Ultragenyx Pharmaceutical (RARE) 10-Q 2 Nov 23 2023 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2023	Oct. 30, 2023
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Trading Symbol	RARE
Entity Registrant Name	ULTRAGENYX PHARMACEUTICAL INC.
Entity Central Index Key	0001515673
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		82,114,350
Entity Shell Company	false
Entity File Number	001-36276
Entity Tax Identification Number	27-2546083
Entity Address, Address Line One	60 Leveroni Court
Entity Address, City or Town	Novato
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94949
City Area Code	415
Local Phone Number	483-8800
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.001 par value
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 72,575	$ 132,944
Marketable debt securities	369,519	614,818
Accounts receivable, net	79,263	40,445
Inventory	31,802	26,766
Prepaid expenses and other current assets	46,029	68,926
Total current assets	599,188	883,899
Property, plant, and equipment, net	296,811	259,726
Equity investments	4,039	5,531
Marketable debt securities	82,071	148,970
Right-of-use assets	26,427	25,961
Intangible assets, net	157,302	160,105
Goodwill	44,406	44,406
Other assets	27,896	16,846
Total assets	1,238,140	1,545,444
Current liabilities:
Accounts payable	33,357	43,274
Accrued liabilities	178,622	204,678
Contract liabilities	0	1,479
Lease liabilities	12,067	11,779
Liabilities for sales of future royalties	29,932	0
Total current liabilities	253,978	261,210
Lease liabilities	34,555	19,814
Deferred tax liabilities	31,667	31,667
Liabilities related to the sale of future royalties	875,996	875,439
Other liabilities	10,230	4,820
Total liabilities	1,206,426	1,192,950
Stockholders’ equity:
Preferred stock -25,000,000 shares authorized; nil outstanding as of outstanding as of September 30, 2023 and December 31, 2022	0	0
Common stock - 250,000,000 shares authorized; 72,174,307 and 70,197,297 shares issued and outstanding as of September 30, 2023 and December 31, 2022, respectively	72	70
Treasury stock, at cost, 8,444 and nil shares held as of September 30, 2023 and December 31, 2022, respectively	(381)	0
Deferred compensation obligation	381	0
Additional paid-in capital	3,298,357	3,140,019
Accumulated other comprehensive loss	(2,244)	(6,573)
Accumulated deficit	(3,264,471)	(2,781,022)
Total stockholders’ equity	31,714	352,494
Total liabilities and stockholders’ equity	$ 1,238,140	$ 1,545,444

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (Unaudited) - shares	Sep. 30, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, shares authorized	25,000,000	25,000,000
Preferred stock, shares outstanding	0	0
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	72,174,307	70,197,297
Common stock, shares outstanding	72,174,307	70,197,297
Treasury stock , shares	8,444	0

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues:
Total revenues	$ 98,052	$ 90,703	$ 306,857	$ 259,981
Operating expenses:
Cost of sales	10,987	8,631	33,158	23,001
Research and development	157,245	237,297	487,892	534,981
Selling, general and administrative	74,917	69,841	232,966	205,290
Total operating expenses	243,149	315,769	754,016	763,272
Loss from operations	(145,097)	(225,066)	(447,159)	(503,291)
Interest income	5,881	3,483	18,135	4,876
Change in fair value of equity investments	(1,419)	(1,626)	(1,492)	(21,139)
Non-cash interest expense on liabilities for sales of future royalties	(17,665)	(14,505)	(48,676)	(27,141)
Other expense	(699)	(1,105)	(2,380)	(1,746)
Loss before income taxes	(158,999)	(238,819)	(481,572)	(548,441)
Provision for income taxes	(650)	(6,287)	(1,877)	(7,147)
Net loss	$ (159,649)	$ (245,106)	$ (483,449)	$ (555,588)
Earnings per share, Basic	$ (2.23)	$ (3.5)	$ (6.81)	$ (7.96)
Earnings per share, Diluted	$ (2.23)	$ (3.5)	$ (6.81)	$ (7.96)
Weighted average number of shares outstanding, Basic	71,664,493	70,054,173	70,987,801	69,834,037
Weighted average number of shares outstanding, Diluted	71,664,493	70,054,173	70,987,801	69,834,037
Product sales
Revenues:
Total revenues	$ 42,349	$ 32,503	$ 128,757	$ 90,019
Royalty revenue
Revenues:
Total revenues	55,703	5,373	106,916	15,634
Collaboration and license
Revenues:
Total revenues	$ 0	$ 52,827	$ 71,184	$ 154,328

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ (159,649)	$ (245,106)	$ (483,449)	$ (555,588)
Other comprehensive income loss:
Foreign currency translation adjustments	(249)	(420)	188	(1,211)
Unrealized gain (loss) on available-for-sale securities	1,103	(888)	4,141	(7,607)
Other comprehensive income (loss):	854	(1,308)	4,329	(8,818)
Total comprehensive loss	$ (158,795)	$ (246,414)	$ (479,120)	$ (564,406)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Treasury Stock	Deferred Compensation Obligation
Beginning balance at Dec. 31, 2021	$ 922,561	$ 69	$ 2,997,497	$ (1,404)	$ (2,073,601)
Beginning balance, shares at Dec. 31, 2021		69,344,998
Stock-based compensation	101,862		101,862
Issuance of common stock under equity plan awards, net of tax	8,812	$ 1	8,811
Issuance of common stock under equity plan awards, net of tax, shares		734,779
Other comprehensive income (loss)	(8,818)			(8,818)
Net Income (Loss)	(555,588)				(555,588)
Ending balance at Sep. 30, 2022	468,829	$ 70	3,108,170	(10,222)	(2,629,189)
Ending balance, shares at Sep. 30, 2022		70,079,777
Beginning balance at Jun. 30, 2022	678,073	$ 70	3,071,000	(8,914)	(2,384,083)
Beginning balance, shares at Jun. 30, 2022		70,010,398
Stock-based compensation	36,096		36,096
Issuance of common stock under equity plan awards, net of tax	1,074		1,074
Issuance of common stock under equity plan awards, net of tax, shares		69,379
Other comprehensive income (loss)	(1,308)			(1,308)
Net Income (Loss)	(245,106)				(245,106)
Ending balance at Sep. 30, 2022	468,829	$ 70	3,108,170	(10,222)	(2,629,189)
Ending balance, shares at Sep. 30, 2022		70,079,777
Beginning balance at Dec. 31, 2022	$ 352,494	$ 70	3,140,019	(6,573)	(2,781,022)
Beginning balance, shares at Dec. 31, 2022	70,197,297	70,197,297
Issuance of common stock in connection with at-the-market offering, net of issuance costs	$ 53,299	$ 1	53,298
Issuance of common stock in connection with at-the-market offering, net of issuance costs, shares	1,175,584	1,175,584
Stock-based compensation	$ 100,780		100,780
Issuance of common stock under equity plan awards, net of tax	4,261	$ 1	4,260
Issuance of common stock under equity plan awards, net of tax, shares		801,426
Deferred compensation						$ (381)	$ 381
Other comprehensive income (loss)	4,329			4,329
Net Income (Loss)	(483,449)				(483,449)
Ending balance at Sep. 30, 2023	$ 31,714	$ 72	3,298,357	(2,244)	(3,264,471)	(381)	381
Ending balance, shares at Sep. 30, 2023	72,174,307	72,174,307
Beginning balance at Jun. 30, 2023	$ 129,030	$ 71	3,236,879	(3,098)	(3,104,822)	(381)	381
Beginning balance, shares at Jun. 30, 2023		71,465,424
Issuance of common stock in connection with at-the-market offering, net of issuance costs	$ 24,792	$ 1	24,791
Issuance of common stock in connection with at-the-market offering, net of issuance costs, shares	611,282	611,282
Stock-based compensation	$ 36,245		36,245
Issuance of common stock under equity plan awards, net of tax	442		442
Issuance of common stock under equity plan awards, net of tax, shares		97,601
Other comprehensive income (loss)	854			854
Net Income (Loss)	(159,649)				(159,649)
Ending balance at Sep. 30, 2023	$ 31,714	$ 72	$ 3,298,357	$ (2,244)	$ (3,264,471)	$ (381)	$ 381
Ending balance, shares at Sep. 30, 2023	72,174,307	72,174,307

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Operating activities:
Net Income (Loss)	$ (483,449)	$ (555,588)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	101,483	101,022
Acquired in-process research and development	0	75,234
Amortization of (discount) premium on marketable debt securities, net	(8,894)	4,349
Depreciation and amortization	17,788	13,263
Change in fair value of equity investments	1,492	21,139
Non-cash royalty revenue	(42,695)	(15,634)
Non-cash interest expense on liabilities for sales of future royalties	48,676	27,141
Other	3,102	564
Changes in operating assets and liabilities:
Accounts receivable	(23,790)	(2,973)
Inventory	(4,974)	(5,496)
Prepaid expenses and other assets	16,584	558
Accounts payable, accrued, and other liabilities	(14,746)	52,416
Contract liabilities	(1,479)	(6,118)
Net cash used in operating activities	(390,902)	(290,123)
Investing activities:
Purchase of property, plant, and equipment	(42,667)	(89,153)
Acquisition, net of cash acquired	0	(75,391)
Purchase of marketable debt securities	(304,789)	(416,161)
Proceeds from sale of marketable debt securities	47,520	82,966
Proceeds from maturities of marketable debt securities	582,230	407,926
Payment for intangible asset	(2,500)	(30,000)
Other	(4,777)	(240)
Net cash provided by (used in) investing activities	275,017	(120,053)
Financing activities:
Proceeds from the sale of future royalties, net	0	490,950
Proceeds from the issuance of common stock in connection with at-the-market offering, net	53,299	0
Proceeds from the issuance of common stock under equity plan awards, net of tax	4,261	8,812
Other	(28)	(436)
Net cash provided by financing activities	57,532	499,326
Effect of exchange rate changes on cash	(641)	(2,427)
Net decrease in cash, cash equivalents and restricted cash	(58,994)	86,723
Cash, cash equivalents and restricted cash at beginning of period	137,601	309,585
Cash, cash equivalents and restricted cash at end of period	78,607	396,308
Supplemental disclosures of non-cash information:
Acquired lease liabilities arising from obtaining right-of-use assets and property, plant, and equipment	23,360	1,168
Stock-based compensation capitalized into ending inventory	2,562	619
Costs of PP&E included in AP, accrued, and other liabilities	1,427	20,435
Non-cash interest expense on liabilities for sales of future royalties capitalized during the year into ending property, plant and equipment	$ 9,430	$ 7,820

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Pay vs Performance Disclosure
Net Income (Loss)	$ (159,649)	$ (245,106)	$ (483,449)	$ (555,588)

Insider Trading Arrangements

Insider Trading Arrangements	9 Months Ended
	Sep. 30, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Organization

Organization	9 Months Ended
	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. Organization Ultragenyx Pharmaceutical Inc., or the Company, is a biopharmaceutical company incorporated in Delaware. The Company is focused on the identification, acquisition, development, and commercialization of novel products for the treatment of serious rare and ultrarare genetic diseases. The Company operates as one reportable segment and has four commercially approved products. Crysvita® (burosumab) is approved in the United States, or U.S., the European Union, or EU, and certain other regions for the treatment of X-linked hypophosphatemia, or XLH, in adult and pediatric patients one year of age and older. Crysvita is also approved in the U.S. and certain other regions for the treatment of fibroblast growth factor 23, or FGF23,-related hypophosphatemia in tumor-induced osteomalacia, or TIO, associated with phosphaturic mesenchymal tumors that cannot be curatively resected or localized in adults and pediatric patients 2 years of age and older. Mepsevii® (vestronidase alfa) is approved in the U.S., the EU and certain other regions, as the first medicine for the treatment of children and adults with mucopolysaccharidosis VII, or MPS VII, also known as Sly syndrome. Dojolvi® (triheptanoin) is approved in the U.S. and certain other regions for the treatment of pediatric and adult patients severely affected by long-chain fatty acid oxidation disorders, or LC-FAOD. Evkeeza® (evinacumab) is approved in the U.S. and the European Economic Area, or EEA, for the treatment of homozygous familial hypercholesterolemia, or HoFH. The Company has exclusive rights to commercialize Evkeeza® (evinacumab) outside of the U.S. In addition to the approved products, the Company has the following ongoing clinical development programs: • UX111 (formerly ABO-102) is an AAV9 gene therapy product candidate for the treatment of patients with Sanfilippo syndrome type A, or MPS IIIA, a rare lysosomal storage disease; • DTX401 is an adeno-associated virus 8, or AAV8, gene therapy product candidate for the treatment of patients with glycogen storage disease type Ia, or GSDIa; • DTX301 is an AAV8 gene therapy product candidate in development for the treatment of patients with ornithine transcarbamylase, or OTC deficiency, the most common urea cycle disorder; • UX143 (setrusumab), which is subject to the Company’s collaboration agreement with Mereo BioPharma 3, or Mereo, is a fully human monoclonal antibody that inhibits sclerostin, a protein that acts on a key bone-signaling pathway and inhibits the activity of bone-forming cells for the treatment of patients with osteogenesis imperfect, or OI; • GTX-102 is an antisense oligonucleotide, or ASO, for the treatment of Angelman syndrome, a debilitating and rare neurogenetic disorder caused by loss-of-function of the maternally inherited allele of the UBE3A gene; • UX701 is an adeno-associated virus 9, or AAV9, gene therapy designed to deliver stable expression of a truncated version of the ATP7B copper transporter following a single intravenous infusion to improve copper distribution and excretion from the body and reverse pathological findings of Wilson liver disease; and • UX053 is a messenger RNA, or mRNA, product candidate designed for the treatment of patients with Glycogen Storage Disease Type III, or GSDIII, a disease caused by a glycogen debranching enzyme, or AGL, deficiency that results in glycogen accumulation in the liver and muscle. The Company has sustained operating losses and expects such annual losses to continue over the next several years. The Company ’ s ultimate success depends on the outcome of its research and development and commercialization activities. Through September 30, 2023 , the Company has relied primarily on its sale of equity securities, its revenues from commercial products, its sale of future royalties, and strategic collaboration arrangements to finance its operations. The Company expects it will need to raise additional capital to fully implement its business plans through the issuance of equity, borrowings, or strategic alliances with partner companies. However, if such financing is not available at adequate levels, the Company would need to reevaluate its operating plans.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiaries and have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP, for interim financial information and in accordance with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. The unaudited interim Condensed Consolidated Financial Statements have been prepared on the same basis as the annual financial statements. In the opinion of management, the accompanying unaudited Condensed Consolidated Financial Statements reflect all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair presentation. These financial statements should be read in conjunction with the audited financial statements and notes thereto for the preceding fiscal year contained in the Company’s Annual Report on Form 10-K filed on February 17, 2023, or Annual Report, with the United States Securities and Exchange Commission, or the SEC. The results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results to be expected for the year ending December 31, 2023. The Condensed Consolidated Balance Sheet as of December 31, 2022 has been derived from audited financial statements at that date, but does not include all of the information required by GAAP for complete financial statements. Use of Estimates The accompanying Condensed Consolidated Financial Statements have been prepared in accordance with GAAP. The preparation of the Condensed Consolidated Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities and the reported amounts of expenses in the Condensed Consolidated Financial Statements and the accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accruals, fair value of assets and liabilities, income taxes, stock-based compensation, revenue recognition, and the liabilities for sales of future royalties. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates. Cash, Cash Equivalents and Restricted Cash Restricted cash primarily consists of money market accounts used as collateral for the Company’s obligations under its facility leases. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the Condensed Consolidated Balance Sheets that sum to the total of the same such amounts shown in the Condensed Consolidated Statement of Cash Flows (in thousands): September 30, 2023 2022 Cash and cash equivalents $ 72,575 $ 391,651 Restricted cash included in prepaid expenses and 1,976 517 Restricted cash included in other assets 4,056 4,140 Total cash, cash equivalents, and restricted cash $ 78,607 $ 396,308 Credit Losses The Company is exposed to credit losses primarily through receivables from customers and collaborators and through its available-for-sale debt securities. For trade receivables and other instruments, the Company uses a forward-looking expected loss model that generally results in the earlier recognition of allowances for losses. For available-for-sale debt securities with unrealized losses, the losses are recognized as allowances rather than as reductions in the amortized cost of the securities. The Company’s expected loss allowance methodology for the receivables is developed using historical collection experience, current and future economic market conditions, a review of the current aging status and financial condition of the entities. Specific allowance amounts are established to record the appropriate allowance for customers that have a higher probability of default. Balances are written off when determined to be uncollectible. The Company’s expected loss allowance methodology for the debt securities is developed by reviewing the extent of the unrealized loss, the size, term, geographical location, and industry of the issuer, the issuers’ credit ratings and any changes in those ratings, as well as reviewing current and future economic market conditions and the issuers’ current status and financial condition. There were no material credit losses recorded for receivables and available-for-sale debt securities for the three and nine months ended September 30, 2023 and 2022. Revenue Recognition Product Sales The Company sells its approved products through a limited number of distributors. Under ASC 606, revenue from product sales is recognized at the point in time when the delivery is made and when title and risk of loss transfers to these distributors. The Company also recognizes revenue from sales of certain products on a “named patient” basis, which are allowed in certain countries prior to the commercial approval of the product. Prior to recognizing revenue, the Company makes estimates of the transaction price, including any variable consideration that is subject to a constraint. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved. Product sales are recorded net of estimated government-mandated rebates and chargebacks, estimated product returns, and other deductions. Provisions for returns and other adjustments are provided for in the period the related revenue is recorded, as estimated by management. These reserves are based on estimates of the amounts earned or to be claimed on the related sales and are reviewed periodically and adjusted as necessary. The Company’s estimates of government mandated rebates, chargebacks, estimated product returns, and other deductions depends on the identification of key customer contract terms and conditions, as well as estimates of sales volumes to different classes of payors. If actual results vary, the Company may need to adjust these estimates, which could have a material effect on earnings in the period of the adjustment. Collaboration, License, and Royalty Revenue The Company has certain license and collaboration agreements that are within the scope of Accounting Standards Codification, or ASC, 808, Collaborative Agreements, which provides guidance on the presentation and disclosure of collaborative arrangements. Generally, the classification of the transactions under the collaborative arrangements is determined based on the nature of contractual terms of the arrangement, along with the nature of the operations of the participants. The Company records its share of collaboration revenue, net of transfer pricing related to net sales in the period in which such sales occur, if the Company is considered as an agent in the arrangement. The Company is considered an agent when the collaboration partner controls the product before transfer to the customers and has the ability to direct the use of and obtain substantially all of the remaining benefits from the product. Funding received related to research and development services and commercialization costs is generally classified as a reduction of research and development expenses and selling, general and administrative expenses, respectively, in the Condensed Consolidated Statements of Operations, because the provision of such services for collaborative partners are not considered to be part of the Company’s ongoing major or central operations. In order to record collaboration revenue, the Company utilizes certain information from its collaboration partners, including revenue from the sale of the product, associated reserves on revenue, and costs incurred for development and sales activities. For the periods covered in the financial statements presented, there have been no material changes to prior period estimates of revenues and expenses. The Company also records royalty revenues under certain of the Company’s license or collaboration agreements in exchange for license of intellectual property. If the Company does not have any future performance obligations for these license or collaboration agreements, royalty revenue is recorded as the underlying sales occur. The Company sold the right to receive certain royalty payments from net sales of Crysvita in certain territories to RPI Finance Trust, or RPI, an affiliate of Royalty Pharma, and to OCM LS23 Holdings LP, an investment vehicle for Ontario Municipal Employees Retirement System, or OMERS, as further described in “Note 8 Liabilities for Sales of Future Royalties”. The Company records the royalty revenue from the net sales of Crysvita in the applicable territories on a prospective basis as royalty revenue in the Condensed Consolidated Statements of Operations over the term of the applicable arrangement. The terms of the Company’s collaboration and license agreements may contain multiple performance obligations, which may include licenses and research and development activities. The Company evaluates these agreements under ASC 606, Revenue from Contracts with Customers, or ASC 606, to determine the distinct performance obligations. The Company analogizes to ASC 606 for the accounting for distinct performance obligations for which there is a customer relationship. Prior to recognizing revenue, the Company makes estimates of the transaction price, including variable consideration that is subject to a constraint. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved. Total consideration may include nonrefundable upfront license fees, payments for research and development activities, reimbursement of certain third-party costs, payments based upon the achievement of specified milestones, and royalty payments based on product sales derived from the collaboration. If there are multiple distinct performance obligations, the Company allocates the transaction price to each distinct performance obligation based on its relative standalone selling price. The standalone selling price is generally determined based on the prices charged to customers or using expected cost-plus margin. The Company estimates the efforts needed to complete the performance obligations and recognizes revenue by measuring the progress towards complete satisfaction of the performance obligations using input measures. Deferred Compensation Plan The Company maintains a nonqualified deferred compensation plan whereby certain employees and members of the board of directors are able to defer certain equity awards and other compensation. Amounts deferred are invested into various mutual funds. The plan complies with the provisions of Section 409A of the Internal Revenue Code. All of the various mutual funds held in the plan are classified as trading securities and recorded at fair value in other non-current assets in the Condensed Consolidated Balance Sheets with changes in fair value recognized as earnings in the period they occur. The corresponding liability for the plan is included in other non-current liabilities in the Condensed Consolidated Balance Sheets. Certain equity awards deferred under the plan are required to be settled through the issuance of Company stock. These awards are recorded as treasury stock and deferred compensation obligation within stockholders’ equity.

Financial Instruments

Financial Instruments	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Financial Instruments	3. Financial Instruments Financial assets and liabilities are recorded at fair value. The carrying amount of certain financial instruments, including cash and cash equivalents, accounts receivable, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities. Assets and liabilities recorded at fair value on a recurring basis in the balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1 —Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; Level 2 —Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities 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 related assets or liabilities; and Level 3 —Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data. The Company determines the fair value of its equity investment in Solid Biosciences Inc., or Solid, by using the quoted market prices, which are Level 1 fair value measurements. The following tables set forth the fair value of the Company’s financial assets remeasured on a recurring basis based on the three-tier fair value hierarchy (in thousands): September 30, 2023 Level 1 Level 2 Level 3 Total Money market funds $ 34,222 $ — $ — $ 34,222 Certificates of deposit and time deposit — 13,844 — 13,844 Corporate bonds — 142,398 — 142,398 Commercial paper — 46,175 — 46,175 Asset-backed securities — 5,826 — 5,826 U.S. Government Treasury and agency securities 66,437 186,910 — 253,347 Investment in Solid common stock 1,315 — — 1,315 Other — 9,890 — 9,890 Total $ 101,974 $ 405,043 $ — $ 507,017 December 31, 2022 Level 1 Level 2 Level 3 Total Money market funds $ 102,847 $ — $ — $ 102,847 Certificates of deposit and time deposit — 25,972 — 25,972 Corporate bonds — 427,598 — 427,598 Commercial paper — 135,393 — 135,393 Asset-backed securities — 11,980 — 11,980 U.S. Government Treasury and agency securities 27,645 129,345 — 156,990 Debt securities in government-sponsored entities — 15,855 — 15,855 Investment in Solid common stock 2,807 — — 2,807 Other — 4,575 — 4,575 Total $ 133,299 $ 750,718 $ — $ 884,017

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Balance Sheet Components	4. Balance Sheet Components Cash Equivalents and Marketable Debt Securities The fair values of cash equivalents and marketable debt securities classified as available-for-sale securities consisted of the following (in thousands): September 30, 2023 Gross Unrealized Amortized Gains Losses Estimated Money market funds $ 34,222 $ — $ — $ 34,222 Certificates of deposit and time deposit 13,844 — — 13,844 Corporate bonds 143,261 39 ( 902 ) 142,398 Commercial paper 46,175 — — 46,175 Asset-backed securities 5,844 — ( 18 ) 5,826 U.S. Government Treasury and agency securities 254,053 1 ( 707 ) 253,347 Total $ 497,399 $ 40 $ ( 1,627 ) $ 495,812 December 31, 2022 Gross Unrealized Amortized Gains Losses Estimated Money market funds $ 102,847 $ — $ — $ 102,847 Certificates of deposit and time deposit 25,972 — — 25,972 Corporate bonds 432,211 87 ( 4,700 ) 427,598 Commercial paper 135,393 — — 135,393 Asset-backed securities 12,002 — ( 22 ) 11,980 U.S. Government Treasury and agency securities 157,933 320 ( 1,263 ) 156,990 Debt securities in government-sponsored entities 16,005 — ( 150 ) 15,855 Total $ 882,363 $ 407 $ ( 6,135 ) $ 876,635 At September 30, 2023 , the remaining contractual maturities of available-for-sale securities were less than three years . There have been no significant realized gains or losses on available-for-sale securities for the periods presented. For investments with unrealized losses, t he Company does not intend to sell the investments and it is not more likely than not that the Company will be required to sell the investments before recovery of their amortized cost basis. Inventory Inventory consists of the following (in thousands): September 30, December 31, 2023 2022 Work-in-process $ 19,173 $ 17,486 Finished goods 12,629 9,280 Total inventory $ 31,802 $ 26,766 Accrued Liabilities Accrued liabilities consist of the following (in thousands): September 30, December 31, 2023 2022 Research, clinical study, and manufacturing expenses $ 51,520 $ 73,558 Payroll and related expenses 76,300 78,938 Other 50,802 52,182 Total accrued liabilities $ 178,622 $ 204,678

Revenue

Revenue	9 Months Ended
	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Revenue	5. Revenue The following table disaggregates total revenues from external customers by product sales, royalty revenue, and collaboration and license revenue (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 Product sales: Crysvita $ 19,200 $ 13,184 $ 57,318 $ 34,980 Mepsevii 5,633 6,045 22,552 15,839 Dojolvi 16,553 13,274 47,347 39,200 Evkeeza 963 — 1,540 — Total product sales 42,349 32,503 128,757 90,019 Crysvita royalty revenue 55,703 5,373 106,916 15,634 Collaboration and license revenue: Crysvita collaboration revenue in profit- — 51,348 69,705 148,121 Daiichi Sankyo — 1,479 1,479 6,207 Total collaboration and license revenue — 52,827 71,184 154,328 Total revenues $ 98,052 $ 90,703 $ 306,857 $ 259,981 The following table disaggregates total revenues based on geographic location (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 North America $ 67,811 $ 67,012 $ 214,232 $ 196,257 Latin America 17,229 14,119 59,096 36,449 Europe 13,012 8,411 32,351 26,114 Japan — 1,161 1,178 1,161 Total revenues $ 98,052 $ 90,703 $ 306,857 $ 259,981 The following table presents changes in the contract liabilities (in thousands): Nine Months Ended September 30, 2023 2022 Balance of contract liabilities at beginning of period $ 1,479 $ 9,076 Additions — 89 Deductions ( 1,479 ) ( 6,207 ) Balance of contract liabilities at end of period, net $ — $ 2,958 See Note 7 for additional details on contract liabilities activities. The Company’s largest accounts receivable balance was from a collaboration partner and accounted for 68 % and 68 % of the total accounts receivable balance as of September 30, 2023 and December 31, 2022, respectively.

GeneTx Acquisition

GeneTx Acquisition	9 Months Ended
	Sep. 30, 2023
Business Combinations [Abstract]
Acquisition	6. GeneTx Acquisition In August 2019, the Company entered into a Program Agreement and a Unitholder Option Agreement with GeneTx Biotherapeutics LLC, or GeneTx, to collaborate on the development of GeneTx’s GTX-102, an ASO for the treatment of Angelman syndrome. Pursuant to the terms of the Unitholder Option Agreement, the Company made an upfront payment of $ 20.0 million for an exclusive option to acquire GeneTx, which was exercisable any time prior to 30 days following FDA acceptance of the Investigational New Drug Application, or IND, for GTX-102. Pursuant to the agreement, upon acceptance of the IND, which occurred in January 2020, the Company elected to extend the option period by paying an option extension payment of $ 25.0 million during the quarter ended March 31, 2020, which was recorded as an in-process research and development expense. In April 2022, the parties entered into an amendment to the Unitholder Option Agreement, or the Amendment, which provided the Company with an additional, earlier option to acquire GeneTx for an option exercise price of $ 75.0 million based on the earlier of receipt of interim data in the Phase 1/2 study or a specified date, such option, the Interim Option. In July 2022, the Company exercised the Interim Option to acquire GeneTx and entered into a Unit Purchase Agreement, or the Purchase Agreement, pursuant to which the Company purchased all the outstanding units of GeneTx. In accordance with the terms of the Purchase Agreement, the Company paid the option exercise price of $ 75.0 million and an additional $ 15.6 million to acquire the outstanding cash of GeneTx, and adjustments for working capital and transaction expenses of $ 0.6 million, for a total purchase consideration of $ 91.2 million. Additionally, the Company may make payments of up to $ 190.0 million upon the achievement of certain milestones, including up to $ 30.0 million in milestone payments upon achievement of the earlier of initiation of a Phase 3 clinical study or product approvals in Canada and the U.K., up to $ 85.0 million in additional regulatory approval milestones for the achievement of U.S. and EU product approvals, and up to $ 75.0 million in commercial milestone payments based on annual worldwide net product sales. In addition, the Company will also pay tiered mid- to high single-digit percentage royalties based on licensed product annual net sales. If the Company receives and resells an FDA priority review voucher, or PRV, in connection with a new drug application approval, GeneTx is entitled to receive a portion of proceeds from the sale or a cash payment from the Company if the Company choses to retain the PRV. The transaction was accounted as an asset acquisition, as substantially all of the fair value of the gross assets acquired was concentrated in a single identifiable in-process research and development intangible asset. Prior to the achievement of certain development and regulatory milestones, the acquired in-process research and development intangible asset has not yet reached technological feasibility and has no alternative future use. Accordingly, the Company recorded the acquisition price of $ 75.0 million, net of cash and working capital acquired, as in-process research and development expense during the year ended December 31, 2022.

License and Research Agreements

License and Research Agreements	9 Months Ended
	Sep. 30, 2023
Research Grant Agreement [Abstract]
License and Research Agreements	7. License and Research Agreements Kyowa Kirin Co., Ltd. In August 2013, the Company entered into a collaboration and license agreement with Kyowa Kirin Co., Ltd., or KKC (formerly Kyowa Hakko Kirin Co., Ltd. or KHK). Under the terms of this collaboration and license agreement, as amended, the Company and KKC collaborate on the development and commercialization of Crysvita in the field of orphan diseases in the U.S. and Canada, or the profit-share territory, and in the European Union, United Kingdom, and Switzerland, or the European territory, and the Company has the right to develop and commercialize such products in the field of orphan diseases in Mexico and Central and South America, or Latin America. Development Activities In the field of orphan diseases, and except for ongoing studies being conducted by KKC, the Company was the lead party for development activities in the profit-share territory and in the European territory until the applicable transition date. The Company shared the costs for development activities in the profit-share territory and the European territory conducted pursuant to the development plan before the applicable transition date equally with KKC. In April 2023, which was the transition date for the profit-share territory, KKC became the lead party and is responsible for the costs of the development activities. However, the Company will continue to share the costs of the studies commenced prior to the applicable transition date equally with KKC. The collaboration and license agreements are within the scope of ASC 808, which provides guidance on the presentation and disclosure of collaborative arrangements. Collaboration and Royalty Revenue for Sales in the Profit-share Territory The Company and KKC shared commercial responsibilities and profits in the profit-share territory until April 2023. Under the collaboration agreement, KKC manufactured and supplied Crysvita for commercial use in the profit-share territory and charged the Company a transfer price of 30 % of net sales. The transfer price on these sales was 35 % prior to December 31, 2022. The remaining profit or loss after supply costs from commercializing products in the profit-share territory was shared between the Company and KKC on a 50 / 50 basis until April 2023. In April 2023, commercialization responsibilities for Crysvita in the profit-share territory transitioned to KKC and KKC assumed responsibility for the commercialization of Crysvita in the territory at and after April 2023. Thereafter, the Company is entitled to receive a tiered double-digit revenue share from the mid- 20 % range up to a maximum rate of 30 %. In September 2022, the Company entered into an amendment to the collaboration agreement which clarified the scope of increased participation by KKC in support of the Company’s commercial activities prior to April 2023 and granted the Company the right to continue to support KKC in commercial field activities in the U.S. through April 2024, subject to the limitations and conditions set forth in the amendment. As a result, the Company will continue to support commercial field and marketing efforts through a cost share arrangement through April 2024, subject to the limits and conditions set forth in the amendment. After April 2024, the Company’s rights to promote Crysvita in the U.S. will be limited to medical geneticists and the Company will solely bear its expenses for the promotion of Crysvita in the profit-share territory. As KKC is the principal in the sale transaction with the customer, the Company recognizes a pro-rata share of collaboration revenue, net of transfer pricing, in the period the sale occurs. The Company concluded that its portion of KKC’s sales in the profit-share territory prior to April 2023 was analogous to a royalty and therefore recorded its share as collaboration revenue, similar to a royalty. Starting in April 2023, the Company began to record the royalty revenue as the underlying sales occur. In July 2022, the Company sold to OMERS its right to receive 30 % of the future royalty payments due to the Company based on net sales of Crysvita in the U.S. and Canada, subject to a cap, beginning in April 2023, as further described in Note 8. The Company records this revenue as royalty revenue. Royalty Revenue for Sales in the European Territory KKC has the commercial responsibility for Crysvita in the European territory. In December 2019, the Company sold its right to receive royalty payments based on sales in the European territory to Royalty Pharma, effective January 1, 2020, as further described in “Note 8. Liabilities for Sales of Future Royalties.” Prior to the Company’s sale of the royalty, the Company received a royalty of up to 10 % on net sales in the European territory, which was recognized as the underlying sales occur. The Company records this revenue as royalty revenue. Product Revenue for Sales in Other Territories The Company is responsible for commercializing Crysvita in Latin America and Turkey. The Company is considered the principal in these territories as the Company controls the product before it is transferred to the customer. Accordingly, the Company records revenue on a gross basis for the sale of Crysvita once the product is delivered and the risk and title of the product is transferred to the distributor. KKC has the option to assume responsibility for commercialization efforts in Turkey from the Company, after a certain minimum period. Under the collaboration agreement, KKC manufactures and supplies Crysvita, which is purchased by the Company for sales in Latin American territories and charges the Company a transfer price of 30 % of net sales. The transfer price on these sales was 35 % prior to December 31, 2022. The Company also pays to KKC a low single-digit royalty on net sales in Latin America. Total Crysvita revenue was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Revenue in profit-share territory: Collaboration revenue $ — $ 51,348 $ 69,705 $ 148,121 Royalty revenue 35,160 — 64,221 — Non-cash royalty revenue 15,070 — 27,524 — Total revenue in profit-share territory 50,230 51,348 161,450 148,121 Product sales 19,200 13,184 57,318 34,980 Non-cash royalty revenue in European territories 5,473 5,373 15,171 15,634 Total Crysvita revenue $ 74,903 $ 69,905 $ 233,939 $ 198,735 Cost Sharing Payments Under the collaboration agreement, KKC and the Company share certain development and commercialization costs. As a result, the Company was reimbursed for these costs and operating expenses were reduced as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Research and development $ 940 $ 3,830 $ 4,665 $ 12,770 Selling, general and administrative 2,060 8,365 15,346 26,510 Total $ 3,000 $ 12,195 $ 20,011 $ 39,280 Collaboration Receivable and Payable The Company had accounts receivable from KKC in the amount of $ 54.1 million and $ 27.5 million from profit-share revenue and royalties and other receivables recorded in prepaid expenses and other current assets of $ 0.4 million and $ 6.4 million and accrued liabilities of $ 5.7 million and $ 3.1 million from commercial and development activity reimbursements, as of September 30, 2023 and December 31, 2022, respectively. Daiichi Sankyo In March 2020, the Company executed a License and Technology Access Agreement, or the License Agreement, with Daiichi Sankyo Co., Ltd., or Daiichi Sankyo. Pursuant to the License Agreement, the Company granted Daiichi Sankyo a non-exclusive license to intellectual property, including know-how and patent applications, with respect to its Pinnacle PCLTM producer cell line platform, or Pinnacle PCL Platform, and HEK293 transient transfection manufacturing technology platforms for AAV-based gene therapy products. Under the terms of the License Agreement, Daiichi Sankyo made an upfront payment of $ 125.0 million and an additional $ 25.0 million upon completion of the technology transfer of the Pinnacle PCL Platform and HEK293 platform. Daiichi Sankyo reimbursed the Company for all costs associated with the transfer of the manufacturing technology. In June 2020, the Company executed a subsequent license agreement, or the Sublicense Agreement, with Daiichi Sankyo for transfer of certain technology in consideration for an upfront payment of $ 8.0 million and annual maintenance fees, milestone payments, and royalties on any net sales of products incorporating the licensed intellectual property. The Company evaluated the License Agreement and the Sublicense Agreement under ASC 606 and determined that the performance obligations under the agreements are (i) intellectual property with respect to its Pinnacle PCL Platform and HEK293 transient transfection manufacturing technology platform together with the initial technical assistance and technology transfer services, and (ii) the transfer of any know-how and improvements after the completion of the initial technology transfer through the end of the three year technology transfer period. The Company allocated the total transaction price to the two performance obligations on a relative stand-alone selling price basis. Revenue allocated to the intellectual property and the technology transfer services was recognized over an initial period which was completed during the first quarter of 2022, measuring the progress toward complete satisfaction of the individual performance obligation using an input measure. Revenue for know-how and improvements after the completion of technology transfer was recognized on a straight-line basis over the remaining technology transfer period, which ended in March 2023, as it was expected that Daiichi Sankyo would receive and consume the benefits consistently throughout the period. The Company’s current obligations under the License Agreement and the Sublicense Agreement were completed following the conclusion of the technology transfer period. Total revenue recognized under the arrangement through September 30, 2023 was $ 183.3 million. The Company recognized nil and $ 1.5 million for the three and nine months ended September 30, 2023, respectively, and $ 1.5 million and $ 6.2 million for the three and nine months ended September 30, 2022 , respectively, in revenue for this arrangement. Accordingly, the Company recorded nil and $ 1.5 million of contract liabilities, net, for this arrangement as of September 30, 2023 and December 31, 2022, respectively. Mereo In December 2020, the Company entered into a License and Collaboration Agreement with Mereo to collaborate on the development of setrusumab. Under the terms of the agreement, the Company will lead future global development of setrusumab in both pediatric and adult patients with Osteogenesis Imperfecta, or OI. The Company was granted an exclusive license to develop and commercialize setrusumab in the U.S., Turkey, and the rest of the world, excluding the European Economic Area, United Kingdom, and Switzerland, or the Mereo Territory, where Mereo retains commercial rights. Each party will be responsible for post-marketing commitments and commercial supply in their respective territories. Upon the closing of the transaction in January 2021, the Company made a payment of $ 50.0 million to Mereo and will be required to make payments of up to $ 254.0 million upon the achievement of certain clinical, regulatory, and commercial milestones. The Company recognized nil and $ 9.0 million for the three and nine months ended September 30, 2023, respectively, in research and development expense for achievement of a clinical milestone under this arrangement. The Company will pay for all global development costs as well as tiered double-digit percentage royalties to Mereo on net sales in the U.S., Turkey, and the rest of the world (excluding the Mereo Territory), and Mereo will pay the Company a fixed double-digit percentage royalty on net sales in the Mereo Territory. Although Mereo is a variable interest entity, the Company is not the primary beneficiary as it does not have the power to direct the activities that would most significantly impact the economic performance of Mereo. Prior to the achievement of certain development milestones, all consideration paid to Mereo represents rights to potential future benefits associated with Mereo’s in-process research and development activities, which have not reached technological feasibility and have no alternative future use. Regeneron In January 2022, the Company announced a collaboration with Regeneron Pharmaceuticals, or Regeneron, to commercialize Evkeeza for HoFH outside of the U.S. Evkeeza is approved in the U.S., where it is marketed by Regeneron, and in the EU and U.K. as a first-in-class therapy for use together with diet and other low-density lipoprotein-cholesterol-lowering therapies to treat adults and adolescents aged 12 years and older with HoFH. Pursuant to the terms of the agreement, the Company received the rights to develop, commercialize and distribute the product for HoFH in countries outside of the U.S. The Company is obligated to pay up to $ 63.0 million in future milestone payments, contingent upon the achievement of certain regulatory and sales milestones. The Company may share in certain costs for global trials led by Regeneron and also received the right to opt into other potential indications. The collaboration agreement is within the scope of ASC 808 which provides guidance on the presentation and disclosure of collaborative arrangements. As the Company would be the principal in future sale transactions with the customer, the Company will recognize product sales and cost of sales in the period the related sales occur and the related revenue recognition criteria are met. Under the collaboration agreement, Regeneron supplies the product and charges the Company a transfer price from the low 20 % range up to 40 % on net sales, which is recognized as cost of sales in the Company’s Condensed Consolidated Statement of Operations. Upon the closing of the transaction in January 2022, the Company paid Regeneron a $ 30.0 million upfront payment. As the upfront payment was for the Company’s usage of intellectual property with respect to Evkeeza for HoFH, the upfront payment was recorded as an intangible asset, which is amortized over its useful life of 10.5 years. Under the collaboration agreement, the Company reimbursed Regeneron for development costs of $ 1.9 million and $ 6.9 million for the three and nine months ended September 30, 2023 , respectively, and $ 2.5 million and $ 4.3 million for the three and nine months ended September 30, 2022, respectively, recorded as research and development expense on the Condensed Consolidated Statements of Operations. The Company had collaboration payables for this arrangement included in accrued liabilities on the Condensed Consolidated Balance Sheets of $ 3.6 million and $ 6.8 million as of September 30, 2023 and December 31, 2022, respectively. Other Arrangements The Company has also entered into several collaborations and/or licensing arrangements in prior periods. Except as disclosed above, there have been no material changes in these arrangements during the nine months ended September 30, 2023 as compared to those disclosed in "Note 8. License and Research Agreements" to the Consolidated Financial Statements in the Annual Report. Under the financial terms of these arrangements, the Company may be required to make payments upon achievement of developmental, regulatory, and commercial milestones, which could be significant. Future milestone payments, if any, will be reflected in the Condensed Consolidated Statements of Operations upon the occurrence of the contingent event. In addition, the Company may be required to pay royalties on future sales if products related to these arrangements are commercialized. The payment of these amounts, however, is contingent upon the occurrence of various future events, which have a high degree of uncertainty of occurrence. As described in the Annual Report, in connection with the Company’s collaborations with Solid and Arcturus Therapeutics Holdings, Inc., or Arcturus, the Company previously held certain equity interests in each entity. As of December 31, 2022, the Company held no shares of Arcturus common stock. The changes in the fair value of the Company’s equity investments in the common stock of Solid and Arcturus were as follows (in thousands): Common stock As of December 31, 2021 $ 32,200 Change in fair value ( 19,299 ) Sale of shares ( 10,094 ) December 31, 2022 2,807 Change in fair value ( 1,492 ) September 30, 2023 $ 1,315

Liabilities for Sales of Future

Liabilities for Sales of Future Royalties	9 Months Ended
	Sep. 30, 2023
Deferred Revenue Disclosure [Abstract]
Liabilities for Sales of Future Royalties	8. Liabilities for Sales of Future Royalties In December 2019, the Company entered into a Royalty Purchase Agreement with RPI. Pursuant to the agreement, RPI paid $ 320.0 million to the Company in consideration for the right to receive royalty payments effective January 1, 2020, arising from the net sales of Crysvita in the EU, the U.K., and Switzerland under the terms of the Company’s Collaboration and License Agreement with KKC dated August 29, 2013, as amended, or the KKC Collaboration Agreement. The agreement with RPI will automatically terminate, and the payment of royalties to RPI will cease, in the event aggregate royalty payments received by RPI are equal to or greater than $ 608.0 million prior to December 31, 2030, or in the event aggregate royalty payments received by RPI are less than $ 608.0 million prior to December 31, 2030, or when aggregate royalty payments received by RPI are equal to $ 800.0 million. In July 2022, the Company entered into a Royalty Purchase Agreement with OMERS. Pursuant to the agreement, OMERS paid $ 500.0 million to the Company in consideration for the right to receive 30 % of the future royalty payments due to the Company from KKC based on net sales of Crysvita in the U.S. and Canada under the terms of the KKC Collaboration Agreement. The calculation of royalty payments to OMERS is based on net sales of Crysvita beginning in April 2023 and will expire upon the earlier of the date on which aggregate payments received by OMERS equals $ 725.0 million or the date the final royalty payment is made to the Company under the KKC Collaboration Agreement. Proceeds from these transactions were recorded as liabilities for sales of future royalties on the Condensed Consolidated Balance Sheets. Upon inception of the respective arrangements, the Company recorded $ 320.0 million and $ 500.0 million, net of transaction costs of $ 5.8 million and $ 9.1 million for RPI and OMERS, respectively, using the effective interest method over the estimated life of the applicable arrangement. In order to determine the amortization of the liabilities, the Company is required to estimate the total amount of future royalty payments to be received by the Company and paid to RPI and OMERS, subject to the capped amount, over the life of the arrangements. The excess of future estimated royalty payments (subject to the capped amount), over the $ 314.2 million and $ 491.0 million, respectively, of net proceeds, is recorded as non-cash interest expense over the life of the arrangements. Consequently, the Company estimates an imputed interest on the unamortized portion of the liabilities and records interest expense relating to the transactions. The Company records the royalty revenue arising from the net sales of Crysvita in the applicable territories as royalty revenue in the Condensed Consolidated Statements of Operations over the term of the arrangements. Royalties earned under the RPI and OMERS arrangements from inception to September 30, 2023 have been $ 67.8 million and $ 27.5 million, respectively. The Company periodically assesses the expected royalty payments using a combination of historical results, internal projections and forecasts from external sources. To the extent such payments are greater or less than the Company’s initial estimates or the timing of such payments is materially different than its original estimates, the Company will prospectively adjust the amortization of the liabilities and the effective interest rate. The Company’s effective annual interest rate was approximately 7.3 % and 8.2 %, for RPI and OMERS, respectively, as of September 30, 2023. There are a number of factors that could materially affect the amount and timing of royalty payments from KKC in the applicable territories, most of which are not within the Company’s control. Such factors include, but are not limited to, the success of KKC’s sales and promotion of Crysvita, changing standards of care, macroeconomic and inflationary pressures, the introduction of competing products, pricing for reimbursement in various territories, manufacturing or other delays, intellectual property matters, adverse events that result in governmental health authority imposed restrictions on the use of Crysvita, significant changes in foreign exchange rates as the royalty payments are made in U.S. dollars, or USD, while significant portions of the underlying sales of Crysvita are made in currencies other than USD, and other events or circumstances that could result in reduced royalty payments from sales of Crysvita, all of which would result in a reduction of royalty revenue and the non-cash interest expense over the life of the arrangement. Conversely, if sales of Crysvita in the relevant territories are more than expected, the royalty revenue and the non-cash interest expense recorded by the Company would be greater over the term of the arrangements. The following table shows the activity within the liability account (in thousands): Liabilities for Sales of Future Royalties RPI OMERS Total December 31, 2021 $ 351,786 $ — $ 351,786 Net proceeds from sale of future — 490,950 490,950 Royalty revenue ( 21,692 ) — ( 21,692 ) Non-cash interest expense 35,095 19,300 54,395 December 31, 2022 365,189 510,250 875,439 Royalty revenue ( 15,171 ) ( 12,446 ) ( 27,617 ) Non-cash interest expense 25,598 32,508 58,106 September 30, 2023 $ 375,616 $ 530,312 $ 905,928

Stock-Based Awards

Stock-Based Awards	9 Months Ended
	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Stock-Based Awards	9. Stock-Based Awards As of September 30, 2023 , there were 462,276 shares subject to outstanding awards under the 2014 Incentive Plan that were cancelled or forfeited and are now available under the 2023 Incentive Plan, or the 2023 Plan. As of September 30, 2023 , there were 4,960,091 shares available under the 2023 Plan, 6,694,377 shares available under the Amended & Restated 2014 Employee Stock Purchase Plan, and 408,189 shares available under the Employment Inducement Plan for the future issuance of equity awards. The table below sets forth the stock-based compensation expense for the periods presented (in thousands): Three Months Ended Nine Months Ended 2023 2022 2023 2022 Cost of sales $ 191 $ 225 $ 862 $ 730 Research and development 19,113 20,251 56,371 57,588 Selling, general and administrative 15,573 15,285 44,236 42,695 Total stock-based compensation expense $ 34,877 $ 35,761 $ 101,469 $ 101,013

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Net Loss Per Share	10. Net Loss Per Share Basic net loss per share has been computed by dividing the net loss by the weighted-average number of shares of common stock outstanding and the weighted average treasury stock for deferred compensation obligations required to be settled in shares of common stock. Diluted net loss per share is calculated by dividing net loss by the weighted-average number of shares of common stock, the weighted average treasury stock for deferred compensation obligations required to be settled in shares of common stock, and potential dilutive securities outstanding during the period. The following weighted-average outstanding common stock equivalents were excluded from the computation of diluted net loss per share for the periods presented because including them would have been antidilutive: Three Months Ended Nine Months Ended 2023 2022 2023 2022 Options to purchase common stock, 14,585,014 11,969,532 14,117,741 11,114,822 Employee stock purchase plan 66,735 44,649 37,156 15,047 14,651,749 12,014,181 14,154,897 11,129,869

Equity Transactions

Equity Transactions	9 Months Ended
	Sep. 30, 2023
Equity [Abstract]
Equity Transactions	11. Equity Transactions In May 2021, the Company entered into an Open Market Sale Agreement with Jefferies LLC, or Jefferies, pursuant to which the Company may offer and sell shares of the Company’s common stock having an aggregate offering proceeds up to $ 350.0 million, from time to time, in at-the-market, or ATM, offerings through Jefferies. During the three and nine months ended September 30, 2023 , there were 611,282 and 1,175,584 shares sold on the ATM, respectively, resulting in net proceeds of $ 24.8 million and $ 53.3 million, respectively. There were no shares sold on the ATM for the three and nine months ended September 30, 2022. As of September 30, 2023 , the Company has sold a total of 2,225,956 shares on the ATM, resulting in net proceeds of $ 132.2 million.

Related Party Transaction

Related Party Transaction	9 Months Ended
	Sep. 30, 2023
Related Party Transactions [Abstract]
Related Party Transaction	12. Related Party Transaction In July 2022, the Company entered into an agreement with a non-profit foundation in which two members of the Company’s board of directors, including the Company’s Chief Executive Officer, also serve as board members of the foundation, whereby a $ 1.0 million contribution will be paid out to the foundation over a four-year period, beginning in the third quarter of 2022, to support rare disease education and awareness. As a result, the Company recorded nil and $ 0.3 million as research and development expense for this agreement for the three and nine months ended September 30, 2023 , respectively, and nil for the three and nine months ended September 30, 2022 . A total of $ 0.5 million has been recorded as research and development expense for this agreement to date.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2023
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Loss	13. Accumulated Other Comprehensive Loss Total accumulated other comprehensive loss consisted of the following (in thousands): September 30, December 31, 2023 2022 Foreign currency translation adjustments $ ( 657 ) $ ( 845 ) Unrealized loss on available-for-sale securities ( 1,587 ) ( 5,728 ) Total accumulated other comprehensive loss $ ( 2,244 ) $ ( 6,573 )

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2023
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Underwritten Public Offering In October 2023, the Company completed an underwritten public offering in which 9,833,334 shares of common stock were sold, including the exercise in full by the underwriters of their option to purchase an additional 1,500,000 shares, at a public offering price of $ 30.00 per share. In connection with the offering, the Company sold to certain investors pre-funded warrants, in lieu of common stock, to purchase 1,666,722 shares of common stock at a purchase price of $ 29.999 per pre-funded warrant, which equals the public offering price per share of common stock less the $ 0.001 exercise price per share of each pre-funded warrant. The total proceeds that the Company received from the offering were $ 326.5 million, net of underwriting discounts and commissions.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiaries and have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP, for interim financial information and in accordance with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. The unaudited interim Condensed Consolidated Financial Statements have been prepared on the same basis as the annual financial statements. In the opinion of management, the accompanying unaudited Condensed Consolidated Financial Statements reflect all adjustments (consisting only of normal recurring adjustments) considered necessary for a fair presentation. These financial statements should be read in conjunction with the audited financial statements and notes thereto for the preceding fiscal year contained in the Company’s Annual Report on Form 10-K filed on February 17, 2023, or Annual Report, with the United States Securities and Exchange Commission, or the SEC. The results of operations for the three and nine months ended September 30, 2023 are not necessarily indicative of the results to be expected for the year ending December 31, 2023. The Condensed Consolidated Balance Sheet as of December 31, 2022 has been derived from audited financial statements at that date, but does not include all of the information required by GAAP for complete financial statements.
Use of Estimates	Use of Estimates The accompanying Condensed Consolidated Financial Statements have been prepared in accordance with GAAP. The preparation of the Condensed Consolidated Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent liabilities and the reported amounts of expenses in the Condensed Consolidated Financial Statements and the accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accruals, fair value of assets and liabilities, income taxes, stock-based compensation, revenue recognition, and the liabilities for sales of future royalties. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Cash, Cash Equivalents, and Restricted Cash	Cash, Cash Equivalents and Restricted Cash Restricted cash primarily consists of money market accounts used as collateral for the Company’s obligations under its facility leases. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the Condensed Consolidated Balance Sheets that sum to the total of the same such amounts shown in the Condensed Consolidated Statement of Cash Flows (in thousands): September 30, 2023 2022 Cash and cash equivalents $ 72,575 $ 391,651 Restricted cash included in prepaid expenses and 1,976 517 Restricted cash included in other assets 4,056 4,140 Total cash, cash equivalents, and restricted cash $ 78,607 $ 396,308
Credit Losses	Credit Losses The Company is exposed to credit losses primarily through receivables from customers and collaborators and through its available-for-sale debt securities. For trade receivables and other instruments, the Company uses a forward-looking expected loss model that generally results in the earlier recognition of allowances for losses. For available-for-sale debt securities with unrealized losses, the losses are recognized as allowances rather than as reductions in the amortized cost of the securities. The Company’s expected loss allowance methodology for the receivables is developed using historical collection experience, current and future economic market conditions, a review of the current aging status and financial condition of the entities. Specific allowance amounts are established to record the appropriate allowance for customers that have a higher probability of default. Balances are written off when determined to be uncollectible. The Company’s expected loss allowance methodology for the debt securities is developed by reviewing the extent of the unrealized loss, the size, term, geographical location, and industry of the issuer, the issuers’ credit ratings and any changes in those ratings, as well as reviewing current and future economic market conditions and the issuers’ current status and financial condition. There were no material credit losses recorded for receivables and available-for-sale debt securities for the three and nine months ended September 30, 2023 and 2022.
Revenue Recognition	Revenue Recognition Product Sales The Company sells its approved products through a limited number of distributors. Under ASC 606, revenue from product sales is recognized at the point in time when the delivery is made and when title and risk of loss transfers to these distributors. The Company also recognizes revenue from sales of certain products on a “named patient” basis, which are allowed in certain countries prior to the commercial approval of the product. Prior to recognizing revenue, the Company makes estimates of the transaction price, including any variable consideration that is subject to a constraint. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved. Product sales are recorded net of estimated government-mandated rebates and chargebacks, estimated product returns, and other deductions. Provisions for returns and other adjustments are provided for in the period the related revenue is recorded, as estimated by management. These reserves are based on estimates of the amounts earned or to be claimed on the related sales and are reviewed periodically and adjusted as necessary. The Company’s estimates of government mandated rebates, chargebacks, estimated product returns, and other deductions depends on the identification of key customer contract terms and conditions, as well as estimates of sales volumes to different classes of payors. If actual results vary, the Company may need to adjust these estimates, which could have a material effect on earnings in the period of the adjustment. Collaboration, License, and Royalty Revenue The Company has certain license and collaboration agreements that are within the scope of Accounting Standards Codification, or ASC, 808, Collaborative Agreements, which provides guidance on the presentation and disclosure of collaborative arrangements. Generally, the classification of the transactions under the collaborative arrangements is determined based on the nature of contractual terms of the arrangement, along with the nature of the operations of the participants. The Company records its share of collaboration revenue, net of transfer pricing related to net sales in the period in which such sales occur, if the Company is considered as an agent in the arrangement. The Company is considered an agent when the collaboration partner controls the product before transfer to the customers and has the ability to direct the use of and obtain substantially all of the remaining benefits from the product. Funding received related to research and development services and commercialization costs is generally classified as a reduction of research and development expenses and selling, general and administrative expenses, respectively, in the Condensed Consolidated Statements of Operations, because the provision of such services for collaborative partners are not considered to be part of the Company’s ongoing major or central operations. In order to record collaboration revenue, the Company utilizes certain information from its collaboration partners, including revenue from the sale of the product, associated reserves on revenue, and costs incurred for development and sales activities. For the periods covered in the financial statements presented, there have been no material changes to prior period estimates of revenues and expenses. The Company also records royalty revenues under certain of the Company’s license or collaboration agreements in exchange for license of intellectual property. If the Company does not have any future performance obligations for these license or collaboration agreements, royalty revenue is recorded as the underlying sales occur. The Company sold the right to receive certain royalty payments from net sales of Crysvita in certain territories to RPI Finance Trust, or RPI, an affiliate of Royalty Pharma, and to OCM LS23 Holdings LP, an investment vehicle for Ontario Municipal Employees Retirement System, or OMERS, as further described in “Note 8 Liabilities for Sales of Future Royalties”. The Company records the royalty revenue from the net sales of Crysvita in the applicable territories on a prospective basis as royalty revenue in the Condensed Consolidated Statements of Operations over the term of the applicable arrangement. The terms of the Company’s collaboration and license agreements may contain multiple performance obligations, which may include licenses and research and development activities. The Company evaluates these agreements under ASC 606, Revenue from Contracts with Customers, or ASC 606, to determine the distinct performance obligations. The Company analogizes to ASC 606 for the accounting for distinct performance obligations for which there is a customer relationship. Prior to recognizing revenue, the Company makes estimates of the transaction price, including variable consideration that is subject to a constraint. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved. Total consideration may include nonrefundable upfront license fees, payments for research and development activities, reimbursement of certain third-party costs, payments based upon the achievement of specified milestones, and royalty payments based on product sales derived from the collaboration. If there are multiple distinct performance obligations, the Company allocates the transaction price to each distinct performance obligation based on its relative standalone selling price. The standalone selling price is generally determined based on the prices charged to customers or using expected cost-plus margin. The Company estimates the efforts needed to complete the performance obligations and recognizes revenue by measuring the progress towards complete satisfaction of the performance obligations using input measures.
Deferred Compensation Plan	Deferred Compensation Plan The Company maintains a nonqualified deferred compensation plan whereby certain employees and members of the board of directors are able to defer certain equity awards and other compensation. Amounts deferred are invested into various mutual funds. The plan complies with the provisions of Section 409A of the Internal Revenue Code. All of the various mutual funds held in the plan are classified as trading securities and recorded at fair value in other non-current assets in the Condensed Consolidated Balance Sheets with changes in fair value recognized as earnings in the period they occur. The corresponding liability for the plan is included in other non-current liabilities in the Condensed Consolidated Balance Sheets. Certain equity awards deferred under the plan are required to be settled through the issuance of Company stock. These awards are recorded as treasury stock and deferred compensation obligation within stockholders’ equity.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2023
Accounting Policies [Abstract]
Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the Condensed Consolidated Balance Sheets that sum to the total of the same such amounts shown in the Condensed Consolidated Statement of Cash Flows (in thousands): September 30, 2023 2022 Cash and cash equivalents $ 72,575 $ 391,651 Restricted cash included in prepaid expenses and 1,976 517 Restricted cash included in other assets 4,056 4,140 Total cash, cash equivalents, and restricted cash $ 78,607 $ 396,308

Financial Instruments (Tables)

Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Summary of Financial Assets Measured on Recurring Basis	The following tables set forth the fair value of the Company’s financial assets remeasured on a recurring basis based on the three-tier fair value hierarchy (in thousands): September 30, 2023 Level 1 Level 2 Level 3 Total Money market funds $ 34,222 $ — $ — $ 34,222 Certificates of deposit and time deposit — 13,844 — 13,844 Corporate bonds — 142,398 — 142,398 Commercial paper — 46,175 — 46,175 Asset-backed securities — 5,826 — 5,826 U.S. Government Treasury and agency securities 66,437 186,910 — 253,347 Investment in Solid common stock 1,315 — — 1,315 Other — 9,890 — 9,890 Total $ 101,974 $ 405,043 $ — $ 507,017 December 31, 2022 Level 1 Level 2 Level 3 Total Money market funds $ 102,847 $ — $ — $ 102,847 Certificates of deposit and time deposit — 25,972 — 25,972 Corporate bonds — 427,598 — 427,598 Commercial paper — 135,393 — 135,393 Asset-backed securities — 11,980 — 11,980 U.S. Government Treasury and agency securities 27,645 129,345 — 156,990 Debt securities in government-sponsored entities — 15,855 — 15,855 Investment in Solid common stock 2,807 — — 2,807 Other — 4,575 — 4,575 Total $ 133,299 $ 750,718 $ — $ 884,017

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Summary of Cash Equivalents and Marketable Debt Securities Classified as Available For Sale Securities	The fair values of cash equivalents and marketable debt securities classified as available-for-sale securities consisted of the following (in thousands): September 30, 2023 Gross Unrealized Amortized Gains Losses Estimated Money market funds $ 34,222 $ — $ — $ 34,222 Certificates of deposit and time deposit 13,844 — — 13,844 Corporate bonds 143,261 39 ( 902 ) 142,398 Commercial paper 46,175 — — 46,175 Asset-backed securities 5,844 — ( 18 ) 5,826 U.S. Government Treasury and agency securities 254,053 1 ( 707 ) 253,347 Total $ 497,399 $ 40 $ ( 1,627 ) $ 495,812 December 31, 2022 Gross Unrealized Amortized Gains Losses Estimated Money market funds $ 102,847 $ — $ — $ 102,847 Certificates of deposit and time deposit 25,972 — — 25,972 Corporate bonds 432,211 87 ( 4,700 ) 427,598 Commercial paper 135,393 — — 135,393 Asset-backed securities 12,002 — ( 22 ) 11,980 U.S. Government Treasury and agency securities 157,933 320 ( 1,263 ) 156,990 Debt securities in government-sponsored entities 16,005 — ( 150 ) 15,855 Total $ 882,363 $ 407 $ ( 6,135 ) $ 876,635
Summary of Inventory	Inventory consists of the following (in thousands): September 30, December 31, 2023 2022 Work-in-process $ 19,173 $ 17,486 Finished goods 12,629 9,280 Total inventory $ 31,802 $ 26,766
Summary of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): September 30, December 31, 2023 2022 Research, clinical study, and manufacturing expenses $ 51,520 $ 73,558 Payroll and related expenses 76,300 78,938 Other 50,802 52,182 Total accrued liabilities $ 178,622 $ 204,678

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2023
Revenue from Contract with Customer [Abstract]
Summary of Disaggregation of Total Revenues	The following table disaggregates total revenues from external customers by product sales, royalty revenue, and collaboration and license revenue (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 Product sales: Crysvita $ 19,200 $ 13,184 $ 57,318 $ 34,980 Mepsevii 5,633 6,045 22,552 15,839 Dojolvi 16,553 13,274 47,347 39,200 Evkeeza 963 — 1,540 — Total product sales 42,349 32,503 128,757 90,019 Crysvita royalty revenue 55,703 5,373 106,916 15,634 Collaboration and license revenue: Crysvita collaboration revenue in profit- — 51,348 69,705 148,121 Daiichi Sankyo — 1,479 1,479 6,207 Total collaboration and license revenue — 52,827 71,184 154,328 Total revenues $ 98,052 $ 90,703 $ 306,857 $ 259,981 The following table disaggregates total revenues based on geographic location (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2023 2022 2023 2022 North America $ 67,811 $ 67,012 $ 214,232 $ 196,257 Latin America 17,229 14,119 59,096 36,449 Europe 13,012 8,411 32,351 26,114 Japan — 1,161 1,178 1,161 Total revenues $ 98,052 $ 90,703 $ 306,857 $ 259,981
Summary of Changes in Contract Liabilities	The following table presents changes in the contract liabilities (in thousands): Nine Months Ended September 30, 2023 2022 Balance of contract liabilities at beginning of period $ 1,479 $ 9,076 Additions — 89 Deductions ( 1,479 ) ( 6,207 ) Balance of contract liabilities at end of period, net $ — $ 2,958

License and Research Agreemen_2

License and Research Agreements (Tables)	9 Months Ended
	Sep. 30, 2023
Share of Collaboration and Royalty Revenue Related to Crysvita	Total Crysvita revenue was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Revenue in profit-share territory: Collaboration revenue $ — $ 51,348 $ 69,705 $ 148,121 Royalty revenue 35,160 — 64,221 — Non-cash royalty revenue 15,070 — 27,524 — Total revenue in profit-share territory 50,230 51,348 161,450 148,121 Product sales 19,200 13,184 57,318 34,980 Non-cash royalty revenue in European territories 5,473 5,373 15,171 15,634 Total Crysvita revenue $ 74,903 $ 69,905 $ 233,939 $ 198,735
Schedule of Cost Sharing Payments	Under the collaboration agreement, KKC and the Company share certain development and commercialization costs. As a result, the Company was reimbursed for these costs and operating expenses were reduced as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Research and development $ 940 $ 3,830 $ 4,665 $ 12,770 Selling, general and administrative 2,060 8,365 15,346 26,510 Total $ 3,000 $ 12,195 $ 20,011 $ 39,280
Solid and Arcturus
Schedule of Changes in Fair Value of Equity Investment	The changes in the fair value of the Company’s equity investments in the common stock of Solid and Arcturus were as follows (in thousands): Common stock As of December 31, 2021 $ 32,200 Change in fair value ( 19,299 ) Sale of shares ( 10,094 ) December 31, 2022 2,807 Change in fair value ( 1,492 ) September 30, 2023 $ 1,315

Liabilities for Sales of Futu_2

Liabilities for Sales of Future Royalties (Tables)	9 Months Ended
	Sep. 30, 2023
Deferred Revenue Disclosure [Abstract]
Schedule of Activity Within Liability for Sale of Future Royalties	The following table shows the activity within the liability account (in thousands): Liabilities for Sales of Future Royalties RPI OMERS Total December 31, 2021 $ 351,786 $ — $ 351,786 Net proceeds from sale of future — 490,950 490,950 Royalty revenue ( 21,692 ) — ( 21,692 ) Non-cash interest expense 35,095 19,300 54,395 December 31, 2022 365,189 510,250 875,439 Royalty revenue ( 15,171 ) ( 12,446 ) ( 27,617 ) Non-cash interest expense 25,598 32,508 58,106 September 30, 2023 $ 375,616 $ 530,312 $ 905,928

Stock-Based Awards (Tables)

Stock-Based Awards (Tables)	9 Months Ended
	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Summary of Stock-Based Compensation Expense	The table below sets forth the stock-based compensation expense for the periods presented (in thousands): Three Months Ended Nine Months Ended 2023 2022 2023 2022 Cost of sales $ 191 $ 225 $ 862 $ 730 Research and development 19,113 20,251 56,371 57,588 Selling, general and administrative 15,573 15,285 44,236 42,695 Total stock-based compensation expense $ 34,877 $ 35,761 $ 101,469 $ 101,013

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2023
Earnings Per Share [Abstract]
Outstanding Shares of Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share	The following weighted-average outstanding common stock equivalents were excluded from the computation of diluted net loss per share for the periods presented because including them would have been antidilutive: Three Months Ended Nine Months Ended 2023 2022 2023 2022 Options to purchase common stock, 14,585,014 11,969,532 14,117,741 11,114,822 Employee stock purchase plan 66,735 44,649 37,156 15,047 14,651,749 12,014,181 14,154,897 11,129,869

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
	Sep. 30, 2023
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Total Accumulated Other Comprehensive Loss	Total accumulated other comprehensive loss consisted of the following (in thousands): September 30, December 31, 2023 2022 Foreign currency translation adjustments $ ( 657 ) $ ( 845 ) Unrealized loss on available-for-sale securities ( 1,587 ) ( 5,728 ) Total accumulated other comprehensive loss $ ( 2,244 ) $ ( 6,573 )

Organization - Additional Infor

Organization - Additional Information (Details)	9 Months Ended
	Sep. 30, 2023 Segment
Organization And Nature Of Business [Line Items]
Number of reportable segments	1

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Accounting Policies [Abstract]
Credit losses recorded for receivables	$ 0	$ 0	$ 0	$ 0
Credit losses recorded for available-for-sale debt securities	$ 0	$ 0	$ 0	$ 0

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Cash and cash equivalents	$ 72,575	$ 132,944	$ 391,651
Restricted cash included in prepaid expenses and other current assets	$ 1,976		$ 517
Restricted Cash and Cash Equivalents, Current, Asset, Statement of Financial Position [Extensible List]	Prepaid expenses and other current assets		Prepaid expenses and other current assets
Restricted cash included in other assets	$ 4,056		$ 4,140
Restricted Cash and Cash Equivalents, Noncurrent, Asset, Statement of Financial Position [Extensible List]	Other assets		Other assets
Total cash, cash equivalents, and restricted cash shown in the statements of cash flows	$ 78,607	$ 137,601	$ 396,308	$ 309,585

Financial Instruments - Summary

Financial Instruments - Summary of Financial Assets Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	$ 507,017	$ 884,017
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	101,974	133,299
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	405,043	750,718
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	34,222	102,847
Money Market Funds | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	34,222	102,847
Asset-backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	5,826	11,980
Asset-backed Securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	5,826	11,980
Certificates of Deposits and Time Deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	13,844	25,972
Certificates of Deposits and Time Deposits | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	13,844	25,972
Corporate Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	142,398	427,598
Corporate Bonds | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	142,398	427,598
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	46,175	135,393
Commercial Paper | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	46,175	135,393
U.S. Government Treasury and Agency Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	253,347	156,990
U.S. Government Treasury and Agency Securities | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	66,437	27,645
U.S. Government Treasury and Agency Securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	186,910	129,345
Debt Securities in Government Sponsored Entities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value		15,855
Debt Securities in Government Sponsored Entities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value		15,855
Investments in Solid Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	1,315	2,807
Investments in Solid Common Stock | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	1,315	2,807
Other
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	9,890	4,575
Other | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value	$ 9,890	$ 4,575

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Cash Equivalents and Marketable Debt Securities Classified as Available For Sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 497,399	$ 882,363
Gross Unrealized Gains	40	407
Gross Unrealized Losses	(1,627)	(6,135)
Estimated Fair Value	495,812	876,635
Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	34,222	102,847
Estimated Fair Value	34,222	102,847
Asset-backed Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	5,844	12,002
Gross Unrealized Gains		0
Gross Unrealized Losses	(18)	(22)
Estimated Fair Value	5,826	11,980
Certificates of Deposits and Time Deposits
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	13,844	25,972
Estimated Fair Value	13,844	25,972
Corporate Bonds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	143,261	432,211
Gross Unrealized Gains	39	87
Gross Unrealized Losses	(902)	(4,700)
Estimated Fair Value	142,398	427,598
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	46,175	135,393
Gross Unrealized Losses	0
Estimated Fair Value	46,175	135,393
U.S. Government Treasury and Agency Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	254,053	157,933
Gross Unrealized Gains	1	320
Gross Unrealized Losses	(707)	(1,263)
Estimated Fair Value	$ 253,347	156,990
Debt Securities in Government Sponsored Entities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		16,005
Gross Unrealized Losses		(150)
Estimated Fair Value		$ 15,855

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details)	9 Months Ended
	Sep. 30, 2023
Maximum
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities remaining contractual maturities	3 years

Balance Sheet Components - Su_2

Balance Sheet Components - Summary of Inventory (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Inventory, Net [Abstract]
Work-in-process	$ 19,173	$ 17,486
Finished goods	12,629	9,280
Total inventory	$ 31,802	$ 26,766

Balance Sheet Components - Su_3

Balance Sheet Components - Summary of Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Research, clinical study, and manufacturing expenses	$ 51,520	$ 73,558
Payroll and related expenses	76,300	78,938
Other	50,802	52,182
Total accrued liabilities	$ 178,622	$ 204,678

Revenue - Summary of Disaggrega

Revenue - Summary of Disaggregation of Total Revenues from Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation Of Revenue [Line Items]
Total revenues	$ 98,052	$ 90,703	$ 306,857	$ 259,981
Collaboration and license
Disaggregation Of Revenue [Line Items]
Total revenues	0	52,827	71,184	154,328
Collaboration and license | Crysvita
Disaggregation Of Revenue [Line Items]
Total revenues	0	51,348	69,705	148,121
Collaboration and license | Daiichi Sankyo
Disaggregation Of Revenue [Line Items]
Total revenues	0	1,479	1,479	6,207
Product Revenue
Disaggregation Of Revenue [Line Items]
Total revenues	42,349	32,503	128,757	90,019
Product Revenue | Crysvita
Disaggregation Of Revenue [Line Items]
Total revenues	19,200	13,184	57,318	34,980
Product Revenue | Mepsevii
Disaggregation Of Revenue [Line Items]
Total revenues	5,633	6,045	22,552	15,839
Product Revenue | Dojolvi
Disaggregation Of Revenue [Line Items]
Total revenues	16,553	13,274	47,347	39,200
Product Revenue | Evkeeza
Disaggregation Of Revenue [Line Items]
Total revenues	963	0	1,540	0
Royalty revenue
Disaggregation Of Revenue [Line Items]
Total revenues	55,703	5,373	106,916	15,634
Royalty revenue | Crysvita
Disaggregation Of Revenue [Line Items]
Total revenues	$ 55,703	$ 5,373	$ 106,916	$ 15,634

Revenue - Summary of Disaggre_2

Revenue - Summary of Disaggregation of Total Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation Of Revenue [Line Items]
Total revenues	$ 98,052	$ 90,703	$ 306,857	$ 259,981
North America
Disaggregation Of Revenue [Line Items]
Total revenues	67,811	67,012	214,232	196,257
Latin America
Disaggregation Of Revenue [Line Items]
Total revenues	17,229	14,119	59,096	36,449
Europe
Disaggregation Of Revenue [Line Items]
Total revenues	13,012	8,411	32,351	26,114
Japan
Disaggregation Of Revenue [Line Items]
Total revenues	$ 0	$ 1,161	$ 1,178	$ 1,161

Revenue - Summary of Changes in

Revenue - Summary of Changes in Contract Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Abstract]
Balance of contract liabilities at beginning of period	$ 1,479	$ 9,076
Additions	0	89
Deductions	(1,479)	(6,207)
Balance of contract liabilities at end of period, net	$ 0	$ 2,958

Revenue - Additional Informatio

Revenue - Additional Information (Details)	Sep. 30, 2023	Dec. 31, 2022
Customer One
Disaggregation of Revenue [Line Items]
Percentage of gross accounts receivable balance	68%	68%

GeneTx Acquisition - Additional

GeneTx Acquisition - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended			3 Months Ended	9 Months Ended		12 Months Ended
	Jul. 31, 2022	Apr. 30, 2022	Aug. 31, 2019	Mar. 31, 2020	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Business Acquisition [Line Items]
Acquired in-process research and development					$ 0	$ 75,234
GeneTx [Member]
Business Acquisition [Line Items]
Business acquisition, consideration transferred	$ 75,000
Regulatory Approval Milestones	85,000
Outstanding Cash and Cash Equivalents Acquired	15,600
Amount on Adjustments for Working Capital and Transaction Expenses	600
Payments to Acquire Businesses, Gross	91,200
GeneTx [Member] | Maximum [Member]
Business Acquisition [Line Items]
Future contingent milestone payments	190,000
Additional Milestone Payments	30,000
Commercial Milestone Payment	$ 75,000
In Process Research and Development [Member] | GeneTx [Member]
Business Acquisition [Line Items]
Acquired in-process research and development							$ 75,000
Gene Tx Biotherapeutics L L C [Member] | Program Agreement And Unitholder Option Agreement [Member]
Business Acquisition [Line Items]
Business acquisition option exercise period, description			the Company made an upfront payment of $20.0 million for an exclusive option to acquire GeneTx, which was exercisable any time prior to 30 days following FDA acceptance of the Investigational New Drug Application, or IND, for GTX-102.
Upfront payment for exclusive option to acquisition			$ 20,000
Option extension payment				$ 25,000
Acquisition cost		$ 75,000

License and Research Agreemen_3

License and Research Agreements - Additional Information (Details) - USD ($) $ in Thousands		1 Months Ended			3 Months Ended		9 Months Ended		113 Months Ended
	Jul. 01, 2022	Jan. 31, 2022	Jan. 31, 2021	Jun. 30, 2020	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development					$ 157,245	$ 237,297	$ 487,892	$ 534,981
Daiichi Sankyo
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred Revenue balance					0		0		$ 1,500
Deferred Revenue Recognized					$ 0	1,500	$ 1,500	6,200
Regeneron Pharmaceuticals, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payments of collaboration		$ 30,000
Intangible assets, remaining amortization period					10 years 6 months		10 years 6 months
Eligible future milestone payments		$ 63,000
Development costs					$ 1,900		$ 6,900
Research and development						$ 2,500		$ 4,300
AccruedCollaborationPayables					3,600		$ 3,600		$ 6,800
Regeneron Pharmaceuticals, Inc. | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Profit loss sharing percentage on net sales		40%
Regeneron Pharmaceuticals, Inc. | Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Profit loss sharing percentage on net sales		20%
License Agreement | Profit Share Territory | Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Tiered double-digit revenue share percentage entitled to receive							20%
License and Collaboration Agreement | Mereo
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payments made under agreement			$ 50,000
Research and development					0		$ 9,000
License and Collaboration Agreement | Maximum | Mereo
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future contingent milestone payments			$ 254,000
Kyowa Kirin Collaboration | License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Profit loss sharing percentage on net sales							30%		35%
Kyowa Kirin Collaboration | License Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Tiered double-digit revenue share percentage entitled to receive							30%
Kyowa Kirin Collaboration | License Agreement | Prepaid Expenses and Other Current Assets
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License agreement other receivables					400		$ 400		$ 6,400
Kyowa Kirin Collaboration | License Agreement | Profit Share Revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License agreement accounts receivable					54,100		54,100		27,500
Kyowa Kirin Collaboration | License Agreement | Commercial and Development Activity Reimbursements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License agreement accrued liabilities					5,700		$ 5,700		$ 3,100
Kyowa Kirin Collaboration | License Agreement | Profit Share Territory
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of right to receive royalty payments on net sales	30%
Remaining profit or loss share percentage on commercializing products							50%
Kyowa Kirin Collaboration | License Agreement | Royalty Revenue in European Territory
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of royalty on net sales receives							10%
License and Technology Access Agreement | Daiichi Sankyo
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received							$ 125,000
Deferred Revenue balance					$ 25,000		25,000
License and Technology Access Agreement | License Agreement | Daiichi Sankyo
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized							$ 183,300
Sublicense Agreement | Daiichi Sankyo
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received				$ 8,000

License and Research Agreemen_4

License and Research Agreements - Share of Collaboration and Royalty Revenue Related to Crysvita (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation Of Revenue [Line Items]
Total Crysvita revenue	$ 98,052	$ 90,703	$ 306,857	$ 259,981
Collaboration and Royalty | Kyowa Kirin Collaboration
Disaggregation Of Revenue [Line Items]
Total Crysvita revenue	74,903	69,905	233,939	198,735
Collaboration and Royalty | Kyowa Kirin Collaboration | Profit Share Territory
Disaggregation Of Revenue [Line Items]
Total Crysvita revenue	50,230	51,348	161,450	148,121
Royalty revenue
Disaggregation Of Revenue [Line Items]
Total Crysvita revenue	55,703	5,373	106,916	15,634
Royalty revenue | Kyowa Kirin Collaboration | Profit Share Territory
Disaggregation Of Revenue [Line Items]
Total Crysvita revenue	35,160	0	64,221	0
Product sales
Disaggregation Of Revenue [Line Items]
Total Crysvita revenue	42,349	32,503	128,757	90,019
Product sales | Kyowa Kirin Collaboration
Disaggregation Of Revenue [Line Items]
Total Crysvita revenue	19,200	13,184	57,318	34,980
Collaboration Revenue | Kyowa Kirin Collaboration | Profit Share Territory
Disaggregation Of Revenue [Line Items]
Total Crysvita revenue	0	51,348	69,705	148,121
Non-cash royalty revenue | Kyowa Kirin Collaboration | Profit Share Territory
Disaggregation Of Revenue [Line Items]
Total Crysvita revenue	15,070	0	27,524	0
Non-cash royalty revenue | Kyowa Kirin Collaboration | Royalty Revenue in European Territory
Disaggregation Of Revenue [Line Items]
Total Crysvita revenue	$ 5,473	$ 5,373	$ 15,171	$ 15,634

License and Research Agreemen_5

License and Research Agreements - Schedule of Cost Sharing Payments (Details) - Kyowa Kirin Collaboration - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Cost Sharing Payments [Line Items]
Research and development	$ 940	$ 3,830	$ 4,665	$ 12,770
Selling, general and administrative	2,060	8,365	15,346	26,510
Total	$ 3,000	$ 12,195	$ 20,011	$ 39,280

License and Research Agreemen_6

License and Research Agreements - Schedule of Changes in Fair Value of Equity Investment (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock, Beginning balance	$ 884,017
Common stock, Ending balance	507,017	$ 884,017
Solid and Arcturus | Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock, Beginning balance	2,807	32,200
Common stock, Change in fair value	(1,492)	(19,299)
Common stock, Sale of shares		(10,094)
Common stock, Ending balance	$ 1,315	$ 2,807

Liabilities for Sales of Futu_3

Liabilities for Sales of Future Royalties - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended		9 Months Ended		12 Months Ended	46 Months Ended
	Jul. 31, 2022	Dec. 31, 2019	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Sep. 30, 2023
Liability For Sale Of Future Royalties [Line Items]
Proceeds from the sale of future royalties, net			$ 0	$ 490,950	$ 490,950
RPI Finance Trust (RPI)
Liability For Sale Of Future Royalties [Line Items]
Proceeds from the sale of future royalties, net					0
OMERS
Liability For Sale Of Future Royalties [Line Items]
Proceeds from the sale of future royalties, net					$ 490,950
Royalty Purchase Agreement
Liability For Sale Of Future Royalties [Line Items]
Profit loss sharing percentage on net sales	30%
Royalty Purchase Agreement | RPI Finance Trust (RPI)
Liability For Sale Of Future Royalties [Line Items]
Proceeds from sale of future royalties		$ 320,000
Royalty payment termination description			The agreement with RPI will automatically terminate, and the payment of royalties to RPI will cease, in the event aggregate royalty payments received by RPI are equal to or greater than $608.0 million prior to December 31, 2030, or in the event aggregate royalty payments received by RPI are less than $608.0 million prior to December 31, 2030, or when aggregate royalty payments received by RPI are equal to $800.0 million.
Royalties transaction costs net		5,800
Proceeds from the sale of future royalties, net		314,200
Effective annual interest rate			7.30%			7.30%
Non-cash collaboration royalty revenue						$ 67,800
Royalty Purchase Agreement | OMERS
Liability For Sale Of Future Royalties [Line Items]
Proceeds from sale of future royalties	$ 500,000
Royalty payment termination description	In July 2022, the Company entered into a Royalty Purchase Agreement with OMERS. Pursuant to the agreement, OMERS paid $500.0 million to the Company in consideration for the right to receive 30% of the future royalty payments due to the Company from KKC based on net sales of Crysvita in the U.S. and Canada under the terms of the KKC Collaboration Agreement. The calculation of royalty payments to OMERS is based on net sales of Crysvita beginning in April 2023 and will expire upon the earlier of the date on which aggregate payments received by OMERS equals $725.0 million or the date the final royalty payment is made to the Company under the KKC Collaboration Agreement.
Royalty agreement termination threshold amount	$ 725,000
Payment from sale of future royalties	500,000
Royalties transaction costs net	$ 9,100
Proceeds from the sale of future royalties, net		491,000
Effective annual interest rate			8.20%			8.20%
Non-cash collaboration royalty revenue						$ 27,500
Royalty Purchase Agreement | Minimum | RPI Finance Trust (RPI)
Liability For Sale Of Future Royalties [Line Items]
Royalty agreement termination threshold amount		$ 608,000	$ 608,000			608,000
Royalty Purchase Agreement | Maximum | RPI Finance Trust (RPI)
Liability For Sale Of Future Royalties [Line Items]
Royalty agreement termination threshold amount			$ 800,000			$ 800,000

Liabilities for Sales of Futu_4

Liabilities for Sales of Future Royalties - Schedule of Activity Within Liability Related to Sale of Future Royalties (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Liability For Sale Of Future Royalties [Line Items]
Liability for sale of future royalties at beginning of year	$ 875,439	$ 351,786	$ 351,786
Net proceeds from sale of future royalties	0	490,950	490,950
Royalty revenue	(27,617)		(21,692)
Non-cash interest expense	58,106		54,395
Liability for sale of future royalties at end of year	905,928		875,439
RPI Finance Trust (RPI)
Liability For Sale Of Future Royalties [Line Items]
Liability for sale of future royalties at beginning of year	365,189	351,786	351,786
Net proceeds from sale of future royalties			0
Royalty revenue	(15,171)		(21,692)
Non-cash interest expense	25,598		35,095
Liability for sale of future royalties at end of year	375,616		365,189
OMERS
Liability For Sale Of Future Royalties [Line Items]
Liability for sale of future royalties at beginning of year	510,250	$ 0	0
Net proceeds from sale of future royalties			490,950
Royalty revenue	(12,446)		0
Non-cash interest expense	32,508		19,300
Liability for sale of future royalties at end of year	$ 530,312		$ 510,250

Stock-Based Awards - Additional

Stock-Based Awards - Additional Information (Details)	Sep. 30, 2023 shares
Amended & Restated 2014 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share reserved for future issuance	6,694,377
Employment Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share reserved for future issuance	408,189
2023 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share of common stock available under 2023 Incentive Plan	462,276
Share reserved for future issuance	4,960,091

Stock-Based Awards - Summary of

Stock-Based Awards - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 34,877	$ 35,761	$ 101,469	$ 101,013
Cost of sales
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	191	225	862	730
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	19,113	20,251	56,371	57,588
Selling, general and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 15,573	$ 15,285	$ 44,236	$ 42,695

Net Loss Per Share - Outstandin

Net Loss Per Share - Outstanding Shares of Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	14,651,749	12,014,181	14,154,897	11,129,869
Options to Purchase Common Stock, RSUs, and PSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	14,585,014	11,969,532	14,117,741	11,114,822
Employee Stock Purchase Plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	66,735	44,649	37,156	15,047

Equity Transactions - Additiona

Equity Transactions - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		29 Months Ended
	May 31, 2021	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023
Stockholders Equity [Line Items]
Stock sold in at-the-market offering		611,282		1,175,584
Net proceeds from at-the-market offering		$ 24,800		$ 53,299	$ 0
Open Market Sale
Stockholders Equity [Line Items]
Common stock shares sold			0		0
Stock sold in at-the-market offering						2,225,956
Net proceeds from at-the-market offering						$ 132,200
Option to sell common stock aggregate offering price	$ 350,000

Related Party Transaction - Add

Related Party Transaction - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended		15 Months Ended
	Jul. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023
Related Party Transaction [Line Items]
Research and development		$ 157,245	$ 237,297	$ 487,892	$ 534,981
Contribution amount paid						$ 1,000
Contribution period	4 years
Non Profit Foundation [Member]
Related Party Transaction [Line Items]
Research and development		$ 0	$ 0	$ 300	$ 0	$ 500

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss - Schedule of Total Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation adjustments	$ (657)	$ (845)
Unrealized loss on available-for-sale securities	(1,587)	(5,728)
Total accumulated other comprehensive loss	$ (2,244)	$ (6,573)

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - Subsequent Event - Underwritten Public Offering $ / shares in Units, $ in Millions	1 Months Ended
	Oct. 31, 2023 USD ($) $ / shares shares
Subsequent Event [Line Items]
Common stock shares sold | shares	9,833,334
Shares purchased by underwriters | shares	1,500,000
Public offering price | $ / shares	$ 30
Pre Funded Warrant
Subsequent Event [Line Items]
Underwritten Public Offering Shares | shares	1,666,722
Pre-funded warrant price | $ / shares	$ 29.999
Exercise price of each pre-funded warrant (in dollars per share) | $ / shares	$ 0.001
Proceeds from the issuance of common stock in connection with underwritten public offerings, net | $	$ 326.5