In vitro hepatic metabolism of mefloquine using microsomes from cats, dogs and the common brush-tailed possum (Trichosurus vulpecula)

Abstract

Feline infectious peritonitis (FIP) is a systemic, fatal, viral-induced, immune-mediated disease of cats caused by feline infectious peritonitis virus (FIPV). Mefloquine, a human antimalarial agent, has been shown to inhibit FIPV in vitro. As a first step to evaluate its efficacy and safety profile as a potential FIP treatment for cats, mefloquine underwent incubation in feline, canine and common brush-tailed possum microsomes and phase I metabolism cofactors to determine its rate of phase I depletion. Tramadol was used as a phase I positive control as it undergoes this reaction in both dogs and cats. Using the substrate depletion method, the in vitro intrinsic clearance (mean ± S.D.) of mefloquine by pooled feline and common brush-tailed possum microsomes was 4.5 ± 0.35 and 18.25 ± 3.18 μL/min/mg protein, respectively. However, phase I intrinsic clearance was too slow to determine with canine microsomes. Liquid chromatography-mass spectrometry (LC-MS) identified carboxymefloquine in samples generated by feline microsomes as well as negative controls, suggesting some mefloquine instability. Mefloquine also underwent incubation with feline, canine and common brush-tailed possum microsomes and phase II glucuronidative metabolism cofactors. O-desmethyltramadol (ODMT or M1) was used as a positive control as it undergoes a phase II glucuronidation reaction in these species. The rates of phase II mefloquine depletion by microsomes by all three species were too slow to estimate. Therefore mefloquine likely undergoes phase I hepatic metabolism catalysed by feline and common brush-tailed possum microsomes but not phase II glucuronidative metabolism in all three species and mefloquine is not likely to have delayed elimination in cats with clinically normal, hepatic function. OPEN ACCESSCitation: Izes AM, Kimble B, Norris JM, Govendir M (2020) In vitro hepatic metabolism of mefloquine using microsomes from cats, dogs and the common brush-tailed possum (Trichosurus vulpecula). PLoS ONE 15(4): e0230975. https://doi.

Assay validation and determination of in vitro binding of mefloquine to plasma proteins from clinically normal and FIP-affected cats

“…There has been recent interest in the suitability of mefloquine as an antiviral treatment for FIP [9,10,23]. The majority of publications that detect and quantify mefloquine use liquid chromatography.…”

“…Liquid chromatography demonstrates good sensitivity (i.e., it can detect low concentrations of mefloquine), is highly specific and the machinery is affordable for veterinary diagnostic laboratories. Although an HPLC assay to detect mefloquine in an in vitro matrix has been reported [23], in contrast, this study describes an assay to quantify mefloquine Table 1. Intra-and inter-day precision and accuracy for the QC samples (250, 1000 and 5000 ng/mL of mefloquine) tested in triplicate for each concentration.…”

“…It also has been shown to reduce the viral load of FIPV and feline calicivirus (FCV) at low concentrations in infected Crandell Rees feline kidney cells without cytotoxic effects [9,10]. Using an in vitro assay, our team demonstrated that while mefloquine undergoes some phase I metabolism in cats, it does not undertake phase II glucuronidative metabolism in this species [11]. In anticipation of conducting in vivo clinical trials of mefloquine to treat FIPV-infected cats, mefloquine's plasma concentrations must be monitored to optimise the dosage regimen.…”

Current status on treatment options for feline infectious peritonitis and SARS-CoV-2 positive cats

“…Both chloroquine and mefloquine are commercially available pharmaceutical agents registered for use in people. Each has an extensive body of supporting literature regarding their pharmacokinetics and safety in non-feline species and some information is now available on mefloquine's pharmacokinetic profile in cats [77,78,79,80,81]. Considerably less is known about hexamethylene amiloride, particularly with respect to its safety [52].…”

“…As Takano et al [75] previously discounted the in vivo efficacy of chloroquine as an antiviral agent for FIP, clinical trials of mefloquine to treat infected cats could be considered. Recent in vitro pharmacokinetic studies have indicated that mefloquine undergoes phase I hepatic metabolism, but not phase II glucuronidative metabolism, when catalysed by feline hepatic microsomes and therefore is not likely to have delayed elimination in cats [77]. Mefloquine's pharmacokinetic profile in cats has been investigated in anticipation of undertaking clinical trials to inhibit feline coronavirus and feline A c c e p t e d M a n u s c r i p t calicivirus in those cats clinically affected by these viral infections [81].…”