Balance Sheet Components

12 Months Ended

Dec. 31, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Cash and Cash Equivalents

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


	December 31,
	2022		2021
Cash	$	135,819	$	111,422
Commercial paper		—		1,000
Money market funds		19,881		58,801
Total cash and cash equivalents	$	155,700	$	171,223

At December 31, 2022 and 2021, a total of $92.5 million and $91.2 million, respectively, 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.

Investments

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):


	December 31, 2022
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Estimated Fair Value
Corporate bonds	$	83,080	$	—	$	(1,072	)	$	82,008
Commercial paper		57,381		—		—			57,381
U.S. government bonds		112,547		5		(1,207	)		111,345
Agency bonds		11,690		—		(222	)		11,468
Asset-backed securities		2,484		—		(10	)		2,474
Foreign government bonds		5,007		—		(27	)		4,980
Convertible promissory note		1,000		—		—			1,000
Total investments	$	273,189	$	5	$	(2,538	)	$	270,656

	December 31, 2021
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Estimated Fair Value
Corporate bonds	$	183,136	$	2	$	(492	)	$	182,646
Commercial paper		68,079		—		—			68,079
U.S. government bonds		91,840		—		(318	)		91,522
Agency bonds		23,339		—		(64	)		23,275
Asset-backed securities		27,105		—		(18	)		27,087
Foreign government bonds		9,165		—		(11	)		9,154
Total investments	$	402,664	$	2	$	(903	)	$	401,763

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):


	December 31, 2022
	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	$	6,738	$	(147	)	$	75,270	$	(925	)	$	82,008	$	(1,072	)
U.S. government bonds		22,326		(13	)		67,909		(1,194	)		90,235		(1,207	)
Agency bonds		—		—			11,468		(222	)		11,468		(222	)
Asset-backed securities		2,474		(10	)		—		—			2,474		(10	)
Foreign government bonds		—		—			4,980		(27	)		4,980		(27	)
Total	$	31,538	$	(170	)	$	159,627	$	(2,368	)	$	191,165	$	(2,538	)

	December 31, 2021
	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	$	177,124	$	(492	)	$	—	$	—		$	177,124	$	(492	)
U.S. government bonds		91,522		(318	)		—		—			91,522		(318	)
Agency bonds		23,274		(64	)		—		—			23,274		(64	)
Asset-backed securities		27,087		(18	)		—		—			27,087		(18	)
Foreign government bonds		9,155		(11	)		—		—			9,155		(11	)
Total	$	328,162	$	(903	)	$	—	$	—		$	328,162	$	(903	)

The contractual maturities of the available-for-sale investments were as follows (in thousands):


	December 31, 2022
	Amortized Cost		Estimated Fair Value
Within one year - Bond and mutual funds	$	268,709	$	266,308
After one year through three years		4,480		4,348
Total investments	$	273,189	$	270,656

The Company periodically reviews its available-for-sale investments for other-than-temporary impairment. The Company considers factors such as the duration, 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. During the three years ended December 31, 2022, the Company did not recognize any other-than-temporary impairment loss.

Inventories

Inventories consisted of the following (in thousands):


	December 31,
	2022		2021
Raw materials	$	1,241	$	1,363
Work-in-progress		36,003		21,499
Finished goods		3,192		8,153
Total inventories	$	40,436	$	31,015

The provision to write-down excess and obsolete inventory were immaterial as of December 31, 2022 and December 31, 2021.

Prepaid expenses and other current assets

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


	December 31,
	2022			2021
Contract assets	$	17,488		$	66,909
Deferred revenues from associated contracts		(17,488	)		(58,909	)
Net unbilled contract assets		—			8,000
Prepaid assets		9,730			7,383
Other current assets		4,353			5,070
Total prepaid expenses and other current assets	$	14,083		$	20,453

The unbilled contract assets of $17.5 million as of December 31, 2022 was related to unbilled co-development revenue under the AstraZeneca China Amendment. The unbilled contract assets as of December 31, 2021 included $49.8 million related to transfer price true up for bulk drug product under the Astellas Europe Agreement, $9.1 million related to unbilled co-development revenue under the AstraZeneca China Amendment, and the $8.0 million unbilled upfront license payment under the Eluminex Agreement. See the Eluminex Agreements section in Note 3, Collaboration Agreements, License Agreement and Revenues, for details.

Property and Equipment

Property and equipment consisted of the following (in thousands):


	December 31,
	2022			2021
Leasehold improvements	$	102,580		$	103,352
Laboratory equipment		21,175			19,300
Machinery		9,642			8,339
Computer equipment		9,486			9,670
Furniture and fixtures		6,200			6,201
Construction in progress		204			2,423
Total property and equipment	$	149,287		$	149,285
Less: accumulated depreciation		(128,682	)		(121,008	)
Property and equipment, net	$	20,605		$	28,277

Depreciation expense for the years ended December 31, 2022, 2021 and 2020 was $10.0 million, $10.2 million and $11.7 million, respectively.

Accrued and Other Current Liabilities

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


	December 31,
	2022		2021
Preclinical and clinical trial accruals	$	57,780	$	56,283
API and bulk drug product price true-up		75,055		—
Acquired in-process research and development asset		—		35,000
Payroll and related accruals		22,562		20,909
Accrued co-promotion expenses - current		36,677		25,746
Contract liabilities to pharmaceutical distributors		390		3,176
Roxadustat profit share to AstraZeneca		7,280		7,895
Property taxes and other taxes		7,691		12,610
Professional services		5,480		6,074
Other		6,858		4,906
Total accrued and other current liabilities	$	219,773	$	172,599

The accrued liabilities of $75.1 million for API and bulk drug product price true-up as of December 31, 2022 resulted from changes in estimated variable consideration of $6.5 million associated with the API shipments fulfilled under the terms of the Astellas Japan Amendment, $57.4 million associated with the bulk drug product transferred under the terms of the Astellas Europe Agreement and the Astellas EU Supply Agreement, and $11.2 million associated with the bulk drug product shipments to AstraZeneca under the terms of the AstraZeneca Master Supply Agreement. See the Drug Product Revenue section in Note 3, Collaboration Agreements, License Agreement and Revenues, for details.

The acquired IPR&D asset of $35.0 million as of December 31, 2021 was related to the upfront payment to HiFiBiO under the HiFiBiO Agreement. See Note 2, Summary of Significant Accounting Policies - License Acquisition Agreement, for details.