PROTHENA CORP PUBLIC LTD CO
For the period ended Sep 30, 2025. Filed Nov 6, 2025.
View on SEC.govAbout this filing
A company's report for each of its first three quarters. The financial statements are not audited. It shows how the business has moved since the last annual report, and what management says changed.
Sep 30, 2025 · Filed Nov 6, 2025
PRTA$7.97+1.0%Stored close · as of Nov 6, 2026
What changed in Management’s Discussion and Analysis?
Read the current filingPrevious report: 10-Q
Period ended 2025-06-30; filed 2025-08-04.
0001559053-25-000031
Item 2. MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONSCurrent report: 10-Q
Period ended 2025-09-30; filed 2025-11-06.
0001559053-25-000044
Item 2. MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONSThe baseline is this issuer’s latest earlier reporting period of the same form that was filed before the current report. A previous 10-Q is a different quarter, not a year-over-year comparison. Amendments are excluded.
Compared 116 previous paragraphs and 110 current paragraphs.
65 unchanged; 37 reworded; 8 added; 13 removed; 1 previous and 0 current paragraphs rearranged.
Tables are not compared: 12 previous and 12 current tables excluded. Dates, whitespace, punctuation and numbering changes are ignored; changes to financial figures remain significant.
A changed paragraph is not evidence that risk increased or decreased. An unchanged paragraph does not establish that risk stayed the same.
Added paragraphs (8)
Current report
Phase 3 PARAISO Clinical Trial
Current report
PARAISO is a Phase 3, randomized, double-blind, placebo-controlled, multicenter clinical trial to evaluate the efficacy and safety of prasinezumab in approximately 900 participants with early-stage Parkinson's disease on stable symptomatic monotherapy with levodopa. Primary endpoint of the trial is time to confirmed motor progression event on Movement Disorder Society - Unified Parkinson’s Disease Rating Scale (“MDS-UPDRS”) Part III score with a timeframe of at least 104 weeks.
Current report
Phase 3 CLEOPATTRA Clinical Trial
Current report
In September 2025, Novo Nordisk initiated the Phase 3 CLEOPATTRA clinical trial evaluating coramitug as a potential treatment for ATTR-CM. CLEOPATTRA is a randomized, double-blind, placebo-controlled, multicenter clinical trial in approximately 1,280 participants with ATTR-CM. Primary endpoint is the number of occurrences of composite endpoint of cardiovascular (CV) deaths and recurrent CV events (CV hospitalizations and urgent heart failure visits) in a timeframe to end of study up to approximately four years.
Current report
Phase 2 Target Tau-1 Clinical Trial
Current report
If promising, we expect to advance our discovery programs into early preclinical development while exploring strategic interest for further development, if appropriate.
Current report
On July 4, 2025, the One Big Beautiful Bill Act (“OBBBA”) was signed into law. The OBBBA includes a broad range of U.S. tax reform measures, including, among other provisions, the immediate expensing of U.S. research and development expenditures. In accordance with ASC 740, the Company has recognized the effects of the new tax law in the period of enactment. As the Company maintains a full valuation allowance on its deferred tax assets, the legislation does not have a material impact on our consolidated financial statements for the period ended September 30, 2025.
Current report
Nine Months Ended September 30, 2024
Removed paragraphs (13)
Previous report
PRX012 for the Potential Treatment of Alzheimer’s Disease
Previous report
PRX012 is an investigational antibody that targets Aβ, or amyloid beta, a protein implicated in Alzheimer’s disease. Our scientists have advanced the understanding of the biology of Alzheimer’s disease and made particularly impactful and fundamental discoveries that elucidated the role amyloid plays in the disease.
Previous report
Monoclonal antibodies targeting key epitopes within the N-terminus of Aβ have demonstrated that reducing amyloid plaque burden is associated with the slowing of clinical decline in Alzheimer’s disease. To address the growing prevalence of Alzheimer’s disease with a therapeutic that can be made widely accessible to patients, we have developed highly potent anti-Aβ antibodies that retain or improve key attributes that are thought to underlie the observed efficacy of N-terminally directed therapeutics such as aducanumab, with the aim of offering similar or improved efficacy with convenient subcutaneous dosing regimens. In preclinical studies, our antibodies demonstrated a higher binding strength to amyloid than aducanumab; specifically, our lead candidate with an approximately 10-fold greater affinity/avidity for fibrillar Aβ than aducanumab that also neutralized soluble, toxic (i.e., oligomeric) Aβ species. Preclinical studies also showed that our antibodies recognize Aβ pathology to a greater extent than aducanumab, demonstrating more extensive plaque area binding at lower antibody concentrations, which are estimated to be clinically relevant exposures in the central nervous system following systemic dosing.
Previous report
We are advancing our lead candidate, PRX012, as a next-generation approach for subcutaneous administration to address the unmet need of millions of patients with presymptomatic or early symptomatic Alzheimer's disease. In March 2022, we announced the FDA clearance of the IND for PRX012 and the initiation of a Phase 1 single ascending dose trial to investigate the safety, tolerability, immunogenicity, and pharmacokinetics of PRX012 in both healthy volunteers and patients with Alzheimer’s disease. In April 2022, we announced that the FDA granted Fast Track designation for PRX012 for the treatment of Alzheimer’s disease. The FDA’s Fast Track designation program is designed to expedite the development and review of drugs intended to treat a serious condition, such as Alzheimer’s disease, with evidence demonstrating the potential to address an unmet medical need. In January 2024, we announced that topline Phase 1 data from the single ascending dose trial and the initial multiple dose cohort (70 mg) supports single-injection once-monthly subcutaneous treatment and dose escalation. The ongoing Phase 1 trial continues as planned and we expect to report initial data in August 2025. Following the data from the Phase 1 ASCENT clinical trials, we will look to advance PRX012 through non-dilutive and capital efficient structures.
Previous report
PRX123, a Dual Aβ-Tau Vaccine for the Potential Treatment and Prevention of Alzheimer’s Disease
Previous report
We are developing a dual vaccine, PRX123, which concomitantly targets key epitopes within both the Aβ and tau proteins. Preclinical models suggest that Aβ and tau act synergistically in the development of Alzheimer’s disease; however, the majority of vaccines and passive immunotherapies under development today target only one of these two pathological features.
Previous report
PRX123 is being developed for the potential prevention and treatment of Alzheimer’s disease. In preclinical studies, PRX123 has generated polyclonal responses against key epitopes within the N-terminal of Aβ and a key region of tau to promote amyloid clearance and blockade of tau transmission. Immunohistochemistry using sera from immunized animals demonstrated an appropriate and balanced immune response with antibodies that react to both Aβ plaques and tau tangles at concentrations expected to be reached in CNS following immunization and resultant titer generation.
Previous report
In March 2022, we delivered an oral presentation at AD/PD 2022 on preclinical data demonstrating that PRX123 generated anti-Aβ and anti-tau antibodies to enable phagocytosis of Aβ and to neutralize tau. These findings provided proof of concept in multiple preclinical species.
Previous report
In January 2024, we announced that the FDA has cleared the IND application for PRX123 and granted PRX123 Fast Track designation. We expect to advance PRX123 through non-dilutive and capital efficient structures.
Previous report
If promising, we expect to advance our discovery programs into preclinical development. New target discovery will focus on areas where we can bring potential new therapies to patients expeditiously through our internal expertise and resources. Existing late discovery-stage or preclinical-stage programs may be partnered or out-licensed.
Previous report
n/m = not meaningful
Previous report
On July 4, 2025, the United States enacted tax reform legislation through the One Big Beautiful Bill Act. As a result of the enactment of the legislation, the Company expects a decrease to its tax expense during the remainder of the year, primarily related to changes in the capitalization requirements of domestic research and development activities.
Previous report
Six Months Ended June 30, 2024
Reworded paragraphs (37)
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 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
In June 2025, Roche announced that it will advance prasinezumab into Phase 3 development for early-stage Parkinson’s disease. Roche cited that the data from the Phase 2b PADOVA study and longer-term follow-up data suggest clinical benefit on top of symptomatic treatment in early-stage Parkinson’s disease.
Current wording
In June 2025, Roche announced that it will advance prasinezumab into Phase 3 development and plans to initiate the Phase 3 PARAISO clinical trial evaluating prasinezumab for early-stage Parkinson’s disease by the end of 2025. Roche cited that the data from the Phase 2b PADOVA study and longer-term follow-up data suggest clinical benefit on top of symptomatic treatment in early-stage Parkinson’s disease.
Previous wording
In December 2024, topline results were announced from the Phase 2b clinical trial (PADOVA) conducted by partner Roche investigating prasinezumab in 586 people with early-stage Parkinson’s disease, treated for a minimum of 18 months while on stable symptomatic treatment. In April 2025, results from the Phase 2b PADOVA trial were presented for the first time in an oral presentation by Roche at the International Conference on Alzheimer’s and Parkinson’s Diseases (“AD/PD 2025”). Prasinezumab showed potential clinical effect in the primary endpoint of time to confirmed motor progression, as assessed by ≥5 point increase in Movement Disorder Society – Unified Parkinson’s Disease Rating Scale (“MDS-UPDRS”) Part III score from baseline, with a HR=0.84 [0.69-1.01] and p=0.0657. The effect of prasinezumab was more pronounced in a pre-specified analysis in the population treated with levodopa (75% of participants), HR=0.79 [0.63-0.99] and nominal p=0.0431. Pre-specified supplementary covariate-adjusted analyses of these endpoints demonstrated nominally significant effects on the primary endpoint (HR=0.81 [0.67-0.98]; nominal p=0.0334) and in the levodopa subgroup (HR=0.76 [0.61-0.95]; nominal p=0.0175). Covariates used for adjustment: medication at baseline, H&Y stage, DaT-SPECT, age, sex, baseline dependent parameter. Consistent positive trends across multiple secondary and exploratory clinical endpoints were also observed. Positive trends towards reduced motor progression at 104 weeks (two years) were observed, showing 30-40% relative reduction versus placebo across the overall and levodopa-treated populations. The PADOVA study also provided the first biomarker evidence of prasinezumab impacting the underlying disease biology. Prasinezumab continues to be well tolerated and no new safety signals were observed in the study.
Current wording
In December 2024, topline results were announced from the Phase 2b clinical trial (PADOVA) conducted by partner Roche investigating prasinezumab in 586 people with early-stage Parkinson’s disease, treated for a minimum of 18 months while on stable symptomatic treatment. In April 2025, results from the Phase 2b PADOVA trial were presented for the first time in an oral presentation by Roche at the International Conference on Alzheimer’s and Parkinson’s Diseases (“AD/PD 2025”). Prasinezumab showed potential clinical effect in the primary endpoint of time to confirmed motor progression, as assessed by ≥5 point increase in MDS-UPDRS Part III score from baseline, with a HR=0.84 [0.69-1.01] and p=0.0657. The effect of prasinezumab was more pronounced in a pre-specified analysis in the population treated with levodopa (75% of participants), HR=0.79 [0.63-0.99] and nominal p=0.0431. Pre-specified supplementary covariate-adjusted analyses of these endpoints demonstrated nominally significant effects on the primary endpoint (HR=0.81 [0.67-0.98]; nominal p=0.0334) and in the levodopa subgroup (HR=0.76 [0.61-0.95]; nominal p=0.0175). Covariates used for adjustment: medication at baseline, H&Y stage, DaT-SPECT, age, sex, baseline dependent parameter. Consistent positive trends across multiple secondary and exploratory clinical endpoints were also observed. Positive trends towards reduced motor progression at 104 weeks (two years) were observed, showing 30-40% relative reduction versus placebo across the overall and levodopa-treated populations. The PADOVA study also provided the first biomarker evidence of prasinezumab impacting the underlying disease biology. Prasinezumab continues to be well tolerated and no new safety signals were observed in the study.
Previous wording
Prasinezumab is the first anti-alpha synuclein antibody to advance into late-stage development. In March 2022, results from the analysis of part 2 of the Phase 2 PASADENA trial of prasinezumab were presented in an oral presentation by Roche at the International Conference on Alzheimer’s and Parkinson’s Diseases (“AD/PD 2022”). Results showed that participants with Parkinson’s disease who were treated with prasinezumab for two years (early-start group) showed slower decline of MDS-UPDRS Part III scores relative to participants treated with placebo in the first year and prasinezumab in the second year (delayed-start group), further supporting a potential effect on delaying motor progression in patients. In October 2024, Roche published results in Nature Medicine from the long term open-label extension of the PASADENA trial, which compared the prasinezumab population with a propensity score-balanced cohort of real-world data (“RWD”) Parkinson’s Progression Markers Initiative (“PPMI”). The data suggests that prasinezumab continued to show reduced motor and functional progression in prazinezumab-treated individuals with early-stage Parkinson’s disease compared to a real-world data arm on MDS-UPDRS Part III score (clinician rated motor examination) OFF and ON symptomatic medication state and MDS-UPDRS Part II score (patient-reported motor experiences of daily living). The Phase 2 PASADENA and Phase 2b PADOVA open-label extension studies will continue in order to further explore the observed effects in both studies.
Current wording
Prasinezumab is the first anti-alpha synuclein antibody to advance into late-stage development. In March 2022, results from the analysis of part 2 of the Phase 2 PASADENA trial of prasinezumab were presented in an oral presentation by Roche at the International Conference on Alzheimer’s and Parkinson’s Diseases. Results showed that participants with Parkinson’s disease who were treated with prasinezumab for two years (early-start group) showed slower decline of MDS-UPDRS Part III scores relative to participants treated with placebo in the first year and prasinezumab in the second year (delayed-start group), further supporting a potential effect on delaying motor progression in patients. In October 2024, Roche published results in Nature Medicine from the long term open-label extension of the PASADENA trial, which compared the prasinezumab population with a propensity score-balanced cohort of real-world data (“RWD”) Parkinson’s Progression Markers Initiative (“PPMI”). The data suggests that prasinezumab continued to show reduced motor and functional progression in prazinezumab-treated individuals with early-stage Parkinson’s disease compared to a real-world data arm on MDS-UPDRS Part III score (clinician rated motor examination) OFF and ON symptomatic medication state and MDS-UPDRS Part II score (patient-reported motor experiences of daily living). The Phase 2 PASADENA and Phase 2b PADOVA open-label extension studies will continue in order to further explore the observed effects in both studies.
Previous wording
Wild-type ATTR (wtATTR) occurs sporadically and primarily involves cardiomyopathy. It is estimated that between 400,000 to 1.4 million patients suffer from ATTR-cardiomyopathy (ATTR-CM). Within this population, between 130,000 to 490,000 patients are estimated to be moderate-to-advanced and categorized as New York Heart Association Class III and IV.
Current wording
Wild-type ATTR (wtATTR) occurs sporadically and primarily involves cardiomyopathy. It is estimated that between 400,000 to 1.4 million patients suffer from ATTR-cardiomyopathy (ATTR-CM).
Previous wording
A Phase 2 clinical trial of coramitug in 105 patients with ATTR amyloidosis with cardiomyopathy was conducted by Novo Nordisk (NCT05442047).
Current wording
A Phase 2 clinical trial of coramitug in 105 patients with ATTR amyloidosis with cardiomyopathy was conducted by Novo Nordisk (NCT05442047). Results are planned to be presented at the American Heart Association Scientific Sessions in November 2025.
Previous wording
BMS-986446 is designed to be a best-in-class anti-tau antibody that specifically binds with high affinity the R1, R2, and R3 repeats within the microtubule binding region (“MTBR”) of tau and targets both 3R and 4R tau isoforms. MTBR-tau has been shown in preclinical studies to be involved in the pathological spread of tau. Neurofibrillary tangles composed of misfolded tau proteins, along with amyloid beta plaques, are pathological hallmarks of Alzheimer’s disease. Cell-to-cell transmission of pathogenic extracellular tau and the accumulation of pathogenic tau also correlate with the progression of symptomatology and clinical decline in patients with Alzheimer’s disease. Recent publications suggest that during the course of Alzheimer’s disease progression, tau appears to spread throughout the brain via synaptically-connected pathways; this propagation of pathology is thought to be mediated by tau “seeds” containing the MTBR of tau. Additionally, it has been recently reported that the presence of MTBR fragments in cerebrospinal fluid correlate with dementia stages and tau tangles in Alzheimer’s disease to a higher degree than fragments of other tau regions. In preclinical research, antibodies targeting this region of tau were superior in blocking tau uptake and neurotoxicity, which has been associated with efficacy in relevant animal models. In these preclinical models, BMS-986446 demonstrated significant reduction of intraneuronal tau pathology and progression protection against behavioral deficit in a tau transgenic mouse model and complete blockade of neuronal tau internalization in vitro.
Current wording
BMS-986446 is a humanized monoclonal antibody that targets multiple domains of the microtubule binding region of tau, a highly pathogenic tau fragment associated with neurofibrillary tangle formation and cognitive decline in Alzheimer’s disease. BMS-986446 binds to specific regions of the tau protein (R1–R3 within the microtubule-binding domain) to prevent the cell-to-cell spread of tau and tau uptake into cells. It also activates microglia—the brain’s immune cells—through its Fc receptor function, promoting the clearance of tau via phagocytosis. Neurofibrillary tangles composed of misfolded tau proteins, along with amyloid beta plaques, are pathological hallmarks of Alzheimer’s disease. Cell-to-cell transmission of pathogenic extracellular tau and the accumulation of pathogenic tau also correlate with the progression of symptomatology and clinical decline in patients with Alzheimer’s disease. Recent publications suggest that during the course of Alzheimer’s disease progression, tau appears to spread throughout the brain via synaptically-connected pathways; this propagation of pathology is thought to be mediated by tau “seeds” containing the MTBR of tau. Additionally, it has been recently reported that the presence of MTBR fragments in cerebrospinal fluid correlate with dementia stages and tau tangles in Alzheimer’s disease to a higher degree than fragments of other tau regions. In preclinical research, antibodies targeting this region of tau were superior in blocking tau uptake and neurotoxicity, which has been associated with efficacy in relevant animal models. In these preclinical models, BMS-986446 demonstrated significant reduction of intraneuronal tau pathology and progression protection against behavioral deficit in a tau transgenic mouse model and complete blockade of neuronal tau internalization in vitro.
Previous wording
In July 2021, we entered into an exclusive US license agreement for BMS-986446 and we received an associated option exercise fee of $80 million. In July 2023, we entered into an exclusive global license agreement for BMS-986446, which as discussed above supersedes and replaces the US license agreement in its entirety and we received an associated option exercise fee of $55 million. We are eligible to receive regulatory and sales milestone payments of up to $563 million, as well as tiered royalties on annual, worldwide net sales.
Current wording
In July 2021, we entered into an exclusive US license agreement for BMS-986446 and we received an associated option exercise fee of $80 million. In July 2023, we entered into an exclusive global license agreement for BMS-986446, which as discussed above supersedes and replaces the US license agreement in its entirety and we received an associated option exercise fee of $55 million. We are eligible to receive regulatory and sales milestone payments of up to $563 million, as well as tiered royalties on annual, worldwide net sales. In October 2025, Bristol Myers Squibb announced that the FDA granted Fast Track designation for BMS-986446 for the treatment of Alzheimer’s disease. The FDA’s Fast Track designation program is designed to expedite the development and review of drugs intended to treat a serious condition, such as Alzheimer’s disease, with evidence demonstrating the potential to address an unmet medical need.
Previous wording
In the first quarter of 2024, BMS advanced the anti-tau program BMS-986446 with the initiation of a Phase 2 clinical trial (NCT06268886). This is a randomized, double-blind, placebo-controlled, global, Phase 2 clinical trial designed to evaluate the efficacy, safety, and tolerability of BMS-986446, an anti-MTBR tau monoclonal antibody, in approximately 310 participants with early Alzheimer's disease. Participants will be randomized into one of three treatment arms including placebo, BMS-986446 Dose A, and BMS-986446 Dose B. The primary outcome measure is change from baseline in brain tau deposition as measured by tau positron emission tomography (PET) at 76 weeks.
Current wording
In the first quarter of 2024, BMS advanced the anti-tau program BMS-986446 with the initiation of the Phase 2 TargetTau-1 clinical trial (NCT06268886). TargetTau-1 is a randomized, double-blind, placebo-controlled, global Phase 2 proof-of-concept study designed to evaluate the efficacy, safety and tolerability of multiple doses of BMS-986446 in approximately 310 participants with early Alzheimer’s disease. The study aims to determine whether targeting MTBR-tau can modify disease progression. In addition to clinical outcome measures, the trial integrates a comprehensive biomarker strategy to assess tau and amyloid-beta biology. The primary outcome measure is change from baseline in brain tau deposition as measured by tau positron emission tomography (PET) at 76 weeks.
Previous wording
A multiple ascending dose (MAD) portion of the Phase 1 clinical trial was ongoing at the time BMS acquired the global rights to the program and control of the Phase 1 trial. All program updates going forward, including results from ongoing and any future BMS-986446 clinical trials, will be reported by BMS.
Current wording
A multiple ascending dose (MAD) portion of the Phase 1 clinical trial was ongoing at the time BMS acquired the global rights to the program and control of the Phase 1 trial.
Previous wording
We are also advancing several discovery and preclinical-stage programs for neurological diseases with significant unmet medical needs.
Current wording
We have a portfolio of unpartnered discovery and preclinical-stage programs for diseases with significant unmet medical needs.
Previous wording
There were no significant changes to our critical accounting policies and estimates during the six months ended June 30, 2025, from the critical accounting policies and estimates disclosed in Management's Discussion and Analysis of Financial Condition and Results of Operations in our 2024 Form 10-K.
Current wording
There were no significant changes to our critical accounting policies and estimates during the nine months ended September 30, 2025, from the critical accounting policies and estimates disclosed in Management's Discussion and Analysis of Financial Condition and Results of Operations in our 2024 Form 10-K.
Previous wording
Except as described in Note 2 to the Condensed Consolidated Financial Statements under the heading “Recent Accounting Pronouncements”, there have been no new accounting pronouncements or changes to accounting pronouncements during the six months ended June 30, 2025, as compared to the recent accounting pronouncements described in our 2024 Form 10-K, that are of significance or potential significance to us.
Current wording
Except as described in Note 2 to the Condensed Consolidated Financial Statements under the heading “Recent Accounting Pronouncements”, there have been no new accounting pronouncements or changes to accounting pronouncements during the nine months ended September 30, 2025, as compared to the recent accounting pronouncements described in our 2024 Form 10-K, that are of significance or potential significance to us.
Previous wording
Comparison of three and six months ended June 30, 2025 and 2024
Current wording
Comparison of three and nine months ended September 30, 2025 and 2024
Previous wording
Total revenue was $4.4 million and$132.0 million for the three months ended June 30, 2025 and 2024, respectively, and $7.2 million and $132.1 million for the six months ended June 30, 2025, and 2024, respectively.
Current wording
Total revenue was$2.4 million and$1.0 million for the three months ended September 30, 2025 and 2024, respectively, and$9.7 million and $133.0 million for the nine months ended September 30, 2025, and 2024, respectively.
Previous wording
Collaboration revenue was $4.4 million and $7.2 million for thethree and six months ended June 30, 2025, compared to$132.0 million and$132.0 million for thethree and six months ended June 30, 2024. Collaboration revenue forthree and six months ended June 30, 2025 was related to the partial performance of our PRX019 Phase 1 Clinical Trial Obligation. Collaboration revenue of$132.0 million for thethree and six months ended June 30, 2024, was related to revenue recognized under our Collaboration Agreement with BMS of which,$107.0 million was from the PRX019 Global License Agreement and PRX019 Phase 1 Clinical Trial Obligation and$25.0 million was related to BMS’s material rights for the US Rights and Global Rights for the TDP-43 Collaboration Target that were fulfilled on May 24, 2024 as a result of the expiration of the research term of the Collaboration Agreement.
Current wording
Collaboration revenue was$2.4 million and$9.6 million for thethree and nine months ended September 30, 2025, compared to$1.0 million and$133.0 million for thethree and nine months ended September 30, 2024. Collaboration revenue forthree and nine months ended September 30, 2025 was related to the partial performance of our PRX019 Phase 1 Clinical Trial Obliga tion. Collaboration revenue of$133.0 million for thenine months ended September 30, 2024 included $107.9 million from the PRX019 Global License Agreement and PRX019 Phase 1 Clinical Trial Obligation and $25.0 million was related to BMS’s material rights for the US Rights and Global Rights for the TDP-43 Collaboration Target that expired unexercised on May 24, 2024 as a result of the expiration of the research term of the Collaboration Agreement.
Previous wording
As of June 30, 2025, the Company has $5.1 million of deferred revenue related to the remaining performance obligations under the PRX019 Global License Agreement relatedto PRX019 Phase 1 Clinical Trial Obligations. See Note 7, “Significant Agreements” to the Condensed Consolidated Financial Statements regarding the Collaboration Agreement with BMS for more information.
Current wording
As of September 30, 2025, the Company has$2.7 million of deferred revenue related to the remaining performance obligations under the PRX019 Global License Agreement relatedto PRX019 Phase 1 Clinical Trial Obligations. See Note 7, “Significant Agreements” to the Condensed Consolidated Financial Statements regarding the Collaboration Agreement with BMS for more information.
Previous wording
License and intellectual property revenue for the six months ended June 30, 2025, and 2024 included $50,000 in each period, respectively, in license fees recognized under the License Agreement entered into on March 1, 2020, between the Company's wholly owned subsidiary, Prothena Biosciences Limited, and F. Hoffmann-La Roche Ltd.
Current wording
License and intellectual property revenue for the nine months ended September 30, 2025, and 2024 included $50,000 in each period, respectively, in license fees recognized under the License Agreement entered into on March 1, 2020, between the Company's wholly owned subsidiary, Prothena Biosciences Limited, and F. Hoffmann-La Roche Ltd.
Previous wording
Total operating expenses consist of R&D expenses, general and administrative (“G&A”) expenses, and restructuring costs. Our operating expenses were $89.0 million and $73.6 million three months ended June 30, 2025 and 2024, respectively, and $157.4 million and $155.2 million for thesix months ended June 30, 2025, and 2024, respectively.
Current wording
Total opera ting expenses consist of R&D expenses, general and administrative (“G&A”) expenses, and restructuring costs. Our operating expenses were $42.7 million and $67.5 million for the three months ended September 30, 2025 and 2024, respectively, and $200.1 million and $222.7 million for thenine months ended September 30, 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, PRX012, 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, including birtamimab and PRX012.
Previous wording
Our R&D expense decreased by $17.0 million or 30% for the three months ended June 30, 2025 and decreased by $30.3 million or 25%for the six months ended June 30, 2025, compared to the same periods in the prior year. The decrease for the three and six months ended June 30, 2025, compared to the same periods in the prior year, was primarily due to lower clinical trial expenses primarily related to PRX012, lower manufacturing expense and lower personnel expenses.
Current wording
Our R&D expense decreased by $21.8 million or 43% for the three months ended September 30, 2025 and decreased by $52.1 million or 30% for the nine months ended September 30, 2025, compared to the same periods in the prior year. The decrease for thethree and nine months ended September 30, 2025, compared to the same periods in the prior year, wasprimarily due to 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, 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 three and six months ended June 30, 2025, and 2024, (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 three and nine months ended September 30, 2025, and 2024, (in thousands):
Previous wording
Our G&A expenses decreasedby $0.2 million or 1% for the three months ended June 30, 2025 and decreased by $0.1 million for thesix months ended June 30, 2025, compared to the same periods in the prior.
Current wording
Our G&A expenses decreasedby$3.5 million or 21% for the three months ended September 30, 2025 and decreased by$3.6 million or 7%for thenine months ended September 30, 2025, compared to the same periods in the prior year primarily due to lower personnel expense.
Previous wording
In June 2025, we commenced a restructuring plan following our decision in May 2025 to discontinue further development of birtamimab. We have incurred aggregate restructuring charges of approximately $32.6 million for thethree and six months ended June 30, 2025.
Current wording
In June 2025, we commenced a restructuring plan following our decision in May 2025 to discontinue further development of birtamimab. We have incurred aggregate restructuring charges of approximately $0.5 million and $33.1 million for thethree and nine months ended September 30, 2025.
Previous wording
Interest income decreasedby $2.7 million or 42%for the three months ended June 30, 2025 and decreased by $5.5 million or 41%for the six months ended June 30, 2025, compared to the same periods in the prior year primarily due to lower interest income from our cash and money market accounts resulting from lower yields and lower cash balances.
Current wording
Interest income decreased by $3.4 million or 50% for the three months ended September 30, 2025 and decreased by $8.9 million or 44% for the nine months ended September 30, 2025, compared to the same periods in the prior year primarily due to lower interest income from our cash and money market accounts resulting from lower cash balances and lower yields.
Previous wording
Other expense, net for thethree and six months ended June 30, 2025, was primarily foreign exchange losses from transactions with vendors denominated in euros.
Current wording
Other expense, net for thethree and nine months ended September 30, 2025, was primarily foreign exchange losses from transactions with vendors denominated in euros.
Previous wording
Income tax expense increasedby $46.8 millionfor the three months ended June 30, 2025 and increasedby $47.9 millionfor the six months ended June 30, 2025, compared to the same periods in the prior year. The increase in income taxes expense for the three and six months ended June 30, 2025, compared to the same periods in the prior year, was primarily due to recording a valuation allowance for the federal deferred tax assets primarily relating to share-based compensation and capitalized R&D related to Section 174 R&D Capitalization during the three and six months ended June 30, 2025.
Current wording
Income tax benefit decreased by $0.5 million for the three months ended September 30, 2025, compared to the same period in the prior year. The current quarter income tax benefit is primarily related to changes in the capitalization requirements of U.S. research and development activities enacted in the OBBBA. Income tax expense increased by $48.3 million for the nine months ended September 30, 2025, compared to the same period in the prior year, primarily due to recording a valuation allowance for the federal deferred tax assets, mainly relating to share-based compensation and R&D expenditure capitalized in previous years.
Previous wording
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$317.7 million as of June 30, 2025, a decrease of $119.2 million from working capital of$436.9 million as of December 31, 2024. This decrease in working capital during the six months ended June 30, 2025, was primarily attributable to cash used in operating activities of $99.7 million.
Current wording
Working capital was$288.5 million as of September 30, 2025, a decrease of $148.4 million from working capital of$436.9 million as of December 31, 2024. This decrease in working capital during the nine months ended September 30, 2025, was primarily attributable to cash used in operating activities of $140.3 million.
Previous wording
As of June 30, 2025, we had $371.4 million in cash and cash equivalents. Based on our current business plans, we believe that our existing cash and cash equivalents at June 30, 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 the Condensed Consolidated Financial Statements for more information).
Current wording
As of September 30, 2025, we had $330.8 million in cash and cash equivalents. Based on our current business plans, we believe that our existing cash and cash equivalents at September 30, 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 the Condensed 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 June 30, 2025, $264.4 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 September 30, 2025, $215.8 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
Net cash used in operating activities was$99.7 million for the six months ended June 30, 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) partially offset byinterest income on investments.
Current wording
Net cash used in operating activities was$140.3 million for the nine months ended September 30, 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 $128 thousand for thesix months ended June 30, 2025, which primarily consisted of expenditures to purchase property and equipment.
Current wording
Net cash used in investing activities was $138 thousand for thenine months ended September 30, 2025, which consisted of expenditures to purchase property and equipment.
Previous wording
Net cash used in financing activities was$122 thousand for thesix months ended June 30, 2025, which primarily consisted of expenditures related to our at-the-market offering.
Current wording
Net cash used in financing activities was$139 thousand for thenine months ended September 30, 2025, which consisted of expenditures related to our at-the-market offering.
Previous wording
Refer to “Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations — Liquidity and Capital Resources” in our second quarter 2024 Quarterly Report on Form 10-Q for a discussion of the cash flows for the six months ended June 30, 2024.
Current wording
Refer to “Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations — Liquidity and Capital Resources” in our third quarter 2024 Quarterly Report on Form 10-Q for a discussion of the cash flows for the nine months ended September 30, 2024.
Previous wording
Our contractual obligations as of June 30, 2025, consisted of minimum cash payments under operating leases of $10.8 million, purchase obligations of $3.3 million (of which $2.6 million is included in current liabilities), obligations under our restructuring plan of $30.3 million (of which all of it is included in current liabilities), and contractual obligations under license agreements of $0.3 million). 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 Condensed Consolidated Financial Statements.
Current wording
Our contractual obligations as of September 30, 2025, consisted of minimum cash payments under operating leases of $9.9 million, purchase obligations of $3.1 million (of which $2.2 million is included in current liabilities), obligations under our restructuring plan of $17.6 million (of which all of it is included in current liabilities), and contractual obligations under license agreements of $0.2 million. 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 Condensed 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 $10.5 million remains outstanding as of June 30, 2025
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 $9.7 million remains outstanding as of September 30, 2025
Rearranged previous paragraphs (1)
Previous report — wording carried elsewhere
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.