Magenta Therapeutics Demonstrates First-ever Successful Gene Therapy Transplant Without Chemotherapy in Primates Using a Single Dose of Antibody-drug Conjugate

Magenta Therapeutics (NASDAQ: MGTA), a clinical-stage biotechnology company developing novel medicines to bring the curative power of immune reset to more patients, today announced that new results from its CD117-ADC patient preparation program were presented at the 61^st Annual Meeting of the American Society of Hematology (ASH). These results, which were highlighted in an oral presentation at ASH by John Tisdale, M.D., Director, Molecular and Clinical Hematology Section, National Institutes of Health, showed the first-ever successful transplant of gene-modified cells in non-human primates using a targeted, single-agent antibody-drug conjugate (ADC), without the use of chemotherapy or radiation.

“Today’s conditioning regimens involve high doses of chemotherapy, often paired with radiation, to remove the disease-causing cells. As a result, patients undergoing gene therapy or stem cell transplant are all faced with a difficult choice: whether to endure severe toxicity and risk infertility and cancer for the chance for a cure. Magenta’s portfolio of targeted ADCs represents an extremely promising new option to prepare patients for gene therapy or transplant with no need for toxic chemotherapy or radiation,” said Dr. Tisdale. “The results presented today show that a single dose of single agent CD117-ADC achieves the same level of depletion as four doses of busulfan chemotherapy to enable successful engraftment and persistence of stem cells modified with the β-globin gene, the gene that causes sickle cell disease and β-thalassemia when mutated. Importantly, the animals undergoing preparation with CD117-ADC showed none of the damaging toxicities associated with busulfan conditioning.”

“Magenta is the only company with the people, platforms and a product engine committed to comprehensively transforming immune and blood system reset, which includes revolutionizing the toxic methods that are used to prepare patients for gene therapy and transplant today.” said Jason Gardner, D.Phil., Chief Executive Officer and President, Magenta Therapeutics. “The gene therapy field has learned that higher levels of stem cell depletion, which meant higher doses of busulfan, were needed to ensure long-term engraftment of the gene-modified cells and persistence of gene therapy. Across all the modalities we have tested, we have seen that ADCs are most effective at achieving these high levels of stem cell depletion without chemotherapy to enable engraftment and long-term durability of the transplant. Today’s impressive results provide important validation of the ADC approach as well as the CD117 target for patient preparation and underscore Magenta’s leadership in the field of conditioning.”