Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 73,933	$ 114,185
Investments	131,149
Prepaid expenses and other current assets	2,528	58
Total current assets	207,610	114,243
Property and equipment, net	7,751	1,264
Restricted cash	1,539	139
Deferred offering costs		1,684
Deferred financing costs		15
Total assets	216,900	117,345
Current liabilities:
Accounts payable	5,397	2,166
Accrued expenses and other current liabilities	5,523	1,737
Notes payable; current portion		1,200
Total current liabilities	10,920	5,103
Lease incentive obligation	586
Notes payable, net of discount		1,304
Preferred stock warrant liability		1,582
Total liabilities	$ 11,506	$ 7,989
Commitments and contingencies:
Stockholders’ equity (deficit):
Common stock, $0.001 par value; 200,000,000 and 38,000,000 shares authorized at December 31, 2015 and 2014, respectively; 39,082,017 and 6,890,250 shares issued and outstanding at December 31, 2015 and 2014, respectively	$ 39	$ 7
Additional paid-in capital	287,937	1,104
Accumulated other comprehensive income (loss)	30
Accumulated deficit	(82,612)	(27,832)
Total stockholders’ equity (deficit)	205,394	(26,721)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 216,900	117,345
Convertible Preferred Stock Series A, A-2, B, C, D and D-1 [Member]
Current liabilities:
Convertible preferred stock (Series A, A-2, B, C, D and D-1), value		$ 136,077