Rönnpagel Vincent, Morof Felix, Römer Sarah, Meyer-Tönnies Marleen J, Tzvetkov Mladen V
Department of General Pharmacology, Institute of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine Greifswald, Greifswald, Germany.
Department of General Pharmacology, Institute of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine Greifswald, Greifswald, Germany.
Drug Metab Dispos. 2025 May;53(5):100074. doi: 10.1016/j.dmd.2025.100074. Epub 2025 Mar 28.
Transporters of the SLC22 family, such as organic cation transporter 1 (OCT1), possess very broad substrate specificity. It is unclear to what extent the inhibitory potencies of OCT1 depend on the substrate used. Here, we describe a multisubstrate drug cocktail that allows for the simultaneous testing of drug-drug interactions using 8 different victim drugs: fenoterol, salbutamol, sumatriptan, zolmitriptan, ipratropium, trospium, methylnaltrexone, and metformin. There were no significant differences in Michaelis constant (K) and v of the OCT1-mediated uptake of the substrates alone or in the cocktail. Depending on the victim drug analyzed, we observed 6.7-fold differences in the inhibitory potency of fenoterol (IC of 0.75 μM for metformin and 5.1 μM for sumatriptan). Similarly, the inhibitory potency of verapamil varied 6.7-fold (IC of 1.3 μM for zolmitriptan and 8.7 μM for ipratropium). Two groups of inhibitors showed strong correlations in their victim-dependent inhibitory potencies. Group 1 comprised verapamil, quinidine, fenoterol, and ipratropium, and group 2 comprised metformin, sumatriptan, and trimethoprim. By comparing OCT1 paralogs and orthologs, the broadest substrate spectra were observed for OCT1 and multidrug and toxin extrusion 1, followed by OCT2, multidrug and toxin extrusion 2-K, and OCT3. In contrast, organic cation transporters novel 1 and organic cation transporters novel 2 exhibited very narrow substrate specificity, transporting only L-carnitine and L-ergothioneine, respectively. In conclusion, OCT1 demonstrates substantial differences in inhibitory potencies, depending on the victim drug used. We developed a cocktail approach that enables rapid screening for such differences, facilitating the identification of drug-drug interactions at the early stages of drug development. This approach can be extended to other transporters with broad substrate specificity. SIGNIFICANCE STATEMENT: Polyspecific transporters have a broad substrate-binding cavity with no defined single binding position. Consequently, inhibitors may exhibit different inhibitory potencies depending on the victim drug used for testing. Here, we demonstrate this for organic cation transporter 1 (OCT1, SLC22A1) and presents a drug cocktail designed to identify varying inhibitory potencies in vitro and prevent false-negative drug-drug interaction results during early drug development. This approach can be extended to other polyspecific drug transporters.
溶质载体家族22（SLC22）的转运蛋白，如有机阳离子转运体1（OCT1），具有非常广泛的底物特异性。目前尚不清楚OCT1的抑制效力在多大程度上取决于所使用的底物。在此，我们描述了一种多底物药物混合物，它允许使用8种不同的受影响药物同时测试药物-药物相互作用：非诺特罗、沙丁胺醇、舒马曲坦、佐米曲坦、异丙托溴铵、曲司氯铵、甲基纳曲酮和二甲双胍。单独或在混合物中，OCT1介导的底物摄取的米氏常数（K）和最大反应速度（V）没有显著差异。根据所分析的受影响药物，我们观察到非诺特罗的抑制效力存在6.7倍的差异（二甲双胍的半数抑制浓度（IC）为0.75 μM，舒马曲坦为5.1 μM）。同样，维拉帕米的抑制效力变化了6.7倍（佐米曲坦的IC为1.3 μM，异丙托溴铵为8.7 μM）。两组抑制剂在其依赖于受影响药物的抑制效力方面表现出很强的相关性。第1组包括维拉帕米、奎尼丁、非诺特罗和异丙托溴铵，第2组包括二甲双胍、舒马曲坦和甲氧苄啶。通过比较OCT1的旁系同源物和直系同源物，观察到OCT1和多药及毒素外排转运体1具有最广泛的底物谱，其次是OCT2、多药及毒素外排转运体2-K和OCT3。相比之下，新型有机阳离子转运体1和新型有机阳离子转运体2表现出非常狭窄的底物特异性，分别仅转运左旋肉碱和左旋麦角硫因。总之，根据所使用的受影响药物，OCT1在抑制效力上表现出显著差异。我们开发了一种混合物方法，能够快速筛选此类差异，有助于在药物开发的早期阶段识别药物-药物相互作用。这种方法可以扩展到其他具有广泛底物特异性的转运体。意义声明：多特异性转运体具有一个宽广的底物结合腔，没有明确的单一结合位点。因此，抑制剂可能会根据用于测试的受影响药物表现出不同的抑制效力。在此，我们针对有机阳离子转运体1（OCT1，SLC22A1）证明了这一点，并提出了一种药物混合物，旨在体外识别不同的抑制效力，并在药物开发早期防止出现假阴性的药物-药物相互作用结果。这种方法可以扩展到其他多特异性药物转运体。
