CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities:
Net loss	$ (25,910)	$ (5,217)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	48	25
Stock-based compensation expense	2,576	85
Non-cash charges related to Vixen acquisition	2,784
Changes in operating assets and liabilities:
Prepaid expenses and other assets	30	(387)
Accounts payable	2,493	(448)
Accrued expenses	1,353	278
Net cash used in operating activities	(16,626)	(5,664)
Cash flows from investing activities:
Purchases of property and equipment	(106)	(242)
Purchases of marketable securities	(11,282)
Proceeds from sales and maturities of marketable securities	31,430	5,897
Net cash provided by investing activities	20,042	5,655
Cash flows from financing activities:
Proceeds from issuance of common stock in connection with private placement, net of issuance costs	18,547
Proceeds from the exercise of employee stock options	1
Payment of deferred offering costs		(895)
Net cash used in financing activities	18,548	(895)
Net increase (decrease) in cash and cash equivalents	21,964	(904)
Cash and cash equivalents at beginning of period	9,851	10,757
Cash and cash equivalents at end of period	31,815	9,853
Supplemental disclosures of non-cash investing and financing activities:
Additions to property and equipment included in accounts payable	18
Accretion of convertible preferred stock to redemption value		1,333
Fair value of stock issued in connection with Vixen acquisition on date of issuance	$ 2,355
Deferred offering costs included in accounts payable		$ 233