Protalix BioTherapeutics (PLX), Chiesi Global Rare Diseases Announce Positive Topline Results from BRIGHT Phase III Open-Label Trial Evaluating Pegunigalsidase

February 23, 2021 6:51 AM EST

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Protalix BioTherapeutics, Inc. (NYSE American: PLX) (TASE: PLX), a biopharmaceutical company focused on the development, production and commercialization of recombinant therapeutic proteins produced by its proprietary ProCellEx® plant cell–based protein expression system, and Chiesi Global Rare Diseases, a business unit of Chiesi Farmaceutici S.p.A., an international research focused healthcare Group (Chiesi Group), today announced positive topline results from the BRIGHT Phase III clinical trial evaluating pegunigalsidase alfa (PRX–102), 2 mg/kg, administered every four weeks, for the potential treatment of Fabry disease. PRX–102 is the Company's plant cell-expressed recombinant, PEGylated, cross-linked α–galactosidase–A product candidate.

The BRIGHT study is a Phase III 12-month, open-label, switch-over study designed to evaluate the safety, efficacy and pharmacokinetics of PRX–102 treatment, 2 mg/kg every four weeks, in up to 30 patients with Fabry disease previously treated with a commercially available enzyme replacement therapy (ERT) (agalsidase alfa – Replagal® or agalsidase beta – Fabrazyme®), for at least three years and on a stable dose administered every two weeks.

Topline results indicate that 2 mg/kg of PRX–102 administered by intravenous infusion every four weeks was found to be well tolerated among treated patients, and stable clinical presentation was maintained in adult Fabry patients. No new patients developed treatment-induced anti-drug antibodies (ADA) following the switch to PRX–102 treatment.

"We are excited to share these topline results from the BRIGHT study, our third consecutive positive clinical trial of PRX–102, following the Phase I/II and the BRIDGE clinical studies. The results indicate that this investigational therapy is well tolerated and potentially an effective treatment for adult patients living with Fabry disease," said Einat Brill Almon, Ph.D., Protalix's Senior Vice President and Chief Development Officer. "We are encouraged to see that all of the patients who completed this study chose to enroll in the long-term extension study. Currently, 80% of the patients enrolled in the BRIGHT study have been treated with this treatment regimen for over two years. We look forward to advancing this study and further evaluating the results."

"These results demonstrate the potential of PRX–102 to be an important treatment option for the Fabry community and that the 2 mg/kg of PRX–102 every four weeks regimen may offer meaningful benefits to both patients and physicians. Treating physicians will be empowered with a potential additional treatment regimen, shown to be well tolerated, that they can offer to Fabry patients, pending approval of PRX-102," said Dror Bashan, Protalix's President and Chief Executive Officer. "We are gratified to have a strong balance sheet supporting our development efforts and look forward to executing and delivering on a year rich with value enhancing milestones."

The BRIGHT study enrolled 30 adult patients (24 males and 6 females). The most common Fabry disease symptoms were acroparesthesia, heat intolerance, angiokeratomas and hypohydrosis. All 30 patients received at least one dose of PRX–102, and 29 patients (mean [SD] age was 40.5 [11.3] years, ranging from 19 to 58 years) completed the 12-month study. Of these 29 patients, 28 received the intended regimen of 2 mg/kg every four weeks throughout the study, while one patient was switched to PRX–102 1 mg/kg every two weeks per protocol. One patient withdrew from the study after the first infusion due to a traffic accident.

Following screening, patients were enrolled and switched from their then current ERT to intravenous (IV) infusions of 2 mg/kg of PRX–102 every four weeks for 52 weeks (a total of 14 infusions). First infusions of PRX-102 were administered under controlled conditions at the investigation site. Based on the protocol-specified criteria, patients were able to receive their PRX-102 infusions at a home care setup once the Investigator and Sponsor Medical Monitor agreed that it was safe to do so. Safety and efficacy exploratory endpoints were assessed throughout the 52-week study.

Study outcome measures showed plasma lyso–Gb3 concentrations remained stable during the study with a mean change of 3.01 nM from baseline (19.36 nM) to Week 52 (22.23 nM). Mean absolute change of eGFR values were stable during the 52–week treatment period, with a mean change from baseline of –1.27 mL/min/1.73 m2.

"Patients participating in the BRIGHT study have expressed their satisfaction with the once every four weeks regimen," said John Bernat, M.D., Ph.D., University of Iowa and a Principal Investigator in the BRIGHT study. "Infusions of 2 mg/kg once every four weeks has the potential to enable patients to maintain their clinical status while reducing their number of treatments by half."

Following a survey of participants using the Quality of Life EQ-5D-5L questionnaire, responses indicate that patient perception of their own health remained high and stable throughout the 52–week study duration, with overall health mean (SE) scores of 78.3 (3.1) and 82.1 (2.9) at baseline and Week 52, respectively, in a 0 to 100 scale. Using the short-form Brief Pain Inventory (BPI) questionnaire, approximately 75% of study participants had an improvement or no change in average pain severity at Week 52 (compared to baseline). The short-form BPI interference items also remained stable during the study. Pain-related results indicate that there was no increase and/or relapse in pain. No Fabry clinical events were reported during the study.

"Of the 30 patients enrolled, 20 patients remained negative for anti-drug antibodies throughout the course of treatment. Of the 10 patients who were initially positive for anti-drug antibodies, four became negative for neutralizing antibodies at 12 months, suggesting tolerization by these patients," added Dr. Almon. "We find this immunogenicity data very encouraging and supportive to the positive benefit-risk profile of PRX–102."

"On behalf of our team at Chiesi, we are grateful to the patients, families, and investigators for their time and participation in this study," said Giacomo Chiesi, head of Chiesi Global Rare Diseases. "Their dedication has helped move this Phase III program forward and these topline data are another important milestone in our collected effort to make PRX–102 available to Fabry patients in need as rapidly as possible."

The Company intends to report final data on the BRIGHT study in the second half of 2021, and to present these findings at an appropriate medical conference.

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