CAMBRIDGE, Mass.--(BUSINESS WIRE)--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 61st 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.

Todays 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. Magentas 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 -globin gene, the gene that causes sickle cell disease and -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. Todays impressive results provide important validation of the ADC approach as well as the CD117 target for patient preparation and underscore Magentas leadership in the field of conditioning.

Results from the CD117-ADC Patient Preparation Program

Title: A Single Dose of CD117 Antibody Drug Conjugate Enables Autologous Gene-Modified Hematopoietic Stem Cell Transplant (Gene Therapy) in Nonhuman Primates (Abstract #610)Presenter: John Tisdale, M.D., Director, Molecular and Clinical Hematology Section, National Institutes of Health, Bethesda, Md.

Magentas most advanced patient preparation program, CD117-ADC, targets CD117, a protein expressed on hematopoietic stem cells. CD117-ADC is designed to remove the genetically mutated cells in the bone marrow that cause certain genetic diseases, such as sickle cell disease, enabling curative stem cell transplant or gene therapy.

Results presented by Dr. Tisdale showed:

About Magenta Therapeutics

Magenta Therapeutics is a clinical-stage biotechnology company developing medicines to bring the curative power of immune system reset through stem cell transplant to more patients with autoimmune diseases, genetic diseases and blood cancers. Magenta is combining leadership in stem cell biology and biotherapeutics development with clinical and regulatory expertise, a unique business model and broad networks in the stem cell transplant world to revolutionize immune reset for more patients.

Magenta is based in Cambridge, Mass. For more information, please visit http://www.magentatx.com.

Follow Magenta on Twitter: @magentatx.

Forward-Looking Statement

This press release may contain forward-looking statements and information within the meaning of The Private Securities Litigation Reform Act of 1995 and other federal securities laws. The use of words such as may, will, could, should, expects, intends, plans, anticipates, believes, estimates, predicts, projects, seeks, endeavor, potential, continue or the negative of such words or other similar expressions can be used to identify forward-looking statements. The express or implied forward-looking statements included in this press release are only predictions and are subject to a number of risks, uncertainties and assumptions, including, without limitation risks set forth under the caption Risk Factors in Magentas Registration Statement on Form S-1, as updated by Magentas most recent Quarterly Report on Form 10-Q and its other filings with the Securities and Exchange Commission. In light of these risks, uncertainties and assumptions, the forward-looking events and circumstances discussed in this press release may not occur and actual results could differ materially and adversely from those anticipated or implied in the forward-looking statements. You should not rely upon forward-looking statements as predictions of future events. Although Magenta believes that the expectations reflected in the forward-looking statements are reasonable, it cannot guarantee that the future results, levels of activity, performance or events and circumstances reflected in the forward-looking statements will be achieved or occur. Moreover, except as required by law, neither Magenta nor any other person assumes responsibility for the accuracy and completeness of the forward-looking statements included in this press release. Any forward-looking statement included in this press release speaks only as of the date on which it was made. We undertake no obligation to publicly update or revise any forward-looking statement, whether as a result of new information, future events or otherwise, except as required by law.

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