Pharmacokinetics of Roxadustat: A Population Analysis of 2855 Dialysis- and Non-Dialysis-Dependent Patients with Chronic Kidney Disease.

BACKGROUND: Roxadustat is a novel, small-molecule, first-in-class therapeutic that stimulates erythropoiesis by inhibiting hypoxia-inducible factor prolyl hydroxylase enzymes. This agent (roxadustat) is in clinical development for the treatment of anemia in patients with non-dialysis-dependent (NDD) and dialysis-dependent (DD) chronic kidney disease. A population pharmacokinetic analysis was undertaken to evaluate the effect of intrinsic and extrinsic factors on roxadustat pharmacokinetics. METHODS: Non-linear mixed-effects models implemented in NONMEM software were fitted to 8209 pharmacokinetic samples from 2855 DD and NDD subjects enrolled in four phase III studies with roxadustat dose concentrations of 20-400 mg as orally administered tablets. Effects of intrinsic and extrinsic factors were evaluated using a stepwise covariate modeling procedure in combination with the full covariate approach, and defined no-effect boundaries for exposure were based on the difference in exposure between 70 and 100 mg of roxadustat (i.e., - 30%, + 43%). RESULTS: A two-compartment model with first-order absorption adequately described roxadustat pharmacokinetics, with parameter estimates (relative standard error) for apparent clearance of 1.1 (0.0223) L/h in NDD subjects, and apparent central and peripheral volumes of distribution of 14.9 (0.0278) L and 9.5 (0.0872) L, respectively. Stepwise covariate modeling identified bodyweight, dialysis status, race, and dose as statistically significant covariates on apparent clearance, and bodyweight, sex, and albumin as statistically significant covariates on apparent central volume of distribution. However, the effects of these covariates did not result in roxadustat area under the curve or maximum plasma concentration changes outside of the defined no-effect boundaries. The effects of concomitant oral iron, clopidogrel, and staggered sevelamer, calcium carbonate, or calcium acetate were investigated using a full covariate approach but did not result in roxadustat area under the curve or maximum plasma concentration changes outside of the defined no-effect boundaries. CONCLUSIONS: A population pharmacokinetic model was developed for the pharmacokinetics of roxadustat in the target population. None of the investigated intrinsic or extrinsic factors resulted in a significant change in roxadustat exposure outside of the defined no-effect boundaries.

Pharmacokinetic profile after multiple deltoid or gluteal intramuscular injections of paliperidone palmitate in patients with schizophrenia.

Paliperidone palmitate (PP) is a once-monthly long-acting injectable antipsychotic approved for the treatment of schizophrenia in many countries. To evaluate the different injection-site options, we compared the pharmacokinetic profile of paliperidone after multiple injections of PP 100 mg eq. (156 mg of PP, equivalent to 100 mg of paliperidone) on days 1, 8, 36, and 64 into the deltoid (n = 24) or gluteal muscle (n = 25) in patients with schizophrenia. After four injections in the deltoid muscle, paliperidone exposure was higher for AUCτ and Cmax , compared with the gluteal muscle (geometric mean AUCτ -based ratio: 120% [90% CI: 93.1-154.7%], and geometric mean Cmax -based ratio: 130% [90% CI: 100.6-168.9%]). The mean [SD] fluctuation index was higher, with a larger interpatient variability, after deltoid-injections (75.9% [30.9%]) than gluteal-injections (58.5% [14.3%]). The median tmax was similar for both sites. PP was generally tolerable in patients, with more favorable local-site tolerability for gluteal-injection. In conclusion, to achieve therapeutic-concentrations quickly, the first-two injections of PP are best administered into the deltoid muscle, whereas thereafter maintenance-injections can be administered either in the deltoid or gluteal muscle.

Effect of carbamazepine on the pharmacokinetics of paliperidone extended-release tablets at steady-state.

Given the potential concomitant use of carbamazepine and paliperidone extended-release (ER) in the treatment of schizophrenia or schizoaffective disorder, this open-label, two-treatment sequential study investigated the effect of repeated administration of carbamazepine on the steady-state pharmacokinetics of paliperidone. Sixty-four patients with a diagnosis of schizophrenia or bipolar-I disorder received the following treatments in a fixed sequential order, without washout between treatments: (i) paliperidone ER 6 mg tablet once daily for 7 days, and (ii) paliperidone ER 6 mg once daily concomitantly with carbamazepine 200 mg twice daily for the subsequent 21 days. Upon coadministration with carbamazepine, paliperidone steady-state total exposure (AUC24 h ) and peak plasma concentrations (Cmax ) decreased by approximately 37% [LSM ratio-AUC24 h : 63.4 (90% CI: 57.19; 70.29); Cmax : 62.47 (90% CI: 55.77; 69.98)]. This decrease is accounted for to a substantial degree by a 35% increase in renal clearance of paliperidone, likely as a result of induction of renal P-glycoprotein by carbamazepine. A 14% decrease in the amount of drug excreted unchanged in the urine suggests that carbamazepine coadministration has a limited effect on the intestinal absorption or cytochrome metabolism of paliperidone.

A randomized, placebo-controlled study to assess the efficacy and safety of 3 doses of paliperidone palmitate in adults with acutely exacerbated schizophrenia.

This study assessed the efficacy and the safety of a dosing regimen that was revised from earlier studies for the investigational injectable atypical antipsychotic paliperidone palmitate (approved in the USA, August 2009) for adult patients with acutely exacerbated schizophrenia. The patients (N = 652) were randomly assigned (1:1:1:1) to paliperidone palmitate at 25, 100, or 150 mg eq. or placebo in this 13-week double-blind study. The patients received an injection of paliperidone palmitate at 150 mg eq. or placebo in the deltoid muscle on day 1 and the assigned fixed dose or placebo in the deltoid or gluteal [corrected] on day 8 and then once monthly (days 36 and 64). No oral supplementation was used. Target plasma levels were achieved by day 8 in all paliperidone palmitate groups. The mean change in Positive and Negative Syndrome Scale total score from baseline to end point improved significantly (P < or = 0.034) in all the paliperidone palmitate dose-groups versus placebo. Paliperidone palmitate treatment with this revised dosing regimen led to the achievement of rapid and consistent therapeutically effective plasma levels that were maintained by once-monthly dosing in either the deltoid or gluteal muscle. Common treatment-emergent adverse events (> or =2% of patients in any of the treatment groups) that occurred more frequently in the total paliperidone palmitate group versus the placebo group (with > or =1% difference) were injection-site pain (7.6% vs 3.7%), dizziness (2.5% vs 1.2%), sedation (2.3% vs 0.6%), pain in the extremity (1.6% vs 0.0%), and myalgia (1.0% vs 0.0%). The paliperidone palmitate treatment was efficacious and generally tolerated across the dose range (25, 100, or 150 mg eq.) in adult patients with acutely exacerbated schizophrenia.

Risperidone long-acting injection: pharmacokinetics following administration in deltoid versus gluteal muscle in schizophrenic patients.

Long-acting injectable (LAI) risperidone for intramuscular injection into the gluteal muscle every 2 weeks is approved for schizophrenia. The deltoid muscle provides a more accessible injection site and could therefore facilitate patient acceptance of an injectable medication. Two studies in chronic schizophrenic subjects evaluated the pharmacokinetics and tolerability of LAI risperidone administered into the deltoid muscle. The pharmacokinetics following deltoid injection and bioequivalence between deltoid and gluteal administration were assessed in an open-label, single-dose, crossover, fully powered bioavailability study. Tolerability and safety of deltoid LAI risperidone were investigated in an open-label multiple-dose study in subjects who were previously being treated with gluteal injections of LAI risperidone. Patients received 4 sequential intramuscular injections of LAI risperidone, administered every 2 weeks into the deltoid muscle. Deltoid and gluteal injections of LAI risperidone were shown to be bioequivalent at equal doses with respect to peak and total plasma exposure and exhibited dose-proportional pharmacokinetics, independent of injection site. In addition, deltoid injection was safe and well tolerated. Injection of LAI risperidone into the deltoid muscle can be considered an alternative route of administration, because deltoid and gluteal injections are interchangeable in terms of drug exposure, with no additional safety or tolerability issues.

Safety and tolerability of deltoid and gluteal injections of paliperidone palmitate in schizophrenia.

Paliperidone palmitate is an investigational, injectable atypical antipsychotic. The safety and tolerability of initiating treatment with paliperidone palmitate via deltoid versus gluteal injections given once monthly, and of switching injection sites, in adults with stable schizophrenia were assessed. In this crossover trial, stable outpatients (N=252) were randomly assigned 1:1:1 to 3 dose groups (paliperidone palmitate 50, 75, or 100 mg eq.) and 2 treatment sequences (blinded to dose): deltoid muscle (period 1 [13 weeks]) followed by gluteal muscle (period 2 [12 weeks]) or the reverse. The intent-to-treat analysis set had 249 patients: mean age=43 (SD: 12.8) years; 57% men, 81% white, baseline mean Positive and Negative Syndrome Scale (PANSS) total score=56 (SD: 11.5). A total of 170 (68%) patients completed the study, with a similar proportion completing each treatment sequence. The incidence of systemic treatment-emergent adverse events (TEAEs) was similar between the 2 injection sites across doses during period 1 (deltoid [D]: 61% to 67%; gluteus [G]: 58% to 65%), and during the last 8 weeks of the 2 study periods (DG: 32% to 45% [period 1], 29% to 42% [period 2]; GD: 31% to 40% [period 1], 30% to 41% [period 2]). During the first treatment week, median plasma paliperidone concentrations were higher with treatment initiation in the deltoid muscle compared with the gluteal muscle. At apparent steady state, there was little difference in plasma paliperidone concentrations between the deltoid and gluteus sites for a given dose. Local tolerability was slightly better with gluteal injections. Patient preference for injection sites differed between geographical regions, e.g. patients from the US preferred deltoid to gluteal sites. The most common (>or=5% overall) TEAEs were: (period 1) insomnia, anxiety, headache, and agitation; and (period 2) insomnia, psychotic disorder, weight increased, and tachycardia. Paliperidone palmitate treatment was tolerated, irrespective of injection site, and thus could offer the choice of administration into either the deltoid or gluteal muscle to meet patient and physician preference.

CYP3A5 genotype has significant effect on quinine 3-hydroxylation in Tanzanians, who have lower total CYP3A activity than a Swedish population.

OBJECTIVES: To study the correlation between CYP3A5 genotype and quinine 3-hydroxylation in black Tanzanian and Swedish Caucasians as well as to investigate the interethnic differences in CYP3A activity between the two populations. METHODS: Tanzanian (n=144) and Swedish (n=136) healthy study participants were given a single oral 250 mg dose of quinine hydrochloride and a 16-h post-dose blood sample was collected. The metabolic ratio of quinine/3-hydroxyquinine was determined in plasma by high-performance liquid chromatography. All the participants were genotyped for the known mutations of CYP3A5, which are relevant for the respective population. Correlation between quinine metabolic ratio and CYP3A5 genotype as well as the interethnic difference in CYP3A activity between the two populations was studied. RESULTS: Tanzanians had significantly higher (P<0.0001) mean quinine metabolic ratio (9.5+/-3.5) than Swedes (7.6+/-3.1). As expected, the frequency of high CYP3A5 expression alleles was higher in Tanzanians (51%) than in Swedes (7%). The mean+/-SD quinine metabolic ratio (10.7+/-3.9) in Tanzanians homozygous for low CYP3A5 expression gene was significantly higher than the corresponding mean metabolic ratio in participants heterozygous (9.5+/-3.3; P=0.02) or homozygous (8.1+/-3.1; P=0.002) for high expression CYP3A5 alleles, respectively. A tendency to higher quinine metabolic ratio in Swedes with low expression alleles compared with those with one or two high expression alleles was observed. Tanzanians homozygous for low CYP3A5 expression gene (i.e. only CYP3A4 is expressed) had significantly (P<0.0001) higher quinine metabolic ratio (10.7+/-3.9) than corresponding Swedes (7.7+/-3.1). CONCLUSIONS: Clear interethnic differences were observed in the activity of CYP3A between Tanzanians and Swedes. A significant association is noted between CYP3A5 genotype and quinine 3-hydroxylation in Tanzanians, indicating a significant contribution of CYP3A5 to total 3A activity. The CYP3A4 catalyzed hydroxylation of quinine (two low CYP3A5 expression alleles) was lower in Tanzanians than in Swedes.

Urinary and fecal excretion of topotecan in patients with malignant solid tumours.

PURPOSE: The objectives of the study were to determine the pharmacokinetics and routes of excretion of topotecan following intravenous or oral administration to patients with refractory solid tumours. METHODS: Patients were randomized to receive either oral (2.3 mg/m(2)) or intravenous (1.5 mg/m(2)) topotecan once daily for 5 days in course 1. Patients who received in course 1 oral topotecan received in course 2 intravenous topotecan on day 1 followed by oral topotecan on days 2 to 5. Patients who received in course 1 intravenous topotecan received in course 2 oral topotecan once daily for 5 days. Plasma pharmacokinetics were performed on day 1 of course 1 (all patients) and course 2 (only patients receiving intravenous topotecan on that day). In course 1, urine and feces were collected for up to 9 days after the first dosage. The amounts of topotecan and N-desmethyl topotecan in plasma, urine and feces were determined by validated high-performance liquid chromatographic assays. RESULTS: A total of 11 patients were enrolled in the study. Nine patients were evaluable for pharmacokinetics. Plasma pharmacokinetics were similar to those previously reported. The principal route of excretion was the urine, with approximately 49% of the intravenously administered topotecan dose and 20% of the oral dose collected in the urine as parent drug. Approximately 18% and 33% of the intravenous and oral dose, respectively, were recovered unchanged in the feces. Only small amounts of N-desmethyl topotecan were found in the excreta. CONCLUSIONS: Fecal and urinary excretion of unchanged topotecan were the major routes of topotecan elimination. Approximately 28% of the intravenous dose and 43% of the oral dose of topotecan were unaccounted for and eliminated through other routes.

Topoisomerase I levels in white blood cells of patients with ovarian cancer treated with paclitaxel-cisplatin-topotecan in a phase I study.

Topotecan stabilizes the topoisomerase I (Topo I) cleavable complex. We measured Topo I levels in white blood cells of patients with ovarian cancer treated with topotecan. Topotecan was given i.v. daily x 5 q 3 weeks in combination with paclitaxel (1 day before topotecan) and cisplatin (just prior topotecan). Our aim was to correlate Topo I levels to pharmacokinetics and toxicity. Topo I levels were determined using Western blotting and were expressed relative to the Topo I level present in 10 microg cell lysate of the human IGROV1 ovarian cancer cell line. We found no correlation between Topo I levels and (non-)hematological toxicity. Topo I levels after the fifth topotecan infusion were significantly negatively correlated with the AUC of topotecan (R = -0.64, p = 0.026), in contrast with Topo I levels prior to (R = -0.25, p = 0.4) and after (R = -0.30, p = 0.3) the first topotecan infusion. Topo I levels after the fifth topotecan infusion (48 +/- 27%, mean +/- SD) were higher than Topo I levels prior to and after the first topotecan infusion (3.0 +/- 4.7 and 2.7 +/- 3.6%, respectively) (p = 0.001). In conclusion, we detected a significant inverse correlation between Topo I level and topotecan AUC at day 5, and we found increasing Topo I levels during a daily x 5 schedule of treatment with topotecan.