Strategy for a multicenter phase i clinical trial to evaluate globin gene transfer in β-thalassemia

Globin gene transfer in autologous hematopoietic stem cells offers a potentially curative treatment option for patients suffering from β-thalassemia major who lack an HLA-matched hematopoietic stem cell donor. Based on extensive preclinical investigation, we are initiating a phase I clinical trial using G-CSF mobilized, autologous CD34⁺ cells transduced with a vector similar to the original TNS9 vector. Our first mobilizations in adult β-thalassemic subjects have been well tolerated and yielded the required CD34⁺ cell dose. To minimize toxicity to enrolled subjects, and in the absence of a demonstrated requirement for myeloablative conditioning, our trial will use a reduced intensity conditioning regimen. Because low vector titers may adversely affect efficacy and safety, we have focused on vector manufacturing processes. We are now in a position to transfer our globin lentiviral vectors in a clinically relevant dosage (averaging 0.8 vector copy per cell in bulk CD34⁺ cells) and to supply clinical grade vector to collaborating centers in the U.S.A. and in Europe. We anticipate that the first U.S. trial of globin gene transfer will start in 2010.