Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 90,915	$ 65,726
Restricted cash, current portion	0	200
Prepaid expenses and other current assets	3,147	1,505
Total current assets	94,062	67,431
Property and equipment, net	24,568	3,145
Restricted cash, less current portion	909	0
Other assets	0	219
Total assets	119,539	70,795
Current liabilities:
Accounts payable	11,484	6,652
Accrued clinical and other expenses	703	905
Accrued payroll and related expenses	4,995	2,077
Deferred rent, current portion	1,370	124
Total current liabilities	18,552	9,758
Deferred rent, less current portion	12,785	0
Total liabilities	31,337	9,758
Commitments and contingencies (Note 9)
Shareholders’ equity:
Common Stock, $0.0001 par value; 100,000,000 shares authorized, 22,167,529 and 18,261,557 shares issued and outstanding at December 31, 2017 and December 31, 2016, respectively	2	2
Additional paid-in capital	803,071	661,103
Accumulated deficit	(721,514)	(606,711)
Total shareholders’ equity	88,202	61,037
Total liabilities and shareholders’ equity	119,539	70,795
Series C-1 Convertible Preferred Stock [Member]
Shareholders’ equity:
Convertible preferred stock, value	3,906	3,906
Series F Convertible Preferred Stock [Member]
Shareholders’ equity:
Convertible preferred stock, value	$ 2,737	$ 2,737