The US Food and Drug Administration (FDA) has issued a clinical hold letter for Magenta Therapeutics’ investigational new drug application to conduct a Phase I/II clinical trial of MGTA-117.

Magenta filed the IND last month. The trial for the treatment of acute myeloid leukaemia (AML) and myelodysplastic syndrome (MDS) is yet to commence.

The FDA asked the company to develop a bioassay for use with the pharmacokinetic/pharmacodynamic model to help make decisions on dose escalation, apart from safety assessments.

Magenta noted that the bioassay was the single clinical hold factor provided by the FDA and is not associated with MGTA-117’s toxicology or production.

The company has already begun bioassay development and will collaborate with the FDA on the application of the product for dose escalation.

Magenta Therapeutics president and CEO Jason Gardner said: “We are actively developing the bioassay requested by the FDA and do not expect significant technical challenges in its completion.

“We expect to request a ‘Type A’ meeting in the coming weeks and, if successful in resolving this remaining issue, we would anticipate opening the study in Q4 2021.”

MGTA-117 is an antibody-drug conjugate developed to specifically reduce hematopoietic stem cells (HSCs) before the transplant or HSC-based gene therapy.

It acts on the CD117 receptor found on the cell surface of HSCs and leukaemia cells, indicating potential use in treating several diseases such as blood cancers and inherited metabolic disorders.

The Phase I/II trial is designed to assess the safety, pharmacokinetics and pharmacodynamics of MGTA-117 as a monotherapy in patients with relapsed/refractory AML and MDS.

Following adequate results in this patient population, Magenta intends to change the trial to transplant-eligible patients.

In addition, the company plans to develop MGTA-117 as a targeted conditioning agent for genetic disease patients before the use of ex vivo gene treatments.

Magenta reported in May this year that Phase II trial of its MGTA-145 in combination with plerixafor in multiple myeloma patients met the primary endpoint.



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