Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table sets forth the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis based on the three-tier fair value hierarchy (in thousands):

	December 31, 2021
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds	$	206,245	$	—	$	—	$	206,245
U.S. Treasury securities	—		289,706		—		289,706
U.S. government agency securities	—		93,626		—		93,626
Corporate debt securities	—		285,156		—		285,156
Equity warrant investment	—		—		1,067		1,067
Total financial assets	$	206,245	$	668,488	$	1,067	$	875,800
Financial liabilities:
Success payment liabilities	$	—	$	—	$	9,486	$	9,486
Total financial liabilities	$	—	$	—	$	9,486	$	9,486

	December 31, 2020
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds	$	50,513	$	—	$	—	$	50,513
U.S. Treasury securities	—		202,701		—		202,701
U.S. government agency securities	—		205,764		—		205,764
Corporate debt securities	—		211,109		—		211,109
Equity warrant investment	—		—		1,323		1,323
Total financial assets	$	50,513	$	619,574	$	1,323	$	671,410
Financial liabilities:
Success payment liabilities	$	—	$	—	$	5,773	$	5,773
Total financial liabilities	$	—	$	—	$	5,773	$	5,773

Summary of Estimated Fair Value of Success Payment Liability Assumptions

The following assumptions were incorporated into the calculation of the estimated fair value of the Fred Hutch success payment liability:

	December 31,
	2021			2020
Fair value of common stock (Series A convertible preferred stock)	$	7.74		$	9.07
Risk-free interest rate	0.19% - 1.88%			0.10% - 1.52%
Expected volatility	75		%	80		%
Expected term (in years)	0.46 - 5.97			1.00 - 6.97

The following assumptions were incorporated into the calculation of the estimated fair value of the Stanford success payment liability:

	December 31,
	2021			2020
Fair value of common stock (Series A convertible preferred stock)	$	7.74		$	9.07
Risk-free interest rate	0.19% - 1.88%			0.10% - 1.53%
Expected volatility	75		%	80		%
Expected term (in years)	0.46 - 7.75			1.00 - 8.75

Changes in the Estimated Fair Value of Level 3 Financial Assets

The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial assets and liabilities (in thousands):

	Equity Warrant Investment		Success Payment Liabilities
Balance at December 31, 2019	$	—	$	436
Additions	1,380		—
Change in fair value (1)	(57)		5,337
Balance at December 31, 2020	1,323		5,773
Change in fair value (1)	(256)		3,713
Balance at December 31, 2021	$	1,067	$	9,486

__________

(1)The change in fair value associated with the equity warrant investment held is recorded in other (expense) income, net and the change in fair value associated with success payments liabilities is recorded in research and development expense.

Changes in the Estimated Fair Value of Level 3 Financial Liabilities

The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial assets and liabilities (in thousands):

	Equity Warrant Investment		Success Payment Liabilities
Balance at December 31, 2019	$	—	$	436
Additions	1,380		—
Change in fair value (1)	(57)		5,337
Balance at December 31, 2020	1,323		5,773
Change in fair value (1)	(256)		3,713
Balance at December 31, 2021	$	1,067	$	9,486

__________

(1)The change in fair value associated with the equity warrant investment held is recorded in other (expense) income, net and the change in fair value associated with success payments liabilities is recorded in research and development expense.