Case studies addressing human pharmacokinetic uncertainty using a combination of pharmacokinetic simulation and alternative first in human paradigms.

PF-184298 ((S)-2,3-dichloro-N-isobutyl-N-pyrrolidin-3-ylbenzamide) and PF-4776548 ((3-(4-fluoro-2-methoxy-benzyl)-7-hydroxy-8,9-dihydro-3H,7H-pyrrolo[2,3-c][1,7]naphthyridin-6-one)) are novel compounds which were selected to progress to human studies. Discordant human pharmacokinetic predictions arose from pre-clinical in vivo studies in rat and dog, and from human in vitro studies, resulting in a clearance prediction range of 3 to >20 mL min⁻¹ kg⁻¹ for PF-184298, and 5 to >20 mL min⁻¹ kg⁻¹ for PF-4776548. A package of work to investigate the discordance for PF-184298 is described. Although ultimately complementary to the human pharmacokinetic data in characterising the disposition of PF-184298 in humans, these data did not provide any further confidence in pharmacokinetic prediction. A fit for purpose human pharmacokinetic study was conducted for each compound, with an oral pharmacologically active dose for PF-184298, and an intravenous and oral microdose for PF-4776548. This provided a relatively low cost, clear decision making approach, resulting in the termination of PF-4776548 and further progression of PF-184298. A retrospective analysis of the data showed that, if the tools had been available at the time, the pharmacokinetics of PF-184298 in human could have been predicted from a population based simulation tool in combination with physicochemical properties and in vitro human intrinsic clearance.

The application of fully automated on-line solid phase extraction in bioanalysis.

This paper describes the application of fully automated on-line solid phase extraction to the bioanalysis of three example compounds using the Symbiosis platform. The on-line assay performance is compared to off-line methodologies for the same compounds. The three example compounds possess a variety of physicochemical properties and different extraction modes were applied in off-line methods. These methods were developed through optimisation of solid phase or liquid-liquid extraction and chromatographic separation conditions for each of the analytes. Both on-line and off-line methods were evaluated for linearity, carryover, imprecision and inaccuracy. Experiments were also performed investigating modification of ionisation and selectivity against different batches of plasma. On-line and off-line methods were found to be comparable in performance. In conclusion, on-line methodology has distinct advantages for the analysis of large numbers of samples with a marked reduction in manual operation.