Martin Friedrich Fromm

Kynurenine, the major metabolite of tryptophan, plays a crucial role during inflammatory processes. By activating the aryl hydrocarbon receptor kynurenine exhibits anti-inflammatory effects in several diseases such as the inflammatory bowel diseases ulcerative colitis and Crohn’s disease. Adverse outcomes of Crohn’s disease patients were associated with a single nucleotide polymorphism, localized in the gene SLCO3A1 encoding the transport protein organic anion transporting polypeptide (OATP) 3A1. OATP3A1 is ubiquitously expressed throughout the human body and was recently shown to mediate transport of the amino acids tryptophan, tyrosine, and phenylalanine. Our goal was to characterize kynurenine as a substrate of OATP3A1 and to extend the knowledge about this transporter in the context of inflammatory processes. HEK293 cells stably overexpressing OATP3A1 and respective control cells were used in combination with an LC-MS-based untargeted metabolomics approach, uptake studies, and metabolic flux analyses. We identified kynurenine as a substrate of OATP3A1 and determined kinetic transport parameters ( K _m and V _max value) as 133 ± 40 µM and 1863 ± 154 pmol/mg protein/min, respectively. RNA-sequencing data (IBDome database) showed elevated SLCO3A1 expression in colon tissue of patients with inflammatory bowel diseases, which was particularly evident in the inflamed tissue of ulcerative colitis patients. Additionally, SLCO3A1 mRNA expression in primary human blood-derived and ex vivo -stimulated CD4 ⁺ T lymphocytes was induced by addition of kynurenine, regardless of whether the aryl hydrocarbon receptor antagonist CH223191 was added. In summary, we characterized kynurenine as a substrate of OATP3A1, which showed elevated RNA expression in ulcerative colitis. Moreover, kynurenine induced SLCO3A1 mRNA expression in primary human CD4 ⁺ T lymphocytes.

Aim: Increasing use of oral antitumour therapeutics (OAT) in paediatrics is associated with numerous advantages, but also with error‐prone aspects. Based on the randomized AMBORA trial including adults treated with various OAT, we developed a tailored pharmacological/pharmaceutical care programme for children and their caregivers during OAT treatment (youngAMBORA). We now aimed to analyse the impact of the youngAMBORA care programme on medication safety by assessing (1) patient‐reported outcomes (PROs) and (2) medication errors. Methods: Depending on the intended OAT treatment duration, the youngAMBORA care programme included three or four consultation sessions starting at therapy initiation (Week 0) and using developed information material. Validated questionnaires were used to record PROs (e.g., knowledge [Satisfaction with Information about Medicines Scale, SIMS, primary outcome] and side effects [Ped‐PRO‐CTCAE®]). Advanced medication reviews were conducted in every consultation session, and medication errors were systematically categorized (e.g., PCNE V9.1). Results: We counselled 54 patients treated with 61 OAT. The most frequently prescribed OAT was 6‐mercaptopurine (14/61; 23%). Knowledge about the OAT improved significantly between Week 0 at OAT initiation and Week 1 (SIMS total score 8.1 ± 4.2 vs . 15.8 ± 1.6; p < .0001). On average, patients and caregivers reported 2.6 OAT‐related side effects per patient, with gastrointestinal symptoms (i.e., ‘nausea’) being most frequent and severe. Fifty‐six OAT‐related medication errors were detected (mean 1.0 per patient), and of these, 84% (47/56) were completely resolved. Conclusion: The youngAMBORA care programme improved caregivers' knowledge about OAT, enabled structured monitoring of patient‐reported side effects and facilitated the identification and resolution of medication errors during paediatric OAT treatment to optimize medication safety.

Background: Inhibitors of the sodium-glucose cotransporter 2 (SGLT2) provide cardiovascular and renal protection in both diabetic and non-diabetic patients at least in part independently of glycaemic control. Some underlying mechanisms for these clinically beneficial effects were suggested, but the picture is far from complete. In this study we aimed to apply untargeted metabolomics in order to identify new mechanistic leads. Methods: Plasma and 24-hour urine samples of 48 diabetic patients taken before and after 6 weeks of treatment from two prospective, randomized, double-blind, placebo-controlled, cross-over trials with dapagliflozin or empagliflozin were used. Additionally, plasma and urine samples of 24 diabetic patients from a prospective, randomized, controlled, parallel-arm, interventional, open-label, single centre study with either empagliflozin and linagliptin or metformin and insulin glargine for 12 weeks were used for confirmation. Changes of metabolite patterns in plasma and urine were determined by untargeted high-resolution mass spectrometry. Moreover, parameters of arterial stiffness and retinal vascular remodelling were correlated with treatment effects of the SGLT2 inhibitors on the modified nucleoside N4-acetylcytidine (ac4C), a potential biomarker for the activity of the enzyme N-acetyltransferase 10 (NAT10). Results: In accordance with previously reported results treatment with SGLT2 inhibitors led to a reduction of glucose (log ₂ fc: − 0.23, adj. p < 0.01) and uric acid (log ₂ fc: − 0.23, adj. p < 0.001), while 3-hydroxybutyric acid (log ₂ fc: 0.84, adj. p < 0.001) and 3-hydroxybutyrylcarnitine (log ₂ fc: 0.57, adj. p < 0.001) were increased in plasma. As a new finding, plasma concentrations of ac4C were reduced (log ₂ fc: − 0.32, adj. p < 0.001) by SGLT2 inhibitors but not by the non-SGLT2 inhibiting glucose lowering treatment. Reduction of urinary concentrations of ac4C corresponded to its reduction in plasma in groups treated with the SGLT2 inhibitors. Wall thickness of retinal arterioles and central systolic blood pressure were significantly correlated to ac4C in plasma. Conclusions: Treatment with dapagliflozin and empagliflozin reduced plasma concentrations of ac4C, which was correlated with parameters for vascular health. These exploratory findings may indicate inhibition of NAT10 activity as a potential contributor to the beneficial effects on cardiovascular and renal health by SGLT2 inhibitors. Trial registrations: http://www.clinicaltrials.gov : NCT02383238, NCT02471963, NCT02752113.

Purpose: Unrecognized contraindications pose risks for adverse drug reactions, hospitalizations or death. Clinical decision support systems (CDSS) aim to mitigate medication-related harm, particularly originating from contraindications. However, many CDSS provide limited benefit, as they focus largely on singular risk situations such as drug-drug interactions and often generate alerts of limited clinical relevance. Comprehensive integration of contraindications into CDSS may support more clinically meaningful alerts. The aim of this work was the development and analysis of machine-readable contraindication lists, including drug-clinical condition, drug-kidney function and drug-drug (group) contraindications, for integration into CDSS and real-world data analysis. Methods: We extracted and operationalized contraindications, based on Summaries of Product Characteristics (SmPCs), of the 688 most prescribed drugs in Germany, leveraging common medical coding systems. Moreover, we analyzed extracted contraindications based on operationalizability, overall frequency and frequencies within different contraindication categories. Results: In total, we extracted 4676 contraindications, of which 2129 (45.5%) were deemed operationalizable. Of these 2129 contraindications, 1652 (77.6%) were attributed to drug-clinical condition, 83 (3.9%) to drug-kidney, 140 (6.6%) to drug-drug group and 254 (11.9%) to drug-drug. The most frequently mentioned contraindicated risk situations were ‘severe liver insufficiency’ ( n = 74, 3.5%), ‘pregnancy’ ( n = 66, 3.1%), ‘MAO-inhibitors’ ( n = 44, 2.1%), and ‘shock’ ( n = 44, 2.1%). Conclusion: Our results show, that drug-clinical condition contraindications are listed far more frequently in SmPCs than other contraindication categories. Focusing on clinical condition-related contraindications within CDSS could improve the detection of clinically relevant contraindications in routine data and enhance medication safety. The clinical applicability is currently being evaluated in the INTERPOLAR study.

Regulatory agencies request the assessment of the potential of new drugs to cause transporter‐mediated drug‐drug interactions (DDI). This assessment can be improved by integrating endogenous biomarkers during drug development. Regarding the renal excretion of drugs such as metformin, the organic cation transporter (OCT) 2 and multidrug and toxin extrusion proteins (MATE) 1 and 2‐K are of major importance. However, fully validated, sensitive, and specific biomarkers for these transporters are still lacking. In previous in vivo and in vitro studies, 5‐aminovaleric acid betaine (5AVAB), serotonin (5HT), and 1‐methylhistamine (1MH) emerged as promising biomarker candidates for OCT2/MATE‐mediated DDI. Therefore, we further investigated their suitability for clinical risk assessment by evaluating the effects of the OCT2/MATE inhibitor trimethoprim in healthy volunteers and by determining IC ₅₀ values for the inhibition of OCT2‐ and/or MATE1‐mediated uptake of the potential biomarkers by trimethoprim, cimetidine, pyrimethamine, and dolutegravir in vitro . Trimethoprim reduced the amount excreted into urine of 5AVAB, 5HT, and 1MH in vivo by 95.1 ± 5.67%, 78.9 ± 6.56%, and 51.9 ± 14.3%, respectively (all P < 0.001) as well as the renal clearance of 5AVAB and 5HT by 93.6 ± 5.85% and 73.8 ± 12.8%, respectively (both P < 0.001). When comparing the IC ₅₀ values with unbound inhibitor plasma concentrations, trimethoprim, cimetidine, and pyrimethamine preferentially inhibit the MATE1‐mediated transport, whereas dolutegravir inhibits the OCT2‐mediated transport of the biomarker candidates. In conclusion, this study further supports the suitability of 5‐aminovaleric acid betaine (5AVAB), serotonin (5HT), and 1‐methylhistamine (1MH) as promising biomarkers for OCT2/MATE‐mediated DDI.

Background: Transport proteins are important for the uptake, distribution and elimination of endogenous substances and drugs, and therefore essential for, e.g., cellular metabolism or drug effects. While the export of substrates out of cells is mediated by ATP-binding cassette (ABC) transporters, SLC (solute carrier) transporters are mainly responsible for the uptake into cells. In contrast to most well-characterised ABC transporters, many SLC transporters have been studied insufficiently. Such transporters are called orphan transporters. Despite the fact that the SLC21 / SLCO family contains several important transporters for widely prescribed drugs, one of its family members, OATP5A1 ( SLCO5A1 ), is such an orphan transporter. OATP5A1 is ubiquitously expressed throughout the body, including expression in the brain, heart, intestine and various cancerous tissues. However, no substrates have been characterised for this transporter to date. Methods: Using stably-transfected HEK293 cells overexpressing human OATP5A1 (HEK-OATP5A1) and the respective control cells (HEK-VC), we investigated known substrates of other OATP family members as potential OATP5A1 substrates. Furthermore, an untargeted metabolomics analysis of both cell lines was performed after incubation with human plasma. Candidate substances were further characterised as substrates of OATP5A1. Results: After characterisation of the stably-transfected HEK-OATP5A1 cells, uptake assays and untargeted metabolomics analysis identified the hormone conjugate estrone-3-sulfate, the amino acids glutamine, glycine and tyrosine, the vitamins pantothenic acid (vitamin B ₅ ) and thiamine (vitamin B ₁ ) and the nucleotide thymine as potential OATP5A1 substrates. While estrone-3-sulfate, tyrosine and thiamine were further characterised as uptake substrates, glutamine and glycine were exported by OATP5A1. Moreover, pantothenic acid and thymine inhibited OATP5A1-mediated tyrosine uptake. For estrone-3-sulfate, tyrosine and thiamine, kinetic transport parameters (K _m values) of 102.2 µM, 169.9 µM and 15.6 µM were calculated, respectively. Conclusions: In the present study, OATP5A1 was deorphanised by characterising amino acids and vitamins as substrates of this transport protein. Estrone-3-sulfate, tyrosine and thiamine were taken up by OATP5A1. Moreover, OATP5A1 mediated the efflux of the amino acids glutamine and glycine, which play essential roles in brain function.

Background and Introduction Imatinib (IMA) revolutionised the treatment of chronic myeloid leukaemia (CML). Therapeutic drug monitoring (TDM) of IMA is recommended to improve treatment outcomes in adults, but guidance for reliable interpretation of plasma concentrations in children is limited. Using real-world paediatric data, we aimed to develop a practical algorithm with recommendations for an IMA TDM procedure in paediatric oncology. Methods Imatinib plasma concentrations and clinical data were collected from patients enrolled in the multicentre CML-PAED-II study and subsequent registry. We evaluated the method of exponential extrapolation for estimating interpretable IMA trough concentrations and used linear mixed effects models to assess plasma concentration predictors. Associations between IMA trough concentrations and molecular response were analysed, and a paediatric-specific target threshold was evaluated. Findings were integrated into an algorithm for clinical application of IMA TDM. Results In total, 269 IMA trough concentrations from 72 patients and BCR::ABL1/ABL1 transcript ratios from 50 patients were included. Using a correction tool, we obtained estimates of trough concentration by exponential extrapolation. Administered IMA dose was the main predictor of plasma concentrations. Higher trough concentrations tended to correlate with faster initial molecular response. The adult-derived target threshold of 1000 ng/mL proved applicable in paediatric practice. The developed algorithm outlines clinical decision points and consequences, which are key elements of existing intensified clinical pharmacological/pharmaceutical care programmes during oral antitumour therapy. Conclusion The algorithm supports the use of TDM during paediatric IMA treatment, enabling early identification of exposure below the targeted concentration and variations in treatment efficacy to further improve treatment outcomes.

Neural stem/progenitor cells (NSPCs) in the hippocampal dentate gyrus generate neurons throughout life. Growth factors, transcriptional regulators, metabolism and cell homeostatic pathways all impact on NSPC proliferation. How such plethora of signals coordinately regulate the constant supply of sufficient numbers of neurons while avoiding premature proliferation-driven depletion of the NSPC pool is poorly understood. Here, we demonstrate that transcription factor forkhead box O (FOXO)-dependent lipid metabolism is essential to restrict NSPC proliferative activity. We show that FOXO regulated abundance of the monounsaturated fatty acid oleic acid controls vacuolar-ATPase (v-ATPase) proton pump assembly thereby regulating lysosome acidification and autolysosomal activity. Strikingly, promoting v-ATPase assembly corrected FOXO deficiency- and oleic acid-induced excessive NSPC proliferation. Our findings connect three central determinants of NSPC proliferation – FOXOs, lipid metabolism and lysosomal activity – thereby identifying a critical regulatory network capable of integrating growth factor signaling, cellular metabolism and cell homeostatic pathways to coordinate NSPC proliferation.

A considerable number of oral antitumor therapeutics (OAT) has the potential for causing pseudo‐worsening of kidney function (PW) due to inhibition of renal creatinine secretion, i.e., kidney function is unaffected, while creatinine‐based calculation of glomerular filtration rate (eGFR) erroneously indicates an impaired kidney function. Nonrecognition of PW can lead to dose reductions, interruptions, or discontinuations of OAT. The extent and incidence of PW has so far not been studied for a broad set of OAT in clinical routine. In this retrospective, multicenter cohort study, 694 AMBORA patients newly started on OAT were assessed for eligibility. eGFR values were compared between baseline and within 30 days of treatment. OAT were separated into the groups unlikely causing and likely causing/with proven PW. The usage of cystatin C measurements as an alternative method for assessing kidney function was evaluated. A total of 238 patients received 38 OAT likely causing PW/with proven PW. In this group, eGFR decreased significantly (−6.8 ml/min, p < 0.001). In 17.2% of these patients, eGFR decreased by ≥20 ml/min. Significant decreases in eGFR were observed for patients receiving, for example, abemaciclib, ribociclib, and osimertinib. Cystatin C measurements were not performed in 95.8% of the patients. In the group of 67 patients receiving OAT unlikely causing PW, there was no significant change in eGFR. In clinical routine, multiple OAT associated with PW are prescribed. A very low rate of usage of creatinine‐independent methods for assessing kidney function (cystatin C) indicates that further training of oncologists is required on OAT‐induced PW to further improve patient safety.