Prothena Stock Price, News & Analysis

Prothena Corporation plc (NASDAQ: PRTA) is described in its public communications as a late-stage clinical biotechnology company with expertise in protein dysregulation and a pipeline of investigational therapeutics with the potential to change the course of devastating neurodegenerative and rare peripheral amyloid diseases. The company’s ordinary shares trade on The Nasdaq Global Select Market under the symbol PRTA, and it is organized as an Irish public limited company.

According to multiple company press releases, Prothena focuses on diseases in which misfolded or dysregulated proteins play a key role in pathology. Its scientific approach integrates insights into neurological dysfunction with the biology of misfolded proteins. The company reports that its pipeline includes both wholly-owned and partnered programs being developed for the potential treatment of conditions such as ATTR amyloidosis with cardiomyopathy, Alzheimer’s disease, Parkinson’s disease and a number of other neurodegenerative diseases.

Business focus and therapeutic areas

Prothena characterizes itself as a late-stage clinical biotechnology company built around protein dysregulation. Across its public disclosures, it highlights work in:

• Neurodegenerative diseases, including programs in Parkinson’s disease and Alzheimer’s disease.
• Rare peripheral amyloid diseases, including ATTR amyloidosis with cardiomyopathy through partnered development of coramitug (formerly PRX004).
• Broader neurodegenerative targets, where misfolded or pathogenic protein species are central to disease biology.

The company states that its pipeline includes both wholly-owned and partnered programs, reflecting a mix of internal development and collaborations with larger pharmaceutical companies.

Pipeline and partnered programs

In its news releases and SEC filings, Prothena describes several key clinical and preclinical programs:

• Prasinezumab – described as a potential first-in-class antibody for the treatment of Parkinson’s disease that is designed to target a key epitope within the C-terminus of alpha-synuclein. Prothena states that prasinezumab is the focus of a worldwide collaboration with Roche, with advancement into Phase 3 development for early-stage Parkinson’s disease referenced in company updates.
• Coramitug (formerly PRX004) – described as a potential first-in-class amyloid depleter antibody for the treatment of ATTR amyloidosis with cardiomyopathy (ATTR-CM). Prothena reports that coramitug was initially developed by Prothena and that Novo Nordisk acquired Prothena’s ATTR amyloidosis business and pipeline, gaining full worldwide rights. Coramitug is being developed by Novo Nordisk, with Prothena eligible for development and sales milestone payments under the acquisition agreement.
• BMS-986446 (formerly PRX005) – described as a humanized monoclonal antibody that targets multiple domains of the microtubule binding region (MTBR) of tau, a tau fragment associated with neurofibrillary tangle formation and cognitive decline in Alzheimer’s disease. Prothena notes that this program is licensed to Bristol Myers Squibb, which is responsible for development, manufacturing, and commercialization, and that Prothena is eligible for regulatory and sales milestone payments and tiered royalties on net sales.
• PRX019 – described as a potential treatment of neurodegenerative diseases in development in collaboration with Bristol Myers Squibb. Prothena reports that Bristol Myers Squibb obtained an exclusive global license for PRX019 and that Prothena is conducting a Phase 1 first-in-human clinical trial to evaluate safety, tolerability, immunogenicity, and pharmacokinetics, with potential clinical milestone payments tied to further development decisions by Bristol Myers Squibb.
• PRX012 – described in company communications as a wholly-owned, subcutaneous anti-amyloid beta antibody evaluated in the Phase 1 ASCENT clinical program in participants with early symptomatic Alzheimer’s disease. Prothena reports that the ASCENT program established proof-of-mechanism for PRX012 as a once-monthly subcutaneous anti-amyloid beta antibody with dose- and time-dependent reduction of amyloid plaque, and that the company plans to explore potential partnership interest to advance PRX012 and a related preclinical PRX012-TfR antibody.
• PRX123 – described as a wholly-owned potential first-in-class dual Aβ/tau vaccine designed for the treatment and prevention of Alzheimer’s disease, targeting key epitopes within the N-terminus of amyloid beta and MTBR-tau. Prothena states that the U.S. Food and Drug Administration cleared the investigational new drug application and granted Fast Track designation for PRX123 for the treatment of Alzheimer’s disease.
• CYTOPE^® technology – described as a novel drug delivery modality enabling cytosolic delivery of macromolecules in the brain and periphery through an endosomal escape mechanism. Prothena highlights preclinical data from its TDP-43 CYTOPE program in models of ALS and other TDP-43 proteinopathies, noting reductions in intracellular TDP-43 pathology and associated RNA dysregulation in preclinical systems.

Across these programs, Prothena emphasizes a focus on misfolded proteins and disease-modifying mechanisms, often in collaboration with large pharmaceutical partners.

Corporate structure and location

SEC filings identify Prothena Corporation plc as an Irish public limited company registered in Ireland, with its principal executive offices in Dublin, Ireland. The company’s ordinary shares, with a par value of $0.01 per share, are listed on The Nasdaq Global Select Market under the trading symbol PRTA.

Capital structure and shareholder matters

In a definitive proxy statement and related Form 8-K filings, Prothena describes an Extraordinary General Meeting of shareholders held to approve a reduction of the company’s capital to facilitate the creation of distributable reserves. The company explains that this reduction of capital is intended to give the Board of Directors greater flexibility with respect to potential future distributions to shareholders, including the possibility of a share redemption program, subject to shareholder approval, court confirmation under Irish law, and the Board’s discretion.

Workforce and restructuring

In a Form 8-K filing, Prothena reports that it announced an approximate 63% reduction in its workforce to substantially reduce operating costs to levels it believes are necessary to support its remaining wholly-owned programs, obligations to partnered programs, and anticipated business development activities. The filing explains that this workforce reduction followed a decision to discontinue further development of the birtamimab program. The company describes expected severance and related benefits for affected employees and notes that additional details would be provided in subsequent periodic reports.

Board and governance updates

In a press release and corresponding Form 8-K, Prothena discloses that a member of its Board of Directors, Paula Cobb, notified the company of her decision to resign from the Board, effective as of December 31, 2025, in order to take an executive role at another biotechnology company. The company states that her decision was not due to any disagreement with Prothena on matters relating to operations, policies, or practices, and notes that she served on the Board and certain committees through the effective date of her resignation.

Collaborations and milestone economics

Across its news releases, Prothena describes several collaboration and licensing arrangements:

• With Novo Nordisk, under which Novo Nordisk acquired Prothena’s ATTR amyloidosis business and pipeline, including coramitug. Prothena reports that it is eligible to receive up to a stated aggregate amount in clinical development and sales milestones, with a portion already earned, and that additional clinical milestones are tied to enrollment criteria in Phase 3 development of coramitug for ATTR amyloidosis with cardiomyopathy.
• With Bristol Myers Squibb, covering BMS-986446 (formerly PRX005) and PRX019. Prothena notes that it is eligible for regulatory and sales milestone payments and tiered royalties on net sales for BMS-986446, and that it may earn clinical milestones related to further development of PRX019.
• With Roche, in relation to prasinezumab for Parkinson’s disease, where Roche is described as conducting clinical trials and planning Phase 3 development, while Prothena participates in the collaboration.

These arrangements are presented by the company as a way to advance late-stage programs and share development responsibilities while retaining economic participation through milestones and royalties.

Stage of development and financial reporting

In its quarterly financial results press releases, Prothena reiterates that it is a late-stage clinical biotechnology company and provides summaries of its research and development and general and administrative expenses, collaboration revenue, and net income or loss. The company highlights that revenue in the referenced periods is primarily from collaboration revenue related to its agreements with Bristol Myers Squibb. It also notes restructuring charges associated with the discontinuation of birtamimab and the workforce reduction, and describes its cash, cash equivalents, and restricted cash position, as well as the absence of debt, as of the reporting dates.

Summary

Overall, Prothena Corporation plc presents itself, in its own public disclosures and SEC filings, as a Nasdaq-listed, Ireland-based, late-stage clinical biotechnology company focused on protein dysregulation. Its work centers on investigational therapeutics for neurodegenerative diseases and rare peripheral amyloid conditions, with a pipeline that includes both wholly-owned assets and partnered programs with large pharmaceutical companies. The company emphasizes its scientific expertise in misfolded proteins, its collaborations in areas such as Alzheimer’s disease, Parkinson’s disease, and ATTR amyloidosis with cardiomyopathy, and its efforts to align capital structure and operating costs with its development priorities.