CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016		Mar. 31, 2015
Cash flows from operating activities
Net loss	$ (10,086)		$ (9,128)
Adjustments to reconcile loss to net cash used in operating activities:
Stock-based compensation expense	1,453		1,964
Depreciation and amortization	3		11
Amortization of debt discount and debt issuance costs	122		44
Write-off debt discount upon note repayment	27
Change in fair value of warrant liability			89
Changes in operating assets and liabilities:
Prepaids and other assets	(143)		(259)
Accounts payable	128		(1,056)
Accrued clinical expense	231		(887)
Accrued compensation	(677)		(1,258)
Other accrued liabilities	(1,163)		(268)
Deferred revenue	(610)		(853)
Net cash used in operating activities	(10,715)		(11,601)
Cash flows from investing activities
Purchases of marketable securities	(43,514)		(7,942)
Proceeds from maturities of marketable securities	46,913		7,730
Net cash provided by (used in) investing activities	3,399		(212)
Cash flows from financing activities
Proceeds from notes payable	12,500
Principal payments on notes payable	(830)		(1,642)
Payoff notes payable and final payment	(7,153)
Payment of financing fees and debt issuance costs	(229)
Proceeds from issuance of common stock through controlled equity offering facilities, net			10,011
Proceeds from exercise of warrants, stock options and stock purchase rights			42
Net cash provided by financing activities	4,288		8,411
Net decrease in cash and cash equivalents	(3,028)		(3,402)
Cash and cash equivalents at beginning of period	26,886	[1]	22,186
Cash and cash equivalents at end of period	23,858		18,784
Supplemental disclosure of non-cash activities
Fair value of warrants issued in connection with notes payable	$ 537		$ 100

[1] The condensed consolidated balance sheet as of December 31, 2015 has been derived from the audited financial statements as of that date included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2015.