Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net loss	$ (5,999)	$ (1,713)
Adjustments to reconcile net loss to net cash used in operating activities:
PIK interest expense on convertible promissory notes payable - related parties		970
Stock-based compensation expense	602
Changes in operating assets and liabilities:
Accounts receivable - related parties		7
Prepaid expenses and other current assets	520	(103)
Accounts payable	2,018	368
Accrued expense	(912)	28
Accrued interest - related party		5
Net cash used in operating activities	(3,771)	(438)
Cash flows from investing activities:
Purchases of marketable securities	(22,119)
Sales and maturities of marketable securities	11,563
Purchases of property and equipment	(2)
Net cash used in investing activities	(10,558)
Cash flows from financing activities:
Proceeds from issuance of common stock, net of transaction costs	3,399
Proceeds from convertible notes - related parties		750
Net cash provided by financing activities	3,399	750
Net decrease in cash and cash equivalents	(10,930)	312
Cash and cash equivalents at beginning of period	19,145	306
Cash and cash equivalents at end of period	$ 8,215	$ 618