CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 43,446	$ 43,836
Marketable securities	120,591	150,586
Accounts and other receivables	496	1,802
Prepaid and other current assets	3,073	1,619
Total current assets	167,606	197,843
Property and equipment, net	3,496	3,815
Operating lease right-of-use assets, net	2,718	3,449
Intangible assets, net	30,690	30,690
Other assets	41	41
Total assets	204,551	235,838
Current liabilities:
Accounts payable	685	1,048
Accrued expenses	7,851	8,459
Current portion of operating lease liabilities	1,331	1,327
Current portion of other long-term liabilities	4,621	3,372
Total current liabilities	14,488	14,206
Long-term portion of operating lease liabilities	1,446	2,154
Other long-term liabilities	6,335	10,121
Total liabilities	22,269	26,481
Commitments and contingent liabilities
Stockholders' equity:
Convertible preferred stock, $.01 par value; 3,000,000 shares authorized; no shares issued and outstanding at June 30, 2021 and December 31, 2020
Common stock, $.001 par value; 297,000,000 shares authorized; 39,616,696 and 39,603,771 shares issued and outstanding at June 30, 2021 and December 31, 2020, respectively	40	40
Additional paid-in capital	1,282,657	1,279,824
Accumulated other comprehensive income	2,592	2,589
Accumulated deficit	(1,103,007)	(1,073,096)
Total stockholders' equity	182,282	209,357
Total liabilities and stockholders' equity	$ 204,551	$ 235,838