Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended		77 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013
Operating activities
Consolidated net loss	$ (15,155)	$ (10,084)	$ (80,770)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	442	430	2,379
Issuances of common stock for technology	13		57
Stock-based compensation	1,169	106	1,938
Amortization of discounts	129	63	271
Noncash interest expense	134	97	1,156
Deferred rent	(185)	(138)	198
Deferred revenue	(63)	(63)
Initial fair value and change in fair value of exchangeable shares	2,334	(12)	2,885
Change in fair value of preferred stock warrants	(21)	(35)	(64)
Loss on disposal of assets	18		135
Loss on extinguishment of debt		323	332
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(960)	(204)	(1,666)
Accounts payable and accrued expenses	1,350	(363)	3,618
Net cash used in operating activities	(10,795)	(9,880)	(69,531)
Investing activities
Purchase of property and equipment	(94)	(414)	(3,511)
Proceeds from sale of property and equipment	6		208
Restricted cash			(122)
Net cash used in investing activities	(88)	(414)	(3,425)
Financing activities
Issuance of common stock, net of repurchases	23	205	287
Costs paid in connection with initial public offering	(1,381)		(1,381)
Proceeds from convertible promissory notes	23,736		32,236
Proceeds from long-term debt			6,400
Payments on long-term debt	(1,500)		(4,150)
Issuance of convertible preferred stock, net of offering costs		9,166	58,646
Net cash provided by financing activities	20,878	9,371	92,038
Net change in cash and cash equivalents	9,995	(923)	19,082
Cash and cash equivalents at beginning of the period	9,087	6,387
Cash and cash equivalents at end of the period	$ 19,082	$ 5,464	$ 19,082