Stockholders' Equity

12 Months Ended

Dec. 31, 2021

Stockholders' Equity Note [Abstract]

Stockholders' Equity

10. Stockholders’ Equity

Common Stock

Holders of common stock are entitled to one vote per share on all matters to be voted upon by the stockholders of the Company.

As of December 31, 2021 and 2020, the Company had reserved common stock, on an if-converted basis, for issuance as follows:

	December 31,
	2021		2020
Common stock options issued and outstanding		6,512,086		5,439,295
Common stock awards issued and outstanding		2,403,826		666,375
Remaining shares reserved for issuance under 2018 Equity    Incentive Plan and 2021 Equity Inducement Plan		1,504,641		1,710,824
Shares reserved for issuance under 2018 Employee    Stock Purchase Plan		673,251		361,539
Warrants to purchase common stock		127,616		153,070
Total		11,221,420		8,331,103

Preferred Stock

As of December 31, 2021, the Company had 10,000,000 shares of preferred stock authorized with a par value of $0.001. No shares of preferred stock were outstanding as of December 31, 2021 and 2020.

Warrants

In August 2017, the Company issued warrants to Oxford and SVB to purchase an aggregate of 682,230 shares of Series D-2 redeemable convertible preferred stock at an exercise price of $0.6596 per share in connection with the issuance of the August 2017 Loan. If there was a subsequent convertible preferred stock or other senior equity securities financing with a per share price less than the Series D-2 redeemable convertible preferred per share price, then the warrant would automatically convert to a warrant to purchase such class of shares, based on the per share price of such equity. Given that the price per share of the Series E redeemable convertible preferred stock described above was less than the price per share of the Series D-2 redeemable convertible preferred stock, the 2017 Warrant converted into a warrant to purchase a total of 1,682,871 shares of Series E redeemable convertible preferred stock at an exercise price of $0.2674 per share. The warrant is exercisable from the original date of issuance and has a 10-year term.

The Company adjusted the warrant liability for changes in fair value until the completion of its IPO on October 1, 2018, at which time certain convertible preferred stock warrants were converted into warrants for the purchase of common stock and the related convertible preferred stock warrant liability was reclassified to additional paid-in capital and others expired. On October 1, 2018, 1,232,220 shares of the Series C redeemable convertible preferred warrants were canceled, and the remaining 687,928 shares were converted to 25,453 shares of warrants to purchase common stock on a 1-for-0.0370 basis at an exercise price of $12.9649. The common stock warrant was outstanding and exercisable as of December 31, 2020. In November 2021, this common stock warrant was fully net exercised into 9,308 shares of common stock. All Series E redeemable convertible preferred warrants were converted to 46,359 shares of warrants to purchase common stock on a 1-for-0.0275 basis.

In February 2020, in connection with entering into the Loan and Security Agreement, the Company issued to Oxford and SVB the 2020 Warrants, which are exercisable for 54,171 shares and 27,086 shares, respectively, of the Company’s common stock. The 2020 Warrants are exercisable in whole or in part, immediately, and have a per share exercise price of $9.23, which is the closing price of the Company’s common stock reported on the Nasdaq Global Market on the day prior to the Effective Date. The 2020 Warrants will terminate on the earlier of February 28, 2030 or the closing of certain merger or consolidation transactions.