Protalix BioTherapeutics, Chiesi Complete Enrollment for Trial of Pegunigalsidase Alfa

Protalix BioTherapeutics and its development and commercialization partner, Chiesi Farmaceutici announced the completion of enrollment in their Phase III BALANCE clinical study of pegunigalsidase alfa, or PRX‑102, for the treatment of Fabry disease. The head-to-head Phase III BALANCE clinical study is designed to evaluate the safety and efficacy of PRX‑102 compared to agalsidase beta (Fabrazyme®) on renal function in Fabry patients with progressing kidney disease previously treated with agalsidase beta. BALANCE is the third of three Phase III studies, including the Phase III BRIDGE and the Phase III BRIGHT studies which are both fully enrolled and ongoing.

"We are excited to complete enrollment in our third Phase III study of PRX‑102 for the treatment of Fabry disease. This achievement marks a major milestone in our development of PRX‑102," said Dror Bashan, President and CEO of Protalix BioTherapeutics. "We are most grateful to the BALANCE study participants and to our investigators for their support and dedication, and we remain committed to bringing the Fabry community a potentially better treatment option. As we have already disclosed, we are targeting a BLA submission under an accelerated approval pathway for PRX‑102 in the first quarter of 2020 based on data from our completed Phase I/II clinical studies of PRX‑102 and from our ongoing Phase III BRIDGE clinical study. We believe our three, now fully enrolled, studies represent a robust clinical program for Fabry disease, and we look forward to reporting on the results upon completion of the studies."

PRX‑102 is the Company's plant cell-expressed recombinant, PEGylated, cross-linked alpha-galactosidase A enzyme drug candidate. Protalix's products are recombinant therapeutic proteins expressed through its proprietary plant cell-based expression system, ProCellEx®.

"Despite years of current enzyme replacement treatment, there continues to be an unmet medical need in Fabry patients who continue to show progressive loss of renal function," said David G. Warnock, M.D., Professor of Medicine (Emeritus) at the University of Alabama at Birmingham. "The progressive loss of kidney function seen in Fabry patients may be the result of insufficient enzyme coverage combined with the presence of neutralizing antibodies. Given the favorable half-life of pegunigalsidase alfa and its low level of inhibition by pre-existing neutralizing antibodies, there is potential for pegunigalsidase alfa to attenuate and/or stabilize renal function in patients who continue to lose renal function while on currently-available enzyme replacement therapy."

The BALANCE Study is a 24-month, randomized, double blind, active control study of PRX‑102 (pegunigalsidase alfa) in Fabry disease patients with impaired renal function. Patients previously treated with agalsidase beta for approximately one year and on a stable dose for at least six months were screened and then randomized to be switched and treated with 1 mg/kg of PRX‑102 or continue treatment with 1mg/kg of agalsidase beta. Patients receive intravenous infusions of 1mg/kg administered every two weeks. Patients are randomized in a 2:1 ratio to PRX‑102 or agalsidase beta. In the study, randomization is being stratified by urinary protein to creatinine ratio (UPCR) of < or ≥ 1 g/g by spot urine sample. No more than 50% of the patients enrolled in the study are female. Patients participating in the study are being evaluated to, among other disease parameters, determine if their renal function continues to deteriorate at the same rate while being treated with agalsidase beta as measured by eGFR slope. Cardiac assessment, Lyso-Gb3, pain, quality of life, immunogenicity, clinical events and pharmacokinetic and other parameters are also being evaluated. In addition, participating patients are being evaluated to assess the safety and tolerability of PRX‑102.

The BRIDGE study is a 12-month open-label, single arm switch-over study to assess the safety and efficacy of pegunigalsidase alfa, 1 mg/kg infused every two weeks, in Fabry patients previously treated with agalsidase alpha (Replagal®). Enrollment in this study was completed in December 2018.

The BRIGHT study is a 12-month open-label switch-over study to assess the safety, efficacy and pharmacokinetics of pegunigalsidase alfa 2 mg/kg administered every 4 weeks in Fabry patients previously treated with an enzyme replacement therapy: agalsidase alfa or agalsidase beta.  Enrollment in this study was completed in June 2019.

Fabry disease is an X-linked inherited disease that results from deficient activity of the lysosomal enzyme alpha galactosidase A 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. Fabry patients inherit a deficiency of the enzyme alpha-galactosidase-A, 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.

The Company's proprietary pegunigalsidase alfa is an investigational, plant cell culture expressed enzyme, and a chemically modified version of, the recombinant alpha-Galactosidase-A protein. Protein sub-units are covalently bound via chemical cross-linking using short PEG chains, resulting in a more stable molecule with different pharmacokinetic parameters compared to the current available versions of the enzyme.  In clinical studies, pegunigalsidase alfa has been observed to have a favorable circulatory half-life of approximately 80 hours. In addition, in a Fabry mouse model, pegunigalsidase alfa was observed to have favorable levels of enzyme activity in target organs affected by Fabry disease. The Company designed pegunigalsidase alfa to potentially address the continued unmet clinical need in Fabry patients of continuous disease progression, infusion reaction and immunogenicity.

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