New Data Published in Journal Cell Show Robust Mobilization of Highly Engraftable Stem Cells in Mouse Models with Combination of GROβ and Plerixafor

— Publication from scientific collaboration lays foundation for
Magenta Therapeutics data on GROβ and plerixafor in non-human primates
to be presented at ASH annual meeting –

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 announced the publication of research led by Jonathan
Hoggatt, Ph.D., assistant professor of medicine at Harvard Medical
School and the Massachusetts General Hospital (MGH) Cancer Center and
Center for Transplantation Sciences, and a principal faculty member at
Harvard Stem Cell Institute. Dr. Hoggatt is a scientific co-founder of
Magenta.

The research demonstrates that a single administration of a chemokine,
GROβ, in combination with plerixafor (also known as AMD3100) resulted in
rapid mobilization of robust numbers of hematopoietic stem cells (HSCs)
from the bone marrow and into the blood, which were then harvested for
transplant in mouse models. Notably, HSCs obtained with GROβ and
plerixafor mobilization resulted in faster engraftment and higher donor
chimerism, two important factors for the success of a transplant,
compared to cells obtained with the current mobilization standard of
care, G-CSF. The article “Rapid Mobilization Reveals a Highly
Engraftable Hematopoietic Stem Cell” was published in Cell online
on December 7, 2017.

Now under exclusive license to Magenta from Harvard University’s Office
of Technology Development, the technology described in this paper was
co-developed by David Scadden, M.D., the Gerald and Darlene Jordan
Professor of Medicine in Harvard’s Department of Stem Cell and
Regenerative Biology, co-director of Harvard Stem Cell Institute, and
Director of the Center for Regenerative Medicine at MGH. Dr. Scadden is
also a scientific co-founder of Magenta.

“Magenta’s mission is to expand the curative power of bone marrow
transplant to more patients. Improving the standard of care for
mobilization of hematopoietic stem cells has the potential to improve
both the process and outcomes of bone marrow transplant, helping extend
the procedure to a broader range of diseases that could be cured,” said
Michael Cooke, Ph.D., chief scientific officer, Magenta Therapeutics.
“At Magenta we are building on this important research in mouse models
by investigating the combination of GROβ and plerixafor in non-human
primates. We look forward to presenting these primate data this weekend
at the annual meeting of the American Society of Hematology (ASH).”

As part of their research, Dr. Hoggatt and colleagues analyzed a
single-blind dose-escalating pilot study in healthy human volunteers to
assess the tolerability, pharmacokinetics and pharmacodynamics following
administration of single agent GROβ. The study showed that GROβ was well
tolerated.

“Mobilization of HSCs with G-CSF involves repeated injections and often
requires five or more days of treatment and multiple outpatient visits.
G-CSF is also associated with bone pain, nausea, headache and fatigue;
and is contraindicated in some difficult-to-mobilize patient
populations, such as patients with sickle cell disease,” said Dr.
Hoggatt. “In this report, we show that a single administration of GROβ
with plerixafor resulted in peak mobilization of stem cells within 15
minutes in mouse models. Moreover, mice transplanted with the
GROβ-mobilized stem cells experienced robust short- and long-term
engraftment, with faster recovery of neutrophils and platelets compared
to mice transplanted with stem cells mobilized with G-CSF. These data
suggest that the combination of GROβ with plerixafor has the potential
to become a more effective and more patient-friendly approach than the
current standard of care. We may be able to turn a one-week process into
an optimal single day process.”

About Bone Marrow Transplant

Healthy bone marrow stem cells and the blood cells they form 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.

Contacts

Magenta Therapeutics:
Manisha Pai, 857-242-1155
Vice
President, Communications & Investor Relations
mpai@magentatx.com