Metabolism of (R)‐Praziquantel versus the Activation of a Parasite Transient Receptor Potential Melastatin Ion Channel

Praziquantel is an anthelmintic drug activating schistosome worms’ Transient Receptor Potential Melastatin ion channel for which the cyclohexyl moiety is a key pharmacophore and also the main site of CYP-mediated oxidative metabolism. While attempting to limit metabolism, the contribution to the overall activity of both the parent and the main metabolite of praziquantel in humans is discussed.

Abstract

Praziquantel (PZQ) is an essential anthelmintic drug recently established to be an activator of a Transient Receptor Potential Melastatin (TRPM_PZQ) ion channel in trematode worms. Bioinformatic, mutagenesis and drug metabolism work indicate that the cyclohexyl ring of PZQ is a key pharmacophore for activation of trematode TRPM_PZQ, as well as serving as the primary site of oxidative metabolism which results in PZQ being a short-lived drug. Based on our recent findings, the hydrophobic cleft in schistosome TRPM_PZQ defined by three hydrophobic residues surrounding the cyclohexyl ring has little tolerance for polarity. Here we evaluate the in vitro and in vivo activities of PZQ analogues with improved metabolic stability relative to the challenge of maintaining activity on the channel. Finally, an estimation of the respective contribution to the overall activity of both the parent and the main metabolite of PZQ in humans is reported.

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