Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 35,915	$ 38,388
Available-for sale investments, short-term	21,306	33,759
Prepaid expenses and other assets	1,877	2,621
Total current assets	59,098	74,768
Available-for sale investments, long-term		4,002
Property and equipment, net	2,003	1,421
Other assets	371	333
Total assets	61,472	80,524
Current liabilities:
Accounts payable	2,669	2,606
Accrued expenses	4,194	5,450
Current portion of deferred rent		130
Current portion of long-term debt	2,786	339
Total current liabilities	9,649	8,525
Long-term debt, net of current portion and issuance costs	11,792	9,198
Commitments and contingencies (Note 3)
Stockholders’ equity:
Common stock, $0.001 par value; authorized shares – 150,000,000 as of June 30, 2017 and December 31, 2016; issued and outstanding shares – 23,837,204 and 23,744,832 as of June 30, 2017 and December 31, 2016, respectively	24	24
Additional paid-in capital	281,586	278,832
Accumulated other comprehensive loss	(57)	(76)
Accumulated deficit	(241,522)	(215,979)
Total stockholders’ equity	40,031	62,801
Total liabilities and stockholders’ equity	$ 61,472	$ 80,524