8-K: Protalix Elfabrio Dosing Regimen Rejected in EU

The European Medicines Agency's CHMP issued a negative opinion on Protalix BioTherapeutics' request to approve an every-four-week dosing regimen for its Fabry disease treatment, Elfabrio.

Summary

• The Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) issued a negative opinion on the request to approve the 2 mg/kg body weight infused every 4 weeks (E4W) dosing regimen for Elfabrio (pegunigalsidase alfa).
• The currently approved dosing regimen of 1 mg/kg body weight infused every 2 weeks (E2W) for Elfabrio remains in effect in the EU.
• The submission for the E4W regimen was based on data from the BRIGHT trial and its open-label extension study, CLI-06657AA1-03, which combined have a median exposure of almost six years, but these data were not deemed sufficient to conclude on similar efficacy.
• Protalix BioTherapeutics reported $25.4 million in revenue for the first half of 2025 and $53 million for the full year 2024.
• The company held $33.4 million in cash and cash equivalents as of June 30, 2025, with no debt or warrants, providing a cash runway into 2027.
• The development pipeline includes PRX-115 for uncontrolled gout, with a Phase 2 study anticipated to start in Q4 2025, and PRX-119 for NETs-related diseases.
• Elfabrio is approved in the United States, the European Union, and additional markets, with Chiesi Global Rare Diseases as the global partner.
• Elelyso is approved in 23 markets, with Pfizer Inc. as the global partner (excluding Brazil, where Fundaçao Oswaldo Cruz is the partner).

Sentiment

Score: 5

Explanation: While the CHMP's negative opinion on the less frequent Elfabrio dosing regimen is a setback for market differentiation in the EU, the company's core product (Elfabrio 2-week dosing) remains approved and commercialized. Protalix also benefits from a strong financial position with a cash runway into 2027 and a promising pipeline candidate (PRX-115) advancing to Phase 2, which could provide future growth. The negative news impacts a potential enhancement rather than the core business.

Positives

• Elfabrio (pegunigalsidase alfa) is approved for marketing in the United States, the European Union, and additional markets for Fabry disease, with the 1 mg/kg every 2 weeks dosing regimen remaining approved in the EU.
• Elelyso (taliglucerase alfa) is approved in 23 markets for Gaucher disease, generating revenue through a partnership with Pfizer Inc. and Fundaçao Oswaldo Cruz.
• PRX-115, a recombinant PEGylated uricase for uncontrolled gout, showed favorable tolerability and the ability to rapidly reduce and maintain uric acid levels below 6.0 mg/dL for greater than 8 weeks in Phase 1 data.
• The Phase 2 study for PRX-115 is anticipated to start in Q4 2025, with potential for improved dosing (IV infusion every 8 weeks) and no need for co-administered methotrexate, addressing significant unmet needs in the uncontrolled gout market.
• The company is well-capitalized with $33.4 million in cash and cash equivalents as of June 30, 2025, no debt, and no warrants, providing a cash runway into 2027.
• Projected consistent revenue growth in the medium-term from three revenue streams and significant milestone payments expected in the midand long-term.
• The Fabry disease market is projected to grow from approximately $2.1 billion in 2024 to $3.2 billion by 2030, with Elfabrio poised to capture 15% to 20% global market share.
• Strong global partnerships with Chiesi Global Rare Diseases for Elfabrio and Pfizer Inc. for Elelyso provide commercialization and development support.

Negatives

• The Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) issued a negative opinion on the request to approve the 2 mg/kg body weight infused every 4 weeks dosing regimen for Elfabrio.
• The data submitted from the BRIGHT trial and its extension study were not deemed sufficient by the CHMP to conclude on similar efficacy for the every 4 weeks regimen, limiting a potential differentiator for Elfabrio in the EU market.
• This negative opinion means Elfabrio will not be able to offer a reduced treatment burden (less frequent dosing) for Fabry disease patients in the EU at this time, which was a stated goal of the company and its partner.

Risks

• Risks related to the commercialization of Elfabrio, including revenue, expenses, market acceptance, competition, reimbursement, and regulatory actions (e.g., boxed warning in U.S. FDA approval).
• Uncertainty regarding the regulatory approval and commercial success of other product candidates, if approved.
• Potential for failure or delay in the commencement or completion of preclinical studies and clinical trials due to factors such as slow patient recruitment, unforeseen safety issues, dosing issues, lack of effectiveness, inability to demonstrate non-inferiority, or insufficient funding.
• Delays in the approval or potential rejection of any applications filed with regulatory authorities (FDA, EMA) for product candidates.
• Challenges in managing relationships with collaborators, distributors, or partners, including Pfizer Inc. and Chiesi Global Rare Diseases.
• Possible disruption of operations due to geopolitical conflicts, such as the war declared by Israel's security cabinet against the Hamas terrorist organization, and its impact on regulatory authorities, suppliers, partners, and clinical trial sites.
• Risks relating to changes to published interim, topline, or preliminary data from clinical trials.
• Inherent risks and uncertainties in developing drug platforms and products.
• Impact of the development of competing therapies and/or technologies by other companies.
• Risks relating to changes in healthcare laws, rules, and regulations in the United States or elsewhere.

Future Outlook

The company anticipates consistent revenue growth in the medium-term from its three revenue streams and expects significant milestone payments in the midand long-term. For Elfabrio, the focus is on expanding geographic approvals and increasing market share in current geographies between 2025 and 2027. The Phase 2 study for PRX-115 in uncontrolled gout patients is expected to commence in Q4 2025, with plans to seek a development and commercial partner ahead of Phase 3. Protalix aims to grow its internal R&D pipeline, with a three-year goal of having 5-7 programs spanning discovery to clinic, specifically focusing on rare renal diseases.

Management Comments

• Giacomo Chiesi, Executive Vice President, Chiesi Global Rare Diseases: "We are disappointed by the result of this review but want to express our immense appreciation for the collaboration of the patient community, researchers and European Commission throughout this process. We are proud to be a part of this community and will continue to prioritize the potential to advance and evolve safe and effective solutions for Fabry disease with reduced treatment burden."
• Dror Bashan, Protalix's President and Chief Executive Officer: "We, together with Chiesi, remain committed to reducing the treatment burden for patients with Fabry disease. The results of this review do not change this priority. We are grateful to all of the patients and investigators, and their staff members, who participated in the every 4 weeks clinical trial programs."
• Mary Pavlou, President of Fabry International Network (FIN): "We acknowledge this outcome with disappointment but also with gratitude for the dedication shown by all involved from patients and advocates to researchers and regulators. The Fabry International Network remains committed to fostering collaboration that drives meaningful progress both in safety and effectiveness and strives for advancements that make a real difference in daily life and long-term outcomes."

Industry Context

The Fabry disease market is competitive, with Elfabrio positioned against established enzyme replacement therapies (ERTs) like Sanofi's Fabrazyme and Takeda's Replagal, as well as pharmacological chaperones such as Amicus Therapeutics' Galafold. Elfabrio aims to capture a significant global market share (15-20%) in a market projected to grow to $3.2 billion by 2030. In the uncontrolled gout market, PRX-115 is being developed to address significant unmet needs, differentiating itself from current therapies like Horizon Therapeutics' Krystexxa (pegloticase), which generated $1.2 billion in net sales in 2024 but has challenges related to infusion logistics, immunogenicity, and safety. The entry of new therapies like NASP (expected approval in 2026) indicates an expanding and evolving market for gout treatments. Enzyme replacement therapies are expected to remain the gold standard for lysosomal storage diseases.

Comparison to Industry Standards

• Fabry Disease: Elfabrio's currently approved dosing regimen of 1 mg/kg every 2 weeks is comparable to existing ERTs like Sanofi's Fabrazyme (1 mg/kg every 2 weeks) and Takeda's Replagal (0.2 mg/kg every 2 weeks). The rejected 2 mg/kg every 4 weeks regimen aimed to offer a less frequent dosing interval, which would have been a key differentiator against these competitors and Amicus Therapeutics' oral pharmacological chaperone, Galafold (123 mg every other day).
• Uncontrolled Gout: PRX-115 aims to be a best-in-class uricase, differentiating from Horizon Therapeutics' Krystexxa (pegloticase), which had $1.2 billion in net sales in 2024. PRX-115's potential for an every 8-week IV infusion and no need for co-administered methotrexate would offer a significant advantage over Krystexxa, which typically requires more frequent infusions and often co-administration of methotrexate, which is contraindicated in certain co-morbidities. NASP (nano encapsulated sirolimusplus pegadricase) is an upcoming competitor with expected approval in 2026.

Stakeholder Impact

• Shareholders: The negative CHMP opinion may lead to short-term negative sentiment and potential share price pressure due to the loss of a key market differentiator for Elfabrio in the EU. However, the impact is mitigated by existing product approvals, strong financial health, and a promising pipeline.
• Fabry Patients (EU): Patients in the EU will not have access to the less frequent 4-week dosing regimen for Elfabrio, meaning they will continue with the currently approved 2-week regimen, which may not reduce their treatment burden as hoped.
• Chiesi Global Rare Diseases: As Protalix's partner for Elfabrio, Chiesi's efforts to enhance Elfabrio's market appeal and reduce treatment burden in the EU are hampered by this regulatory decision.
• Employees: No direct impact on employees is mentioned in the filing.

Next Steps

• Protalix and Chiesi intend to continue working together to support the Fabry disease community.
• The Phase 2 study for PRX-115 in uncontrolled gout patients is anticipated to start in Q4 2025.
• The company anticipates looking for a development and commercial partner for PRX-115 ahead of Phase 3.
• Elfabrio is expected to expand geographic approvals and increase market share in current geographies between 2025 and 2027.
• Continued internal R&D pipeline growth is planned, with a three-year goal of 5-7 programs spanning discovery to clinic, focusing on rare renal diseases.

Key Dates

Recommendation

The negative CHMP opinion for Elfabrio's less frequent dosing regimen is a setback, limiting a key differentiator in the EU market and potentially impacting future revenue growth from this specific enhancement. However, the company's core product (Elfabrio 2-week dosing) remains approved and commercialized, and Elelyso continues to generate revenue. The strong cash position ($33.4M with runway into 2027) and promising PRX-115 pipeline advancing to Phase 2 provide future growth potential. While the news is negative, it does not fundamentally undermine the company's existing operations or long-term strategy, warranting a 'hold' as investors assess the broader impact and the progress of other pipeline assets.

Keywords

Fabry disease, Elfabrio, pegunigalsidase alfa, CHMP, EMA, rare diseases, gout, PRX-115, Protalix BioTherapeutics, Chiesi Global Rare Diseases, enzyme replacement therapy, biopharmaceutical, clinical trials, regulatory approval