Using plasma cell-free mRNA to profile immune response and myocardial damage in immune checkpoint inhibitor-induced myocarditis

Immune checkpoint inhibitor-induced myocarditis (ICI-m) is a highly fatal cancer treatment complication with challenging diagnosis and invasive diagnostic methods. We developed a plasma cell-free mRNA (cf-mRNA) platform for noninvasive characterization of the immune and myocardial landscape in ICI-m. We sequenced bulk cell-free total RNA from plasma of cancer patients treated with ICIs: without immune-related adverse events (irAE) (group A, n=5), with noncardiac irAE (group B, n=7), and with ICI-m with/without noncardiac irAE (group C, n=10). Publicly available healthy control cfRNA (n=30) served as external controls. Cell type-specific gene panels from single cell RNA-sequencing of circulating immune and cardiac cells were used for cellular deconvolution. Cancer and inflammatory pathways were enriched in ICI-treated patients versus controls. Cardiac pathways and conduction system genes were significantly enriched in group C versus A and B. Temra CD8+ T cell and cardiomyocyte signature scores, with CCL5 and MYH6 expression, were elevated in group C. Our custom ICI-m classifier, containing three cardiac- and three immune cell-specific genes, effectively differentiated group C from A (AUC 0.903, 95% CI 0.858-0.903) and B patients (AUC 0.983, 95% CI 0.970-0.983), outperforming unsupervised feature selection. outperforming unsupervised feature selection. This platform captures disease-specific signatures enabling precision diagnostics for inflammatory diseases.