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

Abstract

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%).

Feline Infectious Peritonitis: European Advisory Board on Cat Diseases Guidelines

“…Another agent that shows promise in cats is mefloquine, and although the full mechanism of its antiviral action is not known [ 340 , 343 ], it is believed to act as a nucleoside analogue [ 341 ]. Studies have been published on mefloquine’s hepatic metabolism using an in vitro model [ 342 ], its pharmacokinetics in healthy cats [ 343 ], and its plasma protein-binding properties in the plasma of healthy cats and cats with FIP [ 344 ]. Although studies are needed on its efficacy in cats with FIP, veterinarians in Australia (Richard Malik, Sally Coggins and Jacqueline Norris, personal communication) are using oral mefloquine to treat cats with FIP when finances prohibit the use of a full course of, or increased dosage of, more effective antivirals, such as GS-441524, as mefloquine is more affordable [ 332 ].…”

“…Hepatic metabolism studied in vitro [342] and pharmacokinetics studied in healthy cats [343]. Its plasma protein binding properties have been studied in the blood of cats with and without FIP, and a simple high performance liquid chromatography assay developed to measure mefloquine [344]. Causes vomiting if not given with food but generally appears safe in healthy cats.…”

Repurposing of FDA Approved Drugs Against SARS-CoV-2 Papain-Like Protease: Computational, Biochemical, and in vitro Studies

“…On the other hand, Mefloquine is an anti-malarial drug with an established activity against the malarial parasite during its life cycle in human red blood cells. With regard to its antiviral activities, Mefloquine has been shown to be effective against Feline calicivirus and Feline coronavirus, and more recently it has also been shown to be effective against SCoV-2, where it was found to target the viral spike protein and act as an entry inhibitor in a prophylactic role (McDonagh et al, 2015 ; Izes et al, 2020 ; Shionoya et al, 2021 ). On the other hand, Mefloquine, an anti-malarial drug, only moderately (IC 50 = 459 μM) inhibited the SCoV-2 PLpro activity in vitro in our enzyme-inhibition assays.…”

“…Nevertheless, as an antiviral candidate, Mefloquine has been shown to be effective against feline calicivirus and feline coronavirus, and more recently it has also been shown to be effective against SCoV-2, where it was found to target the viral spike protein and act as an entry inhibitor in a prophylactic role (McDonagh et al, 2015 ; Izes et al, 2020 ; Shionoya et al, 2021 ). Based on the findings in our study and from other studies, we opine that Mefloquine is a potential interventional drug and therefore needs to be studied in more detail in future preclinical and clinical studies.…”