Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Stock-Based Compensation

Schedule of summary of option activity

	2015 Plan			2005 Plan
		Weighted-			Weighted-
		Average			Average
	Stock	Exercise		Stock	Exercise
	Options	Price		Options	Price
Outstanding at January 1, 2020	3,388,750	$	35.64	501,780	$	64.19
Granted	3,110,566	$	31.16	—	$	—
Exercised	(874,586)	$	31.08	(189,378)	$	44.14
Canceled	(80,366)	$	50.29	(23,329)	$	51.92
Outstanding at September 30, 2020	5,544,364	$	33.66	289,073	$	78.32
Shares exercisable at September 30, 2020	771,002	$	86.28	289,073	$	78.32
Shares available for grant at September 30, 2020	2,814,405

Schedule of stock unit activity

		Per Share
		Weighted-
	Number of	Average
	Shares	Fair Value
Outstanding and Unvested at January 1, 2020	1,102,311	$	5.95
Restricted stock units granted	508,854	$	82.02
Restricted stock units vested	(781,812)	$	6.74
Restricted stock units forfeited	(39,324)	$	45.73
Outstanding and Unvested at September 30, 2020	790,029	$	52.17

Schedule of stock-based compensation expense

The Company recorded all stock-based compensation expense in the consolidated statements of operations as follows (in thousands):

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2020		2019		2020		2019
Research and development	$	28,730	$	723	$	34,735	$	6,347
General and administrative		36,975		1,901		42,867		6,456
Total stock-based compensation expense	$	65,705	$	2,624	$	77,602	$	12,803

Stock options

Stock-Based Compensation

Schedule of assumptions used to estimate grant date fair value of stock options and stock appreciation rights granted using black-scholes option-pricing model

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2020		2019		2020		2019
Weighted average Black-Scholes fair value of stock options and SARs granted		$102.41		$4.91		$78.78		$5.42
Risk-free interest rate		0.2%-0.4%		1.5%-1.6%		0.2%-1.5%		1.5%-2.6%
Dividend yield		0%		0%		0%		0%
Volatility		135.4%-152.2%		128.0%-133.8%		116.0%-152.2%		111.6%-133.8%
Expected term (in years)		4.0-5.3		4.0-4.4		4.0-7.6		4.0-4.5
Expected forfeiture rate		0%		0%		0%		0%

ESPP

Stock-Based Compensation

Schedule of assumptions used to estimate grant date fair value of stock options and stock appreciation rights granted using black-scholes option-pricing model

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2020		2019		2020		2019
Range of Black-Scholes fair values of ESPP shares granted		$3.08-$92.67		$2.57-$35.00		$2.57-$92.67		$2.57-$35.00
Risk-free interest rate		0.2%-2.5%		1.3%-2.6%		0.2%-2.6%		1.2%-2.6%
Dividend yield		0%		0%		0%		0%
Volatility		77.5%-189.7%		59.7%-171.6%		66.6%-189.7%		52.2%-171.6%
Expected term (in years)		0.5-2.0		0.5-2.0		0.5-2.0		0.5-2.0
Expected forfeiture rate		0%		0%		0%		0%