CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 21,467	$ 33,531
Short-term investments	24,902	19,861
Prepaid expenses and other current assets	1,038	978
Total current assets	47,407	54,370
Property and equipment, net	1,280	1,338
Investments		4,964
Total assets	48,687	60,672
Current liabilities:
Accounts payable	1,294	927
Accrued expenses	2,266	1,617
Total current liabilities	3,560	2,544
Other long-term liabilities	107	120
Total liabilities	3,667	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, 40,554,244 issued and 40,525,013 outstanding at June 30, 2018 and December 31, 2017	41	41
Additional paid-in capital	205,279	202,790
Treasury stock at cost, 29,231 shares at June 30, 2018 and December 31, 2017
Accumulated other comprehensive loss	(69)	(96)
Accumulated deficit	(160,231)	(144,727)
Total stockholders’ equity	45,020	58,008
Total liabilities and stockholders’ equity	$ 48,687	$ 60,672