Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 54,437	$ 54,062
Accounts receivable, net	2,548	201
Inventory	954	217
Prepaid expenses and other current assets	2,231	1,713
Total current assets	60,170	56,193
Property and equipment, net	10,151	10,236
Restricted cash	1,764	6,614
Operating lease assets	6,655
Total assets	78,740	73,043
Current liabilities:
Accounts payable	3,268	2,965
Accrued expenses and other current liabilities	7,635	6,194
Operating lease liabilities	1,126
Total current liabilities	12,029	9,159
Other liabilities		3,221
Operating lease liabilities, net of current portion	8,905
Derivative liability	12,124
Notes payable, net of discount	25,007	24,788
2026 convertible notes, net	24,305
Total liabilities	82,370	37,168
Commitments and contingencies (Note 15)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized and no shares issued or outstanding at December 31, 2019 and December 31, 2018, respectively
Common stock, $0.0001 par value; 100,000,000 shares authorized and 50,333,559 and 41,518,091 shares issued and outstanding at December 31, 2019 and December 31, 2018, respectively	5	4
Additional paid-in capital	379,980	333,114
Accumulated deficit	(383,615)	(297,243)
Total stockholders’ equity (deficit)	(3,630)	35,875
Total liabilities and stockholders’ equity (deficit)	$ 78,740	$ 73,043