Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 147,073	$ 298,887
Short-term investment securities	48,636	15,876
Accounts receivable, net	88	1,389
Prepaid research and development	3,627	11,929
Other current assets	3,136	2,884
Total current assets	202,560	330,965
Restricted cash	1,266	1,264
Long-term investment securities	36,078	35,533
Right of use assets	8,783	8,629
Leasehold interest, net	1,733	1,839
Equipment, net	447	600
Goodwill	799	799
Total assets	251,666	379,629
Current liabilities:
Accounts payable and accrued expenses	37,224	51,294
Other current liabilities	1,740	1,512
Loan payable - current portion		975
Lease liability - current portion	1,480	1,437
Accrued compensation	2,882	10,166
Total current liabilities	43,326	65,384
Deferred revenue, net of current portion	381	457
Loan payable - non-current	68,947	66,788
Lease liability - non-current	9,977	9,847
Total liabilities	122,631	142,476
Commitments and contingencies
Stockholders' equity:
Common stock, $0.001 par value per share (175,000,000 shares authorized, 145,198,058 and 143,292,043 shares issued, 145,156,749 and 143,250,734 shares outstanding at June 30, 2022 and December 31, 2021, respectively)	145	143
Additional paid-in capital	1,567,345	1,565,942
Treasury stock, at cost, 41,309 shares at June 30, 2022 and December 31, 2021	(234)	(234)
Accumulated deficit	(1,438,221)	(1,328,698)
Total stockholders' equity	129,035	237,153
Total liabilities and stockholders' equity	$ 251,666	$ 379,629