Background:
In cancer therapy, monoclonal antibodies (mAbs) are used to block immune checkpoints (ICs) and their ligands to enhance the T-cell response against tumors. However, immune checkpoint inhibitor (ICI) therapy (involving CTLA-4, PD-1, and PD-L1 inhibitors) has been associated with severe cardiac side effects, including myocarditis and arrhythmias.
Objectives:
This study aimed to investigate the potential cardiovascular side effects of new ICIs targeting Lag-3, Tim-3, and TIGIT. Additionally, we assessed the effects of ICI therapy in the context of ongoing myocarditis.
Methods:
In the first part of the experiment, 5- to 6-week-old A/J mice were treated intraperitoneally (i.p.) with 250 μg of antibody (anti-Lag-3, anti-Tim-3, anti-TIGIT, their combinations, or an isotype control antibody). The treatment was administered five times at 4-day intervals. In the second part of the experiment, in addition to the treatment described in part I, the mice were immunized subcutaneously with 150 μg of cardiac troponin I peptide (cTnI) three times at 7-day intervals, starting on day 1. All animals underwent echocardiography, blood sampling, histology, and qPCR. Statistical analysis was performed using GraphPad Prism with one-way ANOVA and Tukey's multiple comparisons tests. P-values < 0.05 were considered statistically significant. Values are presented as mean ± SEM.
Results:
In the first part of the experiment, A/J mice were treated with individual ICIs or combinations. No inflammation was observed microscopically. Serum troponin levels were below the 100 pg/ml threshold in all but two mice. The abnormal values were 117 pg/ml in the anti-Lag-3 group and 1240 pg/ml in the anti-Tim-3 + anti-TIGIT group, but without echocardiographic or histological abnormalities. There were no significant differences in the cardiac mRNA expression of TNFα, IL-6, and IL-10 between the intervention and control groups.
Treatment with individual ICIs did not result in any significant differences in ejection fraction (EF) and fractional shortening (FS) between the groups. However, in the group treated with the ICI combination (anti-Lag-3 + anti-TIGIT), significantly lower EF and FS values were observed compared to the control group (anti-Lag-3 + anti-TIGIT vs. control: EF: 69.13% ± 1.45% vs. 76.64% ± 1.59%; FS: 37.63% ± 1.13% vs. 43.88% ± 1.15%).
In the second part of the study, the ICI combination was administered in parallel with the induction of experimental autoimmune myocarditis (EAM). No significant differences were observed between the groups in terms of inflammation, fibrosis, hsTnT levels, FS, EF, heart wall thickness, or the cardiac mRNA expression of TNFα, IL-2, IL-6, IL-10, IFNg, or other ICs.
Conclusions:
Our findings suggest that there is no absolute safety regarding the cardiac side effects of treatment with new ICIs (Lag-3, Tim-3, and TIGIT antibodies). Therefore, we recommend regular cardiological follow-up for patients receiving cancer therapy with these novel ICIs.
