Quantification of OATP1B1 endogenous metabolites coproporphyrin I and III in human urine.

Coproporphyrin (CP)-I and CP-III are the markers of organic anion-transporting polypeptides' (OATPs) activities, and they are porphyrin metabolites that originate from heme synthesis. Furthermore, CP-I and CP-III, which are OATP1B endogenous metabolites, have gradually attracted the attention of scientists and researchers in recent years. Previous studies have also observed CP-I and CP-III levels as clinical biomarkers for predicting OATP1B inhibition in drug-drug interaction studies. To establish an accurate ultra-high performance liquid chromatography-mass spectrometry method for the quantitation of CP-I and CP-III, we reviewed previous methodological publications and applied them to a clinical pharmacology study using a human urine matrix. We used 13.25 M formic acid as a working solution for internal standards (CP-I 15N4 and CP-III d8) to avoid isobaric interference. The calibration curve showed good linearity in the range of 1-100 ng/mL, with a correlation coefficient (R2) higher than 0.996 in each validation batch. Both the between-run and within-run assays achieved good precision and accuracy, and we found that both CP-I and CP-III were stable in the pre-study validation. The method exhibited suitable dilution integrity, allowing for the re-analysis of samples with concentrations exceeding the upper limit of quantification through dilution. Overall, the application of the described method in a clinical study revealed that it can be utilized effectively to monitor drug-drug interactions mediated by OATP1B.

Positive correlation between organic anion transporter 1B function indicated by plasma concentration of coproporphyrin-I and blood concentration of cyclosporin A in real-world patients.

AIMS: Cyclosporin A (CyA) has potent inhibitory activity on organic anion transporting polypeptide 1B (OATP1B), causing drug-drug interactions with its substrate drugs. 3-carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF), a uraemic toxin, has also been suggested to inhibit OATP1B activity. Recent study has identified coproporphyrin-I (CP-I) as a specific endogenous substrate for OATP1B, which is useful to indicate OATP1B activity. We investigated the relationship of CP-I with CyA and CMPF concentrations in patients taking CyA. METHODS: In total, 121 blood samples from 74 patients who took CyA and underwent routine therapeutic drug monitoring were divided into trough and peak samples. RESULTS: CyA and CP-I concentrations were significantly higher in peak samples than in trough samples. A positive correlation between CP-I and CyA concentrations was found in all samples and in trough and peak samples, while no correlation was observed between CP-I and CMPF concentrations. Multiple regression analysis identified CyA and C-reactive protein concentrations as independent factors affecting CP-I concentration, with blood CyA concentration having markedly greater contribution to plasma CP-I concentration. CONCLUSION: The present study suggests that CyA inhibits OATP1B activity in a concentration-dependent manner in clinical setting, and that dose adjustment of OATP1B substrate drugs coadministered with CyA according to plasma CMPF concentration may not be necessary.

Effects of rifampicin on porphyrin metabolism in healthy volunteers.

Pregnane X receptor (PXR) is known to stimulate haem synthesis, but detailed knowledge on the effects of PXR activation on porphyrin metabolism in humans is lacking. We utilized a randomized, crossover, open (blinded laboratory) and placebo-controlled trial with 600-mg rifampicin or placebo dosed for a week to investigate the effects of PXR activation on erythrocyte, plasma, faecal and urine porphyrins. Sixteen healthy volunteers participated on the trial, but the number of volunteers for blood and urine porphyrin analyses was 15 while the number of samples for faecal analyses was 14. Rifampicin increased urine pentaporphyrin concentration 3.7-fold (mean 1.80 ± 0.6 vs. 6.73 ± 4.4 nmol/L, p = 0.003) in comparison with placebo. Urine coproporphyrin I increased 23% (p = 0.036). Faecal protoporphyrin IX decreased (mean 31.6 ± 23.5 vs. 19.2 ± 27.8 nmol/g, p = 0.023). The number of blood erythrocytes was slightly elevated, and plasma bilirubin, catabolic metabolite of haem, was decreased. In conclusion, rifampicin dosing elevated the excretion of certain urinary porphyrin metabolites and decreased faecal protoporphyrin IX excretion. As urine pentaporphyrin and coproporphyrin I are not precursors in haem biosynthesis, increased excretion may serve as a hepatoprotective shunt when haem synthesis or porphyrin levels are increased.

Quantitative prediction of OATP1B-mediated drug-drug interactions using endogenous biomarker coproporphyrin I.

Evaluation of the organic anion transporting polypeptide (OATP) 1B-mediated drug-drug interaction (DDI) potential is important for drug development. The focus of this study was coproporphyrin I (CP-I), an endogenous OATP1B biomarker.We investigated a new approach to OATP1B-mediated DDI prediction based on the mechanistic static pharmacokinetics (MSPK) model.The ratio of the area under the plasma concentration-time curve (AUCR) with and without co-administration of rifampicin (a typical OATP1B inhibitor) was found for CP-I and OATP1B substrate, respectively, and was then used to derive the correlation curve equation. The AUCR with and without co-administration of another OATP1B inhibitor than rifampicin was then predicted for the OATP1B substrates by substituting the AUCR of CP-I in the correlation curve equation to verify the predictability of the AUCR of the OATP1B substrates.The derived correlation curve equation between CP-I and the OATP1B substrates of the AUCRs with and without co-administration of rifampicin matched the observed AUCRs well. Regarding pitavastatin, rosuvastatin, and pravastatin, 92.9% of the predicted AUCR values were within a two-fold range of the observed values, indicating that this approach may be a good way to quantitatively predict DDI potential.

Recent advances in drug transporter sciences: highlights from the year 2020.

Drug Metabolism Reviews has an impressive track record of providing scientific reviews in the area of xenobiotic biotransformation over 47 years. It has consistently proved to be resourceful to many scientists from pharmaceutical industry, academia, regulatory agencies working in diverse areas including enzymology, pharmacology, pharmacokinetics, and toxicology. Over the last 5 years Drug metabolism Reviews has annually published an industry commentary aimed to highlight novel insights and approaches that have made significant impacts on the field of biotransformation (led by Cyrus Khojasteh). We hope to continue this tradition by providing an overview of advances made in the field of drug transporters during 2020. The field of drug transporters is rapidly evolving as they play an essential role in drug absorption, distribution, clearance, and elimination. In this review, we have selected outstanding drug transporter articles that have significantly contributed to moving forward the field of transporter science with respect to translation and improved understanding of diverse aspects including uptake clearance, clinical biomarkers, induction, proteomics, emerging transporters, and tissue targeting. The theme of this review consists of a synopsis that summarizes each article followed by our commentary. The objective of this work is not to provide a comprehensive review but rather to exemplify novel insights and state-of-the-art highlights of recent research that have advanced our understanding of drug transporters in drug disposition. We are hopeful that this effort will prove useful to the scientific community and as such request feedback, and further extend an invitation to anyone interested in contributing to future reviews.

Minimal contribution of the hepatic uptake transporter OATP1B1 to the inter-individual variability in SN-38 pharmacokinetics in cancer patients without severe renal failure.

PURPOSE: SN-38, a pharmacologically active metabolite of irinotecan, is taken up into hepatocytes by organic anion transporting polypeptide (OATP) 1B1. The effects of functional OATP1B1 521T>C on the pharmacokinetics of SN-38 remain controversial. Here, we prospectively examined the effects of OATP1B1 function on the area under the plasma total or unbound concentration-time curve (tAUC or uAUC) of SN-38 by assessing OATP1B1 521T>C and the plasma levels of endogenous OATP1B1 substrates, coproporphyrin (CP)-I and III, in cancer patients treated with irinotecan. METHODS: We enrolled cancer patients who were treated with an irinotecan-containing regimen and did not have severe renal failure. The total and unbound concentrations of SN-38 in the plasma were measured by high-performance liquid chromatography. AUC values were calculated and normalized to the actual irinotecan dose (AUC/dose). The OATP1B1 521T>C was analyzed by direct sequencing. Concentrations of the endogenous substrates in plasma before irinotecan treatment (baseline) were determined by liquid chromatography with tandem mass spectrometry. RESULTS: Twenty-two patients with a median estimated glomerular filtration rate of 74.8 mL/min (range 32.6-99.6) were examined. Both tAUC/dose and uAUC/dose were associated with the grade of neutropenia; however, they were not associated with OATP1B1 521T>C or baseline CP-I and III levels. It is worth noting that these baseline concentrations were significantly higher in patients with OATP1B1 521C, supporting functional changes in OATP1B1. CONCLUSION: The contribution of OATP1B1 activity to inter-patient variability in the systemic exposure to SN-38 is likely minimal in patients without severe renal failure.

Simultaneous quantification of coproporphyrin-I and 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid in human plasma using ultra-high performance liquid chromatography coupled to tandem mass spectrometry.

In chronic kidney disease (CKD), organic anion transporting polypeptide (OATP)1B activity is reduced by mechanisms involving 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), a uremic toxin. Coproporphyrin-I (CP-I) is a sensitive and specific endogenous probe for phenotyping OATP1B activity and a potentially useful tool to individualize the dosage of OATP1B substrates. In this study, we developed and validated an assay for simultaneous quantification of CP-I and CMPF in human plasma using ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS). The samples were prepared by solid phase extraction, and then subjected to UHPLC-MS/MS quantification. The assay fulfilled the requirements of the US Food and Drug Administration (FDA) guideline for assay validation, with a lower limit of quantification of 0.1 for CP-I and 50 ng/mL for CMPF. Recovery rates from human plasma ranged from 97.3%-109.8% for CP-I, and 94.1%-113.3% for CMPF. Matrix effects corrected by internal standards varied between 107.2 % and 119.3 % for CP-I, and between 90.4 % and 107.4 % for CMPF. The validated assay was applied to measurement of plasma CP-I and CMPF concentrations in 10 healthy volunteers, 14 stage 3-5 CKD patients, and 14 stage 5D CKD patients. The concentrations measured in all samples were within the calibration ranges. Our novel method may be clinically useful for simultaneous measurement of plasma CP-I and CMPF concentrations in human samples, and contribute to reveal the in vivo relationship of OATB1B activity with accumulation of CMPF in CKD patients.

Recovery of OATP1B Activity after Living Kidney Transplantation in Patients with End-Stage Renal Disease.

PURPOSE: Recently, several studies have shown that renal failure decreases the metabolic clearance of drugs and the transportation capability of some drug transporters. However, whether organic anion transporting polypeptide (OATP)1B activities decrease in renal failure remains unknown. In this study, we measured plasma concentrations of coproporphyrin-I (CP-I), a specific endogenous OATP1B probe, in patients with end stage renal disease before and after living kidney transplantation and evaluated the effect of renal function on OATP1B activity. METHODS: This prospective study recruited 13 patients with end-stage renal disease. Plasma CP-I concentrations were measured before and 7, 14, 30 and 90 days after living kidney transplantation. RESULTS: Plasma CP-I concentrations decreased over time after living kidney transplantation and showed significant difference on day 90 compared with before living kidney transplantation [1.12 ± 0.59 vs 0.65 ± 0.27 ng/mL, p < 0.05 (95% CI of difference - 0.927, -0.013)]. A significant negative correlation was observed between estimated glomerular filtration rate and plasma CP-I concentration (r = -0.30, p < 0.05), suggesting recovery of OATP1B activity with improvement in renal function. CONCLUSIONS: OATP1B activity may decrease in renal failure and dose adjustment of OATP1B substrates may be needed in patients with renal failure.

Effect of OATP1B1 genotypes on plasma concentrations of endogenous OATP1B1 substrates and drugs, and their association in healthy volunteers.

This study aimed to elucidate the impact of OATP1B1 genotype (*1b/*1b, *1b/*15, and *15/*15) on plasma concentrations of endogenous OATP1B1 substrates. Healthy volunteers with OATP1B1 *1b/*1b (n = 10), *1b/*15 (n = 7), or *15/*15 (n = 2) received oral administration of a cocktail of statins (atorvastatin, pitavastatin, rosuvastatin, and fluvastatin). Mean area under the plasma concentration of atorvastatin, pitavastatin, and rosuvastatin in OATP1B1 *15/*15 were 2.2, 1.7 and 1.58-times greater than the corresponding values in OATP1B1 *1b/*1b, respectively, whereas that of fluvastatin was identical to those in other OATP1B1 genotypes. OATP1B1 *15/*15 also showed higher mean plasma concentrations of OATP1B1 endogenous substrates compared with the other OATP1B1 genotypes, such as coproporphyrin I, glycochenodeoxycholate sulfate (GCDCA-S), lithocholate sulfate (LCA-S), glycolithocholate sulfate (GLCA-S) and taurolithocholate sulfate (TLCA-S), but not total or direct bilirubin, chenodeoxycholate-24-glucuronide, or ω-dicarboxylic long-chain fatty acids. Area under the plasma concentration-time curves of plasma coproporphyrin I and GLCA-S discriminated OATP1B1 genotype *15/*15 from the other genotypes. In combination with previously published clinical studies, these results support the notion that coproporphyrin I, and GLCA-S and GCDCA-S could be a surrogate probe for assessing human in vivo OATP1B1 activities.

Early detection of colorectal adenocarcinoma: a clinical decision support tool based on plasma porphyrin accumulation and risk factors.

BACKGROUND: An increase in naturally-occurring porphyrins has been described in the blood of subjects bearing different kinds of tumors, including colorectal, and this is probably related to a systemic alteration of heme metabolism induced by tumor cells. The aim of our study was to develop an artificial neural network (ANN) classifier for early detection of colorectal adenocarcinoma based on plasma porphyrin accumulation and risk factors. METHODS: We measured the endogenous fluorescence of blood plasma in 100 colorectal adenocarcinoma patients and 112 controls using a conventional spectrofluorometer. Height, weight, personal and family medical history, use of alcohol, red meat, vegetables and tobacco were all recorded. An ANN model was built up from demographic data and from the integral of the fluorescence emission peak in the range 610-650 nm. We used the Receiver Operating Characteristic (ROC) curve to assess performance in distinguishing colorectal adenocarcinoma patients and controls. A liquid chromatography-high resolution mass spectrometry (LC-HRMS) analytical method was employed to identify the agents responsible for native fluorescence. RESULTS: The fluorescence analysis indicated that the integral of the fluorescence emission peak in the range 610-650 nm was significantly higher in colorectal adenocarcinoma patients than controls (p < 0.0001) and was weakly correlated with the TNM staging (Spearman's rho = 0.224, p = 0.011). LC-HRMS measurements showed that the agents responsible for the fluorescence emission were mainly protoporphyrin-IX (PpIX) and coproporphyrin-I (CpI). The overall accuracy of our ANN model was 88% (87% sensitivity and 90% specificity) with an area under the ROC curve of 0.83. CONCLUSIONS: These results confirm that tumor cells accumulate a diagnostic level of endogenous porphyrin compounds and suggest that plasma porphyrin concentrations, indirectly measured through fluorescence analysis, may be useful, together with risk factors, as a clinical decision support tool for the early detection of colorectal adenocarcinoma. Our future efforts will be aimed at examining how plasma porphyrin accumulation correlates with survival and response to therapy.

UHPLC-MS/MS bioanalysis of human plasma coproporphyrins as potential biomarkers for organic anion-transporting polypeptide-mediated drug interactions.

AIM: Coproporphyrins (CP-I and CP-III) have been identified as possible biomarkers to predict human hepatic organic anion-transporting polypeptides-mediated-drug-interactions for a new drug entering clinical development. RESULTS: The method is applicable to quantify plasma CP-I and CP-III within 0.078-15.0 nM. The results identify and address a number of challenges encountered with porphyrin assays such as photodegradation and interferences. To overcome interferences from ubiquitous porphyrins, a surrogate matrix was used to prepare calibration standards. Quality controls were prepared in plasma and surrogate matrix to ensure parallelism between surrogate matrix and plasma. CONCLUSION: A robust UHPLC-MS/MS assay was developed and validated for CP-I and CP-III in plasma, and is currently applied to clinical studies to confirm suitability of Coproporphyrins as a potential substitute for drug-drug interaction study.

A fully automated and validated human plasma LC-MS/MS assay for endogenous OATP biomarkers coproporphyrin-I and coproporphyrin-III.

AIM: A validated LC-MS/MS assay for the quantitation of coproporphyrin-I and -III (CP-I, CP-III) in human plasma has been developed to understand the utility of both as possible endogenous biomarkers for organic anion-transporting polypeptides (OATP)-mediated drug-drug interactions (DDIs). MATERIALS AND METHODS:  Human plasma extracts were analyzed for CP-I and CP-III using a Sciex API 6500+ mass spectrometer. Results: The assay was utilized for plasma samples from a clinical DDI study involving a new chemical entity that presented as an OATP inhibitor in vitro. A formal DDI study, with a probe drug (atorvastatin), was also included as part of the clinical study. CONCLUSION: Changes in CP-I area under the plasma concentration versus time curve (AUC0-48 h) were observed, which were similar to the AUC ratio obtained with atorvastatin. These results support the idea that plasma CP-I may have utility in Phase I by supporting the rapid assessment of OATP inhibition risk.

Effect of OATP1B1/1B3 Inhibitor GDC-0810 on the Pharmacokinetics of Pravastatin and Coproporphyrin I/III in Healthy Female Subjects.

Developed as an oral anticancer drug to treat estrogen receptor-positive breast cancer, GDC-0810 was shown to be a potent inhibitor of organic anion-transporting polypeptide 1B1 and 1B3 (OATP1B1/1B3) from an in vitro assay. A clinical study was conducted to assess the drug-drug interaction potential between GDC-0810 and pravastatin, which is a relatively selective and sensitive OATP1B1/1B3 substrate. Fifteen healthy female subjects of non-childbearing potential were enrolled in the study. On day 1 in period 1, a single 10-mg dose of pravastatin was administered to all subjects. Following a 4-day washout period, 600 mg of GDC-0810 was administered once daily on days 5 through 8 in period 2 to achieve steady-state concentrations. On day 7, a single dose of 10-mg pravastatin was coadministered with the 600-mg GDC-0810 dose. Concentrations of pravastatin (periods 1 and 2) and GDC-0810 (period 2 only) were quantified in blood samples and subsequently used to calculate the pharmacokinetics (PK) parameters. The pravastatin mean maximal concentration and area under the curve values were approximately 20% and 41% higher, respectively, following pravastatin coadministration with GDC-0810 compared to pravastatin alone. Based on the magnitude of change in this drug-drug interaction study, dose adjustments for pravastatin (and other OATP1B1/1B3 substrates) were not considered necessary when administered with GDC-0810. Retrospectively, the endogenous biomarkers of OATP1B1/1B3, coproporphyrin I and III, were also measured and showed changes comparable to those of pravastatin, indicating their utility in detecting weak inhibition of OATP1B1/1B3 in the clinical setting.

Polymeric structure of a coproporphyrin I ruthenium(II) complex: a powder diffraction study.

Porphyrin complexes of ruthenium are widely used as models for the heme protein system, for modelling naturally occurring iron-porphyrin systems and as catalysts in epoxidation reactions. The structural diversity of ruthenium complexes offers an opportunity to use them in the design of multifunctional supramolecular assemblies. Coproporphyrins and metallocoproporphyrins are used as sensors in bioassay and the potential use of derivatives as multiparametric sensors for oxygen and H+ is one of the main factors driving a growing interest in the synthesis of new porphyrin derivatives. In the coproporphyrin I RuII complex catena-poly[[carbonylruthenium(II)]-µ-2,7,12,17-tetrakis[2-(ethoxycarbonyl)ethyl]-3,8,13,18-tetramethylporphyrinato-κ5N,N',N'',N''':O], [Ru(C44H52N4O8)(CO)]n, the RuII centre is coordinated by four N atoms in the basal plane, and by axial C (carbonyl ligand) and O (ethoxycarbonylethyl arm from a neighbouring complex) atoms. The complex adopts a distorted octahedral geometry. Self-assembly of the molecules during crystallization from a methylene chloride-ethanol (1:10 v/v) solution at room temperature gives one-dimensional polymeric chains.