Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 729,685	$ 237,677
Collaboration receivables (all amounts are with a related party)	22,561	8,547
Prepaid expenses and other current assets	8,854	10,000
Short-term investments	152,677	193,692
Total current assets	913,777	449,916
Property and equipment, net	7,621	6,812
Operating lease - right of use asset, net	19,660	23,908
Other assets	1,708	1,793
Long-term investments	4,999	22,477
Total assets	947,765	504,906
Current liabilities:
Accounts payable	8,861	2,295
Accrued expenses	21,917	24,895
Operating lease liability - right of use	6,524	6,183
Total current liabilities	37,302	33,373
Operating lease liability - right of use, net of current portion	15,327	20,201
Warrants to purchase common stock	0	1,856
Total liabilities	52,629	55,430
Commitments and contingencies (Note 13)
Stockholders’ equity:
Common stock, $0.001 par value: 175,000,000 shares authorized; 60,052,046 and 53,123,567 shares issued and outstanding at September 30, 2020 and December 31, 2019, respectively	60	53
Additional paid-in capital	1,715,343	1,160,807
Accumulated deficit	(820,042)	(711,407)
Accumulated other comprehensive (loss) income	(225)	23
Total stockholders’ equity	895,136	449,476
Total liabilities and stockholders’ equity	$ 947,765	$ 504,906