Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (7,825)	$ (19,618)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	364	1,178
Amortization of discount of investments		24
Deferred rent and lease incentive	774	(407)
Stock-based compensation	1,249	1,233
Change in fair value of warrant	(12,524)	673
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(631)	(85)
Other assets, long-term	(375)
Accounts payable	861	(761)
Accounts payable due to Intrexon Corporation		(360)
Accrued expenses	(732)	(578)
Deferred revenue	10,000
Net cash used in operating activities	(8,839)	(18,701)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(1,940)	(132)
Proceeds from maturities of marketable securities	900	6,159
Purchases of marketable securities		(8,004)
Net cash used in investing activities	(1,040)	(1,977)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments on equipment term loan	(178)	(437)
Net proceeds from issuance of common stock	8,164
Proceeds from exercise of warrants	2
Proceeds from exercise of stock options	2	5
Net cash provided by (used in) financing activities	7,990	(432)
Net decrease in cash and cash equivalents and restricted cash	(1,889)	(21,110)
Cash and cash equivalents and restricted cash—Beginning of period	7,218	32,045
Cash and cash equivalents and restricted cash—End of period	5,329	$ 10,935
Supplemental cash flow disclosures from investing and financing activities:
Purchases of property and equipment in accounts payable and accrued expenses	53
Public offering costs in accounts payable and accrued expenses	$ 160