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Stockholders' Equity (Tables)
 3 Months Ended
Mar. 31, 2021
Share-based Payment Arrangement [Abstract]  
Schedule of stock-based compensation expense recognized
The following table presents the components and classification of stock-based compensation expense recognized for stock options, RSUs, and the ESPP:
Three Months Ended
March 31,
20212020
Stock options$5,657 $2,575 
Restricted stock units19 — 
Employee stock purchase plan321 174 
Total stock-based compensation expense$5,997 $2,749 
Cost of goods sold$79 $53 
Research and development1,040 345 
Selling, general and administrative4,878 2,351 
Total stock-based compensation expense$5,997 $2,749 
Summary of the company's stock option activity and related information
A summary of stock option activity and related information is as follows:
OptionsWeighted Average
Exercise Price		Weighted Average
Remaining
Contractual Term
(years)		Aggregate Intrinsic
Value
(in thousands)
Outstanding at December 31, 20202,857,564 $66.09 7.9$351,626
Granted68,802 $207.15 
Exercised(133,421)$26.61 $24,567
Forfeited(42,570)$111.03 
Outstanding at March 31, 20212,750,375 $70.84 7.7$374,706
Exercisable at March 31, 20211,221,474 $24.27 6.3$223,188
Summary of weighted average assumptions for fair value of options granted
The fair value of options granted to employees and non-employee directors was estimated as of the grant date using the Black-Scholes option pricing model using the following assumptions:
Three Months Ended
March 31,
20212020
Expected term (years)
6.25
6.25
Expected volatility
55.2 - 55.7%
42.3 - 48.2%
Risk-free interest rate
0.79 - 1.4%
0.55 - 1.42%
Expected dividend yield0.0%0.0%
Weighted average fair value$109.27$31.48
Schedule of restricted stock units activity
A summary of RSUs and related information is as follows:
Restricted Stock UnitsWeighted Average
Grant Date Fair Value		Aggregate Intrinsic Value (in thousands)
Unvested at December 31, 2020— $— $— 
Granted2,275 $201.51 
Unvested at March 31, 20212,275 $201.51 $471