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Stock Incentive Plans (Tables)
6 Months Ended
Jun. 30, 2021
Stock Incentive Plans  
Summary of stock option activity

Weighted

Average

Weighted-

Remaining

Aggregate

Average Exercise

Contractual

Intrinsic Value

    

Shares

    

 Price

    

Term (years)

    

(in thousands)

Outstanding at December 31, 2020

 

1,367,667

$

11.38

 

8.13

$

Granted

 

6,447,000

$

2.74

Assumed in Quellis Acquisition

332,494

$

0.29

Cancelled or forfeited

 

(208,152)

$

8.71

Expired

(8,675)

$

16.70

Outstanding at June 30, 2021

7,930,334

$

3.96

9.44

$

662

Vested and exercisable at June 30, 2021

 

770,141

$

14.07

7.31

$

207