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Gene Therapy in Hemophilia B

Gene therapy is a huge category of therapies that are currently being studied for future use. Many of the therapies are now in or are approaching Phase 3 clinical trials. In total there are five therapies that are in Phase 3, three Hemophilia A therapies and two Hemophilia B therapies. Today we will look at the early results of the two Hemophilia B therapies.

The first of these studies that we will look at is AMT-061, a therapy called etranacogene dezaparvovec. This therapy study, known as HOPE-B, began on June 27, 2018 and recruited 56 participants. For those interested in the nitty-gritty, this is an open-label, single-dose, multi-center, multinational trial investigating a serotype 5 adeno-associated viral vector containing the Padua variant of a Codon-optimized human factor IX gene. This study is scheduled to run through August of 2024.

The initial data from this trial is very promising. At the end of 2019 their data showed that all 56 patients in the study have stabilized and sustained Factor IX activity at functionally curative levels one year after a single administration. Factor IX activity has been reported at up to 50% of normal with a mean of 41%. This level would exceed the levels considered sufficient to eliminate or significantly reduce the risk of bleeding events.

UniQure, the maker of the therapy, has reported no cytotoxic T-cell-mediated immune response to the capsid. Preclinical and clinical data show that AAV5-based gene therapies may be clinically effective in patients with pre-existing antibodies to AAV5, thereby potentially increasing patient eligibility for treatment. CSL Behring has entered into a licensing agreement with uniQure to acquire the exclusive rights to etranacogene dezaparvovec.

The second of these studies that we will look at is SPK-9001, a therapy called fidanacogene elaparvovec. This Spark Thereapeutics/Pfizer therapy study, a combination study with their hemophilia A therapy, is a Phase 3 study that establishes efficacy data of current prophylaxis replacement therapies for both hemophilia A and hemophilia B prior to the Phase 3 gene therapy study. This study began on July 26, 2018. Enrollment in the SPK-9001 is now complete. As this is a preliminary study of relatively short duration and is a precursor to the actual clinical study, no results have been reported. Phase 2 data shows that many subjects achieved a normal range of clotting activity, while some showed a low mild level, stable at one year.

The actual clinical study of SPK-9001 has not yet begun, so perhaps it was a bit premature to include this therapy in our notes at this time. However, we feel like it is always good to include more rather than less information as time and space allows.

The writer is not a medical professional, and holds no special knowledge of the subjects discussed. I would encourage you to do your own research and have provided links to the sources of information used in creating this article.

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