Population pharmacokinetics of raltitrexed in patients with advanced solid tumours

AIMS: To investigate the population pharmacokinetics of raltitrexed in patients with advanced solid tumours and to identify patient covariates contributing to the interpatient variability in the pharmacokinetics of raltitrexed. METHODS: Patient covariate and concentration-time data were collected from patients receiving 0.1-4.5 mg m(-2) raltitrexed during the early clinical trials of raltitrexed. Data were fitted using nonlinear mixed effects modelling to generate population mean estimates for clearance (CL) and central volume of distribution (V). The relationship between individual estimates of the pharmacokinetic parameters and patient covariates was examined and the influence of significant covariates on the population parameter estimates and their variance was investigated using stepwise multiple linear regression. The performance of the developed model was tested using an independent validation dataset. All patient data were pooled in the total cohort to refine the population pharmacokinetic model for raltitrexed. RESULTS: three-compartment pharmacokinetic model was used to fit the concentration-time data of raltitrexed. Estimated creatinine clearance (CL(CR)) was found to influence significantly the CL of raltitrexed and explained 35% of variability in this parameter, whilst body weight (WT) and serum albumin concentrations (ALB) accounted for 56% of the variability in V. Satisfactory prediction (mean prediction error 0.17 micro g l(-1) and root mean square prediction error 4.99 micro g l(-1)) of the observed raltitrexed concentrations was obtained in the model validation step. The final population mean estimates were 2.17 l h(-1)[95% confidence interval (CI) 2.06, 2.28] and 6.36 l (95% CI 6.02, 6.70) for CL and V, respectively. Interpatient variability in the pharmacokinetic parameters was reduced (CL 28%, V 25%) when influential covariates were included in the final model. The following covariate relationships with raltitrexed parameters were described by the final population model: CL (l h(-1)) = 0.54 + 0.02 CL(CR) (ml min(-1)) and V (l) = 6.64 + 0.08 WT (kg) - 0.16 ALB (g l(-1)). CONCLUSIONS: A population pharmacokinetic model has been developed for raltitrexed in patients with advanced cancer. Pharmacokinetic parameters of raltitrexed are markedly influenced by the patient's renal function, body weight and serum albumin levels, which may be taken into account in dose individualization. The use of influential covariates to guide anticancer dosage selection may result in less variability in drug exposure and potentially a better clinical outcome.     

Pharmacodynamics and pharmacokinetics of oral topotecan in patients with advanced solid tumours and impaired renal function

Aims

The aim of the study was to determine the effect of renal impairment and prior platinum-based chemotherapy on the toxicity and pharmacokinetics of oral topotecan and to identify recommended doses for patients with renal impairment or prior platinum-based (PB) chemotherapy.

Methods

A multicentre phase I toxicity and pharmacokinetic study of oral topotecan was conducted in patients with advanced solid tumours. Patients were grouped by normal renal function with limited or prior PB chemotherapy or impaired renal function (mild [creatinine clearance (CL_cr) = 50–79 ml min⁻¹], moderate [CL_cr = 30–49 ml min⁻¹], severe [CL_cr <30 ml min⁻¹]).

Results

Fifty-nine patients were evaluable. Topotecan lactone and total topotecan area under the concentration–time curve (AUC) was significantly increased in patients with moderate and severe renal impairment (109% and 174%, respectively, topotecan lactone and 148% and 298%, respectively, total topotecan). Asian patients (23 in total) had higher AUCs than non-Asian patients with the same degree of renal impairment. Thirteen dose-limiting toxicities (DLTs) were observed, which were mostly haematological. The maximum tolerated dose (MTD) was 2.3 mg m⁻² day⁻¹, given on days 1 to 5 in a 21 day cycle, for patients with prior PB chemotherapy or mild renal impairment, and 1.2 mg m⁻² day⁻¹ for patients with moderate renal impairment (suggested dose 1.9 mg m⁻² day⁻¹ for non-Asians). Due to incomplete enrolment of patients with severe renal impairment, the MTD was determined as ≥ 0.6 mg m⁻² day⁻¹ in this cohort.

Conclusions

Oral topotecan dose adjustments are not required in patients with prior PB chemotherapy or mildly impaired renal function, but reduced doses are required for patients with moderate or severe renal impairment.     

The pharmacokinetics and pharmacodynamics of denosumab in patients with advanced solid tumours and bone metastases: a systematic review

Aim

The objective of this systematic review was to characterize the pharmacokinetics and pharmacodynamics of denosumab (XGEVA®), a fully human IgG2 monoclonal antibody which binds to receptor activator of nuclear factor kappa-B ligand (RANKL), for the treatment of skeletal-related events (SREs) in patients with advanced cancer and bone metastases.

Methods

A total of 708 patients (116 healthy patients and 592 patients with solid tumours or multiple myeloma and bone metastases) included in seven clinical studies were evaluated for denosumab pharmacokinetics. Denosumab was administered as a single subcutaneous (s.c.) dose or multiple s.c. doses, ranging from 0.1 to 3.0 mg kg⁻¹ or 30 mg to 180 mg fixed dosing, every 1 or 3 months for up to 45 months.

Results

Consistent with the results in healthy adults, single s.c. doses of denosumab demonstrated dose-dependent, non-linear pharmacokinetics in advanced cancer patients with bone metastases across a wide dose range (0.1–3.0 mg kg⁻¹). Reductions in levels of the bone turnover marker, uNTx/Cr, were observed within 1 day. The duration of reductions generally increased with dose and dosing frequency. In patients with solid tumours and bone metastases, pharmacokinetics and pharmacodynamic comparisons across tumour types and concomitant cancer therapies (chemotherapies and/or hormone therapies) suggest that neither tumour type nor type of concomitant therapy markedly affects denosumab pharmacokinetics or pharmacodynamics.

Conclusions

Denosumab displayed non-linear pharmacokinetics at doses below 60 mg but at higher doses, denosumab exposure increased approximately dose-proportionally in advanced cancer patients with bone metastases. Following a 120 mg, every 4 weeks dosing schedule, similar denosumab pharmacokinetics and pharmacodynamics were observed across tumour types and were independent of concomitant cancer therapies.     

Effect of high-fat, high-protein, and high-carbohydrate meals on the pharmacokinetics of a small dose of ethanol

Aims To investigate whether the relative amounts of fat, carbohydrate (CHO), or protein in a meal influence the pharmacokinetics of a small dose of ethanol. Methods Nine healthy men received ethanol (0.30 g kg⁻¹ body weight) on five occasions in a randomized cross-over fashion. On three occasions the dose of ethanol was consumed within 15 min of eating a standardized breakfast of similar volume and calorific value but containing different amounts of fat, CHO, and protein. On two other occasions the same dose of ethanol was ingested on an empty stomach (overnight fast) or administered by intravenous (i.v.) infusion over 30 min. Results The blood-ethanol profiles showed large inter and intraindividual variations, especially when ethanol was ingested after eating food. The peak blood-alcohol concentrations (BAC) were 16.6±4.0, 17.7±7.1, and 13.3±4.0 mg dl⁻¹ (mean±s.d.) after fat, CHO, and protein-rich meals and 30.8±4.3 and 54.3±6.4 mg dl⁻¹ after fasting and i.v. infusion, respectively. The corresponding areas under the concentration-time profiles (AUC) were 1767±549, 1619±760, 1270±406 mg dl⁻¹ min after fat, CHO, and protein-rich meals compared with 3210±527 and 4786±446 mg dl⁻¹ min after fasting and i.v. infusion, respectively. The time required to eliminate ethanol from the blood was shortened by 1–2 h in the fed-state. Conclusions Drinking ethanol after eating a meal, regardless of the nutritional composition, decreases the systemic availability of ethanol. Because gastric emptying is slow and more prolonged with food in the stomach, the delivery of ethanol to the duodenum and the liver will be highly variable as will the hepatic clearance of ethanol. Provided that portal venous BAC remains fairly low and ethanol metabolizing enzymes are not fully saturated then part of the dose of ethanol can be cleared by hepatic first-pass metabolism (FPM), as one consequence of Michaelis-Menten elimination kinetics.     

Population pharmacokinetics of PEGylated liposomal CPT-11 (IHL-305) in patients with advanced solid tumors

Purpose

To investigate pharmacokinetics (PK) of encapsulated CPT-11, released CPT-11 and the active metabolite SN-38 following administration of IHL-305 and to identify factors that may influence IHL-305 PK.

Methods

Plasma samples from 39 patients with solid tumors were collected in a phase I study. IHL-305 was administered as a 1 h IV infusion with doses ranging from 3.5 to 210 mg/m². Plasma concentrations of encapsulated CPT-11, released CPT-11 and SN-38 were used to develop a population PK model using NONMEM®.

Results

PK of encapsulated CPT-11 was described by 1-compartment model with nonlinear clearance and PK of released CPT-11 was described by a 1-compartment model with linear clearance for all patients. PK of the active metabolite SN-38 was described by a 2-compartment model with linear clearance for all patients. Covariate analysis revealed that gender was a significant covariate for volume of distribution of encapsulated CPT-11. V_encap in male patients is 1.5-fold higher compared with female patients.

Conclusions

The developed population PK modeling approach is useful to predict PK exposures of encapsulated and released drug and can be applied to the more than 300 other nanoparticle formulations of anticancer agents that are currently in development. The effect of gender on PK of IHL-305 needs to be further evaluated.     

Effects of steady-state bupropion on the pharmacokinetics of lamotrigine in healthy subjects

STUDY OBJECTIVE: To evaluate the effect of steady-state bupropion SR sustained-release (BUP) on the pharmacokinetics of a single 100-mg dose of lamotrigine (LTG). DESIGN: Randomized, open-label, two-way crossover study SETTING: Clinical Studies Ltd., Fort Lauderdale, Florida. PATIENTS: Twelve healthy subjects. INTERVENTION: Treatment A: LTG 100 mg with steady-state BUP 150 mg twice/day; treatment B: LTG 100 mg. MEASUREMENTS AND MAIN RESULTS: The pharmacokinetics of LTG were determined by noncompartmental methods using plasma and urine concentrations. Geometric least squares mean ratios and 90% confidence intervals were calculated for treatment comparison. Safety assessments included clinical laboratory tests, vital signs, and adverse events monitoring. Pharmacokinetic parameters of LTG were not significantly different between treatments. Five subjects experienced seven mild, potentially drug-related adverse events (insomnia [2]; nausea, headache, facial pain, fatigue, and depression [1 each]) that resolved spontaneously. CONCLUSION: Steady-state BUP caused no clinically relevant changes in the pharmacokinetics of a single dose of LTG.     

Early clinical investigaiton of sulofenur with a daily schedule in advanced solid tumours

Sulofenur, a sulfonylurea, has demonstrated antitumour effect in preclinical studies. A phase I trial was initiated to study the clinical aspects.Sulofenur was given p.o. daily for a period of 28 days in 5-week courses. The initial dosage was 250 mg/m² escalating to 700 mg/m² daily with no dose modification for the individual patient at any given dose level; 38 patients with advanced solid malignant tumours were enrolled.Haemolytic anaemia was the main side effect. The toxicity was marked at dose levels of 600 and 700 mg/m². Moderate methaemoglobinaemia also occurred. One case of reversible toxic hepatitis was observed. Generally was ALAT, and more moderately basic phosphatases, and LDH elevated.Tumour regression was not observed but one patient had stable disease throughout nine courses. The maximal detected plasma concentration of Sulofenur in this study was 348 × 10^-6g/ml.In the present study the maximum tolerated dose (MTD) of Sulofenur was defined to 600 mg/m². One conclusion from this study is that even at doses above that recommended for future studies – 5-600 mg/m² – with this schedule, the suggested effective plasma level from pre-clinical studies could not be reached. The overall conclusion is that this schedule should not be recommended at all for future studies and the recommendation should be to try to find a schedule in which higher plasma levels can be achieved at a clinically tolerated dose.     

Population pharmacokinetic analysis of sorafenib in patients with solid tumours

AIMS

To characterize the pharmacokinetics (PK) of sorafenib in patients with solid tumours and to evaluate the possible effects of demographic, clinical and pharmacogenetic (CYP3A4*1B, CYP3A5*3C, UGT1A9*3 and UGT1A9*5) covariates on the disposition of sorafenib.

METHODS

PK were assessed in 111 patients enrolled in five phase I and II clinical trials, where sorafenib 200 or 400 mg was administered twice daily as a single agent or in combination therapy. All patients were genotyped for polymorphisms in metabolic enzymes for sorafenib. Population PK analysis was performed by using nonlinear mixed effects modelling (NONMEM). The final model was validated using visual predictive checks and nonparametric bootstrap analysis.

RESULTS

A one compartment model with four transit absorption compartments and enterohepatic circulation (EHC) adequately described sorafenib disposition. Baseline bodyweight was a statistically significant covariate for distributional volume, accounting for 4% of inter-individual variability (IIV). PK model parameter estimates (range) for an 80 kg patient were clearance 8.13 l h⁻¹ (3.6–22.3 l h⁻¹), volume 213 l (50–1000 l), mean absorption transit time 1.98 h (0.5–13 h), fraction undergoing EHC 50% and average time to gall bladder emptying 6.13 h.

CONCLUSIONS

Overall, population PK analysis was consistent with known biopharmaceutical/PK characteristics of oral sorafenib. No clinically important PK covariates were identified.     

Safety and pharmacokinetics of sorafenib combined with capecitabine in patients with advanced solid tumors: results of a phase 1 trial

Sorafenib (twice daily [bid]) plus capecitabine (2 weeks on schedule/1 week off schedule) safety and pharmacokinetics were investigated in patients with advanced solid tumors (N = 35). Cohort 1 (n = 13) included sorafenib 200 mg bid and capecitabine 1050 mg/m(2) bid; cohort 2 (n = 4), sorafenib 400 mg bid and capecitabine 1050 mg/m(2) bid; cohort 3 (n = 6), sorafenib 200 mg bid and capecitabine 1050 mg/m(2) bid (cycles 1 and 2), then 400 mg bid and capecitabine 1050 mg/m(2) bid (cycle 3 onwards); and cohort 4 (n = 12), sorafenib 400 mg bid and capecitabine 850 mg/m(2) bid. The combination of sorafenib and capecitabine was generally well tolerated. Most frequent drug-related adverse events were hand-foot skin reaction (HFSR, 89%), diarrhea (71%), and fatigue (69%). The HFSR was dose-limiting toxicities in 6 patients. Sorafenib exposure (C(max) and AUC(0-12)) was unaffected by concomitant capecitabine. Concomitant sorafenib moderately increased capecitabine and 5-fluorouracil (metabolite) exposure when the capecitabine dose was 1050 mg/m(2) bid. Simultaneous administration of 400 mg bid sorafenib and 850 mg/m(2) bid capecitabine, however, had only minor effects on the exposure to capecitabine and 5-fluorouracil. Based on the overall toxicity profile and pharmacokinetic parameters, the recommended phase 2 doses were therefore sorafenib 400 mg bid and capecitabine 850 mg/m(2) bid, as scheduled above.     

Pathway-based pharmacogenomics of gemcitabine pharmacokinetics in patients with solid tumors

Aim: The aim of this study was to evaluate the association of gemcitabine pathway SNPs with detailed pharmacokinetic measures obtained from solid tumor patients receiving gemcitabine-based therapy. Materials & methods: SNPs within nine gemcitabine pathway genes, namely CDA, CMPK, DCK, DCTD, NT5C2, NT5C3, SLC28A1, SLC28A3 and SLC29A1 were analyzed for association with gemcitabine pharmacokinetics. Results: Significant association of gemcitabine clearance with SNPs in NT5C2 was identified. Clearance of 2′,2′-difluorodeoxyuridine, a gemcitabine metabolite was significantly predicted by CDA, SLC29A1 and NT5C2 SNPs. This study reports an association of formation clearance of 2′,2′-difluoro-2′-deoxycytidine triphosphate, an active form of gemcitabine with SNPs within uptake transporters SLC28A1, SLC28A3 and SLC29A1. Conclusion: Genetic variation in gemcitabine pathway genes is associated with its pharmacokinetics and hence could influence gemcitabine response. Our study identified pharmacogenetic markers that could be further tested in larger patient cohorts and could open up opportunities to individualize therapy in solid tumor patients. Original submitted 10 February 2012; Revision submitted 27 April 2012.     

A phase I study of temsirolimus and metformin in advanced solid tumours

The purpose of this phase I trial was to establish the maximum tolerated dose and define the dose-limiting toxicities of a combination of temsirolimus and metformin. Patients with advanced solid tumours who had exhausted standard treatment options were eligible. Treatment included weekly intravenous temsirolimus and daily oral metformin. Eleven patients were enrolled. Dose-limiting toxicities were observed in all patients at the initial dose level of 25 mg weekly of temsirolimus and metformin 500 mg po BID. At dose level -1, 2 of 8 patients experienced dose-limiting toxicities. Toxicities included grade 4 pneumonitis, persistent grade 3 fatigue, and thrombocytopenia requiring dose delays. The maximum tolerated dose (level -1) was 20 mg temsirolimus weekly and 500 mg po daily of metformin. One patient with head and neck cancer experienced a partial response. Five patients had stable disease including a patient with melanoma who had stable disease for 22 months.     

Population pharmacokinetics of weekly docetaxel in patients with advanced cancer

AIMS: Previous pharmacokinetic studies of the 3-weekly regimen (100 mg m(-2) every 3 weeks) of docetaxel have shown that docetaxel clearance is affected by liver function, body surface area, age, serum alpha1-acid glycoprotein and cytochrome P450 3A4 (CYP3A4) activity. However, the pharmacokinetics of a weekly docetaxel (40 mg m(-2) week(-1)) schedule are not well characterized. The aims of this study were (a) to investigate the pharmacokinetics of docetaxel (40 mg m(-2) week(-1)) using sparse concentration-time data collected from patients with advanced cancer and (b) to utilize a population pharmacokinetic approach to identify patient covariates that significantly influence the clearance of docetaxel when administered according to this regimen. METHODS: A two-compartment pharmacokinetic model was used to describe the docetaxel concentration-time data from 54 patients with advanced cancer. The mean population and individual posterior Bayesian estimates of docetaxel clearance were estimated using P-PHARM. The relationships between docetaxel clearance and 21 covariates were investigated. This included estimates of CYP3A4 function in each patient using the erythromycin breath test (1/tmax). Significant covariates were included into the final population pharmacokinetic model. Pharmacokinetic models were validated using a data splitting approach with a dataset consisting of 16 patients. RESULTS: Significant relationships were found between docetaxel clearance and 1/tmax (erythromycin breath test parameter) and several of the liver function enzymes and CL was best described by the equation; CL = 21.51 + 217 (1/tmax) - 0.13 (ALT). This final population pharmacokinetic model provided both precise and unbiased predictions of docetaxel concentrations in a validation group of patients and an estimate of the population mean (95% confidence interval) clearance of docetaxel was 30.13 l h(-1) (12.54, 46.04 l h(-1)) with an intersubject variability 30%. CONCLUSIONS: A population pharmacokinetic model has been developed and validated for weekly docetaxel (40 mg m(-2)) in patients with advanced cancer. These results indicate that CYP3A4 activity and hepatic function have an impact on the pharmacokinetics of docetaxel when administered weekly.     

Effect of Nigerian meals on the pharmacokinetics of chlorpropamide in type II diabetic patients

Food-drug interactions are best evaluated on an individual drug basis, in a group of subjects in a population at risk. This is due to their complex nature, which is a function of type and size of meal, the physical and chemical form of the drug and the time lapse between food intake and drug administration. This work was aimed at investigating the effect of three different Nigerian meals, which are regularly consumed by the three major tribes in Nigeria, on the pharmacokinetics of chlorpropamide, a drug commonly used to treat Type II diabetes in this country. Meal A (maize flour meal) was composed of 81% carbohydrate, 3% protein and 11% fat; meal B (cassava flour meal) was composed of 76% carbohydrate, 3% protein and 15% fat; while meal C (browned yam flour meal) was composed of 85% carbohydrate, 2% protein and 8% fat. The effects of the three meals were investigated by administering each of the meals alone, without the medicinal drug (Treatment I); in Treatment II each meal was administered 30 min following the administration of 250 mg chlorpropamide; in Treatment III the drug was administered together with each of the standard meals. Analysis of the plasma levels of chlorpropamide was performed by high performance liquid chromatography (HPLC). Ingestion of the meal alone (Treatment I) resulted in a significant difference in postprandial plasma glucose levels. The time to maximum plasma chlorpropamide concentration was significantly increased in Treatment III (P < 0.05), while all pharmacokinetic parameters and plasma glucose levels were not significantly altered in Treatment II. Analysis of the results demonstrated a better glycaemic response with meals A and C compared with meal B.