bluebird bio, Inc. and Forty Seven, Inc. announced that they have entered into a research collaboration to pursue clinical proof-of-concept for Forty Seven's novel antibody-based conditioning regimen, FSI-174 (anti-cKIT antibody) plus magrolimab (anti-CD47 antibody), with bluebird's ex vivo lentiviral vector hematopoietic stem cell (LVV HSC) gene therapy platform. This collaboration will focus on a conditioning approach aimed to deliver reduced toxicity and will initially target diseases that have the potential to be corrected with transplantation of autologous gene-modified blood-forming stem cells. If successful, the new conditioning regimen could allow for more patients to undergo gene therapy.

Autologous hematopoietic stem cell transplantation (HSCT) and most ex vivo LVV HSC gene therapies require that a patient's own stem cells first be depleted from the bone marrow to facilitate the engraftment of the new (or gene-modified) HSCs through a process called conditioning. Conditioning is performed using chemotherapy or radiation, which can place patients at risk for infection and require hospitalization until bone marrow cells have recovered. In addition, conventional conditioning can place patients at risk for secondary malignancy and infertility.

As a result, the overall toxicity profile of current conditioning regimens limits the types of patients who are eligible for gene therapy. It is hoped that novel antibody based conditioning regimens could avoid these toxicities. Under the terms of the agreement, bluebird bio will provide its ex vivo LVV HSC gene therapy platform and Forty Seven will contribute its innovative antibody-based conditioning regimen for the collaboration.