Clonal reshaping and clinical outcomes after rechallenge in ICI-associated myocarditis: integrated single-cell and TCR repertoire analysis

Background Immune checkpoint inhibitor-associated myocarditis (ICIAM) poses significant challenges for cancer immunotherapy, particularly regarding the safety and efficacy of immune checkpoint blockade (ICB) rechallenge. Methods The present study analyzed 23 cases of ICIAM by integrating longitudinal clinical data with single-cell RNA sequencing and T-cell receptor profiling of peripheral blood mononuclear cells (PBMCs) obtained from three representative patients before and after ICB rechallenge. The single-cell cohort comprised two patients who experienced recurrent irAEs upon rechallenge and one patient who did not develop recurrent irAEs. Results Among 12 patients (52%) who experienced recurrent irAEs upon rechallenge, myocarditis recurrence occurred in 8 cases, with most (88%) presenting as grade 1— significantly milder than initial episodes (p=0.046). Single-cell analysis revealed that the patient who did not develop recurrent irAEs exhibited a high proportion of effector CD8 + T cells with high TRAV19 expression (CD8 Teff TRAV19), a TCR Vα family associated with SARS-CoV-2 reactivity. In contrast, patients who experienced recurrent irAEs lacked this expanded population. Rechallenge during myocarditis course was associated with higher recurrent irAEs risk (OR=14.0, 95%CI:1.3-147.4, p=0.027). Despite recurrence, tumor response was preserved, with a median progression-free survival (mPFS) of 8.5 months and no significant outcome difference between patients with and without post-rechallenge irAEs. Conclusion ICB rechallenge is feasible in selected ICIAM patients, with most recurrent myocarditis cases being milder. Our exploratory single-cell analysis reveals that a high proportion of CD8 Teff TRAV19 was present in the patient protected from recurrence but absent in those who relapsed, suggesting that pre-existing virus specific memory T cells may modulate recurrent irAEs risk via antigen-specific niche occupation. While limited by sample size, these findings generate the hypothesis that T-cell repertoire composition could inform patient selection for ICB rechallenge, a concept warranting validation in larger cohorts.