Abstract Body: Introduction: Precision and gene-based therapeutics have transformed multiple fields, but translation to cardiovascular disease remains constrained by inadequate cardiac tropism. Systemic delivery results in poor myocardial uptake and off-target accumulation, reflecting a lack of mechanisms for selective cardiac targeting. This challenge is amplified by chamber-specific cardiomyocyte heterogeneity between atria and ventricles. We therefore sought to identify chamber-specific and pan-cardiac cell surface epitopes that enable antibody-mediated targeting of the heart in vivo.

Hypothesis: We hypothesize that there are pan-cardiac and chamber-specific surface epitopes that can be used as targets for antibody-mediated therapeutic delivery.

Methods: Integrated analysis of public single-cell RNA sequencing datasets from adult human heart and whole-body tissues was used to identify surface markers enriched in atrial, ventricular, or pan-cardiac populations. Candidates were prioritized based on minimal extra-cardiac expression, and validated across independent datasets (Tabula Sapiens, Human Protein Atlas) and primary human cardiac tissue (Western blot). For in vivo validation, target-specific antibodies were conjugated to fluorescent dyes and delivered via single intravenous injection in mice, followed by cardiac harvest at 24 hours and histologic assessment of cardiomyocyte targeting.

Results: Cross-dataset integration identified 14 candidate surface markers, including 6 atrial-, 6 ventricular-, and 2 pan-cardiac–enriched targets. Lead candidates demonstrated strong chamber-restricted protein expression in primary human tissue (Atrial Specific 1, “AS1”: atrial; Ventricular-Specific 1, “VS1”: ventricular) with minimal off-target expression across major organs by in silico profiling. Finally, a single intravenous administration of antibody–dye conjugates targeting AS1, VS1, or pan-cardiac markers in mice resulted in robust and selective cardiomyocyte-specific labeling in mice in vivo, confirming efficient delivery.

Conclusions: We define and validate a set of human cardiac surface proteins that enable chamber-specific and pan-cardiac targeting in vivo. These findings establish a modular platform for cardiac-directed delivery of therapeutics and diagnostics, addressing a central barrier in cardiovascular precision medicine and enabling next-generation strategies for gene editing, RNA therapeutics, and targeted pharmacologic interventions.