Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 73,662	$ 73,849
Accounts receivable	369	201
Prepaid expenses and other current assets	860	1,076
Inventories	683	115
Current portion of restricted cash		80
Total current assets	75,574	75,321
Property and equipment, net	10,655	2,760
Restricted cash, net of current portion	260	260
Deferred tax assets		313
Other assets	459	480
Total assets	86,948	79,134
Current liabilities:
Accounts payable	1,228	735
Accrued expenses and other current liabilities	4,162	3,662
Current portion of notes payable	4,471	295
Deferred revenue	2,146	80
Deferred tax liabilities		313
Current portion of lease incentives	268	87
Total current liabilities	12,275	5,172
Notes payable, net of current portion	26,222	20,660
Lease incentives, net of current portion	1,076	106
Other liabilities	$ 436	$ 195
Commitments and contingencies (Note 13)
Stockholders' equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued and outstanding at December 31, 2015 and 2014
Common stock, $0.001 par value; 200,000,000 shares authorized at December 31, 2015 and 2014; 24,175,381 and 20,041,645 shares issued and outstanding at December 31, 2015 and 2014 respectively	$ 24	$ 20
Additional paid-in capital	195,800	156,576
Accumulated deficit	(148,885)	(103,595)
Total stockholders' equity	46,939	53,001
Total liabilities and stockholders' equity	$ 86,948	$ 79,134