Preclinical characterization of 2-[3-[3-[(5-ethyl-4'-fluoro-2-hydroxy[1,1'-biphenyl]-4-yl)oxy]propoxy]-2-propylphenoxy]benzoic acid metabolism: in vitro species comparison and in vivo disposition in rats.

Assessment of the pharmacokinetics of [14C]2-[3-[3-[(5-ethyl-4'-fluoro-2-hydroxy[1,1'-biphenyl]-4-yl)oxy]propoxy]-2-propylphenoxy-]benzoic acid ([14C]LY293111), an experimental anti-cancer agent, suggested long-lived circulating metabolites in rats. In vivo metabolites of LY293111 were examined in plasma, bile, urine, and feces of Fischer 344 (F344) rats after oral administration of [14C]LY293111. Metabolites were profiled by high-performance liquid chromatography-radiochromatography, and identified by liquid chromatography (LC)/mass spectrometry and LC/NMR. The major in vivo metabolites of LY293111 identified in rats were phenolic (ether), acyl, and bisglucuronides of LY293111. Measurement of radioactivity in rat plasma confirmed that a fraction of LY293111-derived material was irreversibly bound to plasma protein and that this bound fraction increased over time. This was consistent with the observed disparity in half-lives between LY293111 and total radioactivity in rats and monkeys, and is likely due to covalent modification of proteins by the acyl glucuronide. In vitro metabolism of [14C]LY293111 in liver slices from CD-1 mice, F344 rats, rhesus and cynomolgus monkeys, and humans indicates that glucuronidation was the primary metabolic pathway in all species. The acyl glucuronide was the most prevalent radioactive peak (16% of total 14C) produced by F344 rat slices, whereas the ether glucuronide was the major metabolite in all other species (26-36% of total 14C). Several minor hydroxylated metabolites were detected in F344 rat slice extracts but were not observed in other species. The data presented suggest that covalent modification of proteins by LY293111 acyl glucuronide is possible in multiple species, although the relative reactivity of this metabolite appears to be low compared with those known to cause adverse drug reactions.

Disposition of LY333531, a selective protein kinase C beta inhibitor, in the Fischer 344 rat and beagle dog.

1. Studies were conducted in the Fischer 344 rat and beagle dog to determine the disposition of LY333531 and its equipotent active des-methyl metabolite, LY338522, both potent and selective inhibitors of the beta-isozyme of protein kinase C. 2. Male Fischer 344 rats and female beagle dogs received a single 5-mg kg(-1) oral dose of (14)C-LY333531. Urine, faeces, bile and plasma were collected and analysed for (14)C, LY333531 and LY338522. 3. LY333531 was eliminated primarily in the faeces (91% by 120 h in rat, 90% by 96 h in dog). Bile contributed the majority of the radioactivity excreted in the faeces in rat (66% in the cannulated bile duct study) and a variable but significant proportion in dog. 4. Pharmacokinetics following a single 5 mg kg(-1) oral dose of (14)C-LY333531 to the male rat produced C(max) and AUC(0-infinity ) for LY333531 of 14.7 ng ml(-1) and 60.8 ng h ml(-1), respectively, with a half-life of 2.5 h. LY338522 and total radioactivity showed similar profiles. 5. In the female dog at the same dose, C(max) and AUC(0-infinity ) of LY333531 were higher, producing 245 +/- 94 ng ml(-1) and 1419 +/- 463 ng h ml(-1), respectively, with a half-life of 5.7 h. 6. The data indicate that the disposition of LY333531 is similar in rat and dog.

Synthesis of [11C]dapoxetine.HCl, a serotonin re-uptake inhibitor: biodistribution in rat and preliminary PET imaging in the monkey.

[11C]Dapoxetine.HCl, S-(+)-N,N-dimethyl-a-[2-(naphthalenyloxy)ethyl] benzenemethanamine hydrochloride, a potent serotonin re-uptake inhibitor was prepared from its mono-methyl precursor, S-(+)-N-methyl-a-[2-(naphthalenyloxy)ethyl]benzene methanamine hydrochloride. Biodistribution was determined in rats at 5, 30 and 60 min after injection and preliminary PET studies were performed in a Rhesus monkey. 11CH3I was bubbled into a solution of S-(+)-N-methyl-alpha-[2-(naphthalenyloxy)ethyl]benzene methanamine hydrochloride (3.0 mg in DMSO) and the mixture was heated at 110 degrees C for 8 min. [11C]Dapoxetine.HCl was purified by HPLC on a C18 cartridge eluted with MeOH:phosphate buffer, pH 7,2 (75:25) with a 10% yield (end of synthesis). The time required for the synthesis was 40 min, from the end of bombardment. Radiochemical purity of the final product was > 99% and specific activity was routinely > 400 mCi/mumol [EOS]. In the biodistribution studies the highest concentration (%ID/g +/- SEM) of dapoxetine.HCl was detected in lung: 4.56 +/- 0.27 (5 min), 1.28 +/- 0.18 (30 min) and 0.67 +/- 0.04 (60 min). Brain accumulation was 0.76 +/- 0.02 (5 min), 0.46 +/- 0.04 (30 min) and 0.27 +/- 0.01 (60 min). Preliminary PET studies demonstrated significant displaceable binding in the cerebral cortex and subcortical grey matter. These results demonstrate that [11C]dapoxetine.HCl can be prepared in high purity and may be useful for the in vivo evaluation of serotonin re-uptake mechanisms.