Protalix Biotherapeutics, Inc. (NYSE:PLX) has announced positive results from its Phase I clinical trial of PRX-115 for the treatment of severe gout. The trial, a single ascending dose, double-blinded, placebo-controlled study, demonstrated that PRX-115 was well-tolerated and produced a dose-dependent reduction in plasma urate levels in participants with elevated urate levels (>6.0 mg/dL).
The Phase I trial enrolled 64 subjects with elevated urate levels who received a single intravenous (IV) infusion of PRX-115 or placebo, randomized in a 3:1 ratio across eight cohorts. The study assessed the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of PRX-115 over an 85-day monitoring period.
Safety and Tolerability
According to the data presented at the American College of Rheumatology (ACR) meeting, PRX-115 was found to be well-tolerated. Among the subjects treated, 25% (12/48) reported study drug-related adverse events (AEs). One subject experienced an anaphylactic reaction immediately following infusion in cohort 2, which resolved completely. No other subjects experienced this reaction, and there were no other serious adverse events reported.
Pharmacokinetics and Urate Reduction
Plasma concentrations of PRX-115 showed a dose-dependent relationship, with the highest concentrations observed after infusion. Notably, PRX-115 was detectable in plasma for up to 12 weeks after infusion in the highest dosage cohorts (6, 7, and 8), suggesting a prolonged effect.
The trial also demonstrated that PRX-115 effectively reduced plasma urate levels, with the degree of reduction correlating with the dose administered. Following a single dose, mean plasma urate levels remained below 6.0 mg/dL. These results indicate the potential for a wide dosing interval, which could improve patient convenience and reduce treatment costs.
Implications and Future Development
The current standard treatment for chronic gout, Krystexxa, requires intravenous administration every two weeks. The prolonged presence of PRX-115 in plasma suggests the possibility of less frequent dosing, offering a potential advantage over existing therapies.
Protalix is currently planning a Phase II trial for PRX-115, with trial design details expected to be finalized over the next several quarters. The company anticipates launching the Phase II trial in the second half of 2025.
