CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 1,533	$ 1,384
Short-term investments	35,927	12,717
Grant and other receivables	252	379
Prepaid expenses	1,110	251
Other current assets	146	86
Total current assets	38,968	14,817
Property and equipment, net	907	939
Restricted cash	679	679
Other assets	439	100
Total assets	40,993	16,535
Current liabilities:
Accounts payable	5,085	2,329
Accrued expenses	5,476	3,944
Current portion of notes payable, net of discount	1,609	5,600
Total current liabilities	12,170	11,873
Notes payable, net of current portion and discount	30,761	14,898
Deferred rent	8,673	8,148
Commitments and contingencies (Note 8)
Shareholders’ equity:
Preferred stock, par value $0.01 per share: Authorized shares - 20,000,000 at March 31, 2014 (unaudited) and December 31, 2013; Issued and outstanding shares—none
Common stock, par value $0.01 per share: Authorized shares - 150,000,000 at March 31, 2014 (unaudited) and December 31, 2013; Issued and outstanding shares—33,901,591 and 30,359,508 at March 31, 2014 (unaudited) and December 31, 2013, respectively	340	304
Additional paid-in capital	278,055	235,685
Accumulated deficit	(289,006)	(254,373)
Total shareholders’ equity (deficit)	(10,611)	(18,384)
Total liabilities and shareholders’ equity	$ 40,993	$ 16,535