Protalix BioTherapeutics (PLX) Reports Final Results of BRIDGE Phase III Open-Label, Switch-Over Clinical Trial Evaluating Pegunigalsidase Alfa

Protalix BioTherapeutics, Inc. (NYSE: PLX) today announced final study results from the BRIDGE Phase III Open-Label, Switch-Over Clinical Trial Evaluating Pegunigalsidase Alfa for the Treatment of Fabry Disease. Pegunigalsidase alfa is a plant cell-expressed recombinant, PEGylated, cross-linked α-galactosidase-A product candidate under development for the treatment of Fabry disease. Topline results from the BRIDGE study were announced in May 2020.

The BRIDGE study was a Phase III 12 month open-label, single arm switch-over study evaluating the safety and efficacy of pegunigalsidase alfa, 1 mg/kg infused every two weeks, in up to 22 Fabry patients previously treated with agalsidase alfa, marketed by Takeda Pharmaceutical Company Limited (formerly Shire Plc) as Replagal®, for at least two years and on a stable dose for at least six months.

Final results of the data generated in the study showed substantial improvement in renal function as measured by mean annualized estimated Glomerular Filtration Rate (eGFR slope) in both male and female patients who were switched from agalsidase alfa to PRX-102.

Twenty of twenty-two patients completed the 12-month treatment duration. Eighteen of the patients who completed the study opted to roll over to a long-term extension study and continue to be treated with PRX-102.

As announced in May 2020, in the study, the mean annualized eGFR slope of the study participants improved from -5.90 mL/min/1.73m2/year while on agalsidase alfa to -1.19 mL/min/1.73m2/year on PRX-102 in all patients. Male patients improved from -6.36 mL/min/1.73m2/year to -1.73 mL/min/1.73m2/year and female patients improved from -5.03 mL/min/1.73m2/year to -0.21 mL/min/1.73m2/year.

Following the switch to PRX-102, there was a decrease in patients with progressing or fast progressing kidney disease, and most patients achieved a stable status post-switch.

PRX-102 was well-tolerated in the study, with all adverse events being transient in nature without sequelae. Of the 22 patients enrolled in the BRIDGE study, the majority of treatment emergent adverse events were mild or moderate in severity, with two patients (9.1%) withdrawing from the therapy due to hypersensitivity reaction that was resolved. The most common moderate treatment emergent adverse events were nasopharyngitis, headache and dyspnea.

An immunogenicity assessment indicated that four out of 20 patients (20%) developed persistent antidrug antibodies over the course of the study, of which two had neutralizing activity.

Baseline characteristics of the 20 patients that completed the study, ranging from ages 28 to 60 years, were as follows: mean eGFR 75.87 mL/min/1.73m2 in males, and 86.14 mL/min/1.73m2 in females and plasma lyso-Gb3 mean levels were 51.81 nM and 13.81 nM in males and females, respectively. While lyso-Gb3 levels remain slightly high, particularly within the male cohort, continuous reduction in lyso-Gb3 levels was observed of 19.55nM (32.35%) in males and 4.57nM (29.81%) in females.

"We are excited to have completed the final analysis of our Phase III BRIDGE study," said Dror Bashan, Protalix's President and Chief Executive Officer. "We anticipate that the BRIDGE study results will be used to support the filing of a Marketing Authorization Application (MAA) with the European Medicines Agency, and having completed the analysis, we have taken an important step in the preparations for the application."

The Phase III clinical development program consists of three studies, the BRIDGE study, the BALANCE study and the BRIGHT study. The ongoing BALANCE study is a fully enrolled, randomized, double blind, head-to-head, active control study which aims to demonstrate PRX-102's superiority in renal function as measured by the comparison of the mean annualized change (slope) in estimated glomerular filtration rate (eGFRCKD-EPI) between treatment groups over 24 months of treatment as compared to agalsidase beta, marketed by Sanofi Genzyme as Fabrazyme®. The BRIGHT study is a fully enrolled open-label, switch-over study designed to evaluate the safety, efficacy and pharmacokinetics of PRX-102, 2 mg/kg dosed once every 4 weeks, and to assess whether patients maintain clinical stability as measured by certain Fabry disease parameters after being switched to this regimen from an enzyme replacement therapy (ERT), agalsidase alfa or agalsidase beta, dosed every two weeks. The treatment period of the BRIGHT study was completed in July 2020.

"These important final results confirm the topline results announced last May," said Einat Brill Almon, Ph.D., Protalix's Senior Vice President and Chief Development Officer. "We look forward to the continued findings from our other ongoing Phase III studies of PRX-102, with the final results from the BRIGHT study expected in the first quarter of 2021, and interim results from the BALANCE study expected in the first half of 2021."

In May 2020, Protalix and Chiesi Global Rare Diseases announced the submission of a Biologics License Application (BLA) to the U.S. Food and Drug Administration (FDA) for pegunigalsidase alfa for the proposed treatment of adult patients with Fabry disease via the FDA's Accelerated Approval pathway. Subsequently, the FDA accepted the BLA and granted Priority Review designation for PRX-102 for the proposed treatment of adult patients with Fabry disease. The FDA also indicated in the BLA filing communication letter that it is not currently planning to hold an advisory committee meeting to discuss the application. The action date under the Prescription Drug User Fee Act (PDUFA) for the BLA has been updated to April 27, 2021.

"It is clear that many people who are living with Fabry disease are seeking new treatments," said Giacomo Chiesi, Head of Chiesi Global Rare Diseases. "We continue to be encouraged by the clinical data generated by this robust Phase III program and look forward to advancing through the final stages of the regulatory review process in the U.S."

Additional Details about the BRIDGE Study

Patients in the BRIDGE study were screened and evaluated over three months while continuing agalsidase alfa treatment. Following the screening period, each patient was enrolled and switched from agalsidase alfa treatment to receive intravenous infusions of PRX-102, 1 mg/kg every two weeks, for 12 months. Patients had the option to receive PRX-102 infusions in a home care setting based on infusion tolerability and country regulation.

About Fabry Disease

Fabry disease is an X-linked inherited disease that results from deficient activity of the lysosomal α-Galactosidase-A enzyme resulting in progressive accumulation of abnormal deposits of a fatty substance called globotriaosylceramide (Gb3) in blood vessel walls throughout a person's body. Fabry disease occurs in one person per 40,000 to 60,000. Fabry patients inherit a deficiency of the α-Galactosidase-A enzyme, which is normally responsible for the breakdown of Gb3. The abnormal storage of Gb3 increases with time and, accordingly, Gb3 accumulates, primarily in the blood and in the blood vessel walls. The ultimate consequences of Gb3 deposition range from episodes of pain and impaired peripheral sensation to end-organ failure – particularly of the kidneys, but also of the heart and the cerebrovascular system.

About Pegunigalsidase Alfa

Pegunigalsidase alfa (PRX-102) is an investigational, plant cell culture-expressed, and chemically modified stabilized version of the recombinant α-Galactosidase-A enzyme. Protein sub-units are covalently bound via chemical cross-linking using short PEG moieties, resulting in a molecule with unique pharmacokinetic parameters. In clinical studies, PRX-102 has been observed to have a circulatory half-life of approximately 80 hours. The Company designed PRX-102 to potentially address the continued unmet clinical need in Fabry patients.

You May Also Be Interested In

• Brainstorm Cell Therapeutics (BCLI) Announces Management Changes
• Cybin Inc (CYBN) Reports Publication of Research Manuscript in the Journal of Medicinal Chemistry
• Cerevel Therapeutics Holdings (CERE) Reports Positive Topline Results for Tavapadon