Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 86,366	$ 52,080
Available-for-sale securities	36,098	17,014
Prepaid expenses and other current assets	6,175	1,499
Restricted cash		65
Total current assets	128,639	70,658
Property and equipment, net	10,422	2,429
Other non-current assets	209
Restricted cash	327
Deferred offering costs	0	3,106
Total assets	139,597	76,193
Current liabilities:
Accounts payable	3,691	5,066
Accrued expenses	8,235	5,972
Current portion of capital lease obligations	173
Other current liabilities	382	233
Total current liabilities	12,481	11,271
Capital lease obligations, net of current portion	859
Other non-current liabilities	1,074
Total liabilities	14,414	11,271
Commitments and Contingencies (Note 13)
Preferred Units
Preferred Units	0	0
Stockholders’ / Members’ Equity / (Deficit):
Series A, B, C and D Common Units, no units authorized at December 31, 2018 and 20,189,509 units authorized at December 31, 2017; no units issued and outstanding at December 31, 2018 and 19,438,552 units issued and outstanding at December 31, 2017		65,014
Preferred stock, $0.001 par value; 10,000,000 shares authorized at December 31, 2018 and no shares authorized at December 31, 2017; no shares issued and outstanding at December 31, 2018 and December 31, 2017	0	0
Common stock, $0.001 par value; 300,000,000 shares authorized at December 31, 2018 and no shares authorized at December 31, 2017; 35,432,460 shares issued and outstanding at December 31, 2018 and no shares issued and outstanding at December 31, 2017	35
Additional Paid-in Capital	324,209
Accumulated other comprehensive loss	(5)	(13)
Accumulated deficit	(199,056)	(124,258)
Total stockholders'/members’ equity/(deficit)	125,183	(59,257)
Total liabilities, preferred units and stockholders'/members’ equity	139,597	76,193
Series 2 Senior Preferred Units [Member]
Preferred Units
Preferred Units	0	55,002
Series 1 Senior Preferred Units [Member]
Preferred Units
Preferred Units	0	25,000
Junior Preferred Units [Member]
Preferred Units
Preferred Units	$ 0	$ 44,177