Screening apelin analogues and a small molecule agonist as effective cardiovascular therapeutics against reperfusion injury

Ischemic reperfusion injury is a major global health threat, with the development of effective therapeutics still urgently needed. While both peptide therapeutics and small-molecule agonists have been extensively investigated to treat this condition, in this study, we explored the pharmacological potential of retro-inverso apelin peptides, including parent and modified forms, by evaluating their binding activity and physiological effects. We further assessed two metabolically stable apelin peptide analogues previously developed in our lab and compared them to a small-molecule agonist, BMS-986224, for biased agonist properties. Using radioligand displacement assays and blood pressure assays, we found that the retro-inverso peptides lacked apelin receptor binding affinity and physiological activity. However, our metabolically stable analogues and the small molecule demonstrated good receptor binding. Notably, we showed the metabolically stable apelin-13 analogue, NMeLeu13A2, to exhibit little to no blood pressure-lowering effects but retain cardiorestorative effects in the Langendorff assay. In contrast, CbzPEG₆-NMeLeu17A2 not only provided cardioprotective effects but also significantly lowered blood pressure. These findings highlight the potential of NMeLeu13A2 for targeted therapeutics and underscore the promise of apelin-based analogues in addressing ischemic reperfusion injury.