As of June 30, 2021 and December 31, 2020, the Company had reserved shares of common stock for the exercise of outstanding stock options and shares of common stock remaining available for future stock-based awards under the Company’s 2012 Stock Incentive Plan, 2019 Stock Incentive Plan and 2019 Employee Stock Purchase Plan, as shown in the table below:

	June 30, 2021		December 31, 2020
Shares of common stock reserved for future issuance under the 2012 Stock Incentive Plan		885,418		921,824
Shares of common stock reserved for future issuance under the 2019 Stock Incentive Plan		3,175,199		2,396,922
Shares of common stock reserved for future issuance under the 2019 Employee Stock Purchase Plan		503,789		327,454
		4,564,406		3,646,200

In June 2020, the Company entered into the ATM Sales Agreement, under which the Company may issue and sell shares of its common stock, from time to time, having an aggregate offering price of up to $12.0 million. Sales of common stock under the ATM Sales Agreement may be made by any method that is deemed an “at-the-market” offering as defined in Rule 415(a)(4) under the Securities Act of 1933, as amended. The Company is not obligated to make any sales of its common stock under the ATM Sales Agreement. The Company began making sales pursuant to the ATM Sales Agreement in July 2020. During the three and six months ended June 30, 2021, the Company issued and sold an aggregate of 1,365,871 and 2,733,492 shares of common stock, respectively, for gross proceeds of $3.0 million and $7.4 million, respectively, before deducting estimated commissions and allocated fees of $0.2 million and $0.6 million, respectively. As of June 30, 2021, the Company had issued and sold an aggregate of 3,421,368 shares of common stock for gross proceeds of $10.6 million, before deducting estimated commissions and allocated fees of $0.8 million.

On June 18, 2021, the Company entered into a common stock purchase agreement (“LPC Purchase Agreement”) with Lincoln Park Capital Fund, LLC (“Lincoln Park”). The LPC Purchase Agreement provides that, subject to the terms and conditions therein, the Company has the right, but not the obligation, to sell, at its discretion, to Lincoln Park up to $15.0 million of shares of common stock over a 24-month period commencing on July 23, 2021. In addition, under the LPC Purchase Agreement, the Company issued 170,088 shares of common stock to Lincoln Park as consideration for Lincoln Park’s commitment to purchase shares of the Company’s common stock under the LPC Purchase Agreement. The purchase price per share of the shares sold will be based on the market prices prevailing immediately preceding the time of sale as computed under the LPC Purchase Agreement. Lincoln Park has covenanted not to cause or engage in any manner whatsoever, any direct or indirect short selling or hedging of the Company’s common stock. The agreement may be terminated by the Company at any time, at its sole discretion, without any additional cost or penalty.

In April 2019, the Company’s board of directors adopted the 2019 Stock Incentive Plan (the “2019 Plan”), which became effective on May 7, 2019. The 2019 Plan provides for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. The Company’s employees, officers, directors, consultants and advisors are eligible to receive awards under the 2019 Plan. The 2019 Plan is administered by the Company’s board of directors.

The total number of shares of common stock that may be issued under the 2019 Plan and the 2012 Plan was 4,060,617 as of June 30, 2021, of which 858,240 shares remained available for grant under the 2019 Plan. Awards may be made under the 2019 Plan for up to such number of shares of the Company’s common stock as is equal to the sum of i) 1,578,947 shares; plus ii) the number of shares (up to 1,157,894 shares) equal to the number of shares of the Company’s common stock subject to outstanding awards under the 2012 Stock Incentive Plan (the “2012 Plan”) that expire, terminate or are otherwise cancelled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right; plus iii) an annual increase to be added on the first day of each fiscal year, beginning with 2020 and continuing through 2029, equal to the lesser of (a) 2,105,623 shares of common stock, (b) 4% of the number of outstanding shares of the Company’s common stock on such date and (c) an amount determined by the Company’s board of directors. Effective January 1, 2021 and January 1, 2020, respectively, the number of shares reserved for issuance under the 2019 Plan increased pursuant to the terms of the 2019 Plan by an additional 741,871 shares and 713,383 shares, equal to 4% of the Company’s then-outstanding common stock.

The 2012 Plan was adopted by the Company’s board of directors and stockholders. The 2012 Plan provides for the issuance of stock-based awards to the Company’s employees, officers, directors, consultants and advisors. The Company’s board of directors administers the 2012 Plan.

Options granted under the 2019 Plan and the 2012 Plan have a maximum term of ten years. Options granted to employees, officers and non-employees generally vest over four years based on varying vesting schedules that primarily include: 25% vesting on the first anniversary date of grant and the balance ratably over the next 36 months or vesting in equal monthly or quarterly installments over four years. Options granted to directors generally vest over one to two years. As of June 30, 2021 and December 31, 2020, respectively, options to purchase 2,316,959 shares and 1,249,653 shares of common stock were granted and outstanding, net of cancellations, under the 2019 Plan. As of June 30, 2021 and December 31, 2020, options to purchase 885,418 and 921,824 shares of common stock, respectively, were granted and outstanding, net of cancellations, under the 2012 Plan.

In April 2019, the Company’s board of directors adopted a resolution effective on May 7, 2019, that no further stock options or other equity-based awards may be granted under the 2012 Plan.

In February 2021, the compensation committee of the Company’s board of directors approved the grant of stock options with performance-based vesting (“PSOs”) to employees of the Company. The PSOs granted in February 2021, vest based on the timing and successful results of the Company’s PRISM or CANAL clinical trials.

A summary of the Company’s combined stock option activity for the 2019 Plan and the 2012 Plan for the six months ended June 30, 2021 is as follows:

	Number of Option Shares			Weighted Average Exercise Price

Outstanding as of December 31, 2020		2,171,477		$	5.62
Granted		1,363,875		$	3.02
Forfeited		(331,824	)	$	4.57
Expired		(1,151	)	$	10.00
Exercised		—		$	—
Outstanding as of June 30, 2021		3,202,377		$	4.62
Options exercisable as of June 30, 2021		1,393,630		$	5.12
Options unvested as of June 30, 2021		1,808,747		$	4.24

In April 2019, the Company’s board of directors adopted the 2019 Employee Stock Purchase Plan (the “2019 ESPP”), which became effective on May 7, 2019. The 2019 ESPP is administered by the Company’s board of directors.

The total number of shares of common stock that may be issued under the 2019 ESPP Plan was 518,918 as of June 30, 2021, of which 503,789 shares remain available for issuance. The number of shares of the Company’s common stock that have been approved to be issued under the 2019 ESPP is equal to the sum of i) 155,106 shares plus ii) an annual increase to be added on the first day of each fiscal year, beginning with the fiscal year ending December 31, 2020 and continuing for each fiscal year until and including, the fiscal year ending December 31, 2029, equal to the least of (a) 526,315 shares of common stock, (b) 1% of the number of outstanding shares of the Company’s common stock on such date and (c) an amount determined by the Company’s board of directors. Effective January 1, 2021 and January 1, 2020, respectively, the aggregate number of shares of the Company’s common stock that may be issued under the 2019 ESPP increased, pursuant to the terms of the 2019 ESPP, by an additional 185,467 shares and 178,345 shares, equal to 1% of the Company’s then-outstanding common stock.

All of the Company’s employees are eligible to participate in the 2019 ESPP, provided that:

The following table summarizes the classifications of stock-based compensation expenses for the 2012 Plan, the 2019 Plan and the 2019 ESPP recognized in the Condensed Consolidated Statements of Operations:

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Research and development expense	$	251	$	84	$	424	$	177
General and administrative expense		494		505		1,039		1,142
	$	745	$	589	$	1,463	$	1,319