BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 207,177	$ 38,367
Investments in marketable securities	451,820	457,534
Prepaid expenses and other current assets	10,270	3,969
Total current assets	669,267	499,870
Property and equipment, net	8,345	8,410
Operating lease right-of-use assets	39,731	5,775
Other long-term assets	2,275	2,839
Total assets	719,618	516,894
Current liabilities:
Accounts payable	13,960	5,963
Accrued expenses and other current liabilities	8,490	7,098
Total current liabilities	22,450	13,061
Operating lease liabilities, net of current portion	42,773	8,112
Total liabilities	65,223	21,173
Commitments and contingencies (Note 6)
Stockholders’ equity:
Preferred stock, $0.001 par value per share; 20,000 shares authorized as of December 31, 2020 and 2019; no shares issued and outstanding as of December 31, 2020 and 2019	0	0
Common stock, $0.001 par value per share; 200,000 shares authorized as of December 31, 2020 and 2019; 53,081 and 48,668 shares issued and outstanding as of December 31, 2020 and 2019, respectively	53	48
Additional paid-in capital	997,298	685,020
Accumulated other comprehensive gain	8	137
Accumulated deficit	(342,964)	(189,484)
Total stockholders’ equity	654,395	495,721
Total liabilities and stockholders’ equity	$ 719,618	$ 516,894