PROTHENA CORP PUBLIC LTD CO

Previous wording

Fueled by our deep scientific expertise built over decades of research, we are advancing a pipeline of therapeutic candidates for a number of indications and novel targets for which our ability to integrate scientific insights around neurological dysfunction and the biology of misfolded proteins can be leveraged. Our wholly-owned programs include birtamimab for the potential treatment of AL amyloidosis, and a portfolio of programs for the potential treatment of Alzheimer’s disease including PRX012, which targets amyloid beta (Aβ), and PRX123, a novel dual Aβ-tau vaccine. Our partnered programs include prasinezumab for the potential treatment of Parkinson’s disease and other related synucleinopathies that targets alpha-synuclein in collaboration with Roche. In addition, we have partnered BMS-986446 (formerly PRX005) for the potential treatment for Alzheimer’s disease that targets tau and PRX019 for the potential treatment of neurodegenerative diseases with an undisclosed target in two separate license agreements with Bristol Myers Squibb (BMS). We are also entitled to certain potential milestone payments pursuant to our share purchase agreement with Novo Nordisk pertaining to our ATTR amyloidosis business (inclusive of coramitug, formerly PRX004).

Current wording

Fueled by our deep scientific expertise built over decades of research, we are advancing a pipeline of therapeutic candidates for a number of indications and novel targets for which our ability to integrate scientific insights around neurological dysfunction and the biology of misfolded proteins can be leveraged. These programs include prasinezumab for the potential treatment of Parkinson’s disease and other related synucleinopathies that targets alpha-synuclein in collaboration with Roche. In addition, we have partnered BMS-986446 (formerly PRX005) for the potential treatment for Alzheimer’s disease that targets tau and PRX019 for the potential treatment of neurodegenerative diseases with an undisclosed target in two separate license agreements with Bristol Myers Squibb (BMS). We are also entitled to certain potential milestone payments pursuant to our share purchase agreement with Novo Nordisk pertaining to our ATTR amyloidosis business (inclusive of coramitug, formerly PRX004). Our wholly-owned and unpartnered portfolio includes clinical and preclinical-stage programs that we are exploring strategic interest to further develop.

Previous wording

Significant judgment is required to apply the authoritative accounting guidance at the outset of a collaboration arrangement, and over time. Our Collaboration Agreement with BMS and our License Agreement with Roche contain multiple performance obligations. In the identification of performance obligations, there is judgment involved in identifying the promised goods or services in the collaboration agreement, determining whether these are distinct in the context of the contract, and determining if these represent a performance obligation to a customer. These determinations are highly subjective and can differ between arrangement based on specific contractual terms. The identified performance obligations will impact most significantly the timing of revenue recognition, and is a point-in-time assessment performed at the outset of a collaboration arrangement. We account for the individual performance obligations separately if they are distinct. Factors considered in the determination of whether the license performance obligations are distinct included, among other things, the research and development capabilities of each of BMS and Roche and their respective sublicense rights, and for the remaining performance obligations the fact that they are not proprietary and can be and have been provided by other vendors. The transaction price is allocated to the separate performance obligation on a relative standalone selling price basis.

Current wording

Significant judgment is required to apply the authoritative accounting guidance at the outset of a collaboration arrangement, and over time. Our Collaboration Agreement with BMS and our License Agreement with Roche contained multiple performance obligations. In the identification of performance obligations, there is judgment involved in identifying the promised goods or services in the collaboration agreement, determining whether these are distinct in the context of the contract, and determining if these represent a performance obligation to a customer. These determinations are highly subjective and can differ between arrangement based on specific contractual terms. The identified performance obligations will impact most significantly the timing of revenue recognition, and is a point-in-time assessment performed at the outset of a collaboration arrangement. We account for the individual performance obligations separately if they are distinct. Factors considered in the determination of whether the license performance obligations are distinct included, among other things, the research and development capabilities of each of BMS and Roche and their respective sublicense rights, and for the remaining performance obligations the fact that they are not proprietary and can be and have been provided by other vendors. The transaction price is allocated to the separate performance obligation on a relative standalone selling price basis.

Previous wording

At the inception of each arrangement that includes developmental, regulatory or commercial milestone payments, we evaluate whether achieving the milestones is considered probable and estimate the amount to be included in the transaction price using the most likely amount method, which includes judgment. If it is probable that a significant revenue reversal would not occur, the value of the associated milestone (such as a regulatory submission by Prothena) is included in the transaction price. Milestone payments that are not within our control, such as approvals from regulators or where attainment of the specified event is dependent on the development activities of a third party, are not considered probable of being achieved until those approvals are received or the specified event occurs. In general, we consider such milestone payments as variable consideration with constraint and therefore we recognize the revenue from such milestone payments as collaboration revenue at point in time when we can conclude it is probable that a significant revenue reversal will not occur in future periods.

Current wording

At the inception of each arrangement that includes developmental, regulatory or commercial milestone payments, we evaluate whether achieving the milestones is considered probable and estimate the amount to be included in the transaction price using the most likely amount method, which includes judgment. If it is probable that a significant revenue reversal would not occur, the value of the associated milestone (such as a regulatory submission by Prothena) is included in the transaction price. Milestone payments that are not within our control, such as approvals from regulators or where attainment of the specified event is dependent on the development activities of a third party, are not considered probable of being achieved until those approvals are received or the specified event occurs. In general, we consider such milestone payments as variable consideration with constraint and therefore we recognize the revenue from such milestone payments as collaboration revenue at the point in time when we can conclude it is probable that a significant revenue reversal will not occur in future periods.

Previous wording

Consolidated Balance Sheets. The level of judgment required to estimate research and development expenses varies based on the nature of the services being performed and the underlying support obtained. We recognize costs for certain development activities, such as clinical trials, based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, or information provided to us by our vendors on their actual costs incurred. We recognize costs for contract manufacturing based on evaluation of the progress to completion of specific tasks. As such, expense accruals related to clinical trialsand contract manufacturing are recognized based on our estimate of the degree of completion of the events specified in the specific clinical study or trial contract or drug development and manufacturing contract, respectively. We estimate the amount of work completed through discussions with internal personnel and external service providers as to the progress or stage of completion of the services and the agreed-upon fee to be paid for such services. As actual costs become known, we adjust our accrued estimates. These estimates are based on certain assumptions and inputs that can be challenging to assess, including the evaluation of the status of and costs incurred for manufacturing activities, outsourced research and development programs and project milestones achieved. Although we do not expect our estimates to be materially different from amounts actually incurred, incomplete or inaccurate data from vendors could impact our understanding of the status and timing of services performed which could result in us reporting expenses that are too high or too low in any particular period.

Current wording

We expense R&D costs as incurred. R&D expenses include, but are not limited to, salary and benefits, share-based compensation, clinical trial activities, drug development and manufacturing prior to FDA approval and third-party service fees, including clinical research organizations, investigative sites and contract manufacturing organizations. A significant portion of our research and development expenses in the Consolidated Statements of Operations are external costs, which we track on a program-specific basis when the applicable program was separately tracked in preclinical development. These research and development expenses include the conduct of preclinical studies and clinical trials, contract manufacturing activities and consulting services. The measurement of these research and development costs and/or effort can impact the research and development expenses in the Consolidated Statements of Operations and of prepaid assets and accrued liabilities on the Consolidated Balance Sheets. The level of judgment required to estimate research and development expenses varies based on the nature of the services being performed and the underlying support obtained. We recognize costs for certain development activities, such as clinical trials, based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, or information provided to us by our vendors on their actual costs incurred. We recognize costs for contract manufacturing based on evaluation of the progress to completion of specific tasks. As such, expense accruals related to clinical trialsand contract manufacturing are recognized based on our estimate of the degree of completion of the events specified in the specific clinical study or trial contract or drug development and manufacturing contract, respectively. We estimate the amount of work completed through discussions with internal personnel and external service providers as to the progress or stage of completion of the services and the agreed-upon fee to be paid for such services. As actual costs become known, we adjust our accrued estimates. These estimates are based on certain assumptions and inputs that can be challenging to assess, including the evaluation of the status of and costs incurred for manufacturing activities, outsourced research and development programs and project milestones achieved. Although we do not expect our estimates to be materially different from amounts actually incurred, incomplete or inaccurate data from vendors could impact our understanding of the status and timing of services performed which could result in us reporting expenses that are too high or too low in any particular period.

Previous wording

Collaboration revenue from BMS increased $43.8 millionfor the year ended December 31, 2024, compared tothe year ended December 31, 2023. Collaboration revenue from BMS for 2024 included recognition of $110.1 million from the PRX019 Global License Agreement and related development services and $25.0 millionwas related to BMS’s material rights for the US Rights and Global Rights for the TDP-43 Collaboration Target that expired unexercised as a result of the expiration of the research term of the Collaboration Agreement. Collaboration revenue from BMS for 2023 included recognition of$91.3 million from the Tau Global License Agreement and related development services. See Note 7, “Significant Agreements” to the Consolidated Financial Statements regarding the Collaboration Agreement with BMS for more information.

Current wording

Collaboration revenue from BMSwas$9.6 million for theyear ended December 31, 2025, compared to$135.1 millionfor theyear ended December 31, 2024, a decrease of $125.5 million compared tothe prior year. Collaboration revenue for theyear ended December 31, 2025 was related to the partial performance of our PRX019 Phase 1 Clinical Trial Obliga tion. Collaboration revenue from BMS for 2024 included recognition of $110.1 million from the PRX019 Global License Agreement and related development services and $25.0 millionwas related to BMS’s material rights for the US Rights and Global Rights for the TDP-43 Collaboration Target that expired unexercised as a result of the expiration of the research term of the Collaboration Agreement. See Note 7, “Significant Agreements” to the Consolidated Financial Statements regarding the Collaboration Agreement with BMS for more information.

Previous wording

Total operating expenses consist of R&D expenses, general and administrative (“G&A”) expenses. Our operating expenses were $289.7 million and$282.4 million for the years ended December 31, 2024, and 2023, respectively.

Current wording

Total operating expenses consist of research and development (“R&D”) expenses, general and administrative (“G&A”) expenses, and restructuring costs. Our operating expenses were $224.3 million and$289.7 million for the years ended December 31, 2025, and 2024, respectively.

Previous wording

Our research activities are aimed at developing new drug products. Our development activities involve the translation of our research into potential new drugs. Our R&D expenses primarily consist of personnel costs and related expenses, including share-based compensation and external costs associated with clinical activities and drug development related to our drug programs, including birtamimab, BMS-986446 (PRX005), PRX012, PRX123, PRX019 and preclinical activities related to our discovery programs.

Current wording

Our research activities are aimed at developing new drug products. Our development activities involve the translation of our research into potential new drugs. Our R&D expenses primarily consist of personnel costs and related expenses, including share-based compensation and external costs associated with clinical activities and drug development related to our drug programs, and preclinical activities related to our discovery programs. We also incurred wind down costs for programs that we are no longer advancing in clinical development, including birtamimab and PRX012.

Previous wording

Our R&D expense increased by $1.9 million for the year ended December 31, 2024, compared to the prior year. The increase for the year ended December 31, 2024, was primarily due to higher clinical trial expenses primarily related to the PRX012 and birtamimab programs, higher personnel expenses; offset in part by lower manufacturing expense and lower other R&D expenses.

Current wording

Our R&D expense decreased by $87.7 million for the year ended December 31, 2025, compared to the prior year. The decrease for the year ended December 31, 2025, was primarily dueto lower clinical trial expenses primarily related to PRX012 wind down, lower personnel expenses and lower manufacturing and consulting expenses.

Previous wording

The following table sets forth the R&D expenses for our major programs (specifically, any active program with successful first dosing in a Phase 1 clinical trial), which were birtamimab, prasinezumab, coramitug, BMS-986446 (PRX005), PRX012, PRX019 and other R&D expenses for the years ended December 31, 2024, and 2023 (in thousands):

Current wording

The following table sets forth the R&D expenses for our major programs (specifically, programs with successful first dosing in a Phase 1 clinical trial and have material expenditures in the periods presented), which were birtamimab, PRX012, PRX019, and other R&D expenses for the years ended December 31, 2025, and 2024, (in thousands):

Previous wording

(3) Other R&D is comprised primarily of preclinical development and discovery programs that have not progressed to first patient dosing in a Phase 1 clinical trial and close out costs for programs that we are no longer advancing.

Current wording

(2) Other R&D is comprised primarily of preclinical development and discovery programs that have not progressed to first patient dosing in a Phase 1 clinical trial, close out costs for programs that we are no longer advancing, and immaterial costs incurred on ongoing partnered programs.

Previous wording

Our G&A expe nses increased by $5.4 million, for theyear ended December 31, 2024, compared to the prior year primarily due to higher personnel expense.

Current wording

Our G&A expe nses decreased by $7.8 million, for theyear ended December 31, 2025, compared to the prior year primarily due to lower personnel and consulting expenses.

Previous wording

Interest income decreased by $5.2 million for the year ended December 31, 2024, compared to the prior year, primarily due to lower interest income from our cash and money market accounts resulting from lower interest rates and lower cash and money market balances.

Current wording

Interest income decreased by $11.7 million for the year ended December 31, 2025, compared to the prior year, primarily due to lower interest income from our cash and money market accounts resulting from lower interest rates and lower cash and money market balances.

Previous wording

Other income (expense), net for the year ended December 31, 2024, was primarily foreign exchange losses from transactions with vendors denominated in euros.

Current wording

Other expense, net for the year ended December 31, 2025, was primarily foreign exchange losses from transactions with vendors denominated in euros.

Previous wording

The tax provisions for all periods presented primarily reflect U.S. federal taxes associated with recurring profits attributable to intercompany services that our U.S. subsidiary performs for the Company. No tax benefit has been recorded related to tax losses recognized in Ireland and any deferred tax assets for those losses are offset by a valuation allowance.

Current wording

No tax benefit has been recorded related to tax losses recognized in Ireland or the U.S. and any deferred tax assets for those losses are offset by a valuation allowance.

Previous wording

Working capital was$436.9 million as of December 31, 2024, a decrease of $145.5 million from working capital of$582.4 million as of December 31, 2023. This decrease in working capital during the year ended December 31, 2024, was primarily attributable to cash useof $289.7 million for operating expenses (adjusted to exclude non-cash charges) offset in part by$80.0 million option exercise payment from BMS, interest income on investments of$25.8 million, and net proceeds received from stock option exercises of approximately$1.9 million.

Current wording

Working capital was $274.4 million as of December 31, 2025, a decrease of $162.6 million from working capital of $436.9 million as of December 31, 2024. This decrease in working capital during the year ended December 31, 2025, was primarily attributable to cash used in operating activities of $163.6 million.

Previous wording

As of December 31, 2024, we had $471.4 million in cash and cash equivalents. Based on our current business plans, we believe that our existing cash and cash equivalents at December 31, 2024 are sufficient to meet our obligations for at least the next twelve months. To operate beyond such period, or if we elect to increase our spending on research and development programs significantly above current long-term plans or enter into potential licenses and/or other acquisitions of complementary technologies, products or companies, we may need additional capital. Additionally, in order to develop and obtain regulatory approval for our potential products we will need to raise substantial additional capital. We expect to continue to finance future capital needs that exceed our existing cash and cash equivalents, payments pursuant to our agreements with Roche, BMS, and Novo Nordisk, and, to the extent necessary, other collaboration agreements with corporate partners, or other arrangements, and through proceeds from public or private equity or debt financings, and loans, including pursuant to the Amended Distribution Agreement (See Note 8, “Shareholders’ Equity” to the Consolidated Financial Statements for more information). We cannot assume that such additional financings will be available on acceptable terms, if at all, and such financings may only be available on terms dilutive to our shareholders.

Current wording

As of December 31, 2025, we had $307.5 million in cash and cash equivalents. Based on our current business plans, we believe that our existing cash and cash equivalents at December 31, 2025 are sufficient to meet our obligations for at least the next twelve months. To operate beyond such period, or if we elect to increase our spending on research and development programs significantly above current long-term plans or enter into potential licenses and/or other acquisitions of complementary technologies, products or companies, we may need additional capital. Additionally, in order to develop and obtain regulatory approval for our potential products we will need to raise substantial additional capital. We expect to continue to finance future capital needs that exceed our existing cash and cash equivalents, payments pursuant to our agreements with Roche, BMS, and Novo Nordisk, and, to the extent necessary, other collaboration agreements with corporate partners, or other arrangements, and through proceeds from public or private equity or debt financings, and loans, including pursuant to the Amended Distribution Agreement (See Note 8, “Shareholders’ Equity” to our Consolidated Financial Statements for more information). We cannot assume that such additional financings will be available on acceptable terms, if at all, and such financings may only be available on terms dilutive to our shareholders.

Previous wording

In managing our liquidity needs in Ireland, we do not rely on unrepatriated earnings as a source of funds. As of December 31, 2024, $265.3 million of our outstanding cash and cash equivalents related to U.S. operations are considered permanently reinvested. We do not intend to repatriate these funds. However, if these funds were repatriated back to Ireland, we would incur a withholding tax from the dividend distribution.

Current wording

In managing our liquidity needs in Ireland, we do not rely on unrepatriated earnings as a source of funds. As of December 31, 2025, $232.5 million of our outstanding cash and cash equivalents related to U.S. operations are considered permanently reinvested. We do not intend to repatriate these funds. However, if these funds were repatriated back to Ireland, we would incur a withholding tax from the dividend distribution.

Previous wording

The adequacy of our cash resources depends on many assumptions, including assumptions with respect to our expenses. These assumptions may prove to be wrong, and we could use our available capital resources sooner than we currently expect. Because of the numerous risks and uncertainties associated with the development and commercialization of our product candidates, we are unable to estimate the amounts of increased capital outlays and operating expenses associated with completing the development of our product candidates. Our future capital requirements will depend on numerous factors, including, without limitation, the timing of initiation, progress, results and costs of our clinical trials; the results of our research and nonclinical studies; the costs of clinical manufacturing and of establishing commercial manufacturing arrangements; the costs of preparing, filing and prosecuting patent applications and maintaining, enforcing and defending intellectual property-related claims; the costs and timing of capital asset purchases; our ability to establish research collaborations, strategic collaborations, licensing or other arrangements; the costs to satisfy our obligations under current and potential future collaborations; the costs of any in-licensing transactions; and the timing, receipt, and amount of revenues or royalties, if any, from any approved drug candidates.

Current wording

The adequacy of our cash resources depends on many assumptions, including assumptions with respect to our expenses. These assumptions may prove to be wrong, and we could use our available capital resources sooner than we currently expect. Because of the numerous risks and uncertainties associated with the development of our product candidates, we are unable to estimate the amounts of increased capital outlays and operating expenses associated with completing the development of our product candidates. Our future capital requirements will depend on numerous factors, including, without limitation, the timing of initiation, progress, results and costs of our clinical trials; the results of our research and nonclinical studies; the costs of clinical manufacturing; the costs of preparing, filing and prosecuting patent applications and maintaining, enforcing and defending intellectual property-related claims; the costs and timing of capital asset purchases; our ability to establish research collaborations, strategic collaborations, licensing or other arrangements; the costs to satisfy our obligations under current and potential future collaborations; the costs of any in-licensing transactions; and the timing, receipt, and amount of revenues or royalties, if any, from any approved drug candidates.

Previous wording

Net cash used in operating activities was $150.1 million for the year ended December 31, 2024, which was primarily due to ongoing research and development activities and general and administrative expenses to support those activities for a total of $289.7 million in operating expenses (adjusted to exclude non-cash charges of approximately $40.2 million) partially offset by$80.0 million option exercise payment from BMS, interest income on investments of $25.8 million, and cash from collection of accounts receivable of $5.2 million.

Current wording

Net cash used in operating activities was$163.6 million for the year ended December 31, 2025, which was primarily due to ongoing research and development activities, general and administrative expenses to support those activities (adjusted to exclude non-cash charges for share-based compensation expense) and payments related to our restructuring activities, partially offset byinterest income on investments.

Previous wording

Net cash used in investing activities was $0.3 million for the year ended December 31, 2024, which primarily consisted of expenditures to purchase property and equipment.

Current wording

Net cash used in investing activities was$138 thousand for the year ended December 31, 2025, which consisted of expenditures to purchase property and equipment.

Previous wording

Refer to “Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations — Liquidity and Capital Resources” in our 2023 Annual Report on Form 10-K for a discussion of the cash flows for the years ended December 31, 2023 and 2022.

Current wording

Refer to “Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations — Liquidity and Capital Resources” in our 2024 and 2023 Annual Report on Form 10-K for a discussion of the cash flows for the years ended December 31, 2024 and 2023, respectively.

Previous wording

Our contractual obligations as of December 31, 2024, consisted of minimum cash payments under operating leases of $12.1 million, purchase obligations of $12.7 million (of which $1.8 million is included in current liabilities), and contractual obligations under license agreements of $0.3 million (of which nil is included in current liabilities). Purchase obligations consist of non-cancelable purchase commitments to suppliers. Operating leases represent our future minimum rental commitments under our non-cancelable operating leases. For additional information regarding the timing for our contractual obligations see Note 6, “Commitments and Contingencies” to Consolidated Financial Statements.

Current wording

Our contractual obligations as of December 31, 2025, consisted of minimum cash payments under operating leases of $9.1 million, purchase obligations of $3.1 million (of which $2.7 million is included in current liabilities), obligations under our restructuring plan of $13.3 million (of which all of it is included in current liabilities), and contractual obligations under license agreements of $50 thousand. Purchase obligations consist of non-cancelable purchase commitments to suppliers. Operating leases represent our future minimum rental commitments under our non-cancelable operating leases. For additional information regarding the timing for our contractual obligations see Note 6, “Commitments and Contingencies” to our Consolidated Financial Statements.

Previous wording

In October 2022, we entered into a noncancelable operating sublease to lease approximately 31,157 square feet of office and laboratory space in Brisbane, California. We are obligated to make lease payments totaling approximately $14.9 million over the lease term, which expires on September 30, 2028, unless terminated earlier. Of this obligation, approximately$12.0 million remains outstanding as of December 31, 2024.

Current wording

In October 2022, we entered into a noncancelable operating sublease to lease approximately 31,157 square feet of office and laboratory space in Brisbane, California. We are obligated to make lease payments totaling approximately $14.9 million over the lease term, which expires on September 30, 2028, unless terminated earlier. Of this obligation, approximately $9.0 million remains outstanding as of December 31, 2025

Previous wording

In addition to the contractual obligations above, we also expect to have future material cash requirements related to ourclinical trials, discovery and pre-clinical programs, human capital and intellectual property. Assuming no significant change in our business, we expect the full year 2025 net cash used in operating and investing activities to be approximately $168 million to $175 million.

Current wording

In addition to the contractual obligations above, we also expect to have future material cash requirements related to our clinical trials, discovery and pre-clinical programs, human capital and intellectual property. Assuming no significant change in our business, we expect the full year 2026 net cash used in operating and investing activities to be approximately $50 million to $55 million.