Convertible Preferred Stock, Tranche Liability and Warrant Liability (Tables)

12 Months Ended

Dec. 31, 2021

Convertible Preferred Stock Tranche Liability and Warrant Liability [Abstract]

Summary of Convertible preferred stock

Convertible preferred stock consisted of the following as of December 31, 2020 (in thousands, except share and per share data):

	Shares Authorized		Shares Issued and Outstanding		Weighted Average Issuance Price per Share		Carrying Value		Liquidation Preference
Series A		711,203		477,297	$	2.24	$	1,067	$	1,067
Series A-1		11,898,177		7,537,879		2.24		16,333		16,847
Series B		29,457,450		11,862,043		3.80		39,253		45,070
Total		42,066,830		19,877,219			$	56,653	$	62,984

Summary of Assumptions Used in Estimating the Fair Value of Preferred Stock Tranche Liability

The following assumptions were used in the estimation of the fair value of the tranche liability as a forward contract as of each of the dates indicated:

	June 17, 2021			December 31, 2020
Risk-free interest rate		0.07	%		0.12	%
Expected time to Milestone Closing (in years)		0.8			1.3
Probability of achievement of Milestone Closing		100	%		65	%

Summary of Fair Value of the Warrant Liability

The following assumptions were used in the estimation of the fair value of the warrant liability using the OPM backsolve method as of each of the dates indicated:

	June 22, 2021	December 31, 2020
Risk-free interest rate	0.25%	0.13%
Expected term (in years)	2.0	2.0
Expected volatility	90%	90%
Expected dividend yield	0%	0%

Summary of the Tranche Liability and Warrant Liability Measured at Fair Value using Level 3 Significant Unobservable Inputs

The following table provides a reconciliation of the tranche liability and warrant liability measured at fair value using Level 3 significant unobservable inputs (in thousands):

	Series A-1 Preferred Stock Warrant			Series B Tranche Rights			Total
Balance, December 31, 2019	$	577		$	—		$	577
Fair value at issuance of Series B convertible preferred stock (November 2020)		—			5,422			5,422
Change in fair value		(197	)		(389	)		(586	)
Balance, December 31, 2020		380			5,033			5,413
Change in fair value		5,000			76,157			81,157
Settlement of tranche liability due to issuance of Milestone Shares		—			(81,190	)		(81,190	)
Settlement of warrant liability upon exercise of warrant		(5,380	)		—			(5,380	)
Balance, December 31, 2021	$	—		$	—		$	—