CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 27,181	$ 33,531
Short-term investments	24,839	19,861
Prepaid expenses and other current assets	1,698	978
Total current assets	53,718	54,370
Property and equipment, net	1,315	1,338
Investments		4,964
Total assets	55,033	60,672
Current liabilities:
Accounts payable	797	927
Accrued expenses	997	1,617
Total current liabilities	1,794	2,544
Other long-term liabilities	114	120
Total liabilities	1,908	2,664
Stockholders' equity:
Preferred stock, $0.001 par value; 25,000,000 shares authorized, no shares issued and outstanding
Common stock, $0.001 par value; 100,000,000 shares authorized, 40,549,936 issued and 40,520,705 outstanding at March 31, 2018 and December 31, 2017	41	41
Additional paid-in capital	203,917	202,790
Treasury stock at cost, 29,231 shares at March 31, 2018 and December 31, 2017
Accumulated other comprehensive loss	(107)	(96)
Accumulated deficit	(150,726)	(144,727)
Total stockholders’ equity	53,125	58,008
Total liabilities and stockholders’ equity	$ 55,033	$ 60,672