CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 123,456	$ 46,928
Short-term investments	128,942	186,452
Prepaid expenses and other current assets	12,095	8,247
Total current assets	264,493	241,627
Property and equipment, net	5,210	6,398
Operating lease right-of-use assets	1,323	1,927
Restricted cash	210	210
Deferred offering costs	205
Deferred tax assets		4,372
Total assets	271,441	254,534
Current liabilities:
Accounts payable	2,373	5,693
Accrued expenses	16,499	20,415
Operating lease liabilities	1,680	1,697
Other current liabilities		25
Total current liabilities	20,552	27,830
Non-current liabilities:
Non-current operating lease liabilities	139	955
Other long-term liabilities	334	326
Total liabilities	21,025	29,111
Commitments and contingencies (Note 12)
Shareholders' equity:
Additional paid-in capital	670,371	581,467
Accumulated other comprehensive income	9	33
Accumulated deficit	(419,980)	(356,092)
Total shareholders' equity	250,416	225,423
Total liabilities and shareholders' equity	271,441	254,534
Class A common shares
Shareholders' equity:
Common stock value	7	6
Class B common shares
Shareholders' equity:
Common stock value	1	1
Class A1 common shares
Shareholders' equity:
Common stock value	4	4
Class B1 common shares
Shareholders' equity:
Common stock value	$ 4	$ 4