Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities
Net loss	$ (22,811,000)	$ (4,003,000)	$ (5,387,000)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation expense	2,921,000	319,000
Imputed interest on related party promissory notes	13,000	128,000
Unrealized foreign currency transaction losses	11,000	44,000	14,000
Net amortization of premiums and accretion of discounts on marketable debt securities	311,000
Depreciation and amortization	80,000	0	0
Non-cash consideration received for licenses granted			(303,000)
Other non-cash adjustments		3,000
Changes in operating assets and liabilities
Trade receivables	(1,342,000)	(799,000)	(36,000)
Related party receivables	750,000	174,000	(924,000)
Unbilled receivables	327,000	(213,000)	109,000
Prepaid expenses	(992,000)	(28,000)
Other current assets	(851,000)
Other assets	(168,000)
Accounts payable	590,000	33,000	257,000
Accrued expenses and other current liabilities	2,221,000	764,000	107,000
Due to related party under services agreement	(34,000)	768,000	3,192,000
Other related party payables	(3,761,000)	258,000	(41,000)
Advance payments	(26,000)	153,000
Deferred rent	246,000
Net cash used in operating activities	(22,515,000)	(2,399,000)	(3,012,000)
Cash flows from investing activities
Purchases of marketable securities	(163,278,000)
Purchases of property and equipment	(522,000)
Net cash used in investing activities	(163,800,000)
Cash flows from financing activities
Proceeds from issuance of Series B preferred units, net of transaction costs			1,965,000
Proceeds from related party promissory notes		2,400,000
Proceeds from exercise of stock options	107,000	1,000
Proceeds from initial public offering of common stock, net of transaction costs	145,184,000
Net cash provided by financing activities	239,310,000	2,401,000	1,965,000
Net increase (decrease) in cash and cash equivalents	52,995,000	2,000	(1,047,000)
Cash and cash equivalents
Beginning of period	1,121,000	1,119,000	2,166,000
End of period	54,116,000	1,121,000	1,119,000
Supplemental cash flow information
Cash paid for interest	7,000	164,000
Supplemental disclosures of non-cash investing and financing activities
Conversion of related party promissory notes into Series C convertible preferred stock	1,389,000
Conversion of convertible preferred stock into common stock upon initial public offering	111,392,000
Purchases of property and equipment in accounts payable and accrued expenses	96,000
Deferred issuance costs for Series C convertible preferred stock in accrued expenses		$ 157,000
Non-cash consideration received for licenses granted			303,000
Series B Preferred Units [Member]
Supplemental disclosures of non-cash investing and financing activities
Conversion of accrued service fees to related party			$ 5,892,000
Series C Convertible Preferred Stock [Member]
Cash flows from financing activities
Proceeds from issuance of convertible preferred stock, net of transaction costs	26,021,000
Supplemental disclosures of non-cash investing and financing activities
Conversion of accrued service fees to related party	2,403,000
Series D Convertible Preferred Stock [Member]
Cash flows from financing activities
Proceeds from issuance of convertible preferred stock, net of transaction costs	$ 67,998,000