Protalix Reports 12-Week Uric Acid Control With PRX-115

Carmiel, Israel, November 9, 2026

Phase 1 Results Demonstrate Extended Uric Acid Reduction

The newly presented analysis evaluated individual participant data from three higher-dose cohorts in Protalix’s Phase 1 single-ascending-dose clinical study. The cohorts received 18 mg, 24 mg or 36 mg of PRX-115, with six participants in each group. Participants received a single infusion and were monitored for 85 days to evaluate pharmacokinetic (PK) and pharmacodynamic (PD) responses. The analysis demonstrated that PRX-115 exposure increased with the administered dose and that higher doses remained measurable in circulation for longer periods. Participants with prolonged measurable drug concentrations generally maintained lower plasma uric acid levels for longer durations. At the 36 mg dose, mean plasma uric acid remained below the 6.0 mg/dL therapeutic threshold for up to 12 weeks after administration. Drug concentrations were measurable for as long as 85 days in the study. As PRX-115 concentrations gradually declined, plasma uric acid levels also began to recover, supporting the relationship between drug exposure and uric acid reduction. These findings are important because maintaining uric acid below the recommended target is a central objective of long-term gout management. However, the higher-dose analysis involved small cohorts, and the results should be considered preliminary rather than evidence of established long-term clinical effectiveness.

PRX-115 Targets Uncontrolled Gout Through Uricase Activity

PRX-115 is a plant cell-expressed recombinant PEGylated uricase designed to reduce elevated uric acid levels in patients with uncontrolled gout. Gout is a metabolic inflammatory disease caused by excess uric acid in the blood, which can lead to the formation of urate crystals in joints and surrounding tissues. These deposits can trigger sudden episodes of severe pain, swelling and inflammation, and prolonged uncontrolled disease may result in joint damage and other complications. Uricase is an enzyme that breaks down uric acid into a more soluble substance that can be eliminated from the body. Protalix developed PRX-115 using its proprietary ProCellEx plant cell-based protein expression platform. The candidate is designed to provide high specific activity, an extended circulating half-life and potentially reduced immunogenicity. These characteristics are intended to address some limitations associated with existing uricase-based treatments, including infusion burden, immune responses and loss of treatment effectiveness. In the earlier Phase 1 safety evaluation, PRX-115 was generally well tolerated, with most treatment-related adverse events described as mild to moderate and transient. One anaphylactic reaction was reported and resolved completely. This safety information remains important as the candidate advances into larger clinical studies.

Phase 2 RELEASE Study to Evaluate Longer Dosing Intervals

Following the Phase 1 findings, Protalix is advancing PRX-115 through its Phase 2 RELEASE clinical trial, a randomized, double-blind, placebo-controlled study in patients with uncontrolled gout. The trial is designed to evaluate a fixed 36 mg dose across five treatment groups, with approximately 30 participants in each group. The study includes PRX-115 administered every four weeks without methotrexate, as well as dosing every four, six or eight weeks in combination with methotrexate. A separate group receives placebo. The primary endpoint is the proportion of participants who maintain serum uric acid levels below 6.0 mg/dL for at least 80% of the time during Month 6. By investigating different dosing schedules, the study aims to determine whether longer intervals can maintain uric acid control while potentially reducing treatment burden. Protalix expects to report top-line Phase 2 results in the second half of 2027. If successful, the findings could support further development of a treatment approach designed to improve convenience for people with difficult-to-control gout. PRX-115 remains investigational, and additional clinical evidence will be required to establish its safety, efficacy and appropriate dosing schedule.

Source: Protalix BioTherapeutics press release