Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 49,410	$ 36,797
Grants and other receivables	231	384
Inventory	241	0
Deposits and other current assets	438	3,494
Total current assets	50,320	40,675
Property and equipment, net	1,433	323
Deferred offering costs	2,285	0
Deposits and other assets — long-term	1,097	553
Total assets	55,135	41,551
Current liabilities:
Accounts payable	3,876	3,369
Accrued expenses	5,606	2,541
Deferred other income	217	0
Total current liabilities	9,699	5,910
Convertible notes payable, net	0	15,256
Accrued interest	0	3,409
Total liabilities	9,699	24,575
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	236,542	168,173
Stockholders' deficit:
Common stock, $0.001 par value; 13,067,149 and 10,624,486 shares authorized at September 30, 2017 and December 31, 2016, respectively; 4,067,717 shares issued and outstanding at September 30, 2017 and December 31, 2016	4	4
Additional paid-in capital	0	0
Accumulated deficit	(191,001)	(151,102)
Accumulated other comprehensive loss	(109)	(99)
Total stockholders' deficit	(191,106)	(151,197)
Total liabilities, redeemable convertible preferred stock and stockholders' deficit	55,135	41,551
Redeemable Convertible Preferred Stock, Series A
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	5,381	5,381
Redeemable Convertible Preferred Stock, Series B1
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	673	673
Redeemable Convertible Preferred Stock, Series B2
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	14,760	14,760
Redeemable Convertible Preferred Stock, Series C
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	112,974	105,738
Redeemable Convertible Preferred Stock, Series C1
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	44,354	41,621
Redeemable Convertible Preferred Stock, Series C2
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	20,345	0
Redeemable Convertible Preferred Stock, Series D
Redeemable convertible preferred stock, $0.001 par value:
Redeemable shares, carrying amount	$ 38,055	$ 0