Unaudited Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 49,317	$ 47,674
Investments	111,688	75,493
Prepaid expenses and other current assets	5,612	2,326
Total current assets	166,617	125,493
Property and equipment, net	4,463	1,638
Investments, non-current	8,014	0
Restricted cash	417	290
Deferred offering costs	0	2,012
Total assets	179,511	129,433
Liabilities, redeemable convertible preferred stock and stockholders’ equity (deficit)
Accounts payable	3,621	2,663
Accrued expenses and other current liabilities	4,262	2,802
Total current liabilities	7,883	5,465
Other liabilities	474	434
Total liabilities	8,357	5,899
Commitments and contingencies (Note 7)
Redeemable convertible preferred stock	0	209,230
Stockholders’ equity (deficit)
Preferred stock, $0.0001 par value. 10,000,000 shares and no shares authorized, no shares issued or outstanding at September 30, 2019 and December 31, 2018, respectively.	0	0
Common stock, $0.0001 par value; 150,000,000 and 20,988,730 shares authorized at September 30, 2019 and December 31, 2018, respectively; 24,033,032 and 914,602 shares issued at September 30, 2019 and December 31, 2018, respectively; 23,944,083 and 726,990 shares outstanding at September 30, 2019 and December 31, 2018, respectively.	2	0
Additional paid-in capital	340,686	0
Accumulated other comprehensive income (loss)	230	(106)
Accumulated deficit	(169,764)	(85,590)
Total stockholders’ equity (deficit)	171,154	(85,696)
Total liabilities, redeemable preferred stock and stockholders’ equity (deficit)	179,511	129,433
Series A redeemable convertible preferred stock
Liabilities, redeemable convertible preferred stock and stockholders’ equity (deficit)
Redeemable convertible preferred stock	0	72,980
Series B redeemable convertible preferred stock
Liabilities, redeemable convertible preferred stock and stockholders’ equity (deficit)
Redeemable convertible preferred stock	$ 0	$ 136,250