9. Stockholders’ Equity and Stock‑Based Compensation Expense

Aspire Common Stock Purchase Agreement

In October 2019, the Company entered into a common stock purchase agreement, or CSPA, with Aspire Capital Fund, LLC, or Aspire, which provided that, upon the terms and subject to the conditions and limitations set forth therein, Aspire is committed to purchase up to an aggregate of $20.0 million of shares of the Company’s common stock over the 30-month term of the CSPA. Under the CSPA, on any trading day selected by the Company on which the closing price of its common stock is equal to or greater than $0.25 per share, the Company has the right, in its sole discretion, to present Aspire with a purchase notice directing Aspire to purchase up to 50,000 shares of common stock per business day, at a purchase price equal to the lesser of the lowest sale price of common stock on the purchase date, or the arithmetic average of the three lowest closing sale prices during the 10 consecutive business days ending on the trading day immediately preceding the purchase date. The Company and Aspire also may mutually agree to increase the number of shares that may be sold to as much as 2,000,000 shares per business day.

In addition, on any date on which the Company submits a purchase notice to Aspire in an amount equal to 50,000 shares, the Company also has the right, in its sole discretion, to present Aspire with a volume-weighted average price purchase notice, or the VWAP Purchase Notice, directing Aspire to purchase an amount of stock equal to up to 30% of the aggregate shares of the Company’s common stock traded on its principal market on the next trading day, or the VWAP Purchase Date, subject to a maximum number of shares the Company may determine. The purchase price per share pursuant to such VWAP Purchase Notice is generally 97% of the volume-weighted average price for the Company’s common stock traded on its principal market on the VWAP Purchase Date.

Under the CSPA, the Company controls the timing and amount of any sales to Aspire, and is not limited with respect to use of proceeds or by any financial or business covenants, restrictions on future financings, rights of first refusal, participation rights, penalties or liquidated damages in the CSPA. The CSPA may be terminated by the Company at any time, at its discretion, without any cost to the Company. Aspire has no trading volume requirements or restrictions and has no right to require any sales by the Company but is obligated to make purchases as directed by the Company in accordance with the CSPA. Aspire has agreed that neither it nor any of its agents, representatives and affiliates shall engage in any direct or indirect short-selling or hedging of common stock during any time prior to the termination of the CSPA.

The CSPA further provides that the number of shares that may be sold pursuant to the CSPA will be limited to 2,626,165 shares, including 104,167 shares of common stock issued to Aspire as a commitment fee, which represented 19.99% of the Company’s outstanding shares of common stock as of October 21, 2019, unless stockholder approval is obtained to issue more than 19.99%. This limitation will not apply under certain circumstances specified in the CSPA. During the quarter ended March 31, 2020, there were no shares purchased by Aspire pursuant to the CSPA.

Concurrently with entering into the CSPA, the Company also entered into a registration rights agreement with Aspire, pursuant to which the Company filed with the SEC a prospectus supplement to the Company’s effective shelf registration statement on Form S-3 (File No. 333-234041), registering all of the shares of common stock that may be offered to Aspire from time to time under the CSPA. The Company’s ability to sell shares to Aspire under the CSPA is subject to certain limitations arising under the Securities Purchase Agreement with Innoviva, which is discussed in Note 13, Subsequent Events.

Stock Incentive Plans

In September 2018, the Company’s board of directors adopted, and its stockholders approved the 2018 Equity Incentive Plan, or the 2018 Plan, which became effective on September 25, 2018, at which point no further grants will be made under the 2015 Stock Incentive Plan, or the 2015 Plan. Under the 2018 Plan, the Company may grant incentive stock options, or ISOs, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. As of March 31, 2020, options to purchase an aggregate of 2,226,406 shares had been granted and 150,720 shares were available for future issuance under the 2018 Plan.

At its inception, the aggregate number of shares of the Company’s common stock available for issuance under the 2018 Plan was 2,350,000. The number of shares of the Company’s common stock reserved for issuance under the 2018 Plan automatically increases on January 1 of each year, for a period of 10 years, from January 1, 2019 continuing through January 1, 2028, by 4% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by the Company’s board of directors. Accordingly, on January 1, 2020 and 2019, 531,662 and 524,993 shares were added to the number of available shares, respectively. The maximum number of shares that may be issued pursuant to the exercise of ISOs under the 2018 Plan is 7,500,000.

The maximum number of shares of the Company’s common stock subject to awards granted under the 2018 Plan or otherwise during a single calendar year to any nonemployee director, taken together with any cash fees paid by the Company to such nonemployee director during the calendar year for serving on the Company’s board of directors, will not exceed $500,000 in total value, or, with respect to the calendar year in which a nonemployee director is first appointed or elected to the Company’s board of directors, $800,000.

All options and awards granted under the 2015 Plan consisted of the Company’s common stock. As of September 25, 2018, no additional stock awards have been or will be granted under the 2015 Plan. Although the 2015 Plan was terminated as to future awards in September 2018, it continues to govern the terms of options that remain outstanding under the 2015 Plan.

Stock Option Activity

Stock option activity under both plans during the three months ended March 31, 2020 is summarized as follows:


				Weighted-
		Weighted-		Average
		Average		Remaining	Aggregate
	Number of	Exercise		Contractual	Intrinsic
	Options	Price		Term (Years)	Value (in thousands)
Outstanding as of December 31, 2019	2,388,400	$	6.20	8.44	$	906
Granted	839,200		4.87
Exercised	—		—
Forfeited	(11,100)		5.01
Outstanding as of March 31, 2020	3,216,500	$	5.86	8.58	$	—

Exercisable as of March 31, 2020	1,110,613	$	5.66	7.50	$	—

The aggregate intrinsic value of options is calculated as the difference between the exercise price of the options and the fair value of the Company’s common stock for those options that had exercise prices lower than the fair value of the Company’s common stock.

During the three months ended March 31, 2020, the weighted-average grant date fair value per granted option was $3.34.

Employee Stock Purchase Plan

In September 2018, the Company’s board of directors and its stockholders approved the 2018 Employee Stock Purchase Plan, or the ESPP, which became effective as of September 25, 2018. The ESPP is intended to qualify as an “employee stock purchase plan” within the meaning of Section 423 of the U.S. Internal Revenue Code of 1986, as amended. The number of shares of common stock initially reserved for issuance under the ESPP was 140,000 shares. The ESPP provides for an annual increase on the first day of each year beginning in 2019 and ending in 2028, in each case subject to the approval of the board of directors, equal to the lesser of (i) 1% of the shares of common stock outstanding on the last day of the prior fiscal year or (ii) 250,000 shares; provided, that prior to the date of any such increase, the board of directors may determine that such increase will be less than the amount set forth in clauses (i) and (ii). Pursuant to the terms of the 2018 Employee Stock Purchase Plan, an additional 132,915 and 131,248 shares were added to the number of available shares effective January 1, 2020 and 2019, respectively. As of March 31, 2020, no shares of common stock had been issued under the ESPP and 404,163 shares remained available for future issuance under the ESPP. No offering period under the ESPP has been set by the Company’s board of directors.

Stock‑Based Compensation

Stock‑based compensation expense was classified in the consolidated statement of operations as follows (in thousands):


	Three Months Ended March 31,
	2020		2019
Research and development	$	349	$	232
General and administrative		436		346
Total stock-based compensation expense	$	785	$	578

As of March 31, 2020, total unrecognized stock‑based compensation expense related to unvested options was $8.0 million, which is expected to be recognized over the weighted average period of approximately 2.9 years. The total unrecognized stock-based compensation expense will be adjusted for actual forfeitures as they occur.