Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

Summary of Financial Assets Measured at Fair Value on a Recurring Basis

The following tables summarize the Company’s Level 1 and Level 2 financial assets measured at fair value on a recurring basis within the fair value hierarchy as of March 31, 2024 and December 31, 2023 (in thousands):

		March 31, 2024
	Valuation Hierarchy	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Aggregate Fair Value
Assets:
Money market funds(1)	Level 1	$	142,405	$	—	$	—	$	142,405
U.S. government treasuries	Level 2	986,450		112		(384)		986,178
U.S. government agency bonds and discount notes	Level 2	97,634		57		(75)		97,616
Yankee bonds	Level 2	10,967		—		(12)		10,955
Asset-backed securities	Level 2	15,849		4		(2)		15,851
Corporate bonds	Level 2	236,306		74		(273)		236,107
Equity securities	Level 1	N/A		N/A		N/A		3,927
Total financial assets		$	1,489,611	$	247	$	(746)	$	1,493,039

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(1)Includes $19.8 million of restricted cash equivalents.

		December 31, 2023
	Valuation Hierarchy	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Aggregate Fair Value
Assets:
Money market funds(1)	Level 1	$	278,187	$	—	$	—	$	278,187
U.S. government treasuries	Level 2	1,162,124		1,017		(80)		1,163,061
U.S. government agency bonds and discount notes	Level 2	181,189		27		(50)		181,166
Equity securities	Level 1	N/A		N/A		N/A		9,853
Total financial assets		$	1,621,500	$	1,044	$	(130)	$	1,632,267

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(1)Includes $19.7 million of restricted cash equivalents.

Estimated Fair Value of Significant Unobservable Inputs

As of March 31, 2024, the Company calculated the estimated fair value of the remaining clinical and regulatory milestones related to tobevibart (formally as VIR-3434), an investigational subcutaneously administered HBV-neutralizing monoclonal antibody, or mAb, using the following significant unobservable inputs:

Unobservable input	Range (Weighted-Average)1
Discount rates	10.9% - 11.4% (11.1%)
Probability of achievement	14.4% - 60.0% (42.5%)

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(1)Unobservable inputs were weighted based on the relative fair value of the clinical and regulatory milestone payments.

As of March 31, 2024, the Monte Carlo simulation assumed a commercial product launch and associated discrete revenue forecasts, as well as the following significant unobservable inputs for the remaining commercial milestones related to tobevibart:

Unobservable input	Value
Volatility	70.0%
Discount rate	10.0%
Probability of achievement	29.1%

Summary of Changes in Estimated Fair Value of Contingent Consideration

The following table sets forth the changes in the estimated fair value of the Company’s contingent consideration obligations (in thousands):

	Contingent Consideration
Balance at December 31, 2023	$	25,961
Changes in fair value	1,649
Balance at March 31, 2024	$	27,610