Business Overview
Prothena Corporation plc operates as a late-stage clinical biotechnology company focusing predominantly on the science of protein dysregulation. The firm aims to alter the clinical course of devastating neurodegenerative and rare peripheral amyloid diseases. Prothena’s scientific foundation is built on decades of research regarding misfolded proteins and neurological dysfunction. The company’s pipeline consists of a mix of wholly-owned and partnered clinical programs targeting indications such as Parkinson’s disease, ATTR amyloidosis with cardiomyopathy (ATTR-CM), Alzheimer’s disease, and Amyotrophic lateral sclerosis (ALS). Furthermore, the company is advancing its proprietary CYTOPE® technology to target a broad spectrum of intracellular disease pathways in both the brain and the periphery.
Key Financial Performance Highlights
Profitability and Earnings: For the fourth quarter of 2025, Prothena reported a net loss of $21.6 million, representing a substantial improvement compared to the net loss of $58.0 million recorded in the fourth quarter of 2024. On a per-share basis, the Q4 2025 net loss was $0.40, a narrowing from $1.08 in the corresponding period of the prior year.
However, for the full year 2025, the net loss widened significantly to $244.1 million, compared to $122.3 million in the full year 2024. The full-year net loss of $4.53 per share, up from $2.27 per share in 2024, was heavily impacted by one-time and non-cash items. Specifically, the 2025 net loss includes $30.1 million in restructuring charges related to the discontinuation of the birtamimab program and a subsequent workforce reduction announced in June 2025. Additionally, the company recorded a $43.2 million net non-cash income tax expense to book a full valuation allowance against its federal deferred tax assets.
Revenue: Revenues saw a sharp year-over-year decline. For Q4 2025, total revenue was $21 thousand, down from $2.1 million in Q4 2024. Full-year 2025 total revenue was $9.7 million, compared to $135.2 million in 2024. This decrease is primarily attributable to challenging baseline effects; the 2024 revenue included an $80 million upfront payment resulting from the execution of the PRX019 Global License Agreement by Bristol Myers Squibb. The total revenue generated in 2025 was primarily derived from collaboration revenue with Bristol Myers Squibb related to the partial performance of the company’s PRX019 Phase 1 clinical trial obligations.
Operating Expenses: Operating expenses demonstrated a downward trajectory throughout 2025 due to targeted cost-saving measures and program discontinuations. Research and development (R&D) expenses for Q4 2025 were $14.6 million, a significant reduction from $50.2 million in Q4 2024. Full-year R&D expenses were $134.9 million, down from $222.5 million in the prior year. Management attributes this decrease to lower clinical trial expenses, reduced personnel expenses, and lower manufacturing and consulting costs. Included within R&D were non-cash share-based compensation expenses of $2.1 million and $14.1 million for Q4 and the full year 2025, respectively.
General and administrative (G&A) expenses also declined, totaling $12.6 million for Q4 2025 (down from $16.8 million in Q4 2024) and $59.4 million for the full year 2025 (down from $67.2 million in 2024). The decrease in G&A was primarily driven by lower personnel and consulting expenses. Non-cash share-based compensation within G&A was $5.0 million for Q4 2025 and $21.5 million for the full year 2025.
Balance Sheet, Operational Metrics, and Financial Guidance
Prothena concluded the 2025 fiscal year with a solid liquidity position, reporting $308.4 million in cash, cash equivalents, and restricted cash, carrying no outstanding debt. For the fourth quarter of 2025, net cash used in operating and investing activities was $23.3 million. For the full year 2025, net cash used in these activities totaled $163.7 million.
Looking ahead, management provided distinct financial guidance parameters for 2026. The company expects full-year 2026 net cash used in operating and investing activities to decline to a range of $50 to $55 million. Prothena anticipates ending 2026 with approximately $255 million in cash at the midpoint of its guidance. This expected cash burn is primarily driven by an estimated net loss of $67 to $72 million for the year, a figure that includes approximately $24 million of non-cash share-based compensation expense. It is critical to note that this financial guidance excludes the potential to earn up to $105 million in aggregate clinical milestone payments from strategic partners Novo Nordisk and Bristol Myers Squibb in 2026.
Segment-wise Clinical Portfolio Performance
Prothena’s late-stage clinical strategy is fundamentally tied to high-value collaborations with major pharmaceutical entities. The active clinical portfolio is segmented into the following key partnered programs:
Prasinezumab: is positioned as a potential first-in-class antibody designed to target a key epitope within the C-terminus of alpha-synuclein for the treatment of Parkinson’s disease. In the fourth quarter of 2025, Roche initiated the Phase 3 PARAISO clinical trial evaluating the drug in approximately 900 participants with early-stage Parkinson’s disease. The primary completion date for this pivotal trial is expected in 2029. Roche has publicly stated that prasinezumab possesses a peak sales potential of greater than $3.5 billion on an unadjusted basis, highlighting its potential to become the first disease-modifying treatment for a condition affecting 10 million individuals globally.
Coramitug :Coramitug is a potential first-in-class amyloid depleter antibody intended for the treatment of ATTR amyloidosis with cardiomyopathy (ATTR-CM). The therapeutic is designed to deplete the pathogenic, non-native forms of the transthyretin (TTR) protein. This program was acquired by Novo Nordisk as part of a transaction valued at up to $1.2 billion for Prothena’s ATTR amyloidosis business and pipeline. In the fourth quarter of 2025, Novo Nordisk initiated the Phase 3 CLEOPATTRA clinical trial, which will evaluate the therapeutic in approximately 1,280 participants with ATTR-CM, with primary completion anticipated in 2029. Prior to this, Phase 2 results were presented by Novo Nordisk at the American Heart Association Scientific Sessions on November 10, 2025. Prothena holds the potential to earn a clinical milestone payment in the first half of 2026 if prespecified enrollment criteria in the CLEOPATTRA trial are successfully met.
BMS-986446 :Designed as a potential best-in-class antibody for Alzheimer’s disease, BMS-986446 targets a key epitope within the microtubule binding region (MTBR) of tau, a protein implicated in the causal pathophysiology of the disease. Bristol Myers Squibb has fully enrolled the Phase 2 TargetTau-1 clinical trial involving approximately 310 patients with early Alzheimer’s disease, with primary completion expected in the first half of 2027. Additionally, Bristol Myers Squibb completed a Phase 1 open-label single-dose clinical trial to evaluate a subcutaneous administration of the drug. The FDA has formally granted Fast Track designation for BMS-986446 for the treatment of Alzheimer’s disease.
PRX019: PRX019 is being evaluated as a potential treatment for neurodegenerative diseases. Bristol Myers Squibb secured the exclusive global license for this asset in 2024. Currently, Prothena is executing a Phase 1 first-in-human clinical trial designed to assess the safety, tolerability, immunogenicity, and pharmacokinetics of single ascending and multiple doses in healthy adults. This trial is expected to reach completion in 2026. A clinical milestone could be triggered by the end of 2026 subject to Bristol Myers Squibb deciding to further develop PRX019.
Management Commentary and Corporate Strategy
Gene Kinney, Ph.D., President and Chief Executive Officer of Prothena, underscored the significant advancement of the company’s partnered pipeline over the last year. Kinney specifically emphasized the initiation of pivotal Phase 3 trials for both prasinezumab and coramitug by partners Roche and Novo Nordisk, respectively. Addressing the long-term capitalization of the pipeline, Kinney noted, “These partnered programs have the potential to earn up to approximately $3 billion in future aggregate milestones in addition to potential future royalties”.
On the corporate governance front, Prothena has taken distinct steps to optimize its capital structure. Following an Extraordinary General Meeting convened on November 19, 2025, shareholders voted to approve a reduction in the company’s share capital in order to create distributable reserves, an action that was subsequently confirmed by the Irish High Court. This maneuver provides the Board of Directors with the necessary flexibility to potentially return capital to shareholders via a share redemption program. Management noted that such a program could be executed in 2026 through open market purchases or other permissible means, subject to the discretion of the Board of Directors and the company’s financial condition at that time.
Notable Risks and Challenges
The financial and operational updates outline several explicit risks and challenges facing the enterprise:
Pipeline Attrition and Restructuring Impact: The company absorbed a significant $30.1 million restructuring charge in 2025, which was directly tied to the discontinuation of its birtamimab program and a subsequent reduction in the workforce.
Adverse Event Profiles in Wholly-Owned Assets: The Phase 1 ASCENT data for PRX012 revealed that despite demonstrating robust efficacy in plaque clearance, the asset exhibited non-competitive rates of ARIA-E. This adverse safety profile forced a strategic pivot to re-engineer the drug with transferrin receptor technology (PRX012-TfR), transitioning the program back to preclinical development and prompting a search for external partnership opportunities to bear future costs.
Heavy Reliance on Partners for Milestone Realization: While the theoretical milestone potential is vast ,the realization of these capital inflows is highly contingent on the successful clinical execution and strategic prioritization by Prothena’s partners. Specifically, the near-term 2026 milestone potential of $105 million depends entirely on prespecified enrollment criteria being met by Novo Nordisk and a positive advancement decision being made by Bristol Myers Squibb.
Tax Allowances: The company recorded a $43.2 million net non-cash income tax expense representing a full valuation allowance against its federal deferred tax assets, indicating a structural reassessment of near-term profitability realization.
The post Prothena FY25 Earnings Review: Partnered Programs Advance Toward Milestones as Wholly-Owned Assets Pivot first appeared on Alphastreet.
