Fair Value Measurements

6 Months Ended

Jun. 30, 2023

Fair Value Disclosures [Abstract]

Fair Value Measurements

FAIR VALUE MEASUREMENTS

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs.

The three-level hierarchy for the inputs to valuation techniques is briefly summarized as follows:

Level 1 –	Valuations are based on quoted prices in active markets for identical assets or liabilities and readily accessible by us at the reporting date.
Level 2 –	Valuations based on inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.
Level 3 –	Valuations based on unobservable inputs for which there is little or no market data, which require us to develop our own assumptions.

The following table sets forth the fair value of our financial assets and liabilities that are measured or disclosed on a recurring basis by level within the fair value hierarchy (in thousands):

	June 30, 2023
	Total Fair Value		Level 1		Level 2		Level 3
Assets:
Money market funds	$	28,658	$	28,658	$	—	$	—
Commercial paper	61,605		—		61,605		—
U.S. government-sponsored agency bonds	28,021		—		28,021		—
Asset-backed securities	7,895		—		7,895		—
Total	$	126,179	$	28,658	$	97,521	$	—
Liabilities:
Derivative liabilities for exit fees	$	1,737	$	—	$	—	$	1,737
Total	$	1,737	$	—	$	—	$	1,737

	December 31, 2022
	Total Fair Value		Level 1		Level 2		Level 3
Assets:
Money market funds	$	84,313	$	84,313	$	—	$	—
Commercial paper	25,291		—		25,291		—
Corporate bonds	999		—		999		—
U.S. government-sponsored agency bonds	1,479		—		1,479		—
Total	$	112,082	$	84,313	$	27,769	$	—
Liabilities:
Derivative liability for exit fee	$	1,656	$	—	$	—	$	1,656
Total	$	1,656	$	—	$	—	$	1,656

Where quoted prices are available in an active market, securities are classified as Level 1. We classify money market funds as Level 1. When quoted market prices are not available for the specific security, we estimate fair value by using benchmark yields, reported trades, broker/dealer quotes and issuer spreads. We classify U.S. government-sponsored agency bonds, U.S. treasury notes, corporate bonds, commercial paper, and asset-backed securities as Level 2. In certain cases, where there is limited activity or less transparency around inputs to valuation, securities or derivative liabilities, such as the 2018 Exit Fee and the 2022 Exit Fee, as defined and discussed in Note 9. Derivative Liabilities, are classified as Level 3.

The carrying amounts reflected in the condensed balance sheets for cash equivalents, short-term investments, accounts receivable, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values at both June 30, 2023 and December 31, 2022, due to their short-term nature.

Based on our procedures under the expected credit loss model, including an assessment of unrealized losses in our portfolio, we concluded that any unrealized losses on our marketable securities were not attributable to credit and, therefore, we have not recorded an allowance for credit losses for these securities as of June 30, 2023 and December 31, 2022.

Fair Value of Debt

The principal amount outstanding under our term loan facilities is subject to a variable interest rate. Therefore, we believe the carrying amount of the term loan facility approximates fair value as of June 30, 2023 and December 31, 2022. See Note 8. Borrowing for a description of the Level 2 inputs used to estimate the fair value of the liability.

The carrying value of the deferred royalty obligation related to the sale of future royalties approximates its fair value as of June 30, 2023 and December 31, 2022 and is based on our current estimates of future royalties and commercialization

milestones expected to be paid to us by Kyowa Kirin Co., Ltd. ("Kyowa Kirin") over the life of the agreement. See Note 7. Deferred Royalty Obligation Related to the Sale of Future Royalties for a description of the Level 3 inputs used to estimate the fair value of the liability.