First Clinical Data with MGTA-145 Show Single-Day Dosing and Collection of Robust Numbers of High-Quality Stem Cells in Healthy Volunteers

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 MGTA-145 stem cell mobilization program were presented at the 61^st Annual Meeting of the American Society of Hematology (ASH). These results, which were presented by John DiPersio, M.D., Ph.D., Professor of Medicine and Chief of the Oncology Division, Washington University School of Medicine, St. Louis, Missouri, showed that MGTA-145 in combination with plerixafor met all the endpoints in the study, and safely mobilized a large number of high-quality stem cells in a single day. The cells were then shown to engraft in a humanized mouse model.

Mobilized peripheral blood is used for the majority of the 65,000 stem cell transplants performed each year across the United States and Europe, but the current standard of care, G-CSF, requires at least five days of dosing and is associated with significant side effects, including bone pain that often requires narcotics. Further, patients with autoimmune diseases or sickle cell disease can have severe side effects with G-CSF, including potentially fatal complications.

Magenta is developing MGTA-145 as the new first-line standard of care for stem cell mobilization in a broad range of diseases, including autoimmune diseases and genetic diseases. MGTA-145, a CXCR2 agonist, works in combination with plerixafor, a CXCR4 antagonist, to harness the physiological mechanism of stem cell mobilization.

“The current standard of care for stem cell mobilization, G-CSF, requires five or more days of injections, which is difficult for patients, donors and the healthcare system. The novel mechanism of MGTA-145 may enable single-day dosing, mobilization and collection in all donors and patients, including those with sickle cell disease or autoimmune diseases, and positions it as a promising new first-line standard of care for all transplants as well as gene therapy,” said Dr. DiPersio.

“These initial results in a healthy volunteer setting validate the unique mechanism of action of MGTA-145 and its ability to mobilize sufficient hematopoietic stem cells for transplant in combination with plerixafor. We are particularly pleased to see the high percentage of CD34+CD90+ cells collected in healthy volunteers, as preclinical data suggest that these cells are correlated with engraftment. Our initial results support this, with rapid engraftment of the collected cells observed in humanized mouse models,” said John Davis, M.D., M.P.H., Chief Medical Officer, Magenta. “The unique mechanism, single-day dosing and collection of robust numbers of cells that engraft quickly highlight the potential utility for MGTA-145 across multiple diseases and hold promise for future development in allogenic donors as well as patients.”