Higher Single PRX-115 Doses Kept Plasma Uric Acid Levels Below Therapeutic Target for Longer Durations

Protalix BioTherapeutics Presents Data Supporting Potential for Less Frequent Dosing in Phase 2 RELEASE Study for Uncontrolled Gout

• The Company previously reported that higher single doses of PRX–115 lowered mean plasma uric acid for longer durations in participants with elevated plasma uric acid levels (ACR 2024)
• New individual patient data presented at ACR 2026 reinforce this finding and show the effect associated with PRX-115 plasma levels remaining measurable for up to 85 days
• The Company believes PRX-115 has best-in-class potential in uncontrolled gout, a high unmet need with top-line results from the Phase 2 RELEASE study expected in the second half of 2027

CARMIEL, Israel, Nov. 9, 2026 /PRNewswire/ -- Protalix BioTherapeutics, Inc. (NYSE American: PLX), a biopharmaceutical company focused on the discovery, development, production, and commercialization of innovative therapeutics for rare diseases with significant unmet needs, today announced individual participant results from a pharmacokinetic (PK) and pharmacodynamic (PD) analysis of the higher-dose cohorts of its Phase 1 single ascending dose study of PRX-115, a plant cell–expressed recombinant PEGylated uricase in development for uncontrolled gout. The Company is presenting the analysis in a poster at the American College of Rheumatology (ACR) Convergence 2026 taking place in Orlando, Florida from November 6-11, 2026.

Uncontrolled gout is a disease with low quality of life and high unmet need. Current uricase therapy has challenges including infusion burden, immunogenicity with loss of efficacy, and safety concerns. PRX-115 is designed for high specific activity, prolonged circulating half-life, and reduced immunogenicity.¹ In the Phase 1 study of adults with elevated plasma uric acid, single infusions of PRX–115 lowered plasma uric acid levels rapidly and were generally well–tolerated. At 36 mg, mean plasma uric acid levels stayed below the 6.0 mg/dL target for up to 12 weeks after a single infusion. These data support the Phase 2 RELEASE study (NCT07280156) of PRX-115 for the treatment of uncontrolled gout.

"Uncontrolled gout is a high unmet need, and PRX-115 has the potential to be a differentiated therapy," said Dror Bashan, President and Chief Executive Officer of Protalix BioTherapeutics. "The Phase 1 data support the potential for less frequent dosing, which could reduce infusion burden and improve patient adherence. The Phase 2 RELEASE study is designed to test two potential differentiators: dosing every four weeks without methotrexate and dosing every eight weeks with methotrexate. We anticipate top-line results in the second half of 2027."

Phase 1 Data Support Testing Longer Dosing Intervals in Phase 2 RELEASE Study

Plasma Uric Acid Lowering Increased With Dose and Lasted for Weeks

• The analysis is being presented at the ACR Convergence 2026 covers the 18 mg, 24 mg and 36 mg cohorts, with six participants per cohort who received a single infusion and were followed for 85 days.
• PRX-115 exposure increased with dose and persisted longer at higher doses.
• Participants with prolonged measurable PRX-115 concentrations kept plasma uric acid levels below the therapeutic target longer; declining concentrations matched gradual plasma uric acid recovery.

Safety data from the Phase 1 study showed PRX-115 was generally well tolerated, with mostly mild to moderate and transient related adverse events and one anaphylactic reaction that resolved; no other serious adverse events were reported (ACR 2024).²

The poster will be made available on the Company's website here: Publications | Protalix.

About Uncontrolled Gout

Gout is a metabolic disorder characterized by elevated blood uric acid that causes recurrent inflammatory arthritis and joint damage. An estimated 11.3 million people in the U.S. have gout.³ Rheumatologists report that approximately 25% of their patients have blood uric acid levels above target, which can lead to uncontrolled gout.² An estimated 180,000 patients in the U.S. have uncontrolled gout.⁴ Uncontrolled gout is a severe disease with high morbidity, severe pain, and low quality of life.

About PRX-115

PRX-115 is a recombinant PEGylated uricase in development for uncontrolled gout, produced using Protalix's ProCellEx^® plant cell-based protein expression platform. Current uricase therapy has challenges including infusion burden, immunogenicity with loss of efficacy, and safety concerns. PRX-115 is designed for high specific activity, prolonged circulating half-life, and reduced immunogenicity.⁵ In the Phase 1 study of adults with elevated plasma uric acid levels, single infusions of PRX-115 lowered plasma uric acid levels rapidly and were generally well tolerated. At 36 mg, mean plasma uric acid stayed below the 6.0 mg/dL target for up to 12 weeks after a single infusion. Protalix believes PRX-115 has best-in-class potential for uncontrolled gout.

About the Phase 2 RELEASE Study (PRX-115)

RELEASE (NCT07280156) is a Phase 2, double-blind, placebo-controlled study of PRX-115 in patients with uncontrolled gout. The study tests a fixed 36 mg dose in five treatment arms of 30 patients each: PRX-115 every 4 weeks without methotrexate, PRX-115 every 4, 6, or 8 weeks with methotrexate, and placebo. The primary endpoint is the proportion of patients who demonstrated a reduction in serum uric acid levels to below 6.0 mg/dL for at least 80% of the time during Month 6. Top–line results are expected in the second half of 2027.

About Protalix BioTherapeutics, Inc.

Protalix is a biopharmaceutical company focused on the discovery, development, production, and commercialization of innovative therapeutics for rare diseases. Protalix has researched, developed, and currently manufactures two enzyme replacement therapies that are currently available in multiple markets. These therapies are recombinant therapeutic proteins expressed through Protalix's proprietary plant cell-based expression system, ProCellEx^®. ProCellEx is a unique plant cell-based system that enables Protalix to produce recombinant proteins in an industrial-scale manner with no exposure to mammalian cells. Protalix is the first company to gain U.S. Food and Drug Administration (FDA) approval of a protein produced through plant cell-based in suspension expression system. Protalix has licensed to Pfizer Inc. the worldwide development and commercialization rights to taliglucerase alfa, Elelyso^®, for the treatment of Gaucher disease, excluding in Brazil where Protalix retains full rights.

Protalix has partnered with Chiesi Farmaceutici S.p.A. for the global development and commercialization of Elfabrio^® which was approved by both the FDA and the European Medicines Agency (EMA) in May 2023. Protalix's development pipeline includes, among others, two proprietary versions of recombinant therapeutic proteins that target established pharmaceutical markets: PRX–115, a plant cell-expressed recombinant PEGylated uricase for the treatment of uncontrolled gout; and PRX–119, a plant cell-expressed long-acting DNase I for the treatment of NETs-related diseases. To learn more, please visit www.protalix.com.

¹ Schwabe C, Cohen-Barak O, Cole A, et al. Prolonged plasma urate-lowering after a single intravenous administration of PRX-115, a novel PEGylated uricase, in participants with elevated urate levels. Presented at: ACR Convergence 2024. Abstract L05.

² One participant in cohort 2 had an anaphylactic reaction 6 minutes into the infusion, after exposure to about 5% of the planned dose. The reaction resolved completely and the participant remained in the study. Antihistamine and steroid premedication was then given to all participants. No other participant had a similar reaction, and no other serious adverse events were reported. Source: ACR Convergence 2024 poster (abstract L05).

³ GlobalData, August 2025

⁴ Protalix internal research and proprietary market research (75 rheumatologists).

⁵ Schwabe C, Cohen-Barak O, Cole A, et al. Prolonged plasma urate-lowering after a single intravenous administration of PRX-115, a novel PEGylated uricase, in participants with elevated urate levels. Presented at: ACR Convergence 2024. Abstract L05.

Forward-Looking Statements

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SOURCE Protalix BioTherapeutics, Inc.