Abstract 2171: Amezalpat, a peroxisome proliferator-activated receptor alpha (PPARα) antagonist, inhibits suppressive macrophage development, activation and function

Amezalpat (TPST-1120) is a first-in-class, small molecule competitive antagonist of peroxisome proliferator-activated receptor alpha (PPARα), the master transcriptional regulator of fatty acid oxidation (FAO). Analysis of biomarker data from a previous Phase I study demonstrated amezalpat dose-dependent changes in immune genes associated with myeloid populations. Suppressive M2 macrophages are a prominent myeloid population associated with poor prognosis in many cancers. As M2 macrophages are reliant on FAO, we sought to assess the effects of amezalpat on development, activation and function of these cells. Flow cytometry analysis of M2 macrophages polarized in the presence of amezalpat displayed concentration-dependent reductions in canonical M2 macrophage markers CD163, CD206, and Arg-1 (p<0.05 by Wilcoxon’s test). ELISA measurement of cytokine production by amezalpat-treated M2 macrophages demonstrated a statistically significant reduction in the suppressive cytokines IL-10 (n=8; p<0.05 by Wilcoxon’s test) and TGF-β (n=3 by One-way ANOVA), suggesting amezalpat-induced functional impairment of this population. Additionally, amezalpat treatment of M2 macrophages caused significant reductions in mitochondrial mass, measured with a mitochondria-specific dye by flow cytometry (p<0.01 by two-sample T test). Finally, in co-cultures of M2 macrophages with autologous activated CD8+ T cells and HCC tumor cells (SNU-449), amezalpat induced tumor cell cytotoxicity and M2 cell death commensurate with cell-type specific expression levels of its target PPARα. Together, these data suggest amezalpat modulates suppressive macrophage development and function and supports the contribution of an immune-mediated mechanism to anti-tumor activity reported in clinical studies. Citation Format: Mandy I. Cheng, Ademola Esomojumi, Dara Burdette, Valerie Chen, Jorg H. Fritz, Sam Whiting, Nathan Standifer. Amezalpat, a peroxisome proliferator-activated receptor alpha (PPARα) antagonist, inhibits suppressive macrophage development, activation and function [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2171.