Abstract 4366071: Therapeutic Targeting of fibrosis With ANTXR1 Neutralizing Antibodies Improves Cardiac Function in Heart Disease

Abstract

Background: Fibrosis is a hallmark of heart disease, yet direct antifibrotic therapies remain limited. We identified ANTXR1, a master regulator of fibrosis, overexpressed in diseased cardiac tissue and explored therapeutic targeting using T8Ab, a cross-species neutralizing anti-ANTXR1 monoclonal antibody initially developed for cancer therapy. Methods: ANTXR1 expression was evaluated in human cardiac tissues and murine models of myocardial infarction (MI) and hypertension. Antxr1 knockout (KO) mice and T8Ab (15 mg/kg, 3x/week) were used to assess ANTXR1 function post-MI. T8Ab was administered intraperitoneally starting 1 d post-MI. For the hypertension models, T8Ab treatment was initiated concurrently with angiotensin II and phenylephrine (ANGII/PE) (prevention model) or following damage (reparative model). T8Ab was also tested in a prevention model of heart failure with preserved ejection fraction (HFpEF) induced by a high-fat diet (HFD) and N [ω] -nitro-L-arginine methyl ester (L-NAME). Cardiac function was monitored via echocardiography, and mechanistic insights were obtained through single-cell RNA sequencing, histology, and biochemical analyses. Results: ANTXR1 was highly expressed in cardiac fibroblasts of injured hearts from both humans and mice. Antxr1 KO mice displayed improved cardiac function post-MI (EF%: WT = 28.4±3.7 vs. KO = 50.1±2.5) and reduced scar size. In Antxr1 KO mice, echocardiography 28 days post-MI showed improved cardiac function (WT EF% = 28.4±3.7 vs. Antxr1 KO EF% = 50.1±2.5) and reduced left ventricular scar size (n= 5-6). T8Ab treatment significantly improved cardiac function in multiple models: Post-MI (d 42): EF% = 20.1±1.9 (WT) vs. 48.0±2.5 (WT+T8Ab), n = 17–18 mice/group: Hypertension (ANGII/PE, day 28): EF% = 41.9±2.7 (WT) vs. 54.8±2.1 (WT+T8Ab), n = 15–19 mice/group: HFpEF (HFD/L-NAME, day 35): e/E′ = 22.6±0.4 (control), 32.5±1.0 (HFD/L-NAME), and 25.4±0.6 (HFD/L-NAME+T8Ab), n = 10 mice/group. Single-cell transcriptomics revealed that T8Ab suppressed expression of fibrosis-related genes (e.g., Ccn2, Ccn4, Comp, Cthrc1, Pdgfa, Meox1 ) and reduced maladaptive TGF-β-driven ECM remodeling. Immunofluorescent staining confirmed that T8Ab reduced late-stage aberrant collagen turnover. Conclusions: ANTXR1 contributes to cardiac fibrosis and dysfunction. Treatment with function blocking T8Ab improved cardiac function in diverse cardiac disease models, supporting its potential use as a novel antifibrotic and cardioprotective therapy.