Sangamo’s Shares Goes up after the Announcement of Investigational Hemophilia A Gene Therapy Results
By Rajaneesh K. Gopinath, Ph.D.
SB-525 gene therapy, which is being developed as part of a global collaboration between Sangamo Therapeutics and Pfizer, sees positive growth following promising data from their phase 1/2 Alta study.
Hemophilia A (HA) is a bleeding disorder that is inherited as a mutated F8 gene in the X chromosome, which leads to the genetic deficiency of essential clotting factor VIII (fVIII). Due to this fact, the condition is more prevalent in males than females. Normally, bleeding triggers the activation of a coagulation cascade, wherein fVIII along with factors IXa and X perform blood clotting. However, in the case of HA patients, insufficient levels of these factors result in uncontrolled bleeding either spontaneously or after injuries. Existing treatment for this condition is the replacement of fVIII with recombinant fVIII products. However, the patients often generate inhibitory IgG antibodies in their body that act as inhibitors against the therapy. A recently approved therapy for this condition is Roche’s Hemlibra (Emicizumab) which is a bispecific factor IXa- and X-directed antibody designed to perform the function of fVIII.
SB-525 Gene Therapy
On July 6, Sangamo Therapeutics, and Pfizer announced updated results from the Phase 1/2 Alta study evaluating investigational SB-525 gene therapy for severe hemophilia A at the XXVII Congress of the International Society on Thrombosis and Haemostasis (ISTH), in Melbourne, Australia. SB-525 comprises a recombinant adeno-associated virus serotype 6 vector (AAV6) encoding the complementary deoxyribonucleic acid for B domain deleted human FVIII. It had earlier received Orphan Drug, Fast Track, and regenerative medicine advanced therapy (RMAT) designations from the FDA. As an immediate consequence of the announcement, the shares of Sangamo therapeutics witnessed an upward surge.
Phase 1/2 Alta Study
The Phase 1/2 Alta study is an open-label, dose-ranging clinical trial designed to assess the safety and tolerability of SB-525 in severe hemophilia A patients. Ten male patients with a mean age of 31 years (range of 18-47 years) were assessed in the study. The data showed that the therapy was generally well-tolerated and demonstrated a dose-dependent increase in fVIII activity. The first two patients treated at a dose of 3e13 vg/kg rapidly achieved normal levels of fVIII activity with no reported bleeding events. The response continues to be durable for as long as 24 weeks. The two patients who were treated more recently are also demonstrating similar fVIII activity kinetics, consistent with the results observed in first two patients.
“The initial results of the Alta study presented at ISTH demonstrate that SB-525 has the potential to be a predictable and reliable treatment that may bring clinical benefit to patients with hemophilia A,” said Adrian Woolfson, M.D., Ph.D., Executive Vice President of Research and Development, Sangamo. “The results show that SB-525 is well tolerated, that Factor VIII levels in the first two patients in the 3e13 vg/kg cohort reached normal, sustained levels as measured using a chromogenic assay, and that variability of Factor VIII activity is low, both within each patient and within each dose cohort. We look forward to continuing to follow these patients to further understand the durability of response to SB-525 gene therapy and to working with Pfizer to potentially advance a registrational study.”
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