Part 3 of our Webinar Series: A Focus on Drug Transporters

Impact of Pre-Incubation Time on Transporter Inhibition Potency

This September, Cyprotex, along with our colleagues at Genentech and Novartis, ran a complimentary webinar series on drug transporters. This blog focuses on the third webinar of the series presented by Felix Huth PhD of Novartis, entitled ‘Impact of Pre-incubation Time on Transporter Inhibition Potency’.

If you missed our other blogs in this series, you can catch up by reading here:

• Read the blog: Part 1, Quantitative Prediction of Drug-Drug Interactions with Common Statin Co-medications
• Read the blog: Part 2, P-gp Transport Kinetics – Compound-specific Selection of In Vitro Assay Design and Kinetic Parameter Estimation

Drug permeability is dependent on passive permeability as well as the potential of a drug to undergo active uptake or efflux by drug transporters. Being able to predict whether a drug is a potential substrate or inhibitor of these transporters can explain and predict clinical implications. As recommended by the FDA Guidance for Industry and the EMA Guidance on the Investigation of Drug Interactions, drugs should be investigated in vitro for their potential to inhibit a panel of clinically relevant transporters. Furthermore, the guidance recommends that for OATP1B1 and 1B3, a pre-incubation step with test compound should be performed prior to subsequent co‑incubation with probe substrate, as some known inhibitors of these transporters have demonstrated increased inhibitory potency with time when compared to the co-incubation condition alone.

In this third webinar of our drug transporter series, Felix Huth describes the work undertaken to investigate and characterise the impact of pre-incubation time on IC₅₀ values determined against a range of clinically relevant uptake transporters (OATP1B1, OATP1B3, OAT1, OAT3, OCT1, OCT2, MATE1 and MATE2-K), and how the physicochemical properties of an inhibitor can influence the extent of any IC₅₀ shift. The research also evaluates the effect of plastic binding, cytotoxicity and overall incubation time on the results.

Besides OATPs, this research also indicates that pre-incubation is also important for OCT assays, whereas OATs and MATEs appear to be less impacted by preincubation time under the conditions in the study; however any impact will be related to the inhibitor being investigated and whether it needs to act intracellularly to exert inhibition, rather than to the transporter per se. IC₅₀’s generated following pre-incubation are thought to be more accurate, resulting in improved PBPK (or mechanistic static) predictions for transporter DDI. Depending upon the inhibitor drug, pre-incubation can lead to lower IC₅₀ values resulting in higher DDI risk ratios, which may bring about consideration of new regulatory basic static equation cut-off values in the future.

If you missed out on our webinar series or if you would like the opportunity to watch the webinars again, please click on the links below:

Watch the webinar – Part 1 (Hayley Atkinson PhD, Cyprotex)

Watch the webinar – Part 2 (Birk Poller PhD, Novartis)

Watch the webinar – Part 3 (Felix Huth PhD, Novartis)

To read more about our own work in this field, please click on the links below:

Read our SLC transporter inhibitor preincubation poster: Further investigation of the impact of inhibitor pre-incubation on human OATP1B1, OAT3, OCT2 and MATE1 transporter in vitro inhibitory potencies (2016)

Read our inhibitor preincubation time poster: Investigation of inhibitor pre-incubation condition on human OATP1B1, P-gp and BCRP transporter in vitro inhibitory potencies (2018)