STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net loss	$ (78,231)	$ (9,711)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	122	124
Stock-based compensation	1,093	1,223
Change in fair value of warrants		(82)
Common stock issued in exchange for license agreement	67,285
(Increase) decrease in:
Receivables	83	118
Prepaid expenses and other current assets	282	359
Other noncurrent assets		11
Increase (decrease) in:
Accounts payable	(1,224)	156
Accrued expenses	1,037	(605)
Deferred revenue	(272)	(200)
Deferred rent	108	(47)
Net cash used in operating activities	(9,717)	(8,654)
Cash flows from investing activities:
Purchases of property and equipment	(17)	(2)
Net cash used in investing activities	(17)	(2)
Cash flows from financing activities:
Proceeds from exercise of stock options	2,541	969
Payments to employees for repurchase of common stock	(246)	(132)
Proceeds from the issuance of common stock, net	94,320
Net cash provided by financing activities	96,615	837
Net increase (decrease) in cash and cash equivalents	86,881	(7,819)
Cash and cash equivalents, beginning of period	42,803	68,204
Cash and cash equivalents, end of period	129,684	60,385
Supplementary disclosure of cash flow information:
Cash paid for interest	0	0
Cash paid for income taxes	0	0
Supplementary disclosure of noncash investing and financing activities:
Issuance of common stock in license agreement	$ 67,285