Synthesis and evaluation of dopaminergic prodrugs designed for transdermal iontophoretic drug delivery:highly water-soluble amino acid ester prodrugs applicable for the treatment of Parkinson's disease

Dopamine agonisten worden toegepast als farmacotherapie voor patienten met de ziekte van Parkinson. In dit onderzoek beschrijven we het chemisch bereiden en de evaluatie van zeer wateroplosbare varianten van de dopamine agonist 5-OH-DPAT. Deze varianten zijn chemisch aan elkaar gekoppelde stoffen van 5-OH-DPAT met andere moleculen. In dit geval zijn dat aminozuren. In de farmacie noemt men deze stoffen prodrugs. Een prodrug is een niet werkzame stof die na omzetting in het lichaam het actieve geneesmiddel vrijgeeft. Ons onderzoek heeft geleid tot een aantal bevindingen. Ten eerste blijkt het mogelijk te zijn zeer wateroplosbare prodrugs te maken die voldoende stabiel zijn in de iontoforese pleister (voldoende houdbaarheid), maar eenmaal in de bloedbaan het geneesmiddel direct vrijgeven. Ten tweede, door het koppelen van 5-OH-DPAT aan dipeptiden (twee gecombineerde aminozuren), is het mogelijk de stabiliteit van de prodrug in de pleister nog groter te maken. Ten derde is het mogelijk om 5-OH-DPAT gecontroleerd toe te dienen aan het lichaam wat de ontwikkeling van een feedback systeem in principe mogelijk zou maken. En als laatste vonden we dat de iontoforetische toediening van een zeer wateroplosbare prodrug van 5-OH-DPAT een verlenging van het effect van het geneesmiddel geeft in vergelijking met 5-OH-DPAT zelf. Deze resultaten laten zien dat de toepassing van prodrugs voordelig kan zijn bij de toediening van dopamine agonisten of andere geneesmiddelen met behulp van transdermale iontoforese. Verder onderzoek naar deze farmaceutische toedieningsvorm zou uiteindelijk kunnen leiden tot een nieuwe farmacotherapie voor patiënten met de ziekte van Parkinson

Clinical validity of new genetic biomarkers of irinotecan neutropenia: an independent replication study

The overall goal of this study was to provide evidence for the clinical validity of nine genetic variants in five genes previously associated with irinotecan neutropenia and pharmacokinetics. Variants associated with absolute neutrophil count (ANC) nadir and/ or irinotecan pharmacokinetics in a discovery cohort of cancer patients were genotyped in an independent replication cohort of 108 cancer patients. Patients received single-agent irinotecan every 3 weeks. For ANC nadir, we replicated UGT1A1*28, UGT1A1*93 and SLCO1B1*1b in univariate analyses. For irinotecan area under the concentration–time curve (AUC0-24), we replicated ABCC2 -24C>T; however, ABCC2 -24C>T only predicted a small fraction of the variance. For SN-38 AUC0-24 and the glucuronidation ratio, we replicated UGT1A1*28 and UGT1A1*93. In addition to UGT1A1*28, this study independently validated UGT1A1*93 and SLCO1B1*1b as new predictors of irinotecan neutropenia. Further demonstration of their clinical utility will optimize irinotecan therapy in cancer patients

A Pharmacological Approach to Personalize the Use of Anti-Cancer Drugs

The individualization of anti-cancer therapy has been given much attention over the past decade. There has been a focus on differences between patients in tumor characteristics, but also the individualization of the given dose is extremely important. Many anti-cancer agents have a very narrow therapeutic window, which means that the range between drug concentrations at which severe toxicity is observed during treatment and the levels at which the drug has sub-therapeutic effects is small. As a result of these small therapeutic margins, the individual variability in toxicity during treatment and efficacy of treatment is large. The work described in this thesis provides a pharmacological approach contributing to the knowledge of factors influencing the metabolism and toxicity profiles of three anti-cancer agents known for their large inter-individual variation in pharmacokinetics and pharmacodynamics: the taxanes docetaxel and paclitaxel, and the anti-hormonal agent tamoxifen. Both environmental factors (i.e. smoking) as well as genetic factors (polymorphisms in genes coding for metabolizing enzymes and uptake/efflux transporters) were investigated in translational studies, including cell line experiments, mice experiments, and studies in patients with cancer. Finally, both an endogenous marker and exogenous marker were correlated with taxane and tamoxifen pharmacokinetics, respectively. Future studies should focus on further exploring factors that may influence systemic exposure of anti-cancer agents with a small therapeutic window. Ultimately, bringing these factors together in a predictive model that can be tested and validated in large cohorts of cancer patients should lead to more evidence-based dosing regimens for these drugs

Noradrenaline release from permeabilized synaptosomes is inhibited by the light chain of tetanus toxin

Noradrenaline release from rat brain cortical synaptosomes permeabilized with streptolysin O can be triggered by μM concentrations of free Ca2+. This process was inhibited within minutes by tetanus toxin and its isolated light chain, but not by its heavy chain. The data demonstrate that the effect of tetanus toxin on NA release from purified synaptosomes is caused by the intraterminal action of its light chain

A Crosslinking Analysis of GAP-43 Interactions with Other Proteins in Differentiated N1E-115 Cells

It has been suggested that GAP-43 (growth-associated protein) binds to various proteins in growing neurons as part of its mechanism of action. To test this hypothesis in vivo, differentiated N1E-115 neuroblastoma cells were labeled with [35S]-amino acids and were treated with a cleavable crosslinking reagent. The cells were lysed in detergent and the lysates were centrifuged at 100,000 × g to isolate crosslinked complexes. Following cleavage of the crosslinks and analysis by two-dimensional gel electrophoresis, it was found that the crosslinker increased the level of various proteins, and particularly actin, in this pellet fraction. However, GAP-43 was not present, suggesting that GAP-43 was not extensively crosslinked to proteins of the cytoskeleton and membrane skeleton and did not sediment with them. GAP-43 also did not sediment with the membrane skeleton following nonionic detergent lysis. Calmodulin, but not actin or other proposed interaction partners, co-immunoprecipitated with GAP-43 from the 100,000 × g supernatant following crosslinker addition to cells or cell lysates. Faint spots at 34 kDa and 60 kDa were also present. Additional GAP-43 was recovered from GAP-43 immunoprecipitation supernatants with anti-calmodulin but not with anti-actin. The results suggest that GAP-43 is not present in complexes with actin or other membrane skeletal or cytoskeletal proteins in these cells, but it is nevertheless possible that a small fraction of the total GAP-43 may interact with other proteins

Influence of pharmacogenetic variability on the pharmacokinetics and toxicity of the aurora kinase inhibitor danusertib

Objectives Danusertib is a serine/threonine kinase inhibitor of multiple kinases, including aurora-A, B, and C. This explorative study aims to identify possible relationships between single nucleotide polymorphisms in genes coding for drug metabolizing enzymes and transporter proteins and clearance of danusertib, to clarify the interpatient variability in exposure. In addition, this study explores the relationship between target receptor polymorphisms and toxicity of danusertib. Methods For associations with clearance, 48 cancer patients treated in a phase I study were analyzed for ABCB1, ABCG2 and FMO3 polymorphisms. Association analyses between neutropenia and drug target receptors, including KDR, RET, FLT3, FLT4, AURKB and AURKA, were performed in 30 patients treated at recommended phase II dose-levels in three danusertib phase I or phase II trials. Results No relationships between danusertib clearance and drug metabolizing enzymes and transporter protein polymorphisms were found. Only, for the one patient with FMO3 18281AA polymorphism, a significantly higher clearance was noticed, compared to patients carrying at least 1 wild type allele. No effect of target receptor genotypes or haplotypes on neutropenia was observed. Conclusions As we did not find any major correlations between pharmacogenetic variability in the studied enzymes and transporters and pharmacokinetics nor toxicity, it is unlikely that danusertib is highly susceptible for pharmacogenetic variation. Therefore, no dosing alterations of danusertib are expected in the future, based on the polymorphisms studied. However, the relationship between FMO3 polymorphisms and clearance of danusertib warrants further research, as we could study only a small group of patients