Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net loss	$ (22,709)	$ (18,639)
Adjustments to reconcile net loss to net cash used in operating activities:
PIK interest expense on convertible promissory notes payable - related parties		1,207
Stock-based compensation expense	2,307	8,103
Depreciation and amortization expense	17
Changes in operating assets and liabilities:
Accounts receivable - related parties		7
Prepaid expenses and other current assets	290	282
Accounts payable	638	270
Accrued expense	3,085	(3,564)
Accrued interest - related party		6
Net cash used in operating activities	(16,372)	(12,328)
Cash flows from investing activities:
Cash received from merger transaction		5,849
Purchases of marketable securities	(34,910)	(2,995)
Sales and maturities of marketable securities	6,944	8,579
Purchases of property and equipment	(125)	(1)
Net proceeds from the sale of property, equipment and other assets		483
Net cash provided (used) in investing activities	(28,091)	11,915
Cash flows from financing activities:
Proceeds from issuance of common stock, net of transaction costs	38,278
Proceeds from convertible notes - related parties		8,500
Net cash provided by financing activities	38,278	8,500
Net increase (decrease) in cash and cash equivalents	(6,185)	8,087
Cash and cash equivalents at beginning of period	19,145	306
Cash and cash equivalents at end of period	$ 12,960	8,393
Supplemental disclosure of cash flow information:
Exchange of related party advances payable for convertible notes		500
Related party debt restructuring		$ 13,680