Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2020

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

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 by level within the fair value hierarchy:

		September 30, 2020
	Valuation Hierarchy	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Aggregate Fair Value
		(in thousands)
Assets:
Money market funds(1)	Level 1	$	472,272	$	—	$	—		$	472,272
U.S. government treasuries	Level 2		363,840		235		(1	)		364,074
Total financial assets		$	836,112	$	235	$	(1	)	$	836,346

(1) Includes $10.6 million of restricted cash equivalents.

		December 31, 2019
	Valuation Hierarchy	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Aggregate Fair Value
		(in thousands)
Assets:
Money market funds(1)	Level 1	$	106,127	$	—	$	—		$	106,127
U.S. government treasuries (2)	Level 2		298,256		140		(5	)		298,391
Bank time deposits	Level 2		2,500		—		—			2,500
Total financial assets		$	406,883	$	140	$	(5	)	$	407,018

(1) Includes $13.5 million of restricted cash equivalents.

(2) Includes $24.3 million classified as long-term investments.

Summary of Changes in Estimated Fair Value of Financial Liabilities

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

	Contingent Consideration			Derivative Liability			Total
Balance at December 31, 2019	$	17,580		$	12,449		$	30,029
Changes in fair value		44,432			16,796			61,228
Payment of contingent consideration related to Humabs    acquisition		(10,000	)		—			(10,000	)
Reclassification of derivative liability to additional paid-in    capital upon achievement of development milestone		—			(29,245	)		(29,245	)
Balance at September 30, 2020	$	52,012		$	—		$	52,012

Humabs | Clinical and Regulatory Milestones

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Estimated Fair Value of Significant Unobservable Inputs

As of September 30, 2020, the Company calculated the estimated fair value of the remaining clinical and regulatory milestones using the following significant unobservable inputs:

Unobservable input	Value or Range (Weighted-Average)1
Discount rates	10% - 12% (10%)
Probability of achievement	14% - 100% (56%)

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

Humabs | Commercial Milestones

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Estimated Fair Value of Significant Unobservable Inputs

As of September 30, 2020, the Monte Carlo simulation assumed a commercial product launch and associated discrete revenue forecast, as well as the following significant unobservable inputs:

Unobservable input	Value or Range (Weighted-Average)1
Volatility	60%
Discount rate	11%
Probability of achievement	14% - 32% (30%)

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

TomegaVax

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]

Estimated Fair Value of Significant Unobservable Inputs

As of September 30, 2020, the fair value of the contingent consideration was estimated using the following significant unobservable inputs:

Unobservable input	Range (Weighted-Average)1
Volatility	85%
Discount rates	0.0% - 0.2% (0.1%)

(1) Unobservable inputs were weighted based on the relative fair value of the underlying milestones.