Current research into brain barriers and the delivery of therapeutics for neurological diseases: a report on CNS barrier congress London, UK, 2017.

This is a report on the CNS barrier congress held in London, UK, March 22-23rd 2017 and sponsored by Kisaco Research Ltd. The two 1-day sessions were chaired by John Greenwood and Margareta Hammarlund-Udenaes, respectively, and each session ended with a discussion led by the chair. Speakers consisted of invited academic researchers studying the brain barriers in relation to neurological diseases and industry researchers studying new methods to deliver therapeutics to treat neurological diseases. We include here brief reports from the speakers

Mechanistic Study on the Use of the l-Type Amino Acid Transporter 1 for Brain Intracellular Delivery of Ketoprofen via Prodrug: A Novel Approach Supporting the Development of Prodrugs for Intracellular Targets

l-Type amino acid transporter 1 (LAT1), selectively expressed at the blood–brain barrier (BBB) and brain parenchymal cells, mediates brain delivery of drugs and prodrugs such as l-dopa and gabapentin. Although knowledge about BBB transport of LAT1-utilizing prodrugs is available, there is a lack of quantitative information about brain intracellular delivery and influence of prodrugs on the transporter’s physiological state. We studied the LAT1-mediated intrabrain distribution of a recently developed prodrug of the cyclooxygenase inhibitor ketoprofen as well as its impact on transporter protein expression and function (i.e., amino acid exchange) using brain slice method in mice and rats. The intrabrain distribution of the prodrug was 16 times higher than that of ketoprofen. LAT1 involvement in brain cellular barrier uptake of the prodrug was confirmed, reflected by a higher unbound brain intracellular compared to brain extracellular fluid concentration. The prodrug did not alter LAT1 protein expression and amino acid exchange. Integration of derived parameters with previously performed in vivo pharmacokinetic study using the Combinatory Mapping Approach allowed to estimate the brain extra- and intracellular levels of unbound ketoprofen, prodrug, and released parent drug. The overall efficiency of plasma to brain intracellular delivery of prodrug-released ketoprofen was 11 times higher than after ketoprofen dosing. In summary, this study provides quantitative information supporting the use of the LAT1-mediated prodrug approach for enhanced brain delivery of drugs with intracellular targets.Pharmacolog

Influence of sex on propofol metabolism, a pilot study: implications for propofol anesthesia

The basis of high intersubject variability of propofol metabolism is unclear. Therefore, we examined the influence of genetic polymorphisms of the key metabolizing enzymes cytochrome P450 2B6 (CYP2B6) and uridine diphosphate (UDP)-glucuronosyltransferase 1A9 (UGT1A9), age, and sex on propofol biotransformation in vitro and in vivo. Plasma concentrations of propofol, 4-hydroxypropofol, and their glucuronides were measured over 20 min in 105 patients after a single intravenous bolus of propofol. Propofol 4-hydroxylation activity, genotypes, and content of CYP2B6 protein in 68 human livers were determined. The common single nucleotide polymorphisms (SNPs) for the CYP2B6 and UGT1A9 genes were analyzed by polymerase chain reaction (PCR). Plasma levels of propofol metabolites showed high interindividual variability (range of coefficient of variation 89-128%). This was supported by in vitro data showing similar variability of propofol 4-hydroxylation in liver microsomes and 1.9-fold higher CYP2B6 protein content in the livers from women. No significant relationships were revealed between the SNPs studied and propofol metabolism. However, patients' sex had a pronounced effect on propofol metabolism. Thus, women had higher amounts o No significant effects of CYP2B6 and UGT1A9 SNPs or age on propofol metabolism were revealed in this pilot study, but there was a pronounced effect of sex, a finding that indicates an important factor for the previously described sex difference in systemic clearance of propofol seen

Sex Difference in Formation of Propofol Metabolites: A Replication Study

Women recover faster from propofol anaesthesia and have been described to have a higher incidence of awareness during surgery, compared to men - an effect that may be inherent in sex differences in propofol metabolism. In an observational study, 98 ASA I-II patients treated with continuous propofol infusion were recruited. The associations between sex and CYP2B6 and UGT1A9 polymorphisms with dose-and weight-adjusted area under the total plasma level time curves (AUC) for propofol, and its metabolites propofol glucuronide (PG), 4-hydroxypropofol (OHP) and hydroxyl glucuronide metabolites 4-hydroxypropofol-1-O-beta-D-glucuronide (Q1G) and 4-hydroxypropofol-4-O-beta-D-glucuronide (Q4G), were analysed. Significantly higher AUC of PG (1.3 times, p = 0.03), Q1G (2.9 times, p < 0.001), Q4G (2.4 times, p < 0.01) and OHP (4.6 times, p = 0.01) were found in women (n = 53) than in men (n = 45) after intravenous infusion of propofol using target-controlled infusion system. There was, however, no significant impact of gene polymorphisms on propofol biotransformation. The results, which are supported by a previous pilot study using a propofol bolus dose, suggest that, compared to men, more rapid propofol metabolism may occur in women - a factor that may contribute to the mentioned differences in the efficacy of propofol anaesthesia between male and female patients

Professor Margareta Hammarlund-Udenaes: humbled scientist shaping modern neuropharmacokinetics

Pharmacolog