Full Press Release Details
Magenta Therapeutics Presents Positive MGTA-117 Clinical Data at
the American Society of Hematology (ASH) Annual Meeting and Provides Program Updates
MGTA-117 preliminary clinical results from 15 patients across three dose-escalation cohorts of the ongoing Phase 1/2 clinical trial shows single-agent activity with no dose-limiting toxicities; transition to
patients with transplant-eligible AML/MDS expected in H1 2023 pending regulatory alignment
conjugate (CD45-ADC) IND-enabling studies are advancing
MGTA-145 clinical trial for stem cell mobilization in sickle cell disease patients is
progressing with data now expected to be shared H1 2023
Conference call and webcast scheduled for 8:30am ET / 7:30am
CT on December 13, 2022
Cambridge, MA December 12, 2022 Magenta Therapeutics (Nasdaq: MGTA), a clinical-stage
biotechnology company developing novel medicines designed to bring the curative power of stem cell transplant to more patients, highlights updated clinical data from the ongoing MGTA-117 Phase 1/2 dose-escalation clinical trial made in an oral
presentation today at the American Society of Hematology 2022 Annual (ASH) Meeting in New Orleans and provides program updates across the portfolio.
We have shown that a single dose of MGTA-117 binds target cells, depletes target cells, clears the body quickly
as designed, and does so with a favorable tolerability profile in our ongoing Phase 1/2 clinical trial. We believe that these positive clinical data establishes
proof-of-mechanism, and that we have reached an active dose. Target cell depletion is a critical measurement of success for
MGTA-117, and we are encouraged by the levels of depletion we have observed in both the blood and the bone marrow of relapsed/refractory acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS)
patients. We are excited about our planned next steps to take MGTA-117 into transplant-eligible AML and MDS patients as well as into patients who are receiving gene therapy. We are thankful to all of the
patients and families who have participated in our trial to date as well as our investigators and the clinical site staff, all of whom have contributed greatly to the advancement of MGTA-117 for
patients, said Jason Gardner, President and Chief Executive Officer of Magenta Therapeutics. Together with the progress we are making on CD45-ADC and
MGTA-145, we are pleased with the momentum across our portfolio and the multiple anticipated inflection points for Magenta in the coming year.
MGTA-117 Clinical Data and Continued Development
MGTA-117 is Magenta s most advanced targeted conditioning product candidate designed to deplete
CD117-expressing target cells in the blood and/or bone marrow prior to a patient undergoing stem cell transplant or receiving an ex vivo gene therapy product. MGTA-117 is an anti-CD117 antibody conjugated
to an amanitin payload. CD117, also known as c-Kit receptor, is highly expressed on hematopoietic stem cells, progenitor cells and cancer blast cells.
Current Phase 1/2 Patient Population and Potential Significance for Clinical Development
The ongoing Phase 1/2 clinical trial is in relapsed/refractory (R/R) AML and MDS. These patients are deemed ineligible for transplant due to active disease
characterized by high numbers of cancer blast cells present in the bone marrow and in the bloodstream. Over 80% of patients with AML and MDS express the CD117 receptor on the surface of their cancer cells. In these patients, CD117+ target cells are
a combination of cancer blast cells in the blood and bone marrow and non-malignant stem and progenitor cells in the bone marrow. MGTA-117 is designed to target all of
these cells, and clinical evidence of depletion in this patient population provides valuable support that MGTA-117 will robustly deplete target cells in the proposed next phase of development in
(i) transplant-eligible AML and MDS patients who have significantly lower numbers of cancer blast cells and (ii) gene therapy patients who have no cancer blast cells. Therefore, Magenta expects
MGTA-117 to bind and deplete target cells in the bone marrow in these patient populations, and potentially achieve greater levels of depletion, at the same dose levels studied in R/R AML and MDS patients.
MGTA-117 Proof-of-Mechanism and
Potential Active Dose
MGTA-117 Regulatory Engagement and Clinical Development Next Steps in Transplant-Eligible AML/MDS and Autologous
As previously disclosed, Magenta has initiated formal engagements with regulatory agencies to transition
MGTA-117 into a transplant-eligible AML and MDS patient population. Magenta also plans to engage regulators in H1 2023 for the purposes of initiating a MGTA-117 clinical
trial in autologous ex vivo gene therapy.
CD45-ADC IND-Enabling Plans
Magenta s CD45-ADC is a second targeted
conditioning ADC, designed to selectively target and deplete both stem cells and immune cells, and is intended to replace the use of chemotherapy-based conditioning prior to stem cell transplant in patients with blood cancers and autoimmune
MGTA-145 Phase 2 Progress
Magenta is developing MGTA-145, in combination with plerixafor, to improve the process by which stem
cells are released out of the bone marrow and into the bloodstream, known as stem cell mobilization. The mobilized cells are then collected and available for transplant. This is the first step for patients and is required for the majority of
transplants and stem cell gene therapies.
Magenta will host a conference call and webcast at 8:30 a.m. Eastern Time / 7:30 a.m. Central Time tomorrow, Tuesday, December 13,
2022 to review the MGTA-117 data presented at the 2022 ASH Annual Meeting.
To access the conference call, please
register online at https://register.vevent.com/register/BI872661cff05d4191a7bb100830aae147. Upon registering, each participant will be provided with call details and a conference ID. The live webcast of the call and slide deck may be accessed
at https://edge.media-server.com/mmc/p/hk2eojv2, or by visiting the Investors & Media section of the company s website at https://investor.magentatx.com. A replay of the webcast will be available shortly after the conclusion of
the call and will be archived on the Events & Presentations page.
About Magenta Therapeutics
Magenta Therapeutics is
a clinical-stage biotechnology company developing medicines designed to bring the curative power of stem cell transplant to more patients with blood cancers, genetic diseases and autoimmune diseases. Magenta is combining leadership in stem cell
biology and biotherapeutics development with clinical and regulatory expertise to revolutionize blood and immune reset to allow more patients to take advantage of the curative potential of stem cell transplant and potentially improve eligibility for
future gene therapies.
Magenta is based in Cambridge, Mass. For more information, please visit www.magentatx.com.
Follow Magenta on Twitter: @magentatx
Forward-Looking Statements
This press release contains
forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995, as amended. These statements include, without limitation, implied and express statements relating to: Magenta s future business expectations,
plans and prospects; the potential of, and expectations for, Magenta s product candidate pipeline; proposed study designs; potential collaborations with other companies; the potential benefits and expected performance of Magenta s product
candidates and programs; the development of product candidates and advancement of preclinical and clinical programs, including, without limitation, patient enrollment; expectations, plans and timing for preclinical activities, clinical trials and
related results involving Magenta s product candidates; expectations, plans and timing for the generation, receipt and disclosure of preclinical and clinical trial data, toxicology results, and other results involving Magenta s product
candidates; timing for the disclosure of developmental timelines, developmental plans and program updates regarding Magenta s product candidates; the completion of dose-limiting toxicity observation periods; regulatory interactions and
alignment with regulators; the use of clinical data and supporting insights from PK/PD modeling in regulatory engagement and advancement into transplant eligible AML and MDS patients and gene therapy patients; that
MGTA-117 s pharmacokinetics (PK), pharmacodynamics (PD) and tolerability in Cohorts 1-3 will support alignment with regulatory authorities to study MGTA-117 in AML and MDS transplant-eligible patients; that clinical evidence of depletion in the AML and MDS patient population provides valuable support that MGTA-117 will
robustly deplete target cells in the proposed next phase of development in (i) transplant-eligible AML and MDS patients who have significantly lower numbers of cancer blast cells and (ii) gene therapy patients who have no cancer blast
cells, and Magenta s expectation that MGTA-117 will bind and deplete target cells in the bone marrow in these patient populations at the same or lower dose levels studied in R/R AML and MDS patients; the
planned transition of the MGTA-117 Phase 1/2 clinical trial into transplant-eligible AML and MDS patients, as well as into patients who are receiving gene therapy; and the predictive value of Magenta s MGTA-117 preclinical modeling.
Words such as anticipate, believe, continue,
could, designed, endeavor, estimate, expect, intend, may, might, plan, potential, predict, project,
seek, should, target, preliminary, will, would and similar expressions are intended 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: uncertainties inherent in preclinical and clinical trials and in the availability and timing of
data from ongoing and planned clinical and
preclinical trials; the ability to initiate, enroll, conduct or complete ongoing and planned preclinical and clinical trials; vulnerability and/or fragility of, and the presence of underlying
disorders in, the patient population for the clinical trials of Magenta s product candidates, including the MGTA-117 Phase 1/2 clinical trial in patients with relapsed/refractory AML and MDS; that
preliminary data from Magenta s clinical trials may change materially following a more comprehensive review of the data; the delay of any current or planned preclinical or clinical trials, or the delay in development of Magenta s product
candidates; whether results from preclinical or earlier clinical trials will be predictive of the results of future trials; interactions with regulatory agencies such as the U.S. Food and Drug Administration; the expected timing of submissions for
regulatory approval to conduct or continue trials or to market products; Magenta s ability to successfully demonstrate the safety and efficacy of its product candidates; whether Magenta s cash resources will be sufficient to fund
Magenta s foreseeable and unforeseeable operating expenses and capital expenditure requirements; and risks, uncertainties and assumptions regarding the impact of the continuing COVID-19 pandemic on
Magenta s business, operations, preclinical activities, clinical trials, strategy, goals and anticipated timelines. These and other risks are described in additional detail in Magenta s Quarterly Report on Form 10-Q for the quarter ended September 30, 2022 and its other filings made with the Securities and Exchange Commission from time to time. Any forward-looking statements contained in this press release represent
Magenta s views only as of today and should not be relied upon as representing its views as of any subsequent date. Magenta explicitly disclaims any obligation to update any forward-looking statements, except to the extent required by law.
Jill Bertotti, Real Chemistry (advisor to