CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 178,003	$ 53,774
Short-term investments		208,614
Prepaid expenses and other current assets	3,252	4,189
Total current assets	181,255	266,577
Property and equipment, net	39,684	42,716
Right-of-use assets	6,149
Restricted cash	1,274	1,274
Total assets	228,362	310,567
Current liabilities:
Accounts payable	3,316	2,608
Accrued expenses and other liabilities	8,426	7,644
Operating lease liabilities	2,497
Deferred rent		1,313
Deferred revenue	2,939	809
Total current liabilities	17,178	12,374
Non-current liabilities:
Operating lease liabilities, net of current portion	13,540
Deferred rent, net of current portion		9,544
Deferred revenue, net of current portion	27,422	30,142
Total liabilities	58,140	52,060
Commitments and contingencies (Note 7)
Stockholders’ equity:
Preferred stock, $0.0001 par value, 10,000,000 shares authorized; no shares issued and outstanding
Common stock, $0.0001 par value; 200,000,000 shares authorized; 45,263,849 and 45,138,408 shares issued as of September 30, 2020 and December 31, 2019, respectively; and 45,259,747 and 45,116,742 shares outstanding as of September 30, 2020 and December 31, 2019, respectively	4	4
Additional paid-in capital	468,795	457,994
Accumulated other comprehensive gain		183
Accumulated deficit	(298,577)	(199,674)
Total stockholders’ equity	170,222	258,507
Total liabilities and stockholders' equity	$ 228,362	$ 310,567