, 2021, the Board and stockholders adopted and approved the 2021 ESPP. As of September 30, 2023, the number of shares of the Company’s common stock available for future issuance under the 2021 ESPP was equal to 614,472 shares of common stock.

The 2021 ESPP provides eligible employees of the Company and its subsidiaries with the opportunity to purchase shares of the Company’s common stock at a purchase price equal to 85% of the common stock’s fair market value on the first trading day or last trading day of each purchase period, whichever is lower. The 2021 ESPP provides for two six-month purchase periods every twelve months: May 1 through October 31 and November 1 through April 30. The initial purchase period began on November 1, 2021.

The number of common shares reserved for issuance under the 2021 ESPP plan will be increased automatically on the first day of each fiscal year beginning with the 2022 fiscal year, by a number equal to the least of: (i) 1,452,081 shares; (ii) 1% of the outstanding shares of our common stock on the last day of the immediately preceding fiscal year; or (iii) such other amount as the administrator may determine. The 2021 ESPP is administered by the Board. On January 1, 2022, the number of shares available under the 2021 ESPP increased by 273,667 shares of common stock pursuant to this feature. No additional shares were reserved for issuance on January 1, 2023 pursuant to this feature.

The purpose of the 2021 Plan and 2021 ESPP is to provide a means by which eligible recipients of stock awards may be given an opportunity to benefit from increases in the value of the common stock in order to retain or procure the services of the employees, members of the Board and consultants and provide them with an incentive to promote the Company’s success and accomplish corporate goals.

Stock option awards are granted with an exercise price of no less than 100% of estimated fair market value on the date of grant. Time based awards generally vest over four years as follows, subject to the optionee’s continuing service: (i) one fourth of the total number of shares vest and become exercisable on the one-year anniversary; 1/48th of the total number of shares subject to the option vest and become exercisable on each monthly anniversary thereafter for the remaining three years, or (ii) 1/48th of the total number of shares subject to the option vest and

A summary of the stock option activities related to the Equity Plans for the nine months ended September 30, 2023 is presented below:


	Number of Options			Weighted Average Exercise Price		Weighted Avg Remaining Contractual Life (Years)
Options outstanding as of December 31, 2022		6,339,558		$	11.88		6.48
Granted		1,398,191			15.95
Exercised		(586,789	)		9.13
Forfeited		(112,390	)		13.15
Expired		(64,330	)		18.39
Options outstanding as of September 30, 2023		6,974,240			12.85		6.66
Exercisable as of September 30, 2023		4,152,234		$	11.48		5.28

As of September 30, 2023 and December 31, 2022 the intrinsic value of options vested was $68.2 million and $15.9 million, respectively, and of all options outstanding was $105.0 million and $16.4 million, respectively. During the nine months ended September 30, 2023 and 2022, the total cash received from the exercise of stock options was $5.4 million and $0.7 million, respectively. The total fair value less strike price of these options was $8.4 million and $1.6 million, respectively.

A summary of non-vested restricted stock unit activities for the nine months ended September 30, 2023 is as follows:


				Weighted
				Average
	Number of			Grant Date
	Shares			Fair Value

Unvested at December 31, 2022		492,862		$	15.08
Granted		430,926			16.00
Vested		(261,911	)		14.81
Forfeited		(11,195	)		15.17
Unvested at September 30, 2023		650,682		$	15.80

Stock-based compensation expense was classified in the accompanying condensed consolidated statements of operations and comprehensive income (loss) as follows (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Research and development	$	1,035	$	737	$	2,857	$	2,303
Selling, general and administrative		2,731		1,931		7,642		5,451
Cost of goods sold		305		214		822		681
	$	4,071	$	2,882	$	11,321	$	8,435

As of September 30, 2023 and December 31, 2022, there were 2,822,006 and 2,447,687 unvested options, respectively. As of September 30, 2023 and December 31, 2022, total unrecognized expense related to unvested stock options was approximately $24.6 million and $19.1 million, respectively. Both amounts are expected to be recognized over a weighted average period of approximately 2.6 years.

As of September 30, 2023, and December 31, 2022 , total unrecognized expense related to non-vested restricted stock units was approximately $9.6 million and $6.1 million, respectively. The unrecognized compensation cost is expected to be recognized over a weighted average period of 2.5 years and 2.3 years, respectively.

The following table presents the range and weighted-average assumptions, used in the Black-Scholes option pricing model to determine the fair value of stock options:


	Nine Months Ended September 30,
	2023		2022
	Range	Weighted Average	Range	Weighted Average
Expected volatility	64.9% to 67.7%	65.3%	62.4% to 63.8%	62.8%
Risk-free interest rate	3.4% to 4.6%	4.1%	2.0% to 3.0%	2.3%
Expected life (in years)	5.5 to 6.1 years	6.1 years	6.0 to 10.0 years	6.0 years
Expected dividend yield	0.0%	0.0%	0.0%	0.0%
Grant date fair value	$12.91 to $32.45	$16.89	$10.74 to $15.52	$12.63

Each share of common stock is entitled to one vote. Common stock reserved for future issuance under the Equity Plans, 2021 ESPP and the ATM offering consisted of the following:


	September 30, 2023		December 31, 2022
Stock options issued and outstanding under the Equity Plans		6,974,240		6,339,558
Shares available for future issuance under the Equity Plans		416,652		865,122
Restricted stock units issued under the 2021 Plan		650,682		492,862
Shares available for future issuance under 2021 ESPP		614,472		664,976
Shares available for future sale under the ATM offering (1)		—		3,454,064
Total shares of common stock reserved		8,656,046		11,816,582

(1) Based on the closing stock price of $12.67 as reported on the Nasdaq Global Market on December 30, 2022.

ATM Offering

As of the date of this report, a total of 2,617,964 shares of the Company's common stock, for total gross proceeds of $50.0 million (net proceeds of $47.5 million), have been issued and sold pursuant to the ATM offering, of which 428,000 shares of the Company's common stock, for net proceeds of $11.7 million, were sold during the quarter ended September 30, 2023, which was the remaining authorized value of the common stock under the ATM offering in the third quarter of 2023.