Sangamo Therapeutics and Pfizer presented updated data from the Phase 1/2 Alta study evaluating investigational SB-525 gene therapy for severe hemophilia A. The data showed that SB-525 was generally well-tolerated and demonstrated a dose-dependent increase in Factor VIII (FVIII) activity levels. The data were presented during an oral presentation at the XXVII Congress of the International Society on Thrombosis and Haemostasis (ISTH), in Melbourne, Australia.
Alta is an ongoing open-label, dose-ranging clinical trial designed to assess the safety and tolerability of SB-525 in patients with severe hemophilia A. These data are from 10 male subjects with a mean age of 31 years who were treated across four ascending dose cohorts: 9e11 vg/kg (n=2), 2e12 vg/kg (n=2), 1e13 vg/kg (n=2) and 3e13 vg/kg (n=4). Factor VIII activity data presented at ISTH included results through June 18, 2019. The best response occurred in the 3e13 vg/kg treatment arm. The first two patients treated at the 3e13 vg/kg dose rapidly achieved normal levels of FVIII activity (within 5-7 weeks of treatment with SB-525 gene therapy) and have sustained Factor VIII activity with no bleeding episodes. The response continues to be durable for as long as 24 weeks, the extent of follow-up. Two additional patients more recently treated at the 3e13 vg/kg dose level are demonstrating FVIII activity kinetics that appear consistent with the first two patients treated in this dose cohort at similar early time points. SB-525 showed dose-dependent increases in FVIII activity levels across all dose cohorts evaluated. SB-525 was generally well tolerated. One treatment-related serious adverse event (SAE) was reported. This patient experienced hypotension and fever six hours after completion of SB-525 infusion; this fully resolved with treatment and the patient was discharged as planned within 24 hours. The most common adverse events were alanine aminotransferase and aspartate aminotransferase, pyrexia, fatigue, hypotension, myalgia and tachycardia
The U.S. FDA has granted Orphan Drug, Fast Track, and regenerative medicine advanced therapy (RMAT) designations to SB-525. Orphan Medicinal Product designation has been received from the European Medicines Agency.
SB-525 is being developed as part of a global collaboration between Sangamo and Pfizer.
About Hemophilia A
Hemophilia is a chronic disease that causes longer-than-normal bleeding due to absent or deficient clotting factor in the blood. Hemophilia A is more common than hemophilia B, and affects about 158,225 people, whereas hemophilia B affects about 31,247 people worldwide. Treatment regimens typically include on-demand and/or regular prophylactic infusions of factor replacement therapy to control or prevent the risk of bleeding.
Hemophilia A is caused by a deficiency of clotting Factor VIII protein. SB-525 is a gene therapy that uses an AAV vector to deliver a new therapeutic copy of the Factor 8 gene to the patient’s liver cells, designed to enable the liver to produce and secrete functionally active Factor VIII protein into the bloodstream.