CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 29,429	$ 39,143
Marketable securities	275,523	369,107
Accounts and other receivables	347	172
Prepaid and other current assets	12,394	2,417
Total current assets	317,693	410,839
Property and equipment, net	3,747	3,551
Operating lease right-of-use assets, net	4,001	2,970
Intangible assets	27,190	27,190
Other assets	104	104
Total assets	352,735	444,654
Current liabilities:
Accounts payable	3,340	1,228
Accrued expenses	12,835	12,000
Current portion of operating lease liabilities	1,445	1,746
Current portion of long-term liabilities	990	1,554
Total current liabilities	18,610	16,528
Long-term portion of operating lease liabilities	2,588	1,296
Other long-term liabilities	5,333	7,354
Total liabilities	26,531	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 December 31, 2022 and 2021
Common stock, $.001 par value; 297,000,000 shares authorized; 47,200,695 and 46,730,198 shares issued and outstanding at December 31, 2022 and 2021, respectively	47	47
Additional paid-in capital	1,580,829	1,561,142
Accumulated other comprehensive income	1,260	1,894
Accumulated deficit	(1,255,932)	(1,143,607)
Total stockholders' equity	326,204	419,476
Total liabilities and stockholders' equity	$ 352,735	$ 444,654