Cash and cash equivalents consisted of the following (in thousands):


	March 31, 2024		December 31, 2023
Cash	$	37,167	$	63,396
Commercial paper		15,887		36,016
Money market funds		45,216		12,288
U.S. government bonds		7,464		1,988
Total cash and cash equivalents	$	105,734	$	113,688

At March 31, 2024 and December 31, 2023, a total of $27.6 million and $32.2 million of the Company’s cash and cash equivalents were held outside of the U.S. in its foreign subsidiaries to be used primarily for its China operations, respectively.

The Company’s investments consist primarily of available-for-sale debt investments. The amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s investments by major investments type are summarized in the tables below (in thousands):


	March 31, 2024
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Estimated Fair Value
Corporate bonds	$	6,073	$	2	$	—		$	6,075
Commercial paper		32,098		—		—			32,098
U.S. government bonds		28,747		1		—			28,748
Agency bonds		4,946		—		(2	)		4,944
Total investments	$	71,864	$	3	$	(2	)	$	71,865

	December 31, 2023
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Estimated Fair Value
Corporate bonds	$	13,988	$	9	$	(5	)	$	13,992
Commercial paper		52,273		—		—			52,273
U.S. government bonds		45,783		20		—			45,803
Agency bonds		9,830		1		(1	)		9,830
Total investments	$	121,874	$	30	$	(6	)	$	121,898

The following table summarizes, for all available for sale securities in an unrealized loss position, the fair value and gross unrealized loss by length of time the security has been in a continual unrealized loss position (in thousands):


	March 31, 2024
	Less than 12 Months					12 Months or More					Total
	Estimated Fair Value		Gross Unrealized Holding Losses			Estimated Fair Value		Gross Unrealized Holding Losses			Estimated Fair Value		Gross Unrealized Holding Losses
U.S. government bonds	$	12,956	$	—		$	—	$	—		$	12,956	$	—
Agency bonds		4,944		(2	)		—		—			4,944		(2	)
Total	$	17,900	$	(2	)	$	—	$	—		$	17,900	$	(2	)

	December 31, 2023
	Less than 12 Months					12 Months or More					Total
	Estimated Fair Value		Gross Unrealized Holding Losses			Estimated Fair Value		Gross Unrealized Holding Losses			Estimated Fair Value		Gross Unrealized Holding Losses
Corporate bonds	$	—	$	—		$	3,495	$	(5	)	$	3,495	$	(5	)
U.S. government bonds		4,984		—			—		—			4,984		—
Agency bonds		4,987		(1	)		—		—			4,987		(1	)
Total	$	9,971	$	(1	)	$	3,495	$	(5	)	$	13,466	$	(6	)

The contractual maturities of all available-for-sale investments were within one year as of March 31, 2024.

The Company periodically assesses whether the unrealized losses on its available-for-sale investments were temporary. The Company considers factors such as the severity and the reason for the decline in value, the potential recovery period and its intent to sell. For debt securities, the Company also considers whether (i) it is more likely than not that the Company will be required to sell the debt securities before recovery of their amortized cost basis, and (ii) the amortized cost basis cannot be recovered as a result of credit losses. Based on the results of its review, the Company did not recognize any impairment for its available-for-sale investments during the three months ended March 31, 2024 and 2023.

As described under Note 2, Collaboration Agreements, License Agreement and Revenues above, resulting from the termination and transition agreement related to the AstraZeneca U.S./RoW Agreement, the Company was reimbursed $12.6 million for work-in-progress inventory, which was written off and recognized as cost of goods sold during the three months ended March 31, 2024.

Prepaid expenses and other current assets consisted of the following (in thousands):


	March 31, 2024			December 31, 2023
Contract assets	$	26,894		$	26,481
Deferred revenues from associated contracts		(26,894	)		(26,481	)
Net contract assets		—			—
Insurance proceeds receivable for litigation settlement		28,500			28,500
Prepaid assets		5,780			6,644
Other current assets		1,870			6,711
Total prepaid expenses and other current assets	$	36,150		$	41,855

The unbilled contract assets as of March 31, 2024 and December 31, 2023 included $22.9 million and $22.5 million, respectively, related to unbilled co-development revenue under the AstraZeneca China Amendment. In addition, the unbilled contract assets as of March 31, 2024 and December 31, 2023 each included the $4.0 million unbilled regulatory milestone payment under the AstraZeneca China Agreement. See the AstraZeneca China Agreement section in Note 3, Collaboration Agreements, License Agreement and Revenues, for details.

As of each of March 31, 2024 and December 31, 2023, the Company recorded a $28.5 million receivable in prepaid expenses and other current assets, corresponding to the accrued litigation settlement of the same amount related to the Company’s agreement in principle with plaintiffs to settle the class action lawsuit. As the Company maintains insurance that covers exposure related to the class action lawsuit, this amount is fully recoverable under the Company’s insurance policies. The determination that the recorded receivables are probable of collection is based on the terms of the applicable insurance policies and communications with the insurers. See the Accrued and Other Current Liabilities section below, and the Legal Proceedings and Other Matters section in Note 10, Commitments and Contingencies, for details.

Accrued and other current liabilities consisted of the following (in thousands):


	March 31, 2024		December 31, 2023
Preclinical and clinical trial accruals	$	26,397	$	27,663
API and bulk drug product price true-up		57,370		50,978
Litigation settlement		28,500		28,500
Payroll and related accruals		7,398		20,267
Inventory cost related		8,521		—
Accrued co-promotion expenses - current		11,425		10,309
Roxadustat profit share to AstraZeneca		6,952		7,084
Property taxes and other taxes		7,346		6,615
Professional services		4,711		7,103
Current portion of liability related to sale of future revenues		1,213		5,654
Accrued restructuring charge		—		3,697
Other		4,453		5,021
Total accrued and other current liabilities	$	164,286	$	172,891

The accrued liabilities of $57.4 million and $51.0 million for API and bulk drug product price true-up as of March 31, 2024 and December 31, 2023, respectively, resulted from changes in estimated variable consideration associated with the API shipments fulfilled under the terms of the Astellas Japan Amendment, the bulk drug product transferred under the terms of the Astellas Europe Agreement and the Astellas EU Supply Agreement, and the bulk drug product shipments to AstraZeneca under the terms of the AstraZeneca Master Supply Agreement. Included in the balance as of March 31, 2024, the amount due to AstraZeneca was $11.5 million, as discussed under the Drug Product Revenue, Net section in Note 2, Collaboration Agreements, License Agreement and Revenues, resulting from the termination and transition agreement related to the AstraZeneca U.S./RoW Agreement, and has been settled in April 2024. In addition, the Company recorded an accrued inventory related cost of $8.5 million as of March 31, 2024, as part of the cost of goods sold resulting from this termination and transition agreement. See Note 2, Collaboration Agreements, License Agreement and Revenues, for details.

As of March 31, 2024 and December 31, 2023, the accrued litigation settlement of $28.5 million was related to the Company’s agreement in principle with plaintiffs to settle the class action lawsuit. The Company maintains insurance that covers exposure related to the class action lawsuit. As the amount is fully recoverable under the Company’s insurance policies, the Company recorded a corresponding receivable in prepaid expenses and other current assets in the condensed consolidated balance sheet. The determination that the recorded receivables are probable of collection is based on the terms of the applicable insurance policies and communications with the insurers. See the Legal Proceedings and Other Matters section in Note 10, Commitments and Contingencies, for details.