Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 100,745	$ 57,052
Marketable securities	43,111	55,862
Accounts receivable		2,000
Unbilled accounts receivable	532	531
Prepaid expenses and other current assets	2,599	4,065
Total current assets	146,987	119,510
Property and equipment, net	7,834	8,397
Restricted cash	1,092	1,092
Other assets	563	578
Total assets	156,476	129,577
Current liabilities:
Accounts payable	4,797	4,079
Accrued expenses and other current liabilities	5,236	7,267
Deferred lease incentive, current portion	469	469
Deferred revenue, current portion	12,129	14,910
Total current liabilities	22,631	26,725
Deferred rent, excluding current portion	1,663	1,649
Deferred lease incentive, excluding current portion	2,934	3,051
Deferred revenue, excluding current portion	1,494	2,971
Total liabilities	28,722	34,396
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; 32,677,454 and 28,067,402 shares issued as of March 31, 2021 and December 31, 2020, respectively; 32,594,436 and 27,941,566 shares outstanding as of March 31, 2021 and December 31, 2020, respectively	33	28
Additional paid-in capital	366,344	316,775
Accumulated other comprehensive loss	(4)	(2)
Accumulated deficit	(238,619)	(221,620)
Total stockholders’ equity	127,754	95,181
Total liabilities and stockholders’ equity	$ 156,476	$ 129,577