Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 486,062	$ 135,089
Marketable securities	114,302	266,740
Prepaid expenses and other current assets	8,036	7,488
Total current assets	608,400	409,317
Property and equipment, net	5,757	5,425
Operating lease right-of-use assets	10,292	10,303
Other assets	627	1,559
Total assets	625,076	426,604
Current liabilities
Accounts payable	222	956
Accrued research and development expenses	13,155	19,258
Accrued expenses and other current liabilities	14,167	16,709
Total current liabilities	27,544	36,923
Long-term convertible senior notes	140,715	0
Long-term debt	28,637	28,459
Operating lease liabilities - long-term	7,856	8,737
Total liabilities	204,752	74,119
Commitments and contingencies
Stockholders' equity
Common stock, $0.0001 par value; 700,000,000 shares authorized as of June 30, 2020 and December 31, 2019; 75,811,862 shares issued and 71,972,610 shares outstanding as of June 30, 2020, and 66,284,003 shares issued and 61,635,477 shares outstanding as of December 31, 2019	8	7
Additional paid-in capital	874,863	686,390
Accumulated deficit	(455,114)	(334,170)
Accumulated other comprehensive income	567	258
Total stockholders' equity	420,324	352,485
Total liabilities and stockholders' equity	$ 625,076	$ 426,604