Pharmacokinetics and Target Attainment of Ceftobiprole in Asian and Non-Asian Subjects.

Ceftobiprole is a broad-spectrum cephalosporin. The objective of this study was to test the hypothesis that the pharmacokinetics (PK) and exposure of ceftobiprole in Asian subjects are similar to those in non-Asian subjects. Three approaches were followed. The first compared the individual PK estimates between the 2 subgroups derived from a population PK model previously built. Next, it was determined whether "Asian subject" was a significant covariate. Finally, a pharmacodynamic analysis was performed by comparing measures of exposure and target attainment. No significant differences were found between PK parameter estimates for Asian and non-Asian subjects, with median values (range) for clearance of 4.82 L/h (2.12-10.47) and 4.97 L/h (0.493-20.6), respectively (P = .736). "Asian subject" was not a significant covariate in the population PK model. There were no significant differences between the measures of exposure. The geometric mean ratio for the fAUC was 1.022 (90%CI, 0.91-1.15), indicating bioequivalence. Taking a target of 60% coverage of the dose interval, more than 90% of the population in both subgroups was adequately exposed. This analysis demonstrated that there are no PK or pharmacodynamic differences between Asian and non-Asian subjects for a ceftobiprole dose of 500 mg every 8 hours as a 2-hour infusion.

A phase 2, randomized, double-blind, multicenter trial to evaluate the safety and efficacy of three dosing regimens of isavuconazole compared with fluconazole in patients with uncomplicated esophageal candidiasis.

Esophageal candidiasis is a frequent cause of morbidity in immunocompromised patients. Isavuconazole is a novel, broad-spectrum antifungal developed for the treatment of opportunistic fungal infections. This phase 2 trial compared the efficacy and safety of three oral dosing regimens of isavuconazole with an oral fluconazole regimen in the primary treatment of uncomplicated esophageal candidiasis. The isavuconazole regimens were as follows: 200 mg on day 1 and then 50 mg once daily (arm A), 400 mg on day 1 and then 400 mg once-weekly (arm B), and 400 mg on day 1 and then 100 mg once daily (arm C). Patients in arm D received fluconazole at 200 mg on day 1 and then 100 mg once daily. The minimum treatment duration was 14 days. The primary endpoint was the rate of endoscopically confirmed clinical response at end of therapy. Safety and tolerability were also assessed. Efficacy was evaluated in 153 of 160 enrolled patients. Overall, 146 (95.4%) achieved endoscopically confirmed clinical success. Each of the isavuconazole regimens was shown to be not inferior to fluconazole, i.e., arm A versus D, -0.5% (95% confidence interval [CI] -10.0 to 9.4), arm B versus D, 3.5% (95% CI, -5.6 to 12.7), and arm C versus D, -0.2% (95% CI, -9.8 to 9.4). The frequency of adverse events was similar in arm A (n = 22; 55%), arm B (n = 18; 45%), and arm D (n = 22; 58%), but higher in arm C (n = 29; 71%). In summary, efficacy and safety of once-daily and once-weekly isavuconazole were comparable with once-daily fluconazole in the primary treatment of uncomplicated esophageal candidiasis.

Oral alitretinoin: a review of the clinical pharmacokinetics and pharmacodynamics.

Alitretinoin is an endogenous retinoid related to vitamin A. Studies have shown that oral alitretinoin is effective and well tolerated in the treatment of severe chronic hand eczema. This review summarizes the clinical pharmacokinetic and pharmacodynamic data from a number of studies involving alitretinoin. These include the effect of food on the pharmacokinetics of alitretinoin, interactions between alitretinoin and ketoconazole, simvastatin or cyclosporin A, the effect of alitretinoin on the pharmacokinetics of a combined oral contraceptive, alitretinoin in seminal fluid after repeated dosing, and the pharmacokinetics of alitretinoin and its metabolites in a clinical setting.

Influence of alitretinoin on the pharmacokinetics of the oral contraceptive ethinyl estradiol/norgestimate.

BACKGROUND: Alitretinoin (9-cis retinoic acid) is currently registered in many European countries and in Canada as the only licensed treatment for severe chronic hand eczema unresponsive to potent topical corticosteroids. Alitretinoin, like all retinoids, is teratogenic, and women of child-bearing potential must strictly adhere to pregnancy-prevention measures. AIM: To investigate the influence of alitretinoin on the pharmacokinetics (PK) of ethinyl estradiol/norgestimate (Ortho Tri-Cyclen 28(®)), a commonly prescribed combination oral contraceptive. METHODS: In total, 16 healthy premenopausal women received three consecutive cycles of the triphasic contraceptive ethinyl estradiol/norgestimate together with concomitant oral alitretinoin 40 mg once daily during cycle 2. Steady-state PK (noncompartmental analysis) of ethinyl estradiol, 17-deacetyl norgestimate, alitretinoin and its main metabolite 4-oxo-alitretinoin were assessed alone and in combination. RESULTS: The PK profiles of ethinyl estradiol and 17-deacetyl norgestimate were similar when contraceptives were given alone or with alitretinoin, and the area under the plasma concentration vs. time curve and the maximum concentration met the conventional criteria for PK equivalence. Similarly, the influence of ethinyl estradiol/norgestimate on systemic exposure to alitretinoin and 4-oxo-alitretinoin was not clinically relevant. Alitretinoin was well tolerated when given either alone or with ethinyl estradiol/norgestimate. CONCLUSIONS: There was no clinically relevant influence of alitretinoin on the PK of ethinyl estradiol/norgestimate, and no influence of ethinyl estradiol/norgestimate on systemic exposure to alitretinoin and 4-oxo-alitretinoin. Consequently, oral contraception with ethinyl estradiol/norgestimate is an appropriate primary method of birth control during alitretinoin treatment for women of childbearing potential.

Low levels of alitretinoin in seminal fluids after repeated oral doses in healthy men.

BACKGROUND: Alitretinoin, like all retinoids, is teratogenic, and can only be given to women of childbearing potential if pregnancy is excluded and a strict contraceptive programme is followed. AIM: This study was designed to determine whether alitretinoin in the semen of men treated with alitretinoin poses a teratogenic risk to their female partners. METHODS: In total, 24 healthy men aged 18-45 years received alitretinoin 20 mg (n = 12) or 40 mg (n = 12), once daily for 14 days. Subjects in the 40 mg dose group provided ejaculate at baseline, on day 1, before and approximately 4 h after dosing on day 2, and at follow-up on study day 21 (± 2). RESULTS: Alitretinoin and 4-oxo-alitretinoin were detected in 11 of the 12 semen samples. The highest level of alitretinoin in semen was 7.92 ng/mL. Assuming an ejaculate volume of 10 mL, the amount of drug transferred in semen would be about 80 ng, 1/375,000 of a single 30 mg capsule. Complete absorption of 80 ng of alitretinoin from semen, presuming a volume of distribution confined to 5 L of circulating blood in the partner, would lead to an increase in plasma alitretinoin concentration of 0.016 ng/mL, which appears to be negligible compared with measured endogenous plasma levels. Increases in plasma levels of related retinoids are also negligible. CONCLUSIONS: Alitretinoin in the semen of men receiving up to 40 mg of oral alitretinoin per day is unlikely to be associated with teratogenic risk in their female partners. Barrier contraception is therefore not required for men taking alitretinoin.

Influence of food on the pharmacokinetics of oral alitretinoin (9-cis retinoic acid).

BACKGROUND: Previous studies have shown that concomitant administration of food may enhance the bioavailability of oral retinoids. AIM: To assess the influence of food on the pharmacokinetics (PK) of alitretinoin after a single oral dose. METHODS: This was a single-dose, open-label, randomized, crossover study, which enrolled 30 healthy men, aged 18-44 years. Subjects received sequential doses of alitretinoin 40 mg either after fasting (treatment A) or 5 min after completion of a standard breakfast (treatment B), with the dosing sequence randomized (A/B or B/A). The washout period between the two doses was 1 week. Plasma concentrations over time were plotted and standard PK variables [area under the curve (AUC) of plasma concentration vs. time, maximum plasma concentration (C(max)), time to maximum plasma concentration (t(max)) and elimination half-life (t(1/2)] were determined. RESULTS: Drug exposure was markedly increased when alitretinoin was taken with food compared with fasting, and there were significant increases in mean C(max) (82.8 vs.25.4 ng/mL, respectively) and AUC (220.2 vs. 55.7 ng · h/mL). The delaying effect of food on t(max) was less marked (median of 3.0 vs. 2.0 h). Administration with food also increased exposure to drug metabolites. Variability in exposure was markedly reduced if alitretinoin was taken with vs. without food (percentage coefficient of variation 40% vs. 74% for AUC; 49% vs. 85% for C(max)). Alitretinoin was generally well tolerated, with typical retinoid adverse reactions, mostly comprising headache. CONCLUSIONS: Intake of alitretinoin with food substantially increased the bioavailability of alitretinoin, but variability in exposure was reduced. Consequently, oral alitretinoin should be taken with food as outlined in the manufacturer's summary of product characteristics.

Pharmacokinetic interactions between alitretinoin and ketoconazole or simvastatin or ciclosporin A.

BACKGROUND: Based on in vitro data with isolated cytochrome P450 (CYP) isoenzymes, alitretinoin interacts only with CYP3A4, and the potential for drug-drug interactions is considered negligible. AIM: To confirm in humans the lack of potential interactions between CYP3A4 and alitretinoin in vivo. METHODS: This was a multiple-dose, open-label, parallel-group, single-centre study, which enrolled 54 healthy male volunteers aged 18-45 years. Subjects were divided into three groups, with 18 in each group: group 1 received either alitretinoin 30 mg and ketoconazole 200 mg, group 2 alitretinoin 30 mg and simvastatin 40 mg, and group 3 alitretinoin 30 mg and ciclosporin A 300-mg. RESULTS: At the highest therapeutic dose of 30 mg, alitretinoin had no significant effect on the pharmacokinetics (PK) of ketoconazole and ciclosporin A. There was a significant but not clinically relevant effect of simvastatin on the area under the curve (AUC) of plasma concentration vs. time and on maximum plasma concentration (C(max)) after repeated administration of alitretinoin. Exposure to simvastatin concomitantly with alitretinoin was decreased by 16% for AUC and 23% for C(max). The CYP3A4 ± PgP substrates of simvastatin and ciclosporin A did not affect the single or repeated dose PK of alitretinoin. The strong CYP3A4/PgP inhibitor ketoconazole led to significant increases in both AUC and C(max) values for alitretinoin. CONCLUSIONS: Single and repeated doses of alitretinoin do not alter the PK of ciclosporin A and ketoconazole. Simvastatin levels were slightly but significantly reduced by co-administration of alitretinoin. Substrates of CYP3A4 did not affect the PK of alitretinoin. However, ketoconazole significantly increased the plasma levels of alitretinoin, therefore, co-administration with CYP3A4 inhibitors such as ketoconazole may require a dose reduction of alitretinoin.

Pharmacokinetics, efficacy and safety of alitretinoin in moderate or severe chronic hand eczema.

BACKGROUND: Recent studies have found that alitretinoin can induce clinically significant responses in subjects with severe chronic hand eczema (CHE) unresponsive to topical corticosteroids. AIMS: To assess the pharmacokinetics (PK), efficacy and safety of alitretinoin 10 or 30 mg once daily. METHODS: This was a randomized, double-blind study, which enrolled 32 subjects aged 18-75 years with CHE unresponsive to potent topical corticosteroids. Subjects received alitretinoin 10 mg (n = 16) or 30 mg (n = 16) once daily for 12 or 24 weeks. Standard PK variables [area under the curve (AUC) of plasma concentration vs. time, maximum plasma concentration (C(max)), time to maximum plasma concentration (t(max)), elimination half-life (t(1/2)), total systemic clearance (CL/F) and volume of distribution (Vd/F)] were determined for alitretinoin and metabolites. Efficacy was assessed using the Physician's Global Assessment (PGA) scale. RESULTS: Chronic administration of alitretinoin for up to 24 weeks did not result in accumulation or time-dependent changes in the disposition of alitretinoin. Exposure was found to be proportional to dose. Systemic exposure (AUC) to alitretinoin was proportional to dose for 10 and 30 mg alitretinoin; 62.8% of subjects achieved clear/almost clear hands in the 30 mg group and 12.5% in the 10 mg group. Alitretinoin was well tolerated. CONCLUSIONS: Chronic administration of alitretinoin for 12-24 weeks did not lead to accumulation or time-dependent changes in drug exposure. Alitretinoin was effective and well tolerated in the treatment of subjects with moderate or severe CHE unresponsive to potent topical corticosteroids.

Animal pharmacokinetics and interspecies scaling from animals to man of lamifiban, a new platelet aggregation inhibitor.

Relating pharmacokinetic information obtained in animal species to man (interspecies scaling) can play an important role in enabling understanding of the differences and similarities between species, and helping to predict the kinetic profile of a new compound in man. Interspecies scaling techniques have been applied to lamifiban (Ro 44-9883), a new selective and potent nonpeptidic inhibitor of human glycoprotein IIb-IIIa intended for use in clinical treatment of, for example, acute coronary syndrome. The pharmacokinetic profile of lamifiban in man was predicted from animal data (in rats, dogs and cynomolgus monkeys) by using allometric scaling and concentration-time transformations. These extrapolations for lamifiban were performed prospectively, to help design the first pharmacokinetic studies in man. The approach based on equivalent time was preferred for our prospective predictions, in view of the high values found for the allometric exponents. Using allometric scaling, clearance (CL), half-life (t1/2) and volume of distribution (Vd) were overestimated by approximately two- to fourfold. Compared with allometric scaling, the transformation based on equivalent time improved the prediction for all human pharmacokinetic parameters. For t1/2 and CL, the observed values for man were within the range predicted from the various animal species. Of the individual animal species, the cynomolgus monkey gave the most reliable predictions of these two parameters, as well as accurately predicting the Vd value.

Interspecies scaling of interferon disposition and comparison of allometric scaling with concentration-time transformations.

Interspecies scaling is used to extrapolate pharmacokinetic parameters from animals to humans, through the application of physiologically based models, by empirical allometric procedures, or using concentration-time transformations. The aim of this study was to compare the accuracies of the last two methods for predicting the pharmacokinetic parameters and concentration-time curves in humans. In the first part of this study, interspecies scaling techniques were applied to a hypothetical drug (extracellular distribution and elimination through glomerular filtration), to examine the influence of various laboratory animals (mouse, rat, cynomolgus monkey and dog) on the parameters predicted for man. The same techniques were also applied to interferon-alpha A, using the literature data for various animal species. The kinetic parameters predicted in man were then compared to the values published for man. Our theoretical example showed that, for allometric scaling, each species has a very different influence on the prediction in human. With the approach using concentration-time transformations, however, each animal species potentially makes a similar contribution to the prediction for man. Based on the pharmacokinetic data published for interferon-alpha A in laboratory animals, allometric equations underestimated the observed values of CL and Vdss in man by 2-3-fold, and the prediction of t1/2 was likely to be unreliable, due to a poor correlation. The use of equivalent time, kallynochron, and apolysichron transformations improved the pharmacokinetic predictions for all three parameters in man. In conclusion, concentration-time transformations make more adequate use of the data available in the different species of laboratory animals, to give better predictions of the pharmacokinetic parameters in man.

Mechanistic studies on the ethyl-esterification of acitretin by human liver preparations in vitro.

Studies have been performed with human liver microsome preparations in vitro, to investigate the reaction mechanisms involved in the conversion of acitretin to the corresponding ethyl ester, etretinate. The results indicate that: Three fresh samples of human liver, which had been stored in liquid nitrogen for up to 8 months, all produced traces of etretinate (5.8 +/- 0.8 ng/ml) in the presence of ethanol but not when the acitretin was added in acetone, or when the sample was denatured by preheating. Studies with pooled human liver microsomes, to identify the cellular location of the enzymes and the co-factors involved in this esterification, indicate a primary requirement for both ethanol and CoA + ATP with a secondary potentiation in the presence of an NADPH regenerating system. A possible explanation for these finding is that the microsomal ligase enzymes form an intermediate ester between CoA and acitretin, which is then trans-esterified by the ethanol. The low formation with CoA + ATP may indicate that second stage of this process occurs spontaneously, with the NADPH potentiation suggesting that it could also be mediated enzymically.

A new extrapolation method from animals to man: application to a metabolized compound, mofarotene.

Allometric scaling (a technique which uses data obtained in laboratory animals to predict human pharmacokinetics) works well for drugs that are cleared intact, but is less successful with extensively metabolised compounds. This paper describes a new method to improve the accuracy of such projections, by integrating metabolic data obtained in vitro (e.g. with liver microsomes or hepatocytes) into these calculations. The approach was used prospectively, to predict the clearance of mofarotene (Ro 40-8757) in humans from in vivo kinetic data obtained in mouse, rat and dog. This compound was selected to illustrate this approach because it is exclusively eliminated through metabolism. Without the metabolic correction or using empirical correcting factors, the values predicted for man were 2.7 and 0.6 ml/min/kg. This fell outside the range subsequently obtained in healthy volunteers dosed orally with 300 mg of mofarotene (7.5 +/- 4.0 ml/min/kg, n = 12). However, inclusion of the microsomal or hepatocyte data gave values of 5.1 and 4.2 ml/min/kg, respectively, illustrating that the integration of in vitro metabolic data improves the accuracy of kinetic extrapolations. In contrast to the existing empirical techniques, this approach offers a rational basis to predict clearance of metabolized compounds in human.