Gene therapy for thalassemia normalizes hemoglobin

In both studies, after mobilization, patients’ unmanipulated hematopoietic stem cells and progenitor cells were taken to a central processing facility, where CD34+ cells were enriched and then transduced with the lentiviral vector BB305, which encodes adult hemoglobin (HbA) with a T87Z amino acid substitution and thereby provides functioning Hb beta. Patients received the product via infusion after undergoing myeloablative conditioning with busulfan.

A total of 23 patients, 19 in the international study and 4 in the French study, went through mobilization and apheresis. One patient in the international study had apheresis failure, so a total of 22 patients received LentiGlobin, and all were followed for up to 2 years.

Patients were given the opportunity to participate in a follow-on open label study meant to continue for an additional 13 years after the initial 24-month period; 13 patients are currently enrolled in this long-term follow-up study.

When transfusion volume at baseline was assessed, patients in the international study were receiving a median annual red blood cell transfusion volume of 164 mL/kg per year, while the French study participants were receiving a median 182 mL/kg per year of red blood cell transfusion.