A gene therapy for a rare blood disorder has shown what the manufacturer calls the first evidence of long-term improvement associated with the disease.

New York-based Rocket Pharmaceuticals said Thursday that it had presented long-term follow-up data from the Phase I/II study of RP-L102, its gene therapy for Fanconi anemia, at the annual congress of the European Society of Cell and Gene Therapy in Barcelona, Spain. The company said it represented the first evidence of long-term improvement and stabilization in blood counts and durable mosaicism among patients who received the therapy without the use of the conditioning regimens normally used for allogeneic stem cell transplants, which the company calls Process A.

Shares of Rocket were up slightly on the Nasdaq following the news. RP-L102 is a lentiviral vector-based gene therapy. Most other gene therapies in development, and both of the currently marketed ones Spark Therapeutics Luxturna (voretigene neparvovec-rzyl) and Novartis Zolgensma (onasemnogene abeparvovec-xioi) are adeno-associated viral vector-based.

According to the data, representing four of nine patients, there were improved blood counts and long-term bone marrow mitomycin C (MMC) resistance, thereby indicating durable phenotypic correction. The data met or exceeded a 10 percent threshold that the company said the Food and Drug Administration and European Medicines Agency had agreed to for its upcoming Phase II registration study, for which it plans to start enrolling patients by the end of the year.

FA is a rare, genetic bone marrow failure disorder, half of whose patients are diagnosed before the age of 10, while about 10 percent of patients are diagnosed as adults, according to the National Organization for Rare Disorders. It is often associated with progressive deficiency of production of red and white blood cells and platelets in the bone marrow and can eventually lead to certain solid and liquid tumor cancers. It occurs in 1-in-136,000 births and is more common among Ashkenazi Jews, Spanish Roma and black South Africans.

These results indicate the feasibility of engraftment in FA patients using autologous, gene corrected [hematopoietic stem cells] in the absence of any conditioning regimen, said Dr. Juan Bueren, scientific director of the FA gene therapy program at Spains Center for Energy, Environmental and Technological Research, in a statement. This indicates the potential of this therapeutic approach as a definitive hematologic treatment, while avoiding the burdensome side effects associated with allogeneic transplant, including the risk of post-transplant mortality and a substantially higher risk of head and neck cancer.

Photo: virusowy, Getty Images

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Rocket's gene therapy shows long-term efficacy in rare blood disorder - MedCity News

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