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Published on: October 11, 2013
Membrane Perturbations and Assay Interferences by Ivermectin Explain Its In Vitro SARS-CoV-2 Antiviral Activities and
Richard T Eastman1, Radda Rusinova2, Karl F Herold3
1National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland 20850, United States.
Abstract:
The antiparasitic drug ivermectin was proposed as a repurposed drug for the treatment of SARS-CoV-2 infection based on in vitro studies, but proved ineffective in high-quality clinical trials. When exploring possible reasons for this disconnect, we found that ivermectin interferes with AlphaScreen assays by quenching singlet oxygen transmission, calling into question the original justifications for pursuing ivermectin as an antiviral agent. Furthermore, at the low micromolar concentrations where ivermectin reduced SARS-CoV-2 viral burden in vitro, ivermectin decreased cell viability, modified membrane bilayer properties, and nonspecifically dysregulated membrane protein functions. In this Perspective, we provide molecular-level rationale for why ivermectin, an effective and safe antiparasitic drug at low nanomolar concentrations, becomes cytotoxic at low micromolar concentrations and, in turn, why ivermectin has not translated into an effective antiviral agent. We highlight lessons learned from the failed ivermectin repurposing effort and provide a workflow for identifying membrane-perturbing bioactivity early in drug development.
Insights
Ivermectin
Area of Science:
- Drug repurposing
- Antiviral drug development
- Molecular pharmacology
Background:
- Ivermectin, an antiparasitic drug, was investigated for SARS-CoV-2 treatment based on in vitro data.
- High-quality clinical trials demonstrated ivermectin's ineffectiveness against SARS-CoV-2.
- The discrepancy between in vitro and clinical results necessitates further investigation.
Purpose of the Study:
- To investigate the molecular mechanisms behind ivermectin's in vitro antiviral activity and its failure in clinical trials.
- To explain why ivermectin, effective at nanomolar concentrations, becomes cytotoxic at micromolar concentrations.
- To propose a workflow for early identification of membrane-perturbing bioactivity in drug development.
Main Methods:
- Analysis of ivermectin's interference with AlphaScreen assays.
- Evaluation of ivermectin's effects on cell viability and membrane properties at various concentrations.
- Molecular modeling to understand ivermectin's interaction with cell membranes.
Main Results:
- Ivermectin interferes with AlphaScreen assays by quenching singlet oxygen, questioning initial antiviral justifications.
- At micromolar concentrations, ivermectin decreases cell viability, alters membrane properties, and dysregulates membrane proteins.
- Ivermectin exhibits cytotoxicity at concentrations required for in vitro antiviral effects.
Conclusions:
- Ivermectin's in vitro antiviral effects are likely due to non-specific cytotoxic mechanisms rather than direct antiviral action.
- The drug repurposing effort for ivermectin as an antiviral agent failed due to concentration-dependent cytotoxicity.
- Early identification of membrane-perturbing bioactivity is crucial for successful drug development.
