Handling unstable analytes: literature review and expert panel survey by the Japan Bioanalysis Forum Discussion Group.

Analyzing unstable small molecule drugs and metabolites in blood continues to be challenging for bioanalysis. Although scientific countermeasures such as immediate cooling, immediate freezing, addition of enzyme inhibitors, pH adjustment, dried blood spot or derivatization have been developed, selecting the best practices has become an issue in the pharmaceutical industry as the number of drugs with such problems is increasing, even for generic drugs. In this study, we conducted a comprehensive literature review and a questionnaire survey to determine a suitable practice for evaluating instability and implementing countermeasures. Three areas of focus, matrix selection, effect of hemolysis and selection of esterase inhibitors, are discussed.

Prediction of human percutaneous absorption from in vitro and in vivo animal experiments.

Although anatomical and structural similarities between the skin of minipigs and humans are often reported, few percutaneous pharmacokinetic studies have been conducted in minipigs. The objective of this study was to clarify the usefulness of minipigs for estimating the percutaneous absorption of various drugs in humans. The absorption of several marketed drugs was observed in mice, rats and minipigs both in vivo and in vitro, and results were compared with those in humans. For all six model drugs, after percutaneous administration in vivo, fraction of dose absorbed (F) from the skin was the lowest in minipigs among the four species studied, including humans. In vitro drug permeation results were similar, with the lowest permeability observed in minipigs. However, combined use of both in vitro permeation and in vivo absorption data from minipigs using triple pack approach resulted in better prediction of human F values than data obtained from mice. These results suggest some qualitative, but not quantitative, similarities between the drug absorption process across the skin of minipigs and humans. In conclusion, minipigs appear to be a promising model animal for predicting percutaneous drug absorption in humans, however, more in vivo and in vitro studies are needed to improve predictability.

Usefulness of minipigs for predicting human pharmacokinetics: Prediction of distribution volume and plasma clearance.

In this study, advantages of minipigs to use in preclinical study for new drug development were evaluated in terms of prediction of human pharmacokinetic (PK) parameters of various drugs. Fourteen model drugs having diverse physicochemical properties were selected and intravenously administered to mice, rats and minipigs to obtain their PK parameters. The human volume of distribution (Vd) and clearance (CL) of model drugs were predicted from PK parameters in each animal species. When Vd of 14 drugs in each species were directly compared with those in humans, minipigs showed the highest correlation. Correction of Vd with an unbound fraction of drugs in tissues further improved the correlation. Allometric scaling that included minipig data resulted in high accuracy in the prediction of human Vd, clearly indicating an importance of minipig data. Minipigs also showed the high predictability of human CL. The prediction of human CL by allometric scaling showed a high accuracy when the data of minipigs were included. In conclusion, potential advantages of minipigs for predicting human Vd and CL were clearly demonstrated. Reliable prediction of human PK from data of minipigs appears to be possible in preclinical PK study, without relying on PK analysis in other species.

Mechanism of the 24-hour rhythm of tumor necrosis factor-alpha formed by onset of rheumatoid arthritis.

OBJECTIVE: Morning stiffness and plasma cytokine levels in rheumatoid arthritis (RA) patients exhibit 24-hour variations. Tumor necrosis factor-α (TNF-α) plays a central role in RA clinical conditions, including the invasion of inflammatory cells, destruction of cartilage, systemic inflammatory response and its levels show a 24-hour rhythm after the onset of RA. In this study, we investigated what cytokines and/or transcriptional factors are involved in the formation of 24-hour variations in TNF-α levels after the onset of RA using MRL/Mpj-Tnfrsf6(lpr) (MRL/lpr) mice. METHOD: Blood was drawn at six different times from MRL/lpr mice to measure cytokines, serum amyloid A (SAA), IgG rheumatoid factor (IgG-RF) and corticosterone levels. Cytokine and transcriptional factor levels at the different times were measured in 10- and/or 15-week-old MRL/lpr mice. The promoter activity of TNF-α by lymphotoxins (LTs) was investigated using a dual-luciferase assay. RESULTS: SAA and TNF-α concentrations clearly exhibited 24-hour rhythms with higher levels at the light phase and lower levels at the dark phase after RA crisis. The expression of LT-α and LT-ß showed significant 24-hour rhythms in 15-week-old MRL/lpr mice and the phases of LT-α and LT-ß levels were antiphase compared with that of TNF-α. AP-1 binding sites were found in LT-α and LT-ß promoter regions, and jun mRNA expression corresponded to LT-α and LT-ß levels. TNF-α promoter activity was decreased due to the co-transfection of LT-α and LT-ß. CONCLUSION: LT-α and LT-ß controls the 24-hour rhythm in TNF-α levels after the onset of RA in order to suppress TNF-α promoter activity.

Dosing time-dependency of the arthritis-inhibiting effect of tacrolimus in mice.

Stiffness and cytokine in blood levels show 24-h rhythms in rheumatoid arthritis (RA) patients. We previously revealed that higher therapeutic effects were obtained in RA patients and RA model animals when the dosing time of methotrexate was chosen according to the 24-h rhythms to cytokine. In this study, we examined whether a dosing time-dependency of the therapeutic effect of tacrolimus (TAC) could be detected in collagen-induced arthritis (CIA) and MRL/lpr mice. To measure the levels of cytokines and serum amyloid A (SAA), blood was collected from CIA mice at different times. TAC was administered at two different dosing times based on these findings and its effects on arthritis and toxicity were examined. Plasma tumor necrosis factor (TNF)-α, interleukin-6 (IL-6), and SAA concentrations showed obvious 24-h rhythms with higher levels during the light phase and lower levels during the dark phase after RA crisis. The arthritis score and leukocyte counts were significantly lower in the group treated at 2 h after the light was turned on (HALO) than in the control and 14 HALO-treated groups. Our findings suggest that choosing an optimal dosing time could lead to the effective treatment of RA by TAC.

Methotrexate chronotherapy is effective against rheumatoid arthritis.

Methotrexate (MTX) is the most important drug for treating rheumatoid arthritis (RA). It has been stated that cytokines play an important role in the pathogenesis of RA, and that cytokine levels increase and show 24-h rhythms in RA patients. Previously, we found that arthritis was relieved after the administration of MTX at specific times in synchronization with the 24-h rhythm of tumor necrosis factor (TNF)-α in collagen-induced arthritis (CIA) animals. Based on our findings in an earlier study of the dosing time-dependent effects of MTX in MRL/lpr mice, which develop autoimmune disorders that share similarities with human RA, we examined here the utility of MTX chronotherapy in Japanese RA patients. In an initial animal modeling study, we collected blood from MRL/lpr mice at different times (2, 6, 10, 14, 18, or 22 hours after the light was turned on [HALO]), and we measured TNF-α mRNA expression in leukocytes. MTX was administered to the mice at two different dosing times (6 or 18 HALO), and various blood parameters were measured to estimate arthritis activity. TNF-α mRNA levels showed a clear 24-h rhythm with a peak at 22 HALO and a trough at 18 HALO after RA had developed. In these MRL/lpr mice, inflammation and TNF-α were markedly reduced when the MTX dosing time was matched to the time (18 HALO) when the TNF-α level began to increase. We then applied these findings to Japanese RA patients by switching them from the standard MTX three times/wk (day 1: after breakfast and supper; day 2: after breakfast schedule), to chronotherapy, in which the dose and number of doses/wk were not changed but MTX was administered once-a-day at bedtime. Disease Activity Score (DAS)28, modified health assessment questionnaire (MHAQ), and adverse effects were assessed. With MTX chronotherapy, DAS28, which is commonly used to quantitatively assess RA symptoms, was significantly improved at all follow-up clinical visit times compared with the baseline (vs. 1 mo: p = .0197, 2 mos: p = .0107, 3 mos: p = .0087). Significant symptom recovery was observed in 41.2% of patients, and 23.5% of patients achieved clinical remission during the 3 mos of follow-up. Functional capacity of RA patients, as indicated by the MHAQ, was markedly improved by chronotherapy. There were no severe adverse effects. Thus, we demonstrated (i) inflammation and plasma TNF-α concentrations were significantly reduced in MRL/lpr mice treated with MTX at 18 HALO, the time when TNF-α mRNA level began to increase; and (ii) MTX bedtime chronotherapy was safe, markedly reduced disease activity, and improved the functional capacity of RA patients. The findings on RA patients show that bedtime MTX chronotherapy can improve RA symptoms compared to the current standard dosing methods.