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Moxidectin and the avermectins: Consanguinity but not identity
Roger Prichard1, Cécile Ménez2, Anne Lespine2
1Institute of Parasitology, McGill University, Montreal, Canada.
International Journal for Parasitology. Drugs and Drug Resistance
|February 18, 2014
Summary
Moxidectin (MOX) and avermectins, both macrocyclic lactones, differ in structure and interactions with ion channels and transporters. These distinctions impact efficacy, safety, and resistance, guiding optimal parasite control strategies.
Area of Science:
- Veterinary Parasitology
- Pharmacology
- Molecular Biology
Background:
- Avermectins and milbemycins share a macrocyclic lactone ring but differ in organism of origin and C13 substitution.
- Moxidectin (MOX), a milbemycin, has unique structural features like a C23 methoxime.
- Both avermectins and MOX exhibit broad-spectrum activity against nematodes and arthropods, with varied formulations available.
Purpose of the Study:
- To compare the structural, functional, and resistance profiles of moxidectin (MOX) and avermectins.
- To elucidate the molecular basis for differences in efficacy and safety between MOX and avermectins.
- To inform optimal parasite control strategies by understanding drug interactions and resistance mechanisms.
Main Methods:
- Comparative analysis of chemical structures and fermentation origins.
- Review of known interactions with invertebrate ligand-gated ion channels and mammalian/nematode ABC transporters.
- Examination of pharmacokinetic and pharmacodynamic data, including half-life and safety profiles.
- Analysis of resistance patterns, including cross-resistance and differential efficacy.
Main Results:
- MOX and avermectins exhibit distinct interactions with ion channels and ABC transporters, influencing pharmacokinetics, toxicity, and resistance.
- MOX possesses a longer half-life and favorable safety profile, enabling long-acting formulations.
- While cross-resistance exists, MOX often maintains efficacy where avermectin resistance is prevalent.
- Avermectin resistance is widespread, and MOX resistance is emerging, with non-identical resistance profiles.
Conclusions:
- Differences in molecular interactions and transporter engagement underpin the varied efficacy and safety of MOX and avermectins.
- Understanding these distinctions is crucial for managing and delaying parasite resistance.
- MOX offers a valuable alternative, particularly in cases of avermectin resistance, aiding in anthelmintic combination therapy.
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