Nanobody-Targeted Camk2d Inhibition for Cardiac Arrhythmias

Objective

In cardiac cells, kinase enzymes are key modulators of calcium homeostasis, mitochondrial function, excitation-contraction coupling, and metabolism. Of these, the delta isoform of Ca 2+ /Calmodulin-dependent kinase (Camk2d) is particularly relevant to the induction of life-threatening cardiac arrhythmias.Of the several promising small molecule and peptide Camk2d inhibitors proposed in pre-clinical investigations, none has entered clinical applications. The severity of side effects, a well-known issue for kinase inhibitors, in this case is further amplified by the high homology and the unique Ca 2+ -dependent regulatory physiology among four Camk2 isoforms, plus the delicate role of the ubiquitously expressed Camk2d in non-cardiac tissues. Since the major obstacle to developing a cardio-specific, Camk2d-specific inhibitor mainly relies on reaching high isoform selectivity, the Nab-Heart project will conjugate selected Nanobodies (Nbs) to a new Camk2 inhibitory peptide to develop the first selective kinase inhibitor. Such a molecule will prevent the development of life-threatening arrhythmias in a variety of cardiac conditions, spanning from inherited arrhythmias such as Long QT Syndrome to acquired and highly prevalent diseases such as atrial fibrillation and heart failure. The team will identify Nb candidates with the desired Camk2d isoform-selectivity and affinity. Optimized substrate-mimicking Camk2d-inhibitory peptides will be covalently linked to the selected Nbs (Nb-inibs) to ensure delivery of the inhibitory module to the pathologically active Camk2d target with outstanding selectivity and affinity. The strategy will be validated in vivo through cardio-specific AAV9 delivery of the Nb-inib candidates in a mouse model of Catecholaminergic Polymorphic Ventricular Tachycardia and in a Swine model of acquired heart failure, where Camk2d is known to be the trigger of life-threatening arrhythmias.