Protalix BioTherapeutics (PLX) Issues 2023 Letter to Stockholders

Protalix BioTherapeutics, Inc. (NYSE American: PLX) today announced the following letter from its President and Chief Executive Officer, Dror Bashan, to its stockholders and the investment community.

January 3, 2023

Dear Protalix Shareholders,

2022 was a strong year for Protalix, and I would like to take a moment to reflect on the significant progress we have made. Together with our development and commercialization partner, Chiesi, we executed on key regulatory milestones with the submission of marketing authorization applications in the United States and the European Union for PRX–102 for the treatment of adult patients with Fabry disease, bringing us one step closer to the potential approval and commercialization of this important treatment option. I continue to be immensely grateful to our team and our partners for their steadfast dedication to bringing PRX–102 to patients. I am proud of our accomplishments in 2022, highlighted below, and look forward to continued success in 2023 as we continue to work towards meaningful, value-adding milestones and transformational catalysts.

Regulatory Advancements

Together with Chiesi, we submitted a Marketing Authorization Application (MAA) to the European Medicines Agency (EMA) in February 2022. As you know, our PRX-102 phase III clinical program consists of extensive data from three phase III clinical trials, the BRIDGE study which analyzed 1 mg/kg of PRX–102 every two weeks dosing, the BRIGHT study which analyzed 2 mg/kg of PRX–102 every four weeks dosing and the BALANCE study which analyzed 1 mg/kg of PRX–102 every two weeks dosing. The MAA includes final data from our BALANCE, BRIDGE and BRIGHT clinical trials; and final data from our phase I/II clinical trial generated from naïve/untreated patients including the related extension study using 1 mg/kg of PRX–102 every two weeks dosing. The EMA is currently reviewing the PRX–102 MAA, and interactions with the EMA are ongoing.

In addition, we, together with Chiesi, resubmitted a Biologics License Application (BLA) to the U.S. Food and Drug Administration (FDA) in November 2022. The FDA accepted the submission for review and set an action date of May 9, 2023 under the Prescription Drug User Fee Act (PDUFA). The BLA resubmission includes a comprehensive set of clinical and manufacturing data, identical to the one submitted to the EMA, which was compiled from studies that involved more than 140 Fabry disease patients with up to five years of follow up, including all three completed studies in the PRX–102 phase III clinical program. The BLA resubmission also includes safety data compiled from our ongoing phase III extension studies of PRX–102. If PRX–102 is approved by the FDA, Protalix will be eligible to receive a milestone payment from Chiesi.

Clinical Advancements

With the successful readouts of our BRIGHT and BALANCE studies in 2022, we concluded our phase III clinical program which supported our regulatory submissions to the FDA and EMA as mentioned above. Final results of the data generated in the BALANCE study, completed in July 2022, demonstrated that PRX-102 was statistically non-inferior to agalsidase beta, measured by estimated glomerular filtration rate (eGFR) slope. Similarly, final results from the BRIGHT study were announced in March 2022 and demonstrated stable disease with PRX-102 treatment as measured by eGFR slope and plasma lyso-Gb3. Results from both studies showed a favorable tolerability profile for PRX-102, which is consistent with results from our prior trials.

We are also progressing with our clinical development program for PRX–115, our plant cell-expressed recombinant PEGylated uricase (urate oxidase) – a chemically–modified enzyme under development for the potential treatment of severe gout. Gout is the most common inflammatory arthritis in the United States, affecting an estimated 9.2 million adults. Expressed using ProCellEx®, our proprietary plant cell-based protein expression system, PRX-115 is an optimized recombinant uricase enzyme that we are designing to lower uric acid levels while having low immunogenicity and increased half-life in the circulation. Pre-clinical data demonstrates stable PK profile and long half-life, low immunogenic risk and high specific activity, supporting the potential of PRX–115 to be a safe and effective treatment for severe gout. Preliminary results of the first stage of one-month multiple dosing toxicity studies of PRX–115 in two species show no indication of safety concerns, and our current development plan goal is to initiate a phase I clinical trial in the first quarter of 2023.

Looking Forward

I am excited about our accomplishments in 2022 and look forward to what the future holds as we navigate the company through 2023 and beyond. We believe PRX–102, if approved, has the potential to meaningfully improve the quality of life for many Fabry patients and their families and, together with Chiesi, we are preparing for the anticipated commercial launch. Fabry disease represents a tremendous opportunity in a multi-billion dollar market ready for a potentially better treatment option. We are also making progress with PRX–115 and our other earlier stage pipeline programs.

We thank our employees for their tireless efforts in driving Protalix forward and building on our scientific foundation. We also thank our Board of Directors for their valuable support and guidance in shaping the company's operations and direction. Chiesi deserves our gratitude for their professionalism and the close collaboration we enjoy. Finally, we would like to thank you, our shareholders, for your continued support and look forward to sharing our future successes with you.

Sincerely,

Dror Bashan, President & Chief Executive Officer

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