Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 12,965	$ 22,962
Available-for-sale investments, short-term	30,054	26,583
Collaboration receivable	630
Prepaid expenses and other assets	1,095	1,258
Total current assets	44,744	50,803
Property and equipment, net	1,692	1,853
Right-of-use assets	3,323
Other assets	156	90
Total assets	49,915	52,746
Current liabilities:
Accounts payable	834	1,040
Accrued expenses	1,239	2,026
Contract liability	630
Current portion of operating lease liability	681
Current portion of long-term debt, net of issuance costs and discount	7,791	7,767
Total current liabilities	11,175	10,833
Long-term operating lease liability, net of current portion	2,815
Long-term debt, net of current portion and issuance costs and discount	6,440	8,263
Commitments and contingencies (Note 4)
Stockholders’ equity:
Preferred stock, $0.001 par value; undesignated authorized shares – 5,000,000 at March 31, 2019 and December 31, 2018, respectively; Class X Convertible Preferred Stock issued and outstanding shares – 1,643,961 and 2,285,952 as of March 31, 2019 and December 31, 2018, respectively	2	2
Common stock, $0.001 par value; authorized shares – 150,000,000 as of March 31, 2019 and December 31, 2018, respectively; issued and outstanding shares – 36,500,189 and 30,579,076 as of March 31, 2019 and December 31, 2018, respectively	37	31
Additional paid-in capital	334,324	332,378
Accumulated other comprehensive loss	(40)	(60)
Accumulated deficit	(304,838)	(298,701)
Total stockholders’ equity	29,485	33,650
Total liabilities and stockholders’ equity	$ 49,915	$ 52,746