Abstract 9786: Myocardial Contractile Dysfunction and Anti-Troponin I Immunoreactivity in a Mouse Model of Combination Immune Checkpoint Inhibitors

Abstract

Introduction: Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of many incurable cancers. However, serious cardiotoxic side effects, such as fatal myocarditis, have been reported. Autoimmunity against cardiac proteins has been suspected but the underlying mechanism is not known. Hypothesis: Combination ICIs are more cardiotoxic than monotherapy alone and can induce both T- and B-cell mediated responses against cardiac proteins. Methods: We intraperitoneally administered either 200μg of programmed cell death-1 (PD-1) antibody (Ab), 100μg of cytotoxic T-lymphocyte associated protein-4 (CTLA-4) Ab, both treatment Abs, or IgG control every 3 days for a total of 17 doses in mice. Cardiac function was monitored by MRI and myocardial inflammatory cells were characterized by immunohistochemistry. After identifying specific cardiac troponin I (cTnI) antigenic sequences by bioinformatic analyses, biotinylated peptides were synthesized and immobilized to streptavidin-coated plates for enzyme-linked immunosorbent assays (ELISA) to detect self-reactive anti-troponin Abs. Results: PD-1 Ab, CTLA-4 Ab, and the combination significantly decreased cardiac contractile velocities compared to IgG (peak systolic velocity cm/s: IgG -1.27 ± 0.131, PD-1 Ab -1.14 ± 0.0531, p=0.02 vs. IgG, CTLA-4 Ab -1.07 ± 0.0359, p<0.01 vs. IgG, PD-1+CTLA-4 Ab -1.04 ± 0.0872, p<0.001 vs. IgG). However, ejection fraction (EF) was only reduced with combination treatment (EF%: IgG 60.1 ± 2.80, PD-1+CTLA-4 Ab 56.6 ± 3.17, p=0.03). There were also significantly more myocardial CD8 + cells with combination treatment (cells/mm 2 : IgG 3.03 ± 1.34, PD-1+CTLA-4 Ab 7.93 ± 2.41, p=0.004). Serum ELISA showed cross-reactivity against cTnI, suggesting the formation of auto-antibodies and significantly high titers were detected with combination treatment (450 nm absorbance: IgG 0.162 ± 0.0859, PD-1+CTLA-4 Ab 0.397 ± 0.121, p=0.002). Conclusions: Our study showed that ICI-therapy induced myocardial inflammation (including CD8 + T-cell infiltration), contractile dysfunction, and immune-reactive antibodies directed against immunogenic targets of cTnI. These data suggest a novel mechanism of ICI-induced cardiotoxicity, which warrants further investigation.