13. Common Stock

As of December 31, 2021, the Company’s Fourth Amended and Restated Certificate of Incorporation (the Fourth Certificate of Incorporation), authorized the Company to issue 150,000,000 shares of $0.0001 par value common stock.

The shares of the Company’s common stock, subject to outstanding awards under the 2015 Plan that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right, will be added back to the shares of common stock available for issuance under the 2020 Plan. As of December 31, 2021, there were 1,573,353 shares available for future issuance under the 2020 Plan.