On November 12, 2019 bluebird bio, Inc. (Nasdaq: BLUE) and Forty Seven, Inc. (Nasdaq:FTSV) reported 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 (Press release, bluebird bio, NOV 12, 2019, View Source [SID1234551003]). 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.
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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.
"We are excited about this collaboration, combining our industry-leading LVV HSC gene therapy platform with Forty Seven’s novel antibody-based conditioning regimen," said Philip Gregory, chief scientific officer, bluebird bio. "We believe that, if successful, this novel conditioning modality could not only increase the number of patients and physicians who may consider gene therapy but also improve the overall risk benefit profile for stem cell-based gene therapy, as well as potentially reduce time and costs associated with hospital visits."
"Forty Seven is advancing the pioneering work on CD47 and cKIT from our scientific founder, Irv Weissman’s lab. We have shown that antibody blockade of CD47 can synergize with other antibodies targeting cancer to promote tumor engulfment. Based on this experience, coupled with the results of preclinical studies, we are eager to explore this dual-antibody approach for the potential treatment of non-malignant diseases," says Jens Peter Volkmer, M.D., Founder and Vice President of Research and Development at Forty Seven.
Forty Seven’s President and Chief Executive Officer, Mark McCamish, M.D., Ph.D., commented, "bluebird is a leading gene therapy company and we are excited to collaborate with them. Stem cell transplantation is potentially curative for a variety of blood diseases, including genetic blood disorders like sickle cell disease and beta-thalassemia. If successful, we believe our chemo- and radiation-free, all-antibody approach could expand transplantation beyond genetic blood disorders to a range of indications for which current transplantation approaches are suboptimal. In 2020, we plan to evaluate FSI-174 in healthy volunteers, before initiating a combination study of Forty Seven’s novel all-antibody conditioning regimen and bluebird’s gene therapy product."
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.
About FSI-174 and Magrolimab
FSI-174 is a humanized monoclonal antibody targeting cKIT, which is a receptor that is highly expressed on hematopoietic stem cells. Magrolimab is a humanized monoclonal antibody targeting CD47, which is a "don’t eat me" signal to macrophages and is expressed on all cells. Magrolimab is currently being investigated in Phase 2 clinical trials to treat cancer and has established clinical efficacy in four indications, including myelodysplastic syndrome, acute myeloid leukemia, diffuse large B cell lymphoma and follicular lymphoma, with a favorable safety profile in over 350 patients treated, including some patients treated continuously for over two years. When combined, FSI-174 sends a positive signal to macrophages to target blood forming stem cells for removal and magrolimab disengages inhibitory signals that block phagocytosis. Combination of these antibodies has shown efficient removal of blood forming stem cells, allowing for transplantation in pre-clinical models.