Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current Assets
Cash and cash equivalents	$ 13,969	$ 82,152
Short-term Investments	293,112	386,371
Prepaid expenses and other assets	9,412	6,851
Total Current Assets	316,493	475,374
Operating lease right-of-use assets	10,695
Property and equipment, net	8,536	2,683
Restricted cash	5,450
Long-term assets	3,481	2,764
Total Assets	344,655	480,821
Current Liabilities
Accounts payable	15,567	2,739
Accrued expenses	16,265	11,659
Operating lease liabilities	7,252
Total Current Liabilities	39,084	14,398
Non-Current Liabilities
Operating lease liabilities	4,248
Other liabilities	2,352	230
Total Non-Current Liabilities	6,600	230
Total Liabilities	45,684	14,628
Stockholders' Equity
Common stock, $0.000041666 par value; 300,000,000 and 150,000,000 shares authorized, 126,411,808 and 123,415,576 shares issued and outstanding as of December 31, 2019 and December 31, 2018, respectively	5	5
Accumulated other comprehensive loss	220	(42)
Additional paid-in capital	869,354	838,984
Accumulated deficit	(570,612)	(372,760)
Total Stockholders' Equity	298,971	466,193
Total Liabilities and Stockholders' Equity	344,655	480,821
Series B Convertible Preferred Stock
Stockholders' Equity
Preferred stock, Value	4	6
Total Stockholders' Equity	$ 4	$ 6