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

CYP1A2 contributes to the metabolism of mefloquine: Exploration using in vitro metabolism and physiologically-based pharmacokinetic modelling

Mefloquine is an antimalarial drug routinely used for prophylaxis and in the treatment of malaria. Approximately 50% of mefloquine metabolism, both in vitro and in vivo, is mediated by CYP3A4 with the remaining contributions by other CYP450 isoforms unaccounted for. This study aimed to determine the contribution of CYP450s to mefloquine metabolism and incorporate this knowledge into a physiologically-based pharmacokinetic model. The data in human liver microsomes demonstrated the involvement of CYP3A4/5 as well as the previously unreported contribution of CYP1A2 to mefloquine metabolism. The fraction metabolized by CYP1A2 (fm,CYP1A2) was estimated to be at least 50% using chemical inhibitors and pooled human liver microsomes and confirmed using recombinant human CYP450 enzymes. A physiologically-based pharmacokinetic model built in Simcyp using the fm,CYP values recaptured observed clinical pharmacokinetic data-71 % of the simulated area under the curve (AUC) values were within 1.25-fold of the observed clinical data, and all simulated AUC values were within 2-fold of observed data. Simulated mefloquine exposures increased by 88% when an interaction with fluvoxamine, a CYP1A2 inhibitor was modeled. Modeling showed that heavy smoking, and subsequent induction of CYP1A2, had a notable effect on mefloquine exposure. CYP1A2 genotype status also influenced mefloquine exposure with a predicted AUC ratio of 1.68 in a simulated population of CYP1A2 poor metabolizers. The involvement of CYP1A2 in mefloquine metabolism suggests a previously unreported drug-drug interaction risk. Looking forward, the analysis here suggests the clinical exploration of the interaction between mefloquine and CYP1A2. SIGNIFICANCE STATEMENT: Despite the widespread use of mefloquine in malaria prophylaxis and treatment, its metabolism is not completely characterized. This has implications for understanding and predicting drug-drug interactions involving mefloquine. Here, we identify CYP1A2 as a key enzyme involved in mefloquine metabolism and use physiologically-based pharmacokinetic modeling to demonstrate the contribution of this route to interactions with mefloquine. The in vitro data and revised physiologically-based pharmacokinetic model are important starting points for future exploration of this pathway using clinical data.

Feline Infectious Peritonitis: European Advisory Board on Cat Diseases Guidelines

Feline coronavirus (FCoV) is a ubiquitous RNA virus of cats, which is transmitted faeco-orally. In these guidelines, the European Advisory Board on Cat Diseases (ABCD) presents a comprehensive review of feline infectious peritonitis (FIP). FCoV is primarily an enteric virus and most infections do not cause clinical signs, or result in only enteritis, but a small proportion of FCoV-infected cats develop FIP. The pathology in FIP comprises a perivascular phlebitis that can affect any organ. Cats under two years old are most frequently affected by FIP. Most cats present with fever, anorexia, and weight loss; many have effusions, and some have ocular and/or neurological signs. Making a diagnosis is complex and ABCD FIP Diagnostic Approach Tools are available to aid veterinarians. Sampling an effusion, when present, for cytology, biochemistry, and FCoV RNA or FCoV antigen detection is very useful diagnostically. In the absence of an effusion, fine-needle aspirates from affected organs for cytology and FCoV RNA or FCoV antigen detection are helpful. Definitive diagnosis usually requires histopathology with FCoV antigen detection. Antiviral treatments now enable recovery in many cases from this previously fatal disease; nucleoside analogues (e.g., oral GS-441524) are very effective, although they are not available in all countries.

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

Feline infectious peritonitis (FIP) is a viral-induced, immune-mediated disease of cats caused by virulent biotypes of feline coronaviruses (FCoV), known as the feline infectious peritonitis virus (FIPV). Historically, three major pharmacological approaches have been employed to treat FIP: (1) immunomodulators to stimulate the patient’s immune system non-specifically to reduce the clinical effects of the virus through a robust immune response, (2) immunosuppressive agents to dampen clinical signs temporarily, and (3) re-purposed human antiviral drugs, all of which have been unsuccessful to date in providing reliable efficacious treatment options for FIPV. Recently, antiviral studies investigating the broad-spectrum coronavirus protease inhibitor, GC376, and the adenosine nucleoside analogue GS-441524, have resulted in increased survival rates and clinical cure in many patients. However, prescriber access to these antiviral therapies is currently problematic as they have not yet obtained registration for veterinary use. Consequently, FIP remains challenging to treat. The purpose of this review is to provide an update on the current status of therapeutics for FIP. Additionally, due to interest in coronaviruses resulting from the current human pandemic, this review provides information on domesticated cats identified as SARS-CoV-2 positive.

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

The antimalarial agent mefloquine is currently being investigated for its potential to inhibit feline coronavirus and feline calicivirus infections. A simple, high pressure liquid chromatography assay was developed to detect mefloquine plasma concentrations in feline plasma. The assay’s lower limit of quantification was 250 ng/mL. The mean ± standard deviation intra- and inter-day precision expressed as coefficients of variation were 6.83 ± 1.75 and 5.33 ± 1.37%, respectively, whereas intra- and inter-day accuracy expressed as a percentage of the bias were 11.40 ± 3.73 and 10.59 ± 3.88%, respectively. Accordingly, this validated assay should prove valuable for future in vivo clinical trials of mefloquine as an antiviral agent against feline coronavirus and feline calicivirus. However, the proportion of mefloquine binding to feline plasma proteins has not been reported. The proportion of drug bound to plasma protein binding is an important concept when developing drug dosing regimens. As cats with feline infectious peritonitis (FIP) demonstrate altered concentrations of plasma proteins, the proportion of mefloquine binding to plasma proteins in both clinically normal cats and FIP-affected cats was also investigated. An in vitro method using rapid equilibrium dialysis demonstrated that mefloquine was highly plasma protein bound in both populations (on average > 99%).

Pharmacokinetic Profile of Oral Administration of Mefloquine to Clinically Normal Cats: A Preliminary In-Vivo Study of a Potential Treatment for Feline Infectious Peritonitis (FIP)

Simple Summary

In searching for antiviral agents against feline coronaviruses and feline caliciviruses, mefloquine, a human anti-malarial drug, has been demonstrated to reduce viral load of feline coronaviruses and feline calicivirus in infected cells. In this study, mefloquine was administered orally to seven clinically healthy cats twice weekly for four doses and mefloquine concentrations in blood were measured to investigate the pharmacokinetic profile—the movement of drug in the body. The maximum blood concentration of mefloquine was 2.71 ug/mL and was reached 15 h after a single oral dose was administered. Mefloquine side effects included vomiting following administration without food in some cats, and mild increases in symmetric dimethylarginine (SDMA), an early kidney biomarker. This study provides valuable information on mefloquine’s profile in cats as an introductory step towards investigating it as a potential treatment for feline coronavirus and feline calicivirus infection in cats.

Abstract

The pharmacokinetic profile of mefloquine was investigated as a preliminary study towards a potential treatment for feline coronavirus infections (such as feline infectious peritonitis) or feline calicivirus infections. Mefloquine was administered at 62.5 mg orally to seven clinically healthy cats twice weekly for four doses and mefloquine plasma concentrations over 336 h were measured using high pressure liquid chromatography (HPLC). The peak plasma concentration (Cmax) after a single oral dose of mefloquine was 2.71 ug/mL and time to reach Cmax (Tmax) was 15 h. The elimination half-life was 224 h. The plasma concentration reached a higher level at 4.06 ug/mL when mefloquine was administered with food. Adverse effects of dosing included vomiting following administration without food in some cats. Mild increases in serum symmetric dimethylarginine (SDMA), but not creatinine, concentrations were observed. Mefloquine may provide a safe effective treatment for feline coronavirus and feline calicivirus infections in cats.

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

[This corrects the article DOI: 10.1371/journal.pone.0230975.].