CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 25,293	$ 39,143
Marketable securities	355,175	369,107
Accounts and other receivables	243	172
Prepaid and other current assets	9,988	2,417
Total current assets	390,699	410,839
Property and equipment, net	3,484	3,551
Operating lease right-of-use assets, net	2,564	2,970
Intangible assets, net	27,190	27,190
Other assets	104	104
Total assets	424,041	444,654
Current liabilities:
Accounts payable	1,019	1,228
Accrued expenses	9,234	12,000
Current portion of operating lease liabilities	1,802	1,746
Current portion of long-term liabilities	2,505	1,554
Total current liabilities	14,560	16,528
Long-term portion of operating lease liabilities	841	1,296
Other long-term liabilities	10,539	7,354
Total liabilities	25,940	25,178
Commitments and contingent liabilities
Stockholders' equity:
Convertible preferred stock, $.01 par value; 3,000,000 shares authorized; no shares issued and outstanding at March 31, 2022 and December 31, 2021
Common stock, $.001 par value; 297,000,000 shares authorized; 46,754,348 and 46,730,198 shares issued and outstanding at March 31, 2022 and December 31, 2021, respectively	47	47
Additional paid-in capital	1,564,599	1,561,142
Accumulated other comprehensive income	112	1,894
Accumulated deficit	(1,166,657)	(1,143,607)
Total stockholders' equity	398,101	419,476
Total liabilities and stockholders' equity	$ 424,041	$ 444,654