CONSOLIDATED BALANCE SHEETS - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 217,431,000	$ 53,774,000
Short-term investments	0	208,614,000
Prepaid expenses and other current assets	2,133,000	4,189,000
Total current assets	219,564,000	266,577,000
Property and equipment, net	37,002,000	42,716,000
Right-of-use assets	5,897,000
Restricted cash	1,274,000	1,274,000
Total assets	263,737,000	310,567,000
Current liabilities:
Accounts payable	4,722,000	2,608,000
Accrued expenses and other liabilities	9,803,000	7,644,000
Operating lease liabilities	2,501,000
Deferred rent		1,313,000
Deferred revenue	5,632,000	809,000
Total current liabilities	22,658,000	12,374,000
Non-current liabilities:
Operating lease liabilities, net of current portion	12,941,000
Deferred rent, net of current portion		9,544,000
Deferred revenue, net of current portion	32,143,000	30,142,000
Total liabilities	67,742,000	52,060,000
Stockholders’ equity:
Preferred stock, $0.0001 par value, 10,000,000 shares authorized as of December 31, 2020 and 2019, respectively; no shares issued and outstanding at December 31, 2020 and 2019, respectively
Common stock, $0.0001 par value; 200,000,000 shares authorized as of December 31, 2020 and 2019, respectively; 50,268,666 and 45,138,408 shares issued as of December 31, 2020 and 2019, respectively; and 50,265,575 and 45,116,742 shares outstanding as of December 31, 2020 and 2019, respectively	5,000	4,000
Additional paid-in capital	524,358,000	457,994,000
Accumulated other comprehensive gain		183,000
Accumulated deficit	(328,368,000)	(199,674,000)
Total stockholders’ equity	195,995,000	258,507,000
Total liabilities and stockholders' equity	$ 263,737,000	$ 310,567,000