PET Imaging of Cardiac Inflammation in Viral Myocarditis Using a DPP4‐Targeted Probe

ABSTRACT Myocarditis, primarily induced by viral infection, lacks reliable non‐invasive imaging for early diagnosis. We developed a novel PET probe, ⁶⁸ Ga‐DOTA‐linagliptin (abbreviated as ⁶⁸ Ga‐linagliptin), which targets dipeptidyl peptidase‐4 (DPP4), to assess its potential in detecting myocarditis. Western blotting and immunostaining showed an elevated cardiac DPP4 expression in mice with Coxsackievirus B3 (CVB3) myocarditis. Single‐cell sequencing analysis and cardiac flow cytometry further revealed that the elevated DPP4 expression predominantly originated from infiltrating immune cells, including T cells, dendritic cells, and B cells. Molecular docking and dynamics simulations, together with a DPP4 enzyme inhibition assay, demonstrated high‐affinity and direct binding between ⁶⁸ Ga‐linagliptin and DPP4. ⁶⁸ Ga‐linagliptin showed favorable pharmacokinetics in vivo and shows significantly higher probe uptake in DPP4‐overexpressing cells in vitro and in vivo. PET/CT imaging revealed pronounced ⁶⁸ Ga‐linagliptin accumulation within the inflamed myocardium of mice with myocarditis, with minimal uptake in control animals. The PET/CT signal distribution closely matched histologically identified inflammatory regions. Moreover, pretreatment with the unlabeled precursor drug linagliptin effectively attenuated inflammation and improved cardiac function in CVB3‐infected mice. These findings indicate that ⁶⁸ Ga‐linagliptin enables sensitive and non‐invasive visualization of cardiac inflammation and may offer combined diagnostic and therapeutic benefits for viral myocarditis.