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The inhibition of renal transport proteins organic cation transporter 2 (OCT2), multidrug and toxin extrusion proteins (MATE1, MATE2‐K), and organic anion transporters (OAT1, OAT3) causes clinically relevant drug–drug interactions (DDI). Endogenous biomarkers could be used to improve risk prediction of such renal DDIs. While a number of biomarkers for renal DDIs have been described so far, multiple criteria for valid biomarkers have frequently not been investigated, for example, specificity, metabolism, or food effects. Therefore, there is a need for novel biomarkers of renal DDIs. Here, we investigated the global metabolomic effects following the administration of two classical inhibitors of renal transport proteins [cimetidine (OCT2/MATEs), probenecid (OATs)] in human plasma and urine of healthy volunteers. Additionally, we investigated metabolomic effects of two inhibitors of other transporters [verapamil (P‐glycoprotein), rifampin (organic anion transporting polypeptides)] as controls. This analysis shows that both cimetidine and probenecid affect compounds involved in caffeine metabolism, carnitines, and sulfates. Hierarchical cluster analysis of the effects of all four inhibitors on endogenous compounds identified multiple promising new sensitive and specific biomarker candidates for OCT2/MATE‐ or OAT‐mediated DDIs. For OCT2/MATEs, 5‐amino valeric acid betaine (median log2‐fold change of estimated renal elimination: −3.62) presented itself as a promising candidate. For OATs, estimated renal elimination of 7‐methyluric acid and cinnamoylglycine (median log2‐fold changes −3.10 and −1.92, respectively) was both sensitive and specific. This study provides comprehensive information on metabolomic effects of transport protein inhibition in humans and identifies putative new sensitive and specific biomarkers for renal transporter‐mediated DDIs. [ABSTRACT FROM AUTHOR]

Objective: Oral antitumour therapeutics (OAT) are increasingly used due to improvements in outcomes and their convenient application. However, complex intake regimens pose several challenges. The randomised AMBORA trial (Medication Safety With Oral Antitumour Drugs) demonstrated highly positive outcomes of a clinical pharmacological/pharmaceutical care program for adults treated with numerous OAT, but comparable concepts in paediatrics are lacking so far. Methods: We used a parallel mixed-methods approach to develop a tailored pharmacological/pharmaceutical care program for OAT in paediatrics (youngAMBORA). We combined a quantitative analysis of tumour entities and used OAT in a paediatric cancer centre with a qualitative survey for patients, caregivers, and healthcare professionals to identify particular demands and educational needs (e.g., application problems, side effects). Results: Leukaemia (77/315) and antimetabolites (95/151) were the most frequently observed entity and OAT, respectively. Of 22 surveyed patients, 81.8% wanted to be involved in oral medication education. Compared to caregivers, significantly more healthcare professionals graded the three most common application problems to be challenging ('Smell/taste': 32/36 vs. 23/42, p = 0.001; 'Refusal of intake': 31/36 vs. 16/42, p<0.001; 'Swallowing problems': 28/36 vs. 21/42, p = 0.011). We identified nine relevant side effects, of which two ('Skin dryness', 'Taste changes') were not included in 15 previously published core side effects of the Common Terminology Criteria of Adverse Events (CTCAE) item library. Conclusion: Based on the present findings, the tailored youngAMBORA care program will include: 1) counselling sessions for classic and targeted OAT, 2) child-friendly support with drug application, and 3) systematic evaluation of 17 relevant side effects from patients' and caregivers' points of view including age-appropriate information material. [ABSTRACT FROM AUTHOR]

Amino acids are important for cellular metabolism. Their uptake across the plasma membrane is mediated by transport proteins. Despite the fact that the organic anion transporting polypeptide 4C1 (OATP4C1, Uniprot: Q6ZQN7) mediates transport of l‐arginine and l‐arginine derivatives, other members of the OATP family have not been characterized as amino acid transporters. The OATP family member OATP3A1 (gene symbol SLCO3A1, Uniprot: Q9UIG8) is ubiquitously expressed in human cells and highly expressed in many cancer tissues and cell lines. However, only a few substrates are known for OATP3A1. Accordingly, knowledge about its biological relevance is restricted. Our aim was to identify new substrates of OATP3A1 to gain insights into its (patho‐)physiological function. In an LC‐MS‐based untargeted metabolomics assay using untreated OATP3A1‐overexpressing HEK293 cells and control cells, we identified several amino acids as potential substrates of OATP3A1. Subsequent uptake experiments using exogenously added substrates revealed OATP3A1‐mediated transport of l‐tryptophan, l‐tyrosine, and l‐phenylalanine with 194.8 ± 28.7% (P < 0.05), 226.2 ± 18.7% (P < 0.001), and 235.2 ± 13.5% (P < 0.001), respectively, in OATP3A1‐overexpressing cells compared to control cells. Furthermore, kinetic transport parameters (Km values) were determined (Trp = 61.5 ± 14.2 μm, Tyr = 220.8 ± 54.5 μm, Phe = 234.7 ± 20.6 μm). In summary, we identified the amino acids l‐tryptophan, l‐tyrosine, and l‐phenylalanine as new substrates of OATP3A1. These findings could be used for a better understanding of (patho‐)physiological processes involving increased demand of amino acids, where OATP3A1 should be considered as an important uptake transporter of l‐tryptophan, l‐tyrosine, and l‐phenylalanine. [ABSTRACT FROM AUTHOR]

Determination of serum creatinine concentrations and subsequent calculation of estimated glomerular filtration rates (eGFR) is a cornerstone of clinical medicine. Crucial clinical decisions such as drug treatment discontinuations are based on eGFR calculated from serum creatinine measurements. However, creatinine is not only filtered in the kidneys, but also actively secreted into urine. Creatinine transporters such as OCT2, OCT3, MATE1, MATE2‐K, and OAT2 expressed in proximal tubular cells are responsible for active renal secretion of creatinine. Multiple drugs (e.g., oral antitumor drugs) inhibit these transporters thereby causing a pseudo‐worsening of kidney function with an increase in serum creatinine concentrations and a decrease in eGFR while other methods for eGFR determination (e.g., by cystatin C) reveal normal kidney function. Since US Prescribing Information (PI) and European Summaries of Product Characteristics (SmPCs) are the most relevant source of information for physicians, we investigated the quality of information in US PI/German SmPCs of drugs with clear evidence for pseudo‐worsening of kidney function. 514 drugs putatively interacting with creatinine transporters were identified. For 149 of those drugs, an increase in serum creatinine concentrations has been described. Available data confirmed the existence of pseudo‐worsening of kidney function for 30 of those drugs, for the remaining 119 drugs existing data are insufficient. Only 23.5% (12/51) of the 30 drugs' PI/SmPCs contained unambiguous statements on this proven pseudo‐worsening of kidney function and gave clear recommendations for clinical management. Taken together, inadequate information provided in PI or SmPCs on the pseudo‐worsening of kidney function poses patients at unnecessary risks. [ABSTRACT FROM AUTHOR]

Background: The orexin receptor (OXR) plays a role in drug addiction and is aberrantly expressed in colorectal tumors. Subtype-selective OXR PET ligands suitable for in vivo use have not yet been reported. This work reports the development of 18F-labeled OXR PET ligand candidates derived from the OXR antagonist suvorexant and the OX1R-selective antagonist JH112. Results: Computational analysis predicted that fluorine substitution (1e) and introduction of the fluorobenzothiazole scaffold (1f) would be suitable for maintaining high OX1R affinity. After multi-step synthesis of 1a–1f, in vitro OXR binding studies confirmed the molecular dynamics calculations and revealed single-digit nanomolar OX1R affinities for 1a–f, ranging from 0.69 to 2.5 nM. The benzothiazole 1f showed high OX1R affinity (Ki = 0.69 nM), along with 77-fold subtype selectivity over OX2R. Cu-mediated 18F-fluorination of boroxine precursors allowed for a shortened reaction time of 5 min to provide the non-selective OXR ligand [18F]1c and its selective OX1R congener [18F]1f in activity yields of 14% and 22%, respectively, within a total synthesis time of 52–76 min. [18F]1c and [18F]1f were stable in plasma and serum in vitro, with logD7.4 of 2.28 ([18F]1c) and 2.37 ([18F]1f), and high plasma protein binding of 66% and 77%, respectively. Dynamic PET imaging in rats showed similar brain uptake of [18F]1c (0.17%ID/g) and [18F]1f (0.15%ID/g). However, preinjection of suvorexant did not significantly block [18F]1c or [18F]1f uptake in the rat brain. Pretreatment with cyclosporine A to study the role of P-glycoprotein (P-gp) in limiting brain accumulation moderately increased brain uptake of [18F]1c and [18F]1f. Accordingly, in vitro experiments demonstrated that the P-gp inhibitor zosuquidar only moderately inhibited polarized, basal to apical transport of 1c (p < 0.05) and had no effect on the transport of 1f, indicating that P-gp does not play a relevant role in brain accumulation of [18F]1c and [18F]1f in vivo. Conclusions: The in vitro and in vivo results of [18F]1c and [18F]1f provide a solid basis for further development of suitable OXR PET ligands for brain imaging. [ABSTRACT FROM AUTHOR]

The randomized AMBORA trial showed that medication errors are frequent in patients treated with oral antitumor therapeutics and that they can be substantially reduced by an intensified clinical pharmacological/pharmaceutical care program. While randomized controlled trials are essential to generate clinical evidence, their generalizability in real‐world is not always given. The AMBORA care program was implemented in clinical routine within the AMBORA Competence and Consultation Center (AMBORA Center) at the Comprehensive Cancer Center Erlangen‐EMN, allowing a thorough comparison of medication error frequencies and characteristics. Our primary analysis compared data at therapy initiation of new oral antitumor therapeutics from the AMBORA trial intervention group (n = 98) and the AMBORA Center (n = 142). Medication errors involving the oral antitumor therapeutics were twofold higher in real‐world compared to the randomized controlled trial (mean 0.83 ± 0.80 per patient vs. 0.41 ± 0.53, P < 0.001). We observed more complex oral antitumor therapeutic regimens, a higher median number of medications, and a higher ECOG status in clinical routine vs. the randomized trial. A high percentage of medication errors was completely solved in both groups (85.7% vs. 88.3%, ns). Medication error characteristics within the complete medication (oral antitumor therapeutics and concomitant medication) were similar in both groups (e.g., patient‐related causes, drug–drug/drug–food interactions). Taken together, medication errors were even more frequent in clinical routine than in the randomized controlled trial and a high rate was solved in clinical routine by a clinical pharmacological/pharmaceutical care program. [ABSTRACT FROM AUTHOR]

Accumulating evidence argues for a more widespread use of therapeutic drug monitoring (TDM) to support individualized medicine, especially for therapies where toxicity and efficacy are critical issues, such as in oncology. However, development of TDM assays struggles to keep pace with the rapid introduction of new drugs. Therefore, novel approaches for faster assay development are needed that also allow effortless inclusion of newly approved drugs as well as customization to smaller subsets if scientific or clinical situations require. We applied and evaluated two machine-learning approaches i.e., a regression-based approach and an artificial neural network (ANN) to retention time (RT) prediction for efficient development of a liquid chromatography mass spectrometry (LC-MS) method quantifying 73 oral antitumor drugs (OADs) and five active metabolites. Individual steps included training, evaluation, comparison, and application of the superior approach to RT prediction, followed by stipulation of the optimal gradient. Both approaches showed excellent results for RT prediction (mean difference ± standard deviation: 2.08 % ± 9.44 % ANN; 1.78 % ± 1.93 % regression-based approach). Using the regression-based approach, the optimum gradient (4.91 % MeOH/min) was predicted with a total run time of 17.92 min. The associated method was fully validated following FDA and EMA guidelines. Exemplary modification and application of the regression-based approach to a subset of 14 uro-oncological agents resulted in a considerably shortened run time of 9.29 min. Using a regression-based approach, a multi drug LC-MS assay for RT prediction was efficiently developed, which can be easily expanded to newly approved OADs and customized to smaller subsets if required. [ABSTRACT FROM AUTHOR]

N1‐methylnicotinamide (NMN) has been proposed as endogenous biomarker for drug–drug interactions mediated by inhibition of multidrug and toxin extrusion proteins (MATEs) at the renal proximal tubule. We analyzed NMN in plasma and urine samples of two clinical trials investigating a new probe drug cocktail (consisting of digoxin, metformin, furosemide, and rosuvastatin) dedicated to clinically relevant drug transporters. In trial 1, NMN was investigated after single‐dose treatment with individual cocktail components or after cocktail treatment. In trial 2, NMN was investigated after treatment with cocktail alone or with cocktail + inhibitor (cimetidine, a MATE inhibitor; or rifampin, verapamil, or probenecid, inhibitors of other transporters). In trial 1, NMN kinetics in plasma and urine were essentially not affected by individual cocktail components or after cocktail treatment. In trial 2, NMN renal clearance from 0 to 12 hours (CLR,0–12) geometric mean ratio (GMR) after cocktail + cimetidine vs. cocktail alone was 75% (90% confidence interval (CI): 65–87%). NMN CLR GMR after cocktail + verapamil, + rifampin, or + probenecid vs. cocktail alone was 99% (90% CI: 81–121%), 91% (90% CI: 75–111%), and 107% (90% CI: 91–126%), respectively. Compared with creatinine CLR and creatinine area under the plasma‐concentration time curve, NMN CLR was more specific and more sensitive for renal MATE inhibition. Absence of impact of the cocktail on NMN in trial 1 allows for utilization of NMN in studies using this transporter cocktail. Trial 2 data support that NMN CLR is a specific and sensitive marker for MATE‐mediated renal drug–drug interactions. [ABSTRACT FROM AUTHOR]