Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 49,628	$ 72,797
Prepaid expenses and other current assets	1,738	1,298
Total current assets	51,366	74,095
Property and equipment, net	10,005	10,546
Restricted cash	1,092	1,092
Deferred offering costs	2,064
Other assets	624	38
Total assets	65,151	85,771
Current liabilities:
Accounts payable	3,081	1,263
Accrued expenses and other current liabilities	2,793	2,497
Deferred lease incentive, current portion	469	469
Total current liabilities	6,343	4,229
Deferred rent, excluding current portion	1,496	1,402
Deferred lease incentive, excluding current portion	3,756	3,990
Other liabilities, excluding current portion	101	150
Total liabilities	11,696	9,771
Commitments and contingencies (Note 10)
Stockholders’ deficit:
Common stock, $0.001 par value; 147,500,000 and 135,000,000 shares authorized as of June 30, 2019 and December 31, 2018, respectively; 2,768,596 and 2,791,764 shares issued as of June 30, 2019 and December 31, 2018, respectively; 1,870,286 and 1,587,953 shares outstanding as of June 30, 2019 and December 31, 2018, respectively	2	2
Additional paid-in capital	6,453	4,452
Accumulated deficit	(118,136)	(68,124)
Total stockholders’ deficit	(111,681)	(63,670)
Total liabilities, convertible preferred stock, and stockholders’ deficit	65,151	85,771
Series A Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	59,909	59,909
Series B Convertible Preferred Stock
Current liabilities:
Convertible preferred stock	$ 105,227	$ 79,761