Magenta Therapeutics Announces IND Clearance for MGTA-117 Targeted Conditioning Clinical Trial

–  Phase 1/2 clinical trial expected to open in Q4 2021 in patients with relapsed/refractory acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) –

Magenta Therapeutics, Inc. (Nasdaq: MGTA), a clinical-stage biotechnology company developing novel medicines to bring the curative power of stem cell transplant to more patients, announced today that its Investigational New Drug (IND) application for MGTA-117 is active with the U.S. Food and Drug Administration (FDA). The company expects to open the Phase 1/2 clinical trial in Q4 2021 to evaluate its MGTA-117 antibody-drug conjugate (ADC) targeted conditioning program.

“We are very pleased that our collaboration with the FDA has resulted in the clearance of the MGTA-117 IND. We have addressed the FDA’s request for a bioassay to be incorporated into the clinical trial protocol,” said Jason Gardner, D.Phil., President and Chief Executive Officer, Magenta Therapeutics. “Improving conditioning treatments is essential for broadening patient accessibility to the curative potential of stem cell transplant and gene therapies. We have designed MGTA-117 specifically to replace toxic radiation and chemotherapy-based conditioning agents used in current medical practice. This program holds significant potential for patients across several disease areas.”

The multi-center, open label Phase 1/2 clinical trial with single-dose escalating cohorts will evaluate the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of MGTA-117 as a single agent in relapsed/refractory AML and MDS patients. Magenta will continue to engage with the FDA to transition the trial to the intended primary target population of hematopoietic stem cell transplant-eligible AML and MDS patients. In addition, Magenta has planned gene therapy clinical trial collaborations with AVROBIO and Beam Therapeutics to evaluate the potential utility of MGTA-117 for conditioning gene therapy patients without the use of non-selective busulfan or other toxic chemotherapies.

About MGTA-117

Magenta’s MGTA-117 program is the company’s lead targeted conditioning product candidate, an antibody-drug conjugate (ADC) designed to selectively deplete hematopoietic stem cells (HSCs) from patients prior to transplant or HSC-based gene therapy to reduce the need for high-dose or high-intensity chemotherapeutic agents or, in the case of gene therapy applications, to potentially eliminate the need for chemotherapeutic agents altogether. MGTA-117 targets the CD117 receptor, which is highly expressed on the cell surface of HSCs and leukemia cells, making it a promising target for conditioning across broad sets of diseases, including certain blood cancers, hemoglobinopathies (sickle cell disease and beta thalassemia) and inherited metabolic disorders.

About Magenta Therapeutics

Magenta Therapeutics is a clinical-stage biotechnology company developing medicines to bring the curative power of stem cell transplants 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, a unique business model and broad networks in the stem cell transplant community to revolutionize immune reset for more patients.

Magenta is based in Cambridge, Massachusetts. For more information, please visit www.magentatx.com.

Follow Magenta on Twitter: @magentatx.

Forward-Looking Statement

This press release may contain forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995 and other federal securities laws, including express or implied statements regarding Magenta’s future expectations, plans and prospects, including, without limitation, statements regarding the anticipated timing of clinical trials, expectations and plans for pre-clinical and clinical data, communications with the FDA, the design of product candidates and their potential benefits, the development of product candidates and advancement of preclinical programs, the plans, timing, progress and success of collaborations, as well as other statements containing the words “anticipate,” “believe,” “continue,” “could,” “endeavor,” “estimate,” “expect,” “anticipate,” “intend,” “may,” “might,” “plan,” “potential,” “predict,” “project,” “seek,” “should,” “target,” “will” or “would” and similar expressions that constitute forward-looking statements under the Private Securities Litigation Reform Act of 1995. 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 clinical studies and in the availability and timing of data from ongoing clinical studies; the development of biomarker assays ; whether results from preclinical studies or earlier clinical studies will be predictive of the results of future trials; the expected timing of submissions for regulatory approval or review by governmental authorities; discussions with governmental agencies such as the FDA; regulatory approvals to conduct trials or to market products; whether Magenta's cash resources will be sufficient to fund Magenta's foreseeable and unforeseeable operating expenses and capital expenditure requirements; risks, uncertainties and assumptions regarding the impact of the continuing COVID-19 pandemic on Magenta’s business, operations, strategy, goals and anticipated timelines, Magenta’s ongoing and planned preclinical activities, Magenta’s ability to initiate, enroll, conduct or complete ongoing and planned clinical trials, Magenta’s timelines for regulatory submissions and Magenta’s financial position; and other risks concerning Magenta's programs and operations are described in additional detail in its Annual Report on Form 10-K filed on March 3, 2021, as updated by Magenta’s most recent Quarterly Report on Form 10-Q, and its other filings made with the Securities and Exchange Commission from time to time. Although Magenta's forward-looking statements reflect the good faith judgment of its management, these statements are based only on facts and factors currently known by Magenta. As a result, you are cautioned not to rely on these forward-looking statements. Any forward-looking statement made in this press release speaks only as of the date on which it is made. Magenta undertakes no obligation to publicly update or revise any forward-looking statement, whether as a result of new information, future developments or otherwise.

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