Ultragenyx Pharmaceutical Inc.

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 ultra-rare genetic diseases. The Company operates asone reportable segment and has six 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., the European Economic Area, or EEA, Brazil, Mexico, and Japan for the treatment of homozygous familial hypercholesterolemia, or HoFH. The Company has exclusive rights to commercialize EVKEEZA® (evinacumab) outside of the U.S.

GENGLYCOS® (pariglasgene brecaparvovec-opnr) is approved in the U.S. for the treatment of pediatric and adult patients eight years and older with glycogen storage disease type Ia, or GSDIa.

FAYUVI® (rebisufligene etisparvovec-hopf) is approved in the U.S. for the treatment of pediatric patients with Sanfilippo syndrome type A, or MPS IIIA, a rare lysosomal storage disease.

In addition to the approved products, the Company has the following ongoing clinical development programs:

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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;

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UX016 is a small-molecule prodrug of sialic acid, or SA, being evaluated as a substrate replacement therapy for GNE myopathy; and

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UX143 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 Imperfecta, or OI.

The Company has sustained operating losses to date, and its ultimate success depends on the outcome of its research and development and commercialization activities. Through September 30, 2026, the Company has relied primarily on the sale of equity securities, revenues from commercial products, the sale of certain future royalties, strategic collaboration arrangements, and the sale of U.S. Food and Drug Administration, or FDA, priority review vouchers, or PRVs, to finance its operations. The Company may 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.

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. The Company consolidates any variable interest entity, or VIE, for which it is the primary beneficiary. Certain reclassifications have been made to prior periods in the Condensed Consolidated Financial Statements and accompanying notes to conform with the current presentation.

The financial statements 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. All intercompany accounts and transactions have been eliminated. 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 18, 2026, 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, 2026 are not necessarily indicative of the results to be expected for the year ending December 31, 2026. The Condensed Consolidated Balance Sheet as of December 31, 2025 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.

Segment Reporting

The Company operates asone reportable segment relating to the research, development and commercialization of its products. The segment derives its current revenues from its six commercially approved products.

The Company’s Chief Operating Decision Maker, or CODM, is the Company's Chief Executive Officer. The CODM manages the Company’s operations on an integrated basis for the purpose of allocating resources. When evaluating the Company’s financial performance, the CODM regularly reviews total revenues and total expenses and makes decisions using this information on a consolidated basis.

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 and to guarantee the fulfillment of certain sales orders to certain government-sponsored customers. 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 millions):

Credit Losses

The Company is exposed to credit losses primarily through receivables from customers and collaborators and through its available-for-sale securities. For trade receivables and other financial instruments, the Company uses a forward-looking expected loss model that recognizes a current period charge for losses that are expected to be incurred over the life of the financial instrument.

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 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 wereno material credit losses recorded for receivables and available-for-sale securities which were attributable to credit risk as of September 30, 2026 and December 31, 2025.

Liabilities for Sales of Future Royalties

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.” At inception, the Company recorded a liability based upon estimated future cash flows discounted at a market rate. The liability is amortized using the effective interest method over the estimated life of the applicable arrangement. To determine the amortization of the liability, the Company estimates the total amount of future royalty payments to be received by the Company and paid to RPI and OMERS. Any estimated royalty payments in excess of the initial liability are recorded as non-cash interest expense. Consequently, the Company estimates imputed interest on the unamortized portion of the liabilities and records interest expense based on the estimated term of the arrangements.

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 employs the prospective method to adjust the amortization of the liabilities and the effective interest rate.

Revenue Recognition

Product Sales

The Company sells its approved products through a limited number of distributors. Under Accounting Standards Codification, or ASC, 606, Revenue from Contracts with Customers, revenue from product sales is recognized at the point in time when control is transferred 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 depend 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 ASC 808, Collaborative Arrangements, 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. The Company generally classifies funding received related to research and development services and commercialization costs 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.

The Company utilizes certain information from its collaboration partners to record collaboration revenue, 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 the license of intellectual property.

As described in “Note 8. Liabilities for Sales of Future Royalties”, for certain royalty payments from net sales of CRYSVITA in applicable territories that were sold to RPI and OMERS, the Company records the non-cash royalty revenue on a prospective basis 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, 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.

Restructuring

Restructuring expense consists primarily of costs associated with exit or disposal activities, including contract terminations, employee terminations, and severance costs. For employee terminations accounted for as ongoing benefit arrangements, the Company recognizes a liability for termination benefits when it is probable that the benefits will be paid and the amounts are reasonably estimable. Contract termination costs and other costs associated with exit or disposal activities are recognized when it is probable that the costs will be incurred, i.e., upon contract termination or when the Company ceases using the rights conveyed by the contract and the amounts are reasonably estimable.

These costs are recorded within operating expenses in the Condensed Consolidated Statements of Operations and the related restructuring liabilities are included in accounts payable and accrued liabilities in the Condensed Consolidated Balance Sheets.

Recent Accounting Pronouncements

In November 2024, the FASB issued ASU 2024-03, Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, requiring public entities to disclose additional information about specific expense categories in the notes to the financial statements on an interim and annual basis. ASU 2024-03 is effective for fiscal years beginning after December 15, 2026, and for interim periods beginning after December 15, 2027, with early adoption permitted. The Company is currently evaluating the impact of adopting ASU 2024-03.

3. Financial Instruments

Certain 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. The carrying amounts of liabilities for the sales of future royalties also approximate their fair value. 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 SAFEs issued by Amlogenyx Inc., or Amlogenyx, a consolidated subsidiary of the Company, are classified as liabilities and measured at fair value on a recurring basis, as described in “Note 6. Investment in Amlogenyx Inc.” Because the valuation relies on significant unobservable inputs, the SAFEs are classified as Level 3 fair value measurements. The SAFEs were initially recorded at the $10 million transaction price, which represented fair value at issuance. There were no significant changes in the assumptions used to estimate the fair value of the SAFEs from issuance through September 30, 2026.

The following tables set forth the fair value of the Company’s financial assets and liabilities remeasured on a recurring basis based on the three-tier fair value hierarchy (in millions):

The Company uses foreign exchange forward contracts to manage remeasurement gains and losses on subsidiaries’ foreign currency-denominated net monetary assets and liabilities, which are designed to offset gains and losses on the underlying balance sheet exposures. These foreign exchange forward contracts are economic hedges and are not designated as hedging instruments. Outstanding notional amounts were $27 million andnil at September 30, 2026 and December 31, 2025, respectively, with related fair value liabilities of a nominal amount and nil included in other liabilities. The Company recognized gains of $1 million on these contracts in other income for each of the three and nine month periods ended September 30, 2026.

4. Balance Sheet Components

Cash Equivalents and Marketable Securities

The fair values of cash equivalents and marketable securities classified as available-for-sale securities consist of the following (in millions):

At September 30, 2026, the remaining contractual maturities of available-for-sale securities were less than three years. The cost of securities sold is based on the specific-identification method. There have been no significant realized gains or losses on available-for-sale securities for the periods presented. All marketable securities with unrealized losses at September 30, 2026 have been in a loss position for less than 12 months or the loss is not material and is temporary in nature.

Inventory

Inventory consists of the following (in millions):

Balance sheet classification of inventory was as follows (in millions):

The Company classifies inventory as non-current when it expects that portion of inventory to be sold more than twelve months after the balance sheet date. Manufacturing costs incurred prior to regulatory approval were expensed as research and development and that inventory has no carrying value in the Condensed Consolidated Balance Sheets. Based on current demand forecasts, the Company expects its non-current inventory to be consumed within its remaining shelf life. Non-current inventory is included in other non-current assets on the Condensed Consolidated Balance Sheets.

Accrued Liabilities

Accrued liabilities consist of the following (in millions):

Intangible Assets

Upon FDA approval of GENGLYCOS in August 2026, the Company reclassified $41 million of acquired in-process research and development from an indefinite-lived intangible asset to a finite-lived intangible asset. The Company began amortizing the asset on a straight-line basis over its estimated useful life ofseven years, with amortization recorded in cost of sales. Amortization expense was nominal for the three and nine months ended September 30, 2026.

5. Revenue

The following table disaggregates total revenues from external customers by product sales and royalty revenue (in millions):

The following table disaggregates total revenues based on geographic location (in millions):

The Company’s largest accounts receivable balance was from a collaboration partner and accounted for 36% and 62% of the total accounts receivable balance as of September 30, 2026 and December 31, 2025, respectively. Three other customers accounted for 11%,11%, and 11% of the total accounts receivable balance as of September 30, 2026 and 4%,2%, andnil of the total accounts receivable balance as of December 31, 2025, respectively.

6. Investment in Amlogenyx Inc.

In July 2024, the Company contributed certain intellectual property rights to Amlogenyx, a subsidiary of the Company, and received 9.0 million shares of common stock of Amlogenyx. A third-party investor along with one of its affiliated entities, and the

Company each contributed $7 million to Amlogenyx and in exchange, each received approximately 1.6 million shares of series seed preferred stock of Amlogenyx. The purpose of Amlogenyx is to pursue the application of the Company’s novel adeno-associated virus, or AAV, gene therapy to treat beta-amyloid disorders and related neurodegenerative diseases.

In July 2026, Amlogenyx issued two SAFEs for aggregate proceeds of $10 million. One SAFE for $5 million was issued to Dr. Emil Kakkis, the Company’s Chief Executive Officer and a related party, and one for $5 million was issued to an unaffiliated investor on the same terms. The SAFEs convert into Amlogenyx equity at a 30% discount to the price paid in Amlogenyx's next equity financing. The SAFEs have no valuation cap, no stated maturity date and carry no voting or board rights. The SAFEs are accounted for as freestanding liabilities, included in other current liabilities, and remeasured at fair value through other income. No changes in fair value were recognized during the three or nine months ended September 30, 2026.

Amlogenyx was determined to be a VIE and the Company is the primary beneficiary as it has the power to direct the activities that would most significantly impact the economic performance of Amlogenyx, including the performance of R&D activities relating to its sole product candidate. As the primary beneficiary, the Company has consolidated the financial position, results of operations and cash flows of Amlogenyx in its financial statements and all intercompany balances have been eliminated in consolidation. Upon initial consolidation, the non-controlling interest of the third-party investor was recorded at its estimated fair value of $7 million, which is equal to their original investment.

As of September 30, 2026 and December 31, 2025, the Condensed Consolidated Balance Sheets included Amlogenyx assets of $8 million and $5 million, respectively, and Amlogenyx liabilities of $11 million and a nominal amount, respectively. The assets primarily consisted of cash and cash equivalents which may only be used to settle obligations of Amlogenyx and the liabilities primarily consisted of the SAFEs.

Noncontrolling interest related to the third-party investment in Amlogenyx is reported on the Condensed Consolidated Balance Sheets in mezzanine equity.

Changes in the carrying value of noncontrolling interest for thenine months ended September 30, 2026 are as follows (in millions):

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. 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 North American 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.

The collaboration and license agreements are within the scope of ASC 808, which provides guidance on the presentation and disclosure of collaborative arrangements.

Product Sales Revenue for Latin America and Türkiye

The Company is responsible for commercializing CRYSVITA in Latin America and Türkiye. 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. In Türkiye, KKC has the option to assume responsibility for commercialization efforts.

Transfer Price and Royalties on Product Sales Revenue

Under the collaboration agreement, KKC manufactures and supplies CRYSVITA, which is purchased by the Company for sales in Latin America and Türkiye. KKC charges the Company a transfer price of 30% of net sales for supply of product to Latin America. The Company also pays to KKC a low single-digit royalty on net sales in Latin America.

Royalty Revenue for Sales in the North American Territory

KKC has commercialization responsibilities for CRYSVITA in the North American Territory. The Company is entitled to receive a tiered double-digit revenue share from the mid-20% range up to a maximum rate of 30%, which is recorded as 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 beginning in April 2023, that are due to the Company based on net sales of CRYSVITA in the U.S. and Canada, subject to a cap. In November 2025, the Company sold to OMERS its right to an additional 25% of the future royalty payments, beginning in January 2028, that are due to the Company based on net sales of CRYSVITA in the U.S. and Canada, subject to a cap. These agreements are further described in “Note 8. Liabilities for Sales of Future Royalties.”

Royalty Revenue for Sales in the European Territory

KKC has commercial responsibility for CRYSVITA in the European Territory. The Company is entitled to receive royalties of up to 10% of net sales in the European Territory, which are recorded as royalty revenue as the underlying sales occur. In December 2019, the Company sold its right to receive these royalty payments to Royalty Pharma, effective January 1, 2020, as further described in “Note 8. Liabilities for Sales of Future Royalties.”

Total CRYSVITA revenue was as follows (in millions):

Collaboration Cost Sharing and Payments

Under the collaboration agreement, KKC and the Company share certain development and commercialization costs, and as a result, the Company was reimbursed for these costs and operating expenses were reduced. KKC also receives a transfer price and royalty on net product sales revenue which is recorded in cost of sales. These amounts were recognized in the Company’s Condensed Consolidated Statements of Operations in connection with the collaboration agreement with KKC as follows (in millions):

Collaboration Receivable and Payable

The Company had accounts receivable from KKC in the amount of $60 million and $98 million from royalties, other receivables of $1 million and $1 million recorded in other current assets, and accrued liabilities of $12 million and $12 million from amounts owed for transfer price and royalties as well as commercial and development activity reimbursements, as of September 30, 2026 and December 31, 2025, respectively.

Regeneron

In January 2022, the Company entered into a collaboration with Regeneron to commercialize EVKEEZA for HoFH outside of the U.S. 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 paid Regeneron a $30 million upfront payment. As of September 30, 2026, the Company has recognized an aggregate of $33 million for regulatory and sales milestones under the agreement. As these payments are for the Company’s use of intellectual property for EVKEEZA for HoFH, they were recorded as intangible assets. The Company is required to pay up to an aggregate of $31 millionin the future contingent upon the achievement of certain regulatory andsales milestones. The Company may share in certain costs for global trials led by Regeneron. Additionally, the Company pays Regeneron a product purchase price and royalties on certain revenues.

The collaboration agreement is within the scope of ASC 808, which provides guidance on the presentation and disclosure of collaborative arrangements. As the Company is the principal in sales transactions with the customer, the Company recognizes 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 product purchase 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. The Company also shares certain development and commercialization costs. Amounts recognized in connection with the collaboration agreement with Regeneron were recognized in the Company’s Condensed Consolidated Statements of Operations as follows (in millions):

The Company had collaboration payables for this arrangement included in accrued liabilities on the Condensed Consolidated Balance Sheets of $7 million and $9 million as of September 30, 2026 and December 31, 2025, respectively.

GeneTx Biotherapeutics LLC

In August 2019, the Company entered into a Program Agreement and a Unitholder Option Agreement with GeneTx Biotherapeutics LLC, or GeneTx, as subsequently amended, or the Option Agreement, to collaborate on the development of GeneTx’s GTX-102, an ASO for the treatment of Angelman syndrome. In July 2022, the Company exercised its option to acquire GeneTx, pursuant to the terms of the Option Agreement. During the year ended December 31, 2024, the Company achieved a $30 million regulatory milestone which was classified as in-process research and development expense, as the acquired in-process research and development intangible asset has not yet reached technological feasibility and has no alternative future use. In September 2026, the Company announced the Phase 3 study for Angelman syndrome did not achieve its primary or secondary endpoints, therefore the Company is in the process of winding down the program. The Company does not expect to make any future payments to GeneTx.

Mereo

In December 2020, the Company entered into a License and Collaboration Agreement with Mereo to collaborate on the development of setrusumab and made a payment of $50 million to Mereo on closing of the transaction. As of September 30, 2026, the Company has recognized an aggregate of $9 million for regulatory milestones achieved.

In December 2024, the Company entered into a manufacturing and supply agreement with Mereo where it is responsible for the supply of setrusumab to Mereo in the Mereo territory. Mereo is responsible for reimbursing the Company for a portion of the manufacturing process development costs as well as future commercial supply costs.

Although Mereo is a VIE, 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.

The Company recorded offsets to research and development expense under this arrangement of a nominal amount and $2 million for the three andnine months ended September 30, 2026, respectively, and $2 million and $4 million for the three andnine months ended September 30, 2025, respectively.

The Company had receivables from Mereo in a nominal amount and $1 million recorded in other current assets as of September 30, 2026 and December 31, 2025, 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 three and nine months ended September 30, 2026 as compared to those disclosed in "Note 8. License and Research Agreements" to the Consolidated Financial Statements in the Annual Report.

Underthe 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 reflectedin the financial statements 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.

8. Liabilities for Sales of Future Royalties

The Company has entered into certain royalty purchase agreements pursuant to which it sold interests in certain future royalty payments arising from net sales of CRYSVITA in specified territories upon payment of the specified consideration. The agreements will automatically terminate and the payments or royalties will cease once the aggregate payments as specified in the agreement, or the cap, are reached.

The following table summarizes the key terms and activity to date for these arrangements (in millions except percentages):

Under the 2025 OMERS agreement, OMERS granted the Company an option to repurchase the entire purchased interest that expires in November 2027, for 1.35 times the purchase price, or $540 million.

Proceeds from these transactions, net of transaction costs, were recorded as liabilities for sales of future royalties on the Condensed Consolidated Balance Sheets. 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.

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 millions):

9. Stock-Based Awards

As of September 30, 2026, there were 6.7 million shares available under the 2023 Incentive Plan,6.1 million shares available under the Amended & Restated 2014 Employee Stock Purchase Plan, and 0.6 million 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 millions):

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, pre-funded warrants, and 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 outstanding, pre-funded warrants, and 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:

11. Equity

At-the-Market Offerings

In February 2024, the Company entered into a Sales Agreement with Cowen and Company, LLC, or Cowen, pursuant to which the Company may offer and sell shares of the Company’s common stock having an aggregate offering proceeds up to $350 million, from time to time, in at-the-market, or ATM, offerings through Cowen. During the three andnine months ended September 30, 2026, no shares were sold under the ATM. The Company soldnil and 2.2 million shares under the ATM for net proceeds ofnil and $80 million during the three and nine months ended September 30, 2025, respectively. To date, the Company has sold 2.2 million shares under the ATM for net proceeds of $80 million.

Exercise of Pre-Funded Warrants

In connection with the Company’s October 2023 and June 2024 public offerings, certain investors purchased pre-funded warrants to acquire common stock at an exercise price of $0.001 per share. In September 2026, all outstanding pre-funded warrants were exercised on a cashless basis, resulting in the issuance of 3.2 million shares of common stock; no pre-funded warrants remained outstanding as of September 30, 2026. The warrants were classified as permanent equity, and the underlying shares were included in basic and diluted weighted-average shares outstanding because they were issuable for little or no consideration.

12. Accumulated Other Comprehensive (Loss) Income

Total accumulated other comprehensive (loss) income consisted of the following (in millions):

13. Strategic Restructuring Plan

In February 2026, the Company implemented a strategic restructuring plan designed to reduce operating expenses and focus resources on its highest value drivers. The restructuring plan included a reduction in workforce and the curtailment of certain operating activities, including UX143 manufacturing activities. As part of the restructuring, the Company reduced its workforce by approximately 10%. The workforce reduction was substantially completed during the first quarter of 2026.

The following table presents the details of the Company’s restructuring charges and amounts paid or settled during thenine months ended September 30, 2026 (in millions):

Total restructuring charges recognized on the Condensed Consolidated Statements of Operations during the three andnine months ended September 30, 2026 were as below (in millions):

14. Subsequent Events

Sale of Priority Review Vouchers

In October 2026, the Company entered into agreements to sell the PRVs received upon FDA approval of GENGLYCOS and FAYUVI for $210 million and $203 million, respectively. The sale of the GENGLYCOS PRV closed in October 2026. The Company is obligated to pay the National Institutes of Health, or NIH, $42 million from the sale of the PRV received from GENGLYCOS approval pursuant to the terms of a license agreement with the NIH. The Company expects to reflect net proceeds of $164 million, after payment to NIH and related fees. The closing of the FAYUVI PRV sale is expected to occur by year end 2026, subject to satisfaction of customary closing conditions, including the expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976. The Company is also obligated to pay to a third-party licensor $16 million from the sale of the PRV received upon FDA approval of FAYUVI per the terms of a license agreement entered into on October 26, 2026, pursuant to which the Company obtained an exclusive license, in the field of MPS IIIA, to certain of the licensor’s patents and patent applications. The Company expects to receive net proceeds of $185 million upon the closing of the FAYUVI PRV sale.

Restructuring Plan

In October 2026, the Company’s Board of Directors approved a restructuring plan that includes a reduction of approximately 20% of the Company’s workforce. As a result of this reduction in force, the Company estimates that it will incur restructuring charges of approximately $25 million in total in connection with employee related termination and severance costs and other activities.