On November 2, 2023 Molecular Partners AG (SIX: MOLN; NASDAQ: MOLN), a clinical-stage biotech company developing a new class of custom-built protein drugs known as DARPin therapeutics, reported that it will present preliminary data from its ongoing Phase 1/2a trial of MP0533, a novel tetra-specific T cell engager at the 65th American Society of Hematology (ASH) (Free ASH Whitepaper) Annual Meeting and Exposition being held from December 9–12 in San Diego, California (Press release, Molecular Partners, NOV 2, 2023, View Source [SID1234636664]). MP0533 is in development for the treatment of patients with relapsed/refractory acute myeloid leukemia (r/r AML) and myelodysplastic syndrome (AML/MDS).

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As of data cut-off (20 July 2023) of the abstract published today, five patients across three dosing regimens had been treated. The preliminary data reported indicate an acceptable safety profile, with no dose-limiting toxicity or Grade ≥3 adverse reactions. Grade 1/2 events considered related to MP0533 included infusion-related reactions and cytokine release syndromes. One of the two patients evaluable for MP0533 antitumor activity in the third treatment cohort achieved a response. The study is currently enrolling its fifth cohort with up to seven dose-escalating cohorts planned and a total enrollment of up to 45 patients. The Company anticipates to present data including from the fourth dose cohort at the ASH (Free ASH Whitepaper) Annual Meeting and Exposition in December this year.

"The data from the ASH (Free ASH Whitepaper) abstract represent the beginning of an exciting and encouraging clinical journey for the MP0533 program. We are now able to show initial clinical activity of the first tetra-specific, non-antibody-based T cell engager, MP0533, in patients with r/r AML and MDS/AML," said Patrick Amstutz, Ph.D., Molecular Partners’ CEO. "We see both an acceptable tolerability profile at initial doses, as well as the emergence of single-agent anti-tumor activity at relatively low dose levels and we look forward to presenting additional data on MP0533’s potential to treat this particularly intractable blood cancer at the ASH (Free ASH Whitepaper) Annual Meeting in December."

The clonal heterogeneity and lack of single AML-specific target antigens represent major challenges for the development of targeted immune therapies for AML. To overcome these hurdles, Molecular Partners designed MP0533, a novel tetra-specific T cell-engaging, half-life extended DARPin, which simultaneously targets CD33, CD123 and CD70, as well as CD3 on T cells. This unique mode of action is designed to enable avidity-driven, T cell-mediated killing of leukemic stem cells and malignant blast cells, which commonly co-express at least two of the three target antigens, while preserving a therapeutic window that minimizes damage to healthy cells.

The ongoing single-arm, open-label, multicenter Phase 1/2a study of MP0533 is designed to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics, as well as assess preliminary antileukemic activity of MP0533 as a monotherapy for patients with r/r AML and AML/MDS.

The presentation details are as follows:

Session Name: 616. Acute Myeloid Leukemias: Investigational Therapies, Excluding Transplantation and Cellular Immunotherapies: Poster 2
Publication Number: 2921
Title: MP0533, a CD3-Engaging DARPin Targeting CD33, CD123, and CD70 in Patients with Relapsed/Refractory AML or MDS/AML: Preliminary Results of a Phase 1/2a Study
Session Location & Date: San Diego Convention Center, Halls G-H; Sunday, December 10, 2023
Presentation Time: 6:00–8:00 pm PT

The abstract will become available today on the ASH (Free ASH Whitepaper) website at 9:00 am ET.