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Background: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmia disorder associated with lethal arrhythmias. Most CPVT cases are caused by inherited variants in the gene encoding ryanodine receptor type 2 (RYR2)., Objective: The goal of this study was to investigate the structure-activity relationship of tetracaine derivatives and to test a lead compound in a mouse model of CPVT., Methods: We synthesized >200 tetracaine derivatives and characterized 11 of those. The effects of these compounds on Ca 2+ handling in cardiomyocytes from R176Q/+ mice was tested with confocal microscopy. The effects of lead compound MSV1302 on arrhythmia inducibility and cardiac contractility were tested by programmed electrical stimulation and echocardiography, respectively. Plasma and microsomal stability and cytotoxicity assays were also performed., Results: Ca 2+ imaging revealed that 3 of 11 compounds suppressed sarcoplasmic reticulum Ca 2+ leak through mutant RyR2. Two compounds selected for further testing exhibited a half-maximal effective concentration of 146 nM (MSV1302) and 49 nM (MSV1406). Whereas neither compound altered baseline electrocardiogram intervals, only MSV1302 suppressed stress- and pacing-induced ventricular tachycardia in vivo in R176Q/+ mice. Echocardiography revealed that the lead compound MSV1302 did not negatively affect cardiac inotropy and chronotropy. Finally, compound MSV1302 did not block I Na , I Ca,L , or I Kr ; it exhibited excellent stability in plasma and microsomes, and it was not cytotoxic., Conclusion: Structure-activity relationship studies of second-generation tetracaine derivatives identified lead compound MSV1302 with a favorable pharmacokinetic profile. MSV1302 normalized aberrant RyR2 activity in vitro and in vivo, without altering cardiac inotropy, chronotropy, or off-target effects on other ion channels. This compound may be a strong candidate for future clinical studies to determine its efficacy in CPVT patients., Competing Interests: Disclosures R.M.S. and X.H.T.W. are founding partners and M.S.-V., R.M.S., and X.H.T.W. were shareholders of Elex Biotech Inc, a start-up company that developed drug molecules that target ryanodine receptors to treat cardiac arrhythmia disorders. The other authors do not have relevant disclosures., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Coronary heart disease (CHD) is a prevalent cardiac disease that causes over 370,000 deaths annually in the USA. In CHD, occlusion of a coronary artery causes ischemia of the cardiac muscle, which results in myocardial infarction (MI). Junctophilin-2 (JPH2) is a membrane protein that ensures efficient calcium handling and proper excitation-contraction coupling. Studies have identified loss of JPH2 due to calpain-mediated proteolysis as a key pathogenic event in ischemia-induced heart failure (HF). Our findings show that calpain-2-mediated JPH2 cleavage yields increased levels of a C-terminal cleaved peptide (JPH2-CTP) in patients with ischemic cardiomyopathy and mice with experimental MI. We created a novel knock-in mouse model by removing residues 479-SPAGTPPQ-486 to prevent calpain-2-mediated cleavage at this site. Functional and molecular assessment of cardiac function post-MI in cleavage site deletion (CSD) mice showed preserved cardiac contractility and reduced dilation, reduced JPH2-CTP levels, attenuated adverse remodeling, improved T-tubular structure, and normalized SR Ca 2+ -handling. Adenovirus mediated calpain-2 knockdown in mice exhibited similar findings. Pulldown of CTP followed by proteomic analysis revealed valosin-containing protein (VCP) and BAG family molecular chaperone regulator 3 (BAG3) as novel binding partners of JPH2. Together, our findings suggest that blocking calpain-2-mediated JPH2 cleavage may be a promising new strategy for delaying the development of HF following MI., Competing Interests: Declaration of competing interest XHTW is a consultant for Pfizer and Rocket Pharmaceuticals, and a founding partner and board member of Elex Biotech Inc., a start-up company that developed drug molecules that target ryanodine receptors to treat cardiac arrhythmia disorders. LZ is the co-founder and consultant for Pelagos Pharma Inc., a start-up company that develop drug molecules that target nuclear receptors to treat heart failure and neurodegenerative disorders. Other authors have no potential conflicts to disclose. AI-assisted technology is not used in the preparation of this work (except checking grammar and spelling)., (Copyright © 2024 Elsevier Ltd. All rights reserved.)