CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 94,960,535	$ 51,574,932
Short-term investments	160,547,550	78,083,604
Prepaid expenses and other current assets	6,074,268	1,944,751
Total current assets	261,582,353	131,603,287
Property and equipment, net	6,942,457	3,154,205
Deferred offering costs		1,000,262
Restricted cash	1,789,962	1,772,587
Total assets	270,314,772	137,530,341
Current liabilities:
Accounts payable	5,017,426	2,538,057
Accrued expenses and other liabilities	2,358,433	2,860,025
Deferred rent		122,601
Deferred revenue	3,499,700	3,341,063
Total current liabilities	10,875,559	8,861,746
Non-current liabilities:
Deferred rent, net of current portion	2,893,331	290,923
Deferred revenue, net of current portion	29,747,451	30,069,563
Total liabilities	43,516,341	39,222,232
Commitments and contingencies (Note 6)
Convertible preferred stock:
Total convertible preferred stock		137,762,160
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value, 10,000,000 shares authorized as of June 30, 2018 and no shares authorized as of December 31, 2017; no shares issued and outstanding at June 30, 2018 and December 31, 2017
Common stock, $0.0001 par value; 200,000,000 and 170,000,000 shares authorized as of June 30, 2018 and December 31, 2017, respectively; 37,474,649 and 2,902,109 shares issued as of June 30, 2018 and December 31, 2017, respectively; and 37,254,902 and 2,637,011 shares outstanding as of June 30, 2018 and December 31, 2017, respectively	3,726	264
Additional paid-in capital	290,442,015	799,859
Accumulated other comprehensive loss	(48,646)	(73,308)
Accumulated deficit	(63,598,664)	(40,180,866)
Total stockholders’ equity (deficit)	226,798,431	(39,454,051)
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	$ 270,314,772	137,530,341
Series A Convertible Preferred Stock
Convertible preferred stock:
Total convertible preferred stock		42,994,550
Series B Convertible Preferred Stock
Convertible preferred stock:
Total convertible preferred stock		$ 94,767,610