Substrate-Dependent Inhibition of the Human Organic Cation Transporter OCT2: A Comparison of Metformin with Experimental Substrates

Abstract

The importance of the organic cation transporter OCT2 in the renal excretion of cationic drugs raises the possibility of drug-drug interactions (DDIs) in which an inhibitor (perpetrator) drug decreases OCT2-dependent renal clearance of a victim (substrate) drug. In fact, there are clinically significant interactions for drugs that are known substrates of OCT2 such as metformin. To identify drugs as inhibitors for OCT2, individual drugs or entire drug libraries have been investigated in vitro by using experimental probe substrates such as 1-methyl-4-phenylpyridinium (MPP+) or 4–4-dimethylaminostyryl-N-methylpyridinium (ASP+). It has been questioned whether the inhibition data obtained with an experimental probe substrate such as MPP+ or ASP+ might be used to predict the inhibition against other, clinical relevant substrates such as metformin. Here we compared the OCT2 inhibition profile data for the substrates metformin, MPP+ and ASP+. We used human embryonic kidney (HEK 293) cells stably overexpressing human OCT2 as the test system to screen 125 frequently prescribed drugs as inhibitors of OCT2-mediated metformin and MPP+ uptake. Data on inhibition of OCT2-mediated ASP+ uptake were obtained from previous literature. A moderate correlation between the inhibition of OCT2-mediated MPP+, ASP+, and metformin uptake was observed (pairwise r s between 0.27 and 0.48, all P < 0.05). Of note, the correlation in the inhibition profile between structurally similar substrates such as MPP+ and ASP+ (Tanimoto similarity T = 0.28) was even lower (r s = 0.27) than the correlation between structurally distinct substrates, such as ASP+ and metformin (T = 0.01; r s = 0.48) or MPP+ and metformin (T = 0.01; r s = 0.40). We identified selective as well as universal OCT2 inhibitors, which inhibited transport by more than 50% of one substrate only or of all substrates, respectively. Our data suggest that the predictive value for drug-drug interactions using experimental substrates rather than the specific victim drug is limited.

Lack of Influence of Substrate on Ligand Interaction with the Human Multidrug and Toxin Extruder, MATE1

“…With the information gained from these screens, plus IC 50 values determined for a structurally diverse subset of these compounds, we generated machine-learning and pharmacophore models, respectively. In contrast to the behavior observed with some other multidrug transporters (Ekins et al, 2002b;Garrigues et al, 2002;Westholm et al, 2009;Roth et al, 2011;Belzer et al, 2013;Hacker et al, 2015), the results suggest that substrate identity exerts comparatively little influence on ligand interaction with MATE1. (Aavula et al, 2006).…”

“…Decision tree-based predictions of potential DDIs with multidrug transporters are complicated when the quantitative profile of inhibition of transport by a potential perpetrator is influenced by the choice of substrate used to assess transport activity (e.g., Hacker et al, 2015). Although increasingly viewed as an issue for OCTs, P-glycoprotein, and organic anion-transporting polypeptides (Garrigues et al, 2002;Roth et al, 2011;Belzer et al, 2013;Hacker et al, 2015), the extent to which ligand interaction with MATE1 displays a similar substrate dependence is not clear.…”

“…However, little attention has been given to a critical issue relevant to understanding the influence of MATE1 on unwanted DDI: the potential impact of substrate identity on the profile of drug interaction with MATE1. Increasing evidence suggests that the effectiveness of cationic drugs as inhibitors of multidrug transporters can be significantly influenced by the substrate used to monitor transport activity (Belzer et al, 2013;Thévenod et al, 2013;Hacker et al, 2015), which may complicate the interpretation of decision tree-based assays for assessing potential DDIs (Giacomini et al, 2010;Hillgren et al, 2013). However, the extent to which MATE transporters display such behavior is not clear.…”

A PET Tracer for Renal Organic Cation Transporters, 11C-Metformin: Radiosynthesis and Preclinical Proof-of-Concept Studies

“…A downregulation of OCT2 was associated with an experimental acute renal failure in rats (4,5), indicating that OCT2 may play an important role in renal disease. It was recently demonstrated that OCT2 is important for renal metformin transport, and other cationic drugs may competitively inhibit the renal metformin transport (6).…”

Metformin: od mehanizmov delovanja do napredne klinične uporabe

“…Plazemske koncentracije metformina običajno dosežejo vrednosti med 1 in 50 μM, pri čemer so višje koncentracije dokazali v portalnem sistemu in jetrih (22). Metformin se v telesu večinoma ne presnavlja in se v več kot 90 % izloča z urinom s pomočjo tubulne sekrecije preko prenašalca OCT2 v ledvicah (17,23). Zaradi nezmožnosti pasivnega prestopa v znotrajcelični prostor so terapevtski uspehi zdravila lahko odvisni od izraženosti oziroma različnih genetskih oblik membranskega prenašal-ca OCT (1/2/3) (24,25).…”