ICH S7B In Vitro Assays Do Not Address Mechanisms of QTC Prolongation for Peptides and Proteins - Data in Support of Not Needing Dedicated QTC Studies

Chelerythrine triggers the prolongation of QT interval and induces cardiotoxicity by promoting the degradation of hERG channels

Cardiotoxicity is a serious adverse reaction during drug treatment. The cardiac human ether-a-go-go-related gene (hERG) channels play a crucial role in driving cardiac action potential repolarization and are a key target for drug-induced cardiac toxicity. Chelerythrine (CHE) has anticancer effects on various human cancer cells. But little is known about its drug safety currently. The purpose of this study is to explore the key mechanism of cardiac toxicity induced by CHE under pathological conditions. CHE and hypoxia prolonged QT interval and action potential duration compared with control group in guinea pigs, as measured by BL-420S biological acquisition and processing system in conjunction with optical mapping technology. hERG current was measured by patch-clamp technique, and the interaction between ubiquitin molecules and hERG channels was assessed using immunoprecipitation method at the molecular level. The colocalization of proteins and the function of lysosomes were determined via confocal laser scanning microscopy. Further research indicates that CHE enhances the ubiquitination process of hERG proteins by catalyzing the formation of K63 ubiquitin chains, the ubiquitination modification disrupts hERG channel homeostasis, and promotes the degradation of the channel. Mechanistically, CHE accelerates the degradation of hERG channels through lysosomes via HDAC6, which may easily induce cardiotoxicity caused by prolonged QT interval under hypoxic conditions.

Multiple hERG channel blocking pathways: implications for macromolecules

Numerous non-cardiovascular drugs have a potential to induce life-threatening torsades de pointes (TdP) ventricular cardiac arrhythmias by blocking human ether-à-go-go-related gene (hERG) currents via binding to the channel's inner cavity. Identification of the hERG current-inhibiting properties of candidate drugs is performed focusing on binding sites in the channel pore. It has been suggested that biologicals have a low likelihood of hERG current inhibition, since their poor diffusion across the plasma membrane prevents them from reaching the binding site in the channel pore. However, biologicals could influence hERG channel function by binding to 'unconventional' noncanonical binding sites. This Opinion gives an overview on noncanonical blockers of hERG channels that might be of relevance for the assessment of the possible torsadogenic potential of macromolecular therapeutics.

Scientific Review of the Proarrhythmic Risks of Oligonucleotide Therapeutics: Are Dedicated ICH S7B/E14 Studies Needed for Low-Risk Modalities?

Oligonucleotide therapeutics (ONTs) represent a new modality with unique pharmacological and chemical properties that modulate gene expression with a high degree of target specificity mediated by complementary Watson-Crick base pair hybridization. To date, the proarrhythmic assessment of ONTs has been influenced by International Conference on Harmonization (ICH) E14 and S7B guidance. To document current hERG/QTc evaluation practices, we reviewed US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) Approval Packages (source: PharmaPendium.com) and collated preclinical and clinical studies for 17 marketed ONTs. In addition, clinical QTc data from 12 investigational ONTs were obtained from the literature. Of the marketed ONTs, eight were tested in the hERG assay with no inhibitory effect identified at the top concentration (range: 34-3,000 μM) tested. Fourteen of the ONTs were evaluated in nonhuman primate cardiovascular studies with 11 of them in dedicated telemetry studies. No effect on QTc intervals were observed (at high exposure multiples) in all studies. Clinically, four ONTs were evaluated in TQT studies; an additional six ONTs were assessed by concentration-QTc interval analysis, and six by routine safety electrocardiogram monitoring. None of the clinical studies identified a QTc prolongation risk; the same was true for the 12 investigational ONTs. A search of the FDA Adverse Event Database indicated no association between approved ONTs and proarrhythmias. Overall, the collective weight of evidence from 29 ONTs demonstrate no clinical proarrhythmic risk based on data obtained from ICH S7B/E14 studies. Thus, new ONTs may benefit from reduced testing strategies because they have no proarrhythmic risk, a similar cardiac safety profile as monoclonal antibodies, proteins, and peptides.

The Efficacy, Effectiveness, and Efficiency of Integrated QTc Assessment: Rationalizing Approaches to New Drug Modalities

After nearly 3 decades of regulatory activity concerning new drugs' potential for delayed cardiac repolarization an integrated risk assessment paradigm for small molecule drugs has been established. Regulatory guidance also suggests that for large, targeted proteins and monoclonal antibodies no quantitative clinical QTc assessment is necessary. The expansion of new drug modalities prompts the question: "Should these new modalities be treated like small molecule drugs or like monoclonal antibodies?"