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Common stock and convertible preferred stock (Tables)
12 Months Ended
Dec. 31, 2020
Common stock and convertible preferred stock  
Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]

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June 2, 2020

    

October 6, 2020

 

Volatility rate

 

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79.0

%  

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82.0

%

Risk-free interest rate

 

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0.2

%  

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0.2

%

Expected term (in years)

 

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3.0

 

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2.7

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Strike price (per share)

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$

9.00

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$

9.00

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Fair value of Series A convertible preferred stock

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$

4.44

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$

12.00

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