Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	7 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net loss	$ (277)	$ (9,518)	$ (2,811)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of equipment	6	94	51
Amortization of intangible assets	111	665	666
Stock-based compensation		870	402
Net premium amortization on marketable investments		4
Change in deferred income taxes	(23)		(1,657)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	12	(135)	(12)
Deferred offering costs		(280)	(347)
Accounts payable	29	3	125
Accrued expenses	58	246	305
Deferred grant revenue	(17)		(39)
Net cash used in operating activities	(101)	(8,051)	(3,317)
Cash flows from investing activities:
Purchase of equipment	(46)	(64)	(86)
Cash acquired in connection with acquisition of businesses	1
Purchase of marketable investments		(19,067)
Maturities of marketable investments		4,750
Net cash used in investing activities	(45)	(14,381)	(86)
Cash flows from financing activities:
Common stock issued to founders	8
Net proceeds from private placement	7,147
Proceeds from issuance of common stock from initial public offering, net of issuance costs		20,915
Net cash provided by financing activities	7,155	20,915
Net increase (decrease) in cash	7,009	(1,517)	(3,403)
Cash and cash equivalents at beginning of period		3,606	7,009
Cash and cash equivalents at end of period	7,009	2,089	3,606
Supplemental disclosure of noncash investing and financing activities:
Reclassification of deferred offering costs to additional paid-in capital upon initial public offering		627
Fair value of common stock issued in connection with license agreement	3,785
Fair value of common stock issued in connection with acquisition of businesses	$ 5,411
Equipment purchased in accrued expenses		$ 18	$ 104