STATEMENTS OF CASH FLOWS (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities
Net loss	$ (7,007,000)	$ (2,235,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	2,000	3,000
Stock-based compensation expense	383,000	23,000
Change in fair value of warrant liability		(428,000)
Amortization of debt issuance costs	2,000
Changes in operating assets and liabilities:
Prepaid expenses and other assets	107,000	568,000
Accounts payable and accrued expenses	2,561,000	944,000
Net cash used in operating activities	(3,952,000)	(1,125,000)
Cash flows from investing activities
Purchases of investments	(1,491,000)
Net cash used in investing activities	(1,491,000)
Cash flows from financing activities
Proceeds from exercise of stock options	200,000	28,000
Proceeds from issuance of convertible preferred stock, net of issuance costs		(110,000)
Net cash provided by (used in) financing activities	200,000	(82,000)
Net decrease in cash and cash equivalents	(5,243,000)	(1,207,000)
Cash and cash equivalents-beginning of year	49,720,000	10,037,000
Cash and cash equivalents-end of year	44,477,000	8,830,000
Supplemental disclosure of cash flow information
Cash paid for interest	$ 114,000