Development of Mirror-Image Natural Products as Antiarrhythmic Therapeutics

Project Summary This program focuses on the development of a new class of antiarrhythmic agents that normalize dysfunctional RyR2 channels, the calcium release channel in the sarcoplasmic reticulum (intracellular) membrane. Human RyR2 mutations cause two distinct genetic arrhythmia syndromes: (i) Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) due to RyR2 gain of function mutations, and (ii), Calcium Release Deficiency Syndrome (CRDS) due to RyR2 loss of function mutations. RyR2 gain of function due to post-translational modifications has been implicated mechanistically in heart failure and atrial fibrillation. RyR2-selective modulators are lacking. The overarching goal of this transdisciplinary program is the selection of antiarrhythmic clinical candidates based on ent-verticilide, a potent inhibitor of RyR2-mediated calcium release in cardiomyocytes. Preliminary data for this first potent and selective inhibitor include efficacy in several models of disease, and PKPD in a chronic dosing study. Our collective results support the rationale that selective therapeutics can improve our understanding of RyR2 biology and lead to preclinical candidates. Since ent-verticilide is not a natural product, all compounds must be obtained by de novo chemical synthesis. Chemical synthesis has provided renewable access to drug, and served as a platform for rapid analog development to support pharmacology studies. A comprehensive study of verticilides for therapeutic development is outlined in three Aims. Aim 1 describes the use of cryo-EM and photocrosslinking studies to further elucidate mechanism of action and create a platform for structure-guided design. The goal of Aim 2 is to increase the bioavailability of ent-verticilide and test efficacy of oral dosing in atrial fibrillation and heart failure models. Aim 3 describes lead backup development using ent-verticilide B1, an 18-membered ring oligomer. A strength of this approach is its ability to adapt to changes in the state of the art in RyR2 structural biology, an effort to which we will contribute (Aim 1). Highly potent and selective compounds will be advanced to in vivo safety and efficacy studies (Aim 2) with backup lead identification to de-risk the overall program. This program is highly collaborative and transdisciplinary in nature, and the studies will advance a novel class of compounds never-before- used in therapeutic development. Preliminary results have already advanced our understanding of RyR2 molecular pharmacology and promise new antiarrhythmic agents to improve human health.