Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

	Number of Options and Unvested Shares			Weighted Average Exercise Price		Weighted average remaining contractual life (years)		Aggregate intrinsic value
Balance at December 31, 2019		2,393,934		$	5.35		8.62	$	121,592,682
Options granted		1,710,145			51.16
Options exercised		(124,836	)		9.89
Options cancelled		(210,318	)		42.38
Balance at September 30, 2020		3,768,925			23.92		8.55		102,942,251
Options vested and expected to vest as of September 30, 2020		3,768,925			23.92		8.55		102,942,251
Options exercisable as of September 30, 2020		1,323,339		$	8.57		7.73	$	55,396,069

Summary of Employee and Non-Employee Stock-Based Compensation Expense

The following table summarizes employee and non-employee stock-based compensation expense for the three and nine months ended September 30, 2020 and 2019 and the allocation within the statements of operations and comprehensive loss (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
General and administrative expense	$	2,261	$	313	$	4,915	$	679
Research and development expense		1,897		599		4,596		800
Total stock-based compensation	$	4,158	$	912	$	9,511	$	1,479