CAMBRIDGE, Mass.--(BUSINESS WIRE)-- Magenta Therapeutics, a biotechnology company developing therapeutics to improve and extend the use of curative bone marrow transplant for more patients, today reported Phase 2 clinical data from its MGTA-456 hematopoietic stem cell (HSC) expansion program at the 59^th annual meeting of the American Society of Hematology (ASH) in Atlanta, Ga. MGTA-456 is a single umbilical cord blood unit expanded with an aryl hydrocarbon receptor (AHR) antagonist. It is currently being studied in adult and pediatric patients with hematologic malignancies.

“Bone marrow transplant is a life-saving procedure with curative potential; however, many patients do not have a well-matched stem cell donor. Cord blood can provide a possible source of well-matched stem cells for these patients, but this is often limited by the low stem cell doses typically seen with cord blood,” said Michael Cooke, Ph.D., chief scientific officer, Magenta. “These data extend previous work and show that MGTA-456 gives rise to rapid, robust and durable engraftment when used as the only HSC graft. The ability to use MGTA-456 as a standalone graft is an important milestone in the ongoing clinical development of this product. The rapid engraftment in all patients proves that the expansion process results in significant expansion of HSCs -- a long time goal for the field. Through this expansion process, MGTA-456 has the potential to improve overall survival by allowing more patients to access better HLA-matched cord blood units that were previously not available due to low cell dose. We are currently planning multi-center clinical trials to further study MGTA-456 in both malignant and non-malignant diseases.”

“Based on my clinical transplant experience with cord blood, it is particularly impressive to see that all 18 patients treated in this study achieved rapid and durable engraftment of their stem cells, regardless of the conditioning regimen the patients underwent,” said John Wagner, M.D., Executive Medical Director, BMT Program, University of Minnesota Masonic Children’s Hospital and principal investigator of the study. “These data, along with the data from 18 patients reported in the previous study, show that MGTA-456 preserves the important clinical benefits of transplantation with umbilical cord blood, including low rates of graft vs. host disease (GvHD) and disease relapse and high overall survival.”

“These data are very encouraging and suggest that many patients could potentially benefit from MGTA-456, an expanded stem cell product that enables a high dose of cells that rapidly engraft and confer important disease benefits,” said David Scadden, M.D., Gerald and Darlene Jordan Professor of Medicine at Harvard University and co-founder of the Harvard Stem Cell Institute.

Phase 2 Trials with MGTA-456, Single Cord Blood Units (CBU) Expanded with an Aryl Hyrdrocarbon Receptor (AHR) Antagonist, Demonstrate Uniform Engraftment and Rapid Hematopoietic Recovery in Patients Following Myeloablative or Non-Myeloablative Conditioning (Abstract #662)

Overview and results presented by Dr. Wagner include:

• Survival after bone marrow transplant with cord blood is comparable to transplant with other sources of hematopoietic stem cells, and the survival rates in children and young adults with hematologic malignancies are high; however, adults transplanted with cord blood typically experience relatively poor engraftment and slow recovery after transplant blood due to the low hematopoietic stem cell doses available from cord blood.
• In this study, single cord blood units were expanded for 18 adult and adolescent patients with hematologic malignancies. The median increase in the number of CD34+ cells was 327-fold (range: 67-fold to 848-fold). Nine patients underwent a myeloablative conditioning regimen before transplant, and the other nine patients received non-myeloablative conditioning.
• The transplanted cells successfully engrafted in 18 of 18 patients, with rapid time to engraftment and immune recovery, regardless of conditioning intensity, compared to historical controls. Complete chimerism for patients treated with MGTA-456 was rapid, with no late graft failures.
• This study showed low rates of GvHD and disease relapse with MGTA-456, comparable to historical cohorts. Rates of overall survival at two years were also comparable to those seen with historical controls.
• The ability to expand hematopoietic stem cells has the potential to address the challenge of low cell doses typically obtained from cord blood, allowing more patients to obtain better matched cord blood units.

About Bone Marrow Transplant

Healthy bone marrow stem cells and the blood cells they create are crucial for survival, but certain diseases can affect the bone marrow, interfering with its ability to function properly. A bone marrow transplant is a process to replace unhealthy bone marrow with healthy bone marrow stem cells. Bone marrow transplant can save the lives of patients with blood cancers and genetic diseases and is a potential cure for patients with severe refractory autoimmune diseases. However, the high risks, toxic side effects and complexity of the procedure currently prevent many patients from being able to benefit.

About Magenta Therapeutics

Magenta Therapeutics is a biotechnology company developing therapeutics to revolutionize bone marrow transplant for patients with autoimmune diseases, blood cancers and genetic diseases. By creating a platform focused on critical areas of transplant medicine, Magenta Therapeutics is pioneering an integrated approach to extend the curative power of bone marrow transplant to more patients. Founded by internationally recognized leaders in bone marrow transplant medicine, Magenta Therapeutics was launched in 2016 by Third Rock Ventures and Atlas Venture and is headquartered in Cambridge, Mass. For more information, please visit www.magentatx.com.

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