CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 39,143	$ 43,836
Marketable securities	369,107	150,586
Accounts and other receivables	172	1,802
Prepaid and other current assets	2,417	1,619
Total current assets	410,839	197,843
Property and equipment, net	3,551	3,815
Operating lease right-of-use assets, net	2,970	3,449
Intangible assets, net	27,190	30,690
Other assets	104	41
Total assets	444,654	235,838
Current liabilities:
Accounts payable	1,228	1,048
Accrued expenses	12,000	8,459
Current portion of operating lease liabilities	1,746	1,327
Current portion of long-term liabilities	1,554	3,372
Total current liabilities	16,528	14,206
Long-term portion of operating lease liabilities	1,296	2,154
Other long-term liabilities	7,354	10,121
Total liabilities	25,178	26,481
Commitments and contingent liabilities (Note 14)
Stockholders' equity:
Common stock, $.001 par value; 297,000,000 shares authorized; 46,730,198 and 39,603,771 shares issued and outstanding at December 31, 2021 and 2020, respectively	47	40
Additional paid-in capital	1,561,142	1,279,824
Accumulated other comprehensive income	1,894	2,589
Accumulated deficit	(1,143,607)	(1,073,096)
Total stockholders' equity	419,476	209,357
Total liabilities and stockholders' equity	$ 444,654	$ 235,838