Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net loss	$ (33,150,000)	$ (52,761,000)	$ (37,483,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,484,000	698,000	699,000
Share-based compensation expense	1,750,000	5,573,000	4,407,000
Gain on disposal of property and equipment			(157,000)
Other non-cash adjustments	401,000
Changes in operating assets and liabilities:
Prepaid expenses and other current	1,041,000	(617,000)	(1,579,000)
Accounts payable	(2,700,000)	(981,000)	840,000
Accrued expenses	(2,470,000)	2,066,000	(52,000)
Deferred rent	(5,000)	7,000	17,000
Net cash used in operating activities	(33,649,000)	(46,015,000)	(33,308,000)
Investing activities
Purchase of property and equipment	(1,405,000)	(4,746,000)	(2,322,000)
Expenditures on building construction		(9,168,000)	(8,070,000)
Net cash used in investing activities	(1,405,000)	(13,914,000)	(10,392,000)
Financing activities
Issuance of common stock and warrants, net	32,620,000	1,808,000	75,712,000
Issuance of common stock under stock option plan	703,000	1,136,000	1,348,000
Collection of subscription receivable			410,000
Net cash provided by financing activities	33,323,000	2,944,000	77,470,000
Effect of foreign exchange rate on cash and cash equivalents	(825,000)	258,000	(48,000)
Net change in cash and cash equivalents	(2,556,000)	(56,727,000)	33,722,000
Cash and cash equivalents, beginning of period	34,324,000	91,051,000	57,329,000
Cash and cash equivalents, end of period	31,768,000	34,324,000	91,051,000
Supplemental Information:
Accrued purchases of property and equipment		148,000	940,000
Accrued expenditures on building construction		$ 439,000	$ 1,416,000