Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 85,221	$ 96,713
Marketable securities	41,804
Unbilled accounts receivable	592
Prepaid expenses and other current assets	4,495	3,370
Total current assets	132,112	100,083
Property and equipment, net	8,395	9,205
Restricted cash	1,092	1,092
Other assets	616	59
Total assets	142,215	110,439
Current liabilities:
Accounts payable	3,634	2,186
Accrued expenses and other current liabilities	8,743	5,496
Deferred lease incentive, current portion	469	469
Deferred revenue, current portion	13,609	3,989
Total current liabilities	26,455	12,140
Deferred rent, excluding current portion	1,634	1,559
Deferred lease incentive, excluding current portion	3,169	3,521
Deferred revenue, excluding current portion	5,965	6,011
Other liabilities, excluding current portion	7	55
Total liabilities	37,230	23,286
Commitments and contingencies (Note 12)
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued or outstanding
Common stock, $0.001 par value; 200,000,000 shares authorized; 27,459,196 and 23,335,514 shares issued as of September 30, 2020 and December 31, 2019, respectively; 27,277,983 and 22,654,444 shares outstanding as of September 30, 2020 and December 31, 2019, respectively	27	23
Additional paid-in capital	308,827	237,931
Accumulated other comprehensive income	31
Accumulated deficit	(203,900)	(150,801)
Total stockholders’ equity	104,985	87,153
Total liabilities and stockholders’ equity	$ 142,215	$ 110,439