Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended		33 Months Ended
	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013
Cash flows from operating activities:
Net loss	$ (2,624)	$ (29,044)	$ (13,510)	$ (45,178)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	0	231	93	324
Impairment of property and equipment		364		364
Amortization of premium		586	77	663
Stock-based compensation expense	346	5,094	1,382	6,822
Issuance of common stock for technology access fee		2,500		2,500
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(44)	(76)	(530)	(650)
Accounts payable	276	(721)	599	154
Accrued expenses and other non-current liabilities	486	2,972	733	4,191
Net cash used in operating activities	(1,560)	(18,094)	(11,156)	(30,810)
Cash flows from investing activities:
Purchases of property, plant and equipment		(719)	(849)	(1,568)
Maturities of short-term investments		5,670		5,670
Purchases of short-term investments		(15,974)	(16,698)	(32,672)
Decrease / (increase) in restricted cash		5	(93)	(88)
Net cash used in investing activities		(11,018)	(17,640)	(28,658)
Cash flows from financing activities:
Proceeds from issuance of preferred stock, net of issuance costs	6,099		34,992	41,091
Net proceeds from the issuance of common stock	2	32,414	4,039	36,455
Net cash provided by financing activities	6,101	32,414	39,031	77,546
Net increase in cash and cash equivalents	4,541	3,302	10,235	18,078
Cash and cash equivalents at beginning of period		14,776	4,541
Cash and cash equivalents at end of period	4,541	18,078	14,776	18,078
Supplemental disclosure of non-cash investing and financing activity
Investment in OvaXon		1,500		1,500
Accretion of convertible preferred stock to redemption value	(101)			(101)
Conversion of convertible preferred stock to common stock			$ 41,192	$ 41,192