Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash Flows From Operating Activities
Net loss	$ (6,884)	$ (5,298)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	269	185
Fair value of vested stock options	1,483	1,017
Common stock issued for services	296	450
Changes in assets and liabilities:
Prepaid expenses and other current assets	84	(62)
Accounts payable and accrued expenses	200	249
Net Cash Used In Operating Activities	(4,552)	(3,459)
Cash Flows From Investing Activities
Purchase of money market funds	(10,027)	0
Purchase of short-term investments	(29,273)	0
Maturities of short-term investments	39,155	0
Purchase of property and equipment	(2)	(782)
Net Cash Used In Investing Activities	(147)	(782)
Cash Flows From Financing Activities
Proceeds from the issuance of common stock upon exercise of warrants	0	2,304
Proceeds from the issuance of common stock, net	0	68,308
Net Cash Provided By Financing Activities	0	70,612
Net (decrease) increase in cash and cash equivalents	(4,699)	66,371
Cash and Cash Equivalents, Beginning of Period	13,642	44,909
Cash and Cash Equivalents, End of Period	8,943	111,280
Supplemental Disclosures of Cash Flow Information:
Unrealized gain on short-term investments	$ 20	$ 0