CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 33,531	$ 26,178
Short-term investments	19,861	3,922
Prepaid expenses and other current assets	978	199
Total current assets	54,370	30,299
Property and equipment, net	1,338	1,148
Investments	4,964
Total assets	60,672	31,447
Current liabilities:
Accounts payable	927	2,809
Accrued expenses	1,617	1,775
Current portion of notes payable		3,500
Total current liabilities	2,544	8,084
Notes payable		1,743
Other long-term liabilities	120	141
Total liabilities	2,664	9,968
Commitments and contingencies (Note 9)
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 December 31, 2017 and 19,734,351 issued and 19,705,120 outstanding at December 31, 2016	41	20
Additional paid-in capital	202,790	147,288
Treasury stock at cost, 29,231 shares at December 31, 2017 and 2016
Accumulated other comprehensive loss	(96)
Accumulated deficit	(144,727)	(125,829)
Total stockholders’ equity	58,008	21,479
Total liabilities and stockholders’ equity	$ 60,672	$ 31,447