Common Stock (Tables)

12 Months Ended

Dec. 31, 2019

Common Stock

Schedule of shares of common stock reserved for issuance

	December 31,
	2019	2018	2017
Exchange warrants	1,458,000	—	—
Shares available for future option grants	1,704,183	2,486,637	2,576,535
Outstanding options	5,643,410	3,778,259	3,013,394
Unvested restricted common stock (founders and early exercise of stock options)	—	43,076	319,203
Shares reserved for employee stock purchase plan	400,000	400,000	400,000
Total	9,205,593	6,707,972	6,309,132