Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 127,823	$ 60,625
Short-term investments	176,367	124,057
Unbilled grant receivable	2,906	1,300
Prepaid expenses and other current assets	4,472	6,355
Total current assets	311,568	192,337
Property and equipment, net	2,898	2,649
Operating lease right-of-use asset	1,426	936
Long-term investments	53,467	83,509
Other long-term assets	55	132
Total assets	369,414	279,563
Current liabilities:
Accounts payable	1,687	1,158
Accrued liabilities	2,610	3,123
Current operating lease liability	200	124
Total current liabilities	4,497	4,405
Operating lease liability, less current portion	1,700	876
Total liabilities	6,197	5,281
Stockholders' equity:
Common stock, $0.0001 par value; 900,000,000 shares authorized at March 31, 2021 and December 31, 2020; 37,150,311 and 32,485,784 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	4	3
Additional paid-in capital	413,093	315,288
Accumulated other comprehensive income	28	33
Accumulated deficit	(49,908)	(41,042)
Total stockholders' equity	363,217	274,282
Total liabilities and stockholders' equity	$ 369,414	$ 279,563