Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (4,547)	$ (2,468)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	29	17
Amortization of premium on marketable securities	8
Loss on disposal of property and equipment		2
Amortization of lease allowance liability	(6)	(6)
Stock-based compensation	140	38
Research and development services settled with convertible preferred stock	20	206
Changes in operating assets and liabilities:
Accounts receivable-grant	79
Prepaid expenses and other assets	(447)	(180)
Accounts payable	261	(18)
Accrued and other liabilities	475	(74)
Net cash used in operating activities	(3,988)	(2,483)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(2)	(10)
Purchases of marketable securities	(2,940)
Proceeds from maturities of marketable securities	1,750
Increase in restricted cash		(10)
Net cash used in investing activities	(1,192)	(20)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of convertible preferred stock, net of issuance costs		43,678
Payment of deferred offering costs	(98)
Net cash (used) provided by financing activities	(98)	43,678
NET (DECREASE) INCREASE IN CASH	(5,278)	41,175
CASH
Beginning of period	29,294	2,616
End of period	$ 24,016	43,791
Supplemental Disclosure of Non-Cash Investing and Financing Information:
Deemed dividend to Series A convertible preferred stockholders upon conversion from an LLC to corporation		228
Unpaid amounts related to purchase of property and equipment		$ 64