Implementing the 3R initiative to reduce animal experiments in brain penetration prediction for CNS-targeting drugs requires more predictive in vitro and in silico models. However, animal studies are still indispensable to obtaining brain concentration and determining the prediction performance of in vitro models. To reveal species differences and provide reliable data for IVIVE, in vitro models are required. Systems overexpressing MDR1 and BCRP are widely used to predict BBB penetration, highlighting the impact of the in vitro system on predictive performance. In this study, endogenous Abcb1 knock-out MDCKII cells overexpressing MDR1 of human, mouse, rat or cynomolgus monkey origin were used. Good correlations between ERs of 83 drugs determined in each cell line suggest limited species specificities. All cell lines differentiated CNS-penetrating compounds based on ERs with high efficiency and sensitivity. The correlation between in vivo and predicted K_p,uu,brain was the highest using total ER of human MDR1 and BCRP and optimized scaling factors. MDR1 interactors were tested on all MDR1 orthologs using digoxin and quinidine as substrates. We found several examples of inhibition dependent on either substrate or transporter abundance. In summary, this assay system has the potential for early-stage brain penetration screening. IC₅₀ comparison between orthologs is complex; correlation with transporter abundance data is not necessarily proportional and requires the understanding of modes of transporter inhibition.

Background/Objectives: One of the major risks associated with the concomitant use of herbal products and therapeutic drugs is herb–drug interactions (HDIs). The most common mechanism leading to HDIs is the inhibition and/or induction of transport proteins and drug-metabolizing enzymes by herbal ingredients, causing changes in the pharmacokinetic disposition of the victim drug. The present study aimed to determine the potential interactions of Uncaria tomentosa (UT) (cat’s claw), a popular herb due to its supposed health benefits. Methods: The effect of UT extract and its major oxindole alkaloids was investigated on multispecific solute carrier (SLC) and ATP-binding cassette (ABC) drug transporters, using SLC transporter-overexpressing cell lines and vesicles prepared from ABC transporter-overexpressing cells. Results: UT extract significantly inhibited all ABC transporters and the majority of the SLC transporters tested. Of the investigated oxindole alkaloids, isopteropodine significantly inhibited OATP, OCT1 and OCT2, OAT3, ENT4, MDR1, and BCRP transporters. OCTs, OCTN1-, ENT1-, and MDR1-mediated substrate accumulation was below 50% in the presence of mitraphylline. Conclusions: Based on the calculated intestinal concentration of UT extract, interactions with intestinal transporters, especially OATP2B1, ENTs, MRP1, MRP2, MDR1, and BCRP could be relevant in vivo. Our data can help to predict the clinical consequences of UT co-administration with drugs, such as increased toxicity or altered efficacy. In conclusion, the use of these in vitro models is applicable for the analysis of transporter-mediated HDIs similar to drug–drug interaction (DDI) prediction.

Background/Objectives: Ginger (Zingiber officinale Roscoe) is a flowering plant widely used as a spice and natural medicine for millennia. Ginger demonstrates multiple protective effects, regulates cholesterol, and may reduce the risk of cancer and colitis. However, little attention has been paid to its potential to cause herb–drug interactions (HDIs). The aim of this study was to investigate the interaction of ginger extract and its major components [6]-gingerol and [6]-shogaol with clinically relevant uptake and efflux transporters in vitro. Methods: Transporter-overexpressing cell lines of 25 uptake transporters and inside-out membrane vesicles containing 8 efflux transporters were employed to measure potential interactions. Results: Zingiber officinale extract at 150 µg/mL interacted with 17 of 33 transporters examined. These were further investigated for interactions with the purified active components. Seven and 16 transporters interacted with pure [6]-gingerol (100 µM) and [6]-shogaol (100 µM), respectively. To evaluate the risk of in vivo inhibition, IC₅₀ values were determined for the affected transporters. Based on standard risk assessment calculations, we confirmed previously reported inhibitory effects of ginger components on MDR1 (67.64 µM) and BCRP (9.931 µM), and revealed novel potential interactions with renal OAT3 (0.956 µM) and URAT1 (5.887 µM), hepatic OCT1 (4.287 µM) and BSEP (25.45 µM), and the ubiquitously expressed ENT1 (11.62 µM) ([6]-shogaol IC₅₀ values are shown in parentheses). Strong and isoform-selective inhibition of OAT3 by [6]-shogaol is particularly intriguing. Additionally, via cell viability experiments on a set of human cervical, breast, and oropharyngeal cancer cell lines, we demonstrated the antiproliferative effect of [6]-shogaol in vitro. Conclusions: Prolonged consumption of high-dose ginger supplements may pose a risk of transporter-mediated HDIs when consumed concomitantly with conventional medications. Our study encourages follow-up of the suspected effects in vivo.