Canine and feline P-glycoprotein deficiency: What we know and where we need to go

Assessment of P-glycoprotein function using canine intestinal organoid-derived epithelial interfaces

P-glycoprotein (P-gp), a multidrug efflux pump encoded by the ABCB1 (formerly MDR1) gene, plays a crucial role in limiting drug absorption and eliminating toxic compounds in both humans and dogs. However, species-specific differences in P-gp substrates necessitate the development of canine-specific evaluation systems. Canine intestinal organoids derived monolayers offer a promising platform for studying drug transport, yet P-gp-mediated transport in these models remains unexplored.We generated canine colonoid-derived 2D monolayers to investigate ABCB1 gene expression and P-gp function. We employed widely recognised P-gp substrates, Rhodamine 123 and Doxorubicin, in conjunction with the P-gp inhibitor PSC833 at Days 5 and 10 of culture.A significant increase in gene expression of P-gp encoded by the ABCB1 was noted on Day 10 compared to Day 5 of culture. Despite this disparity in gene expression, the transport activity of P-gp, as assessed by the efflux of Rhodamine 123 and Doxorubicin with PSC833 inhibition, did not exhibit significant differences between these two time points. However, the inhibition of P-gp function by PSC833 confirms the presence of functional P-gp in our model.Canine intestinal organoid-derived monolayers provide a valuable tool for investigating P-gp-mediated drug transport. These findings highlight the potential for predicting drug bioavailability and adverse reactions in veterinary medicine, aligning with principles of ethical and sustainable research.

Impact of concerning excipients on animal safety: insights for veterinary pharmacotherapy and regulatory considerations

OBJECTIVES

Veterinarians and pharmacists are familiar with the efficacy and safety aspects attributed to active pharmaceutical ingredients included in medicines, but they are rarely concerned with the safety of excipients present in medicines. Although generally recognized as safe, excipients are not chemically inert and may produce adverse events in certain animal populations. This review aims to present excipients of concern to these populations and highlight their relevance for rational veterinary pharmacotherapy.

EVIDENCE ACQUISITION

A comprehensive review of the literature about the existence of adverse reactions in animals caused by pharmaceutical excipients was carried out based on an exploratory study. An overview of the correct conditions of use and safety of these excipients has also been provided, with information about their function, the proportion in which they are included in the different pharmaceutical dosage forms and the usual routes of administration.

RESULTS

We identified 18 excipients considered of concern due to their potential to cause harm to the health of specific animal populations: bentonite, benzalkonium chloride, benzoic acid, benzyl alcohol, ethanol, lactose, mannitol, mineral oil, monosodium glutamate, polyethylene glycol, polysorbate, propylene glycol, sodium benzoate, sodium carboxymethylcellulose, sodium lauryl sulfate, sulfites, polyoxyethylene castor oil derivatives, and xylitol. Among the 135 manuscripts listed, only 24 referred to studies in which the substances were correctly evaluated as excipients.

CONCLUSIONS

Based on the information presented in this review, the authors hope to draw the attention of professionals involved in veterinary pharmacotherapy to the existence of excipients of concern in medicines. This information contributes to rational veterinary pharmacotherapy and supports veterinary pharmacovigilance actions. We hope to shed light on the subject and encourage studies and new manuscripts that address the safety of pharmaceutical excipients to the animal population.

Application of eprinomectin-containing parasiticides at label doses causes neurological toxicosis in cats homozygous for ABCB11930_1931del TC

The feline MDR1 mutation (ABCB11930_1931delTC) has been associated with neurological toxicosis after topical application of eprinomectin products labeled for feline use. Information was collected from veterinarians who submitted samples for ABCB11930_1931delTC genotyping. In most cases, the submission form indicated an adverse event involving eprinomectin, in other cases submitting veterinarians were contacted to determine whether the patient had experienced an adverse drug event involving eprinomectin. If so, additional information was obtained to determine whether the case met inclusion criteria. 14 cases were highly consistent with eprinomectin toxicosis. Eight cats were homozygous for ABCB11930_1931del TC (3 died; 5 recovered). Six cats were homozygous wildtype (2 died; 4 recovered). The observed ABCB11930_1931delTC frequency (57%) was higher than the expected frequency (≤1%) in the feline population (Fisher Exact test, p < 0.01). Among wildtype cats, four were concurrently treated with potential competitive inhibitors of P-glycoprotein. Results indicate that topical eprinomectin products, should be avoided in cats homozygous for ABCB11930_1931delTC. This is a serious, preventable adverse event occurring in an identifiable subpopulation treated with FDA-approved products in accordance with label directions. Acquired P-glycoprotein deficiency resulting from drug interactions may enhance susceptibility to eprinomectin-induced neurological toxicosis in any cat, regardless of ABCB1 genotype.

Comparative pharmacokinetics of tyrosine kinase inhibitor, lapatinib, in dogs and cats following single oral administration

Lapatinib is an orally administered tyrosine kinase inhibitor used to treat human epidermal growth factor receptor 2 (HER2) -overexpressing breast cancers in humans. Recently, the potential of lapatinib treatment against canine urothelial carcinoma or feline mammary tumor was investigated. However, the pharmacokinetic studies of lapatinib in dogs and cats are not well-defined. In the present study, the pharmacokinetic characteristics of lapatinib in both cats and dogs after a single oral administration at a dose of 25 mg/kg were compared with each other. Lapatinib was administered orally to four female laboratory cats and four female beagle dogs. Blood samples were collected over time, and the plasma lapatinib concentrations were analyzed by HPLC. Following a single dose of 25 mg/kg, the averaged maximum plasma concentration (Cmax) of lapatinib in cats was 0.47 μg/mL and achieved at 7.1 hr post-administration, while the Cmax in dogs was 1.63 μg/mL and achieved at 9.5 hr post-administration. The mean elimination half-life was 6.5 hr in cats and 7.8 hr in dogs. The average area under the plasma concentration-time curve of dogs (37.2 hr·μg/mL) was significantly higher than that of cats (7.97 hr·μg/mL). These results exhibited slow absorptions of lapatinib in both animals after oral administration. The Cmax observed in cats was significantly lower and the half-life was shorter than those observed in dogs. Based on these results, a larger dose or shorter dosing intervals might be recommended in cats to achieve similar plasma concentration as dogs.

Relevance of pharmacogenetics and pharmacogenomics in veterinary clinical practice: A review

The recent advances in high-throughput next-generation sequencing technologies have heralded the arrival of the Big Data era. As a result, the use of pharmacogenetics in drug discovery and individualized drug therapy has transformed the field of precision medicine. This paradigm shift in drug development programs has effectively reshaped the old drug development practices, which were primarily concerned with the physiological status of patients for drug development. Pharmacogenomics bridges the gap between pharmacodynamics and pharmacokinetics, advancing current diagnostic and treatment strategies and enabling personalized and targeted drug therapy. The primary goals of pharmacogenetic studies are to improve drug efficacy and minimize toxicities, to identify novel drug targets, to estimate drug dosage for personalized medicine, and to incorporate it as a routine diagnostic for disease susceptibility. Although pharmacogenetics has numerous applications in individualized drug therapy and drug development, it is in its infancy in veterinary medicine. The objective of this review is to present an overview of historical landmarks, current developments in various animal species, challenges and future perspectives of genomics in drug development and dosage optimization for individualized medicine in veterinary subjects.

ABCB1 and ABCG2 Regulation at the Blood-Brain Barrier: Potential New Targets to Improve Brain Drug Delivery

The drug efflux transporters ABCB1 and ABCG2 at the blood-brain barrier limit the delivery of drugs into the brain. Strategies to overcome ABCB1/ABCG2 have been largely unsuccessful, which poses a tremendous clinical problem to successfully treat central nervous system (CNS) diseases. Understanding basic transporter biology, including intracellular regulation mechanisms that control these transporters, is critical to solving this clinical problem.In this comprehensive review, we summarize current knowledge on signaling pathways that regulate ABCB1/ABCG2 at the blood-brain barrier. In Section I, we give a historical overview on blood-brain barrier research and introduce the role that ABCB1 and ABCG2 play in this context. In Section II, we summarize the most important strategies that have been tested to overcome the ABCB1/ABCG2 efflux system at the blood-brain barrier. In Section III, the main component of this review, we provide detailed information on the signaling pathways that have been identified to control ABCB1/ABCG2 at the blood-brain barrier and their potential clinical relevance. This is followed by Section IV, where we explain the clinical implications of ABCB1/ABCG2 regulation in the context of CNS disease. Lastly, in Section V, we conclude by highlighting examples of how transporter regulation could be targeted for therapeutic purposes in the clinic. SIGNIFICANCE STATEMENT: The ABCB1/ABCG2 drug efflux system at the blood-brain barrier poses a significant problem to successful drug delivery to the brain. The article reviews signaling pathways that regulate blood-brain barrier ABCB1/ABCG2 and could potentially be targeted for therapeutic purposes.

Assessment of verdinexor as a canine P-glycoprotein substrate

The P-glycoprotein (P-gp) substrate status of antineoplastic drugs intended for veterinary patients is an important characteristic to define for two reasons. First, neoplastic cells expressing P-gp can actively efflux drugs that are P-gp substrates curtailing their efficacy. Second, antineoplastic drugs tend to have a narrow therapeutic index. Antineoplastic drugs that are P-gp substrates can cause severe adverse reactions in animals with P-gp dysfunction such as dogs with ABCB1-1Δ and cats with ABCB11930_1931del TC. Animals with P-gp dysfunction experience greater overall exposure to P-gp substrate drugs due to mechanisms such as increased intestinal absorption, decreased biliary clearance and greater central nervous system penetration compared with animals with normal P-gp function. Accordingly, knowing the P-gp substrate status of antineoplastic drugs is an important safety consideration prior to use in canine or feline cancer patients. This study used a cell line overexpressing canine P-gp to assess the P-gp substrate status of verdinexor. Based on both a cytotoxicity assay and a competitive flow cytometry assay verdinexor is not a substrate for canine P-gp.