Organic anion-transporting polypeptides (OATP) 1B1 and OATP1B3 are drug transporters mediating the active hepatic uptake of their substrates. Because they exhibit overlapping substrate specificities, the contribution of each isoform to the net hepatic uptake needs to be considered when predicting drug-drug interactions. The relative contribution of OATP1B1- and OATP1B3-mediated uptake of statins into hepatocytes was estimated based on either relative transporter protein expression data or relative activity data. Therefore, kinetics of eight statins and OATP1B1- and OATP1B3-specific reference substrates was determined in OATP1B1- and OATP1B3-expressing human embryonic kidney 293 cells and in human cryopreserved hepatocytes. Absolute OATP1B1 and OATP1B3 protein abundance was determined by liquid chromatography-tandem mass spectrometry in all expression systems. Transporter activity data generated in recombinant cell lines were extrapolated to hepatocyte values using relative transporter expression factors (REF) or relative activity factors (RAF). Our results showed a pronounced OATP1B1 and comparatively low OATP1B3 protein expression in the investigated hepatocyte lot. Based on REF scaling, we demonstrated that the active hepatic uptake clearances of reference substrates, atorvastatin, pravastatin, rosuvastatin, and simvastatin were well predicted within twofold error, demonstrating that OATP1B1 and OATP1B3 were major contributors. For other statins, the net hepatic uptake clearance was underpredicted, suggesting the involvement of other hepatic uptake transporters. Summarized, we showed that REF- and RAF-based predictions were highly similar, indicating a direct transporter expression-activity relationship. Moreover, we demonstrated that the REF-scaling method provided a powerful tool to quantitatively assess the transporter-specific contributions to the net uptake clearance of statins in hepatocytes

Organ-on-chip (OoC) technology has led to in vitro models with many new possibilities compared to conventional in vitro and in vivo models. In this review, the potential of OoC models to improve the prediction of human oral bioavailability and intrinsic clearance is discussed, with a focus on the functionality of the models and the application in current drug development practice. Multi-OoC models demonstrating the application for pharmacokinetic (PK) studies are summarized and existing challenges are identified. Physiological parameters for a minimal viable platform of a multi-OoC model to study PK are provided, together with PK specific read-outs and recommendations for relevant reference compounds to validate the model. Finally, the translation to in vivo PK profiles is discussed, which will be required to routinely apply OoC models during drug development.

Iptacopan (LNP023) is an oral, small-molecule, first-in-class, highly potent proximal complement inhibitor that specifically binds factor B and inhibits the alternative complement pathway. Iptacopan is currently in development as a targeted treatment for PNH and multiple other complement-mediated diseases. In this study, the absorption, distribution, metabolism, and excretion (ADME) of iptacopan was characterized in six healthy volunteers after a single 100 mg oral dose of [¹⁴C]iptacopan. This was supplemented with an in vivo rat ADME study and metabolite exposure comparisons between human, rat and dog, in addition to in vitro assays, to better understand the clearance pathways and enzymes involved in the metabolism of iptacopan. The fraction of [¹⁴C]iptacopan absorbed was estimated to be about 71%, with a time to maximum concentration (T_max) of 1.5 h and elimination half-life from plasma of 12.3 h. Following a single dose of [¹⁴C]iptacopan, 71.5% of the radioactivity was recovered in feces and 24.8% in urine. [¹⁴C]iptacopan was primarily eliminated by hepatic metabolism. The main biotransformation pathways were oxidative metabolism via CYP2C8, with M2 being the major oxidative metabolite, and acyl glucuronidation via UGT1A1. The two acyl glucuronide metabolites in human plasma, M8 and M9, each accounted for {less than or equal to}10% of the total circulating drug-related material; systemic exposure was also observed in toxicology studies in rat and dog, suggesting a low risk associated with these metabolites. Binding of iptacopan to its target, factor B, in the bloodstream led to a concentration-dependent blood:plasma distribution and plasma protein binding of [¹⁴C]iptacopan. Significance Statement We characterized the pharmacokinetics, excretion, metabolism and elimination of [¹⁴C]iptacopan (an oral, selective small-molecule inhibitor of factor B) – in healthy human subjects. [¹⁴C]iptacopan was primarily eliminated by metabolism. The primary biotransformation pathways were oxidative metabolism via CYP2C8 and acyl glucuronidation via UGT1A1. Direct secretion of iptacopan into urine and potentially bile represented additional elimination mechanisms. Binding of iptacopan to its target, factor B, in the bloodstream led to a concentration-dependent blood:plasma distribution and plasma protein binding of [¹⁴C]iptacopan.

Fevipiprant, an oral, non-steroidal, highly selective, reversible, and competitive antagonist of the prostaglandin D₂ receptor 2, is eliminated by glucuronidation, and by direct renal excretion. This study aimed to assess the effect of simultaneous UDP-glucuronosyltransferase (UGT) and organic anion transporter (OAT) 3 inhibition by probenecid on the pharmacokinetics of fevipiprant and its acyl glucuronide (AG) metabolite. This was a single-center, open-label, single sequence, two-period, crossover study in healthy subjects. Liquid chromatography with tandem mass spectrometry was used to measure concentrations of fevipiprant and its AG metabolite in plasma and urine. In the presence of probenecid, the mean maximum concentration of fevipiprant increased approximately 1.7-fold, and the area under the curve (AUC)_last and AUC_inf increased approximately 2.5-fold, while the mean apparent volume of distribution as well as the AG metabolite-fevipiprant ratio decreased. The apparent systemic clearance decreased by approximately 60% and the renal clearance decreased by approximately 88% in the presence of probenecid. Using the data from this study and previous studies, the relative contribution of OAT and UGT inhibition to the overall effect of probenecid was determined. This allowed development of a general disposition scheme for fevipiprant and estimation of quantitative contributions for the involved pathways: OATP1B1-mediated hepatic uptake, OAT3-mediated renal excretion and glucuronidation via UGT1A3, UGT2B7 and UGT2B17. Significance Statement In this drug-drug interaction (DDI) study probenecid was used as a tool to inhibit both glucuronidation and renal excretion of fevipiprant. The combination of plasma and urine pharmacokinetic data from this study with available data allowed the development of a quantitative scheme to describe the fate of fevipiprant in the body, illustrating why the DDI effect on fevipiprant is low-to-moderate, even if a perpetrator drug inhibits several elimination pathways.