MRX2843

Herein, we develop an MRX-2843 (MerTK inhibitor) and Mn2+ codelivered defective metal-organic framework (copper-2,3,6,7,10,11-hexaiminotriphenylene (Cu-HITP))-based single-site nanozyme (Ir@D-Cu-HITP-MMP) for antitumor immunotherapy via innate immune-checkpoint blockade...This synergizes with Mn2+ to enhance the stimulator of interferon genes (STING) activation, triggering robust immune responses. Overall, Ir@D-Cu-HITP-MMP demonstrates potent antitumor effects by activating powerful innate and adaptive immune responses.

Combining CTX with the next generation MERTK-selective inhibitor UNC2371 (MRX-2843) drives complete remissions in both models, but durable long-term responses occurred selectively in the basal-like subtype model. Suppressive myeloid programing limits effective adaptive immune engagement in TNBC usually resulting in ICB treatment resistance and tumor recurrence. This study identifies a therapeutically actionable myeloid interferon checkpoint in which MERTK inhibition stabilizes CXCL9⁺ monocyte-macrophage programming to promote CD4⁺ T cell dependent immune memory and durable tumor control in basal-like TNBC.

P1, N=42, Completed, Meryx, Inc. | Active, not recruiting --> Completed | Trial completion date: Apr 2025 --> Dec 2025 | Trial primary completion date: Feb 2025 --> Dec 2025

P1, N=50, Recruiting, Meryx, Inc. | Trial completion date: Mar 2026 --> Sep 2026 | Trial primary completion date: Dec 2025 --> Jul 2026

P1, N=50, Recruiting, Meryx, Inc. | Trial completion date: Dec 2024 --> Mar 2026 | Trial primary completion date: Jul 2024 --> Dec 2025

P1, N=42, Active, not recruiting, Meryx, Inc. | Trial completion date: Jul 2024 --> Apr 2025 | Trial primary completion date: Dec 2023 --> Feb 2025

Host Mertk knock-out or MERTK inhibitor MRX-2843 increased CD8α+ dendritic cells (DCs) with enhanced antigen-presentation capacity in the leukemia microenvironment and inhibited leukemogenesis...Axl-/- did not impact leukemogenesis. These data demonstrate differential TAM kinase roles in the leukemia microenvironment and provide rationale for development of MERTK and/or TYRO3-targeted immunotherapies.

Combined treatment with MRX-2843 and BCL-2 inhibitors venetoclax or navitoclax provided enhanced therapeutic activity compared to single agents. These data highlight MERTK as a promising therapeutic target in EWS and provide rationale for the development of MRX-2843 for the treatment of EWS, especially in combination with BCL-2 inhibitors.

Gilteritinib is a FLT3 inhibitor that is US FDA approved for treating adult patients with relapsed/refractory AML and a FLT3 mutation...Importantly, we found that VEN synergistically enhances cell death induced by MRX-2843 in FLT3-ITD AML cells with acquired resistance to cytarabine (AraC) or VEN+AraC...Mechanistic studies show that MRX-2843 decreases Mcl-1 and c-Myc protein levels via transcriptional regulation and combined MRX-2843 and VEN significantly decreases oxidative phosphorylation in FLT3-ITD AML cells. Our findings highlight a promising combination therapy against FLT3-ITD AML, supporting further in vitro and in vivo testing.

Importantly, pharmacological inhibition of either JAK1 by filgotinib or TAM kinases by UNC2025 sensitizes Ewing sarcoma to chemotherapy in vitro and in vivo. Excitingly, the TAM kinase inhibitor MRX-2843 currently in human clinical trials to treat AML and advanced solid tumors, enhances chemotherapy efficacy to further suppress Ewing sarcoma tumor growth in vivo. Our findings reveal an Ewing sarcoma chemoresistance mechanism with an immediate translational value.

P1, N=69, Recruiting, Emory University | Phase classification: P1b --> P1 | Trial completion date: Dec 2025 --> Dec 2026 | Trial primary completion date: Dec 2024 --> Dec 2025

P1, N=42, Active, not recruiting, Meryx, Inc. | Recruiting --> Active, not recruiting