Metabolic Disposition of Osimertinib in Rats, Dogs, and Humans: Insights into a Drug Designed to Bind Covalently to a Cysteine Residue of Epidermal Growth Factor Receptor.

Preclinical and clinical studies were conducted to determine the metabolism and pharmacokinetics of osimertinib and key metabolites AZ5104 and AZ7550. Osimertinib was designed to covalently bind to epidermal growth factor receptors, allowing it to achieve nanomolar cellular potency (Finlay et al., 2014). Covalent binding was observed in incubations of radiolabeled osimertinib with human and rat hepatocytes, human and rat plasma, and human serum albumin. Osimertinib, AZ5104, and AZ7550 were predominantly metabolized by CYP3A. Seven metabolites were detected in human hepatocytes, also observed in rat or dog hepatocytes at similar or higher levels. After oral administration of radiolabeled osimertinib to rats, drug-related material was widely distributed, with the highest radioactivity concentrations measured at 6 hours postdose in most tissues; radioactivity was detectable in 42% of tissues 60 days postdose. Concentrations of [(14)C]-radioactivity in blood were lower than in most tissues. After the administration of a single oral dose of 20 mg of radiolabeled osimertinib to healthy male volunteers, ∼19% of the dose was recovered by 3 days postdose. At 84 days postdose, mean total radioactivity recovery was 14.2% and 67.8% of the dose in urine and feces. The most abundant metabolite identified in feces was AZ5104 (∼6% of dose). Osimertinib accounted for ∼1% of total radioactivity in the plasma of non-small cell lung cancer patients after 22 days of 80-mg osimertinib once-daily treatment; the most abundant circulatory metabolites were AZ7550 and AZ5104 (<10% of total osimertinib-related material). Osimertinib is extensively distributed and metabolized in humans and is eliminated primarily via the fecal route.

The relative bioavailability of gefitinib administered by granular formulation.

BACKGROUND: Gefitinib (IRESSA) is normally administered as a once-daily oral tablet. However, many patients with head and neck cancer have difficulty swallowing medication in a tablet form. A granular formulation has recently been developed to facilitate the administration of gefitinib to patients who are unable to swallow tablets. OBJECTIVES: The aims of this study were to determine the relative bioavailability of a single dose of gefitinib when administered as 250 mg of a new granular formulation compared with the standard 250 mg tablet, and to assess the intra-subject variability of the granular formulation, in healthy subjects. METHODS: This was a randomized, open-label, three-period crossover study. Healthy male subjects (n = 18) received either a single gefitinib 250 mg tablet (once), or a 250 mg granular formulation of gefitinib (on two separate occasions) over the three dosing periods, in randomized order. Plasma concentrations of gefitinib were measured up to 240 h post-dose. RESULTS: The treatment ratio estimates for area under the plasma concentration versus time curve (AUC) and peak plasma concentration (C (max)) for the granular formulation when compared with the tablet were 1.05 (90% confidence intervals [CI] for the ratio 0.97-1.13) and 1.14 (90% CI for the ratio 1.01-1.28), respectively. The estimate for the intra-subject standard deviation for the granular formulation when given on 2 separate occasions was 0.143 for AUC and 0.165 for C (max), equivalent to a 1.4- and 1.7-fold intra-subject variability in AUC and C (max), compared with that observed for the tablet of two and threefold, respectively. CONCLUSIONS: There was little difference in exposure to gefitinib administered as the 250 mg granular formulation compared with the 250 mg standard tablet. The granular formulation of gefitinib could provide an alternative treatment regimen for patients unable or unwilling to swallow the standard tablet formulation, without compromizing exposure to gefitinib.

Pharmacokinetics of gefitinib in humans: the influence of gastrointestinal factors.

PURPOSE: To investigate whether differences in plasma pharmacokinetic profiles of gefitinib between healthy subjects having normal (N; t(1/2)>20h) and altered (A; t(1/2)<20h) pharmacokinetic (PK) profiles might be explained by inter-individual variability in gastric emptying and/or precipitation/dissolution of gefitinib in the proximal small intestine. METHODS: One hundred healthy male subjects were screened to enable identification of subjects with the two PK profiles. Twenty five subjects from the screening were subsequently enrolled in an intubation study where a 250mg gefitinib dispersion preparation (IRESSA AstraZeneca) was administered directly into the stomach. Intestinal fluid samples were withdrawn continuously for 180min post-dose using the Loc-I-Gut catheter positioned in the jejunum. The crystalline form of gefitinib was determined using Raman microscopy. RESULTS: There were no differences between normal and altered subjects with regard to gastric emptying or the precipitation/dissolution of gefitinib in jejunal fluid. Due to difficulties in crystalline identification in the jejunal fluid samples, only the same crystalline form as the dosed form was identified. CONCLUSIONS: There was no pronounced difference in gastric emptying, precipitation and re-dissolution of gefitinib in proximal human jejunum between normal and altered subjects. Other mechanism(s) are also likely to be important in explaining the inter-individual differences in plasma exposure to gefitinib, such as polymorphism in various metabolic enzymes and/or transport proteins. However, the difference between altered and normal subjects cannot be easily explained and it is likely a multifactorial explanation including low jejunal pH, increased expression of enzymatic and transporter activity and rapid small intestine transit.

Exploring the relationship between expression of cytochrome P450 enzymes and gefitinib pharmacokinetics.

BACKGROUND AND OBJECTIVES: Exposure to gefitinib (IRESSA, ZD1839), an epidermal growth factor receptor-tyrosine kinase inhibitor, is highly variable between subjects. In an attempt to explain this variability, three pharmacokinetic studies were carried out in healthy volunteers to investigate the relationship between exposure to gefitinib and cytochrome P450 (CYP) 3A phenotype (study 1), CYP3A5 genotype (study 2) and CYP2D6 genotype (study 3). METHODS: In study 1 all 15 healthy volunteers received single oral doses of midazolam (7.5 mg), as a CYP3A probe, and gefitinib (500 mg), separated by an appropriate washout period. Plasma concentrations of midazolam and gefitinib were measured. In study 2, 73 healthy volunteers with previously defined single-dose gefitinib pharmacokinetic profiles were genotyped for CYP3A5. In study 3 a single oral dose of gefitinib (250 mg) was administered to poor and extensive CYP2D6 metabolisers (n = 15 in each group). Plasma concentrations of gefitinib and its major metabolite, M523595, were measured. Plasma concentrations of gefitinib, M523595 and midazolam were measured using high-performance liquid chromatography with tandem mass spectrometric detection, and appropriate pharmacokinetic parameters were determined by non-compartmental methods. Genetic analysis of CYP3A5 (study 2) and CYP2D6 (study 3) alleles was carried out using standard methodology. RESULTS: In study 1 there was some indication of a correlation between the area under the plasma concentration-time curve from time zero to infinity (AUCinfinity) values of midazolam and gefitinib, although this did not reach statistical significance (p = 0.062, regression analysis). In study 2 eight of 73 volunteers (11%) were identified as CYP3A5 expressers. No apparent relationship was observed between the occurrence of the CYP3A5 expresser genotype and gefitinib plasma clearance or terminal elimination halflife. In study 3 M523595 was not detected in any plasma samples collected from poor CYP2D6 metabolisers. Gefitinib geometric mean AUCinfinity and peak plasma drug concentration were higher in poor CYP2D6 metabolisers compared with extensive metabolisers (AUCinfinity 3060 vs 1430 ng . h/mL, p < 0.05, ANOVA), although the range of values was wide with considerable overlap between the groups. Gefitinib was well tolerated in both groups. CONCLUSIONS: Individual differences in CYP3A expression do not explain all the interindividual variability in gefitinib exposure. There is no apparent relationship between CYP3A5 genotype and gefitinib clearance. The lack of measurable levels of M523595 in poor CYP2D6 metabolisers confirms that production of this metabolite is mediated by CYP2D6. Although higher exposure to gefitinib occurs in individuals who are poor CYP2D6 metabolisers, genotyping prior to initiation of therapy and dosage adjustment are not warranted.

A phase I study to determine the effect of tamoxifen on the pharmacokinetics of a single 250 mg oral dose of gefitinib (IRESSA) in healthy male volunteers.

OBJECTIVES: To determine the effect of tamoxifen on the pharmacokinetics of a single 250 mg oral dose of gefitinib (IRESSA) in healthy volunteers. METHODS: An open-label, single-center, phase I study in healthy male volunteers. Each volunteer received a single 250 mg oral dose of gefitinib on day 1. On days 11-14, oral loading doses of 60 mg tamoxifen were administered, followed by 20 mg tamoxifen for a further 16 days to maintain steady-state exposure. On day 24, volunteers received a second single 250 mg oral dose of gefitinib. The last dose of tamoxifen was given on day 30. Pharmacokinetic and safety assessments were conducted throughout the trial. RESULTS: A total of 18 volunteers were recruited. The presence of tamoxifen did not have a clinically significant effect on the primary variables AUC and Cmax of gefitinib, nor on the secondary variables AUC(0-t), tmax, t1/2, and lambdaz. The geometric least square mean values for AUC were 3,407.6 versus 3,397.9 ng.h/ml in the absence and presence of tamoxifen, respectively (90% CL 0.894, 1.112) and for Cmax were 110.8 versus 103.6 ng/ml, respectively (90% CL 0.786, 1.111). The combination of gefitinib with tamoxifen was generally well tolerated by the volunteers. There were no serious adverse events and no volunteer discontinued the study due to an adverse event. NCI-CTC grade 1/2 drug-related adverse events were observed in seven volunteers, including loose stools and skin events associated with gefitinib, and lethargy and headache, flushing, and dizziness associated with tamoxifen. CONCLUSIONS: This study suggests that tamoxifen has no significant effect on the pharmacokinetics, tolerability, or safety of a single 250 mg oral dose of gefitinib. Therefore, in clinical investigations of this combination, no dose adjustment of gefitinib is indicated.

Effect of itraconazole on the pharmacokinetics of rosuvastatin.

BACKGROUND: Rosuvastatin is a new 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor. Itraconazole, an inhibitor of cytochrome P450 (CYP) 3A4 and the transport protein P-glycoprotein, is known to interact with other HMG-CoA reductase inhibitors. The current trials aimed to examine in vivo the effect of itraconazole on the pharmacokinetics of rosuvastatin. METHODS: Two randomized, double-blind, placebo-controlled, 2-way crossover trials were performed. Healthy male volunteers (trial A, n = 12; trial B, n = 14) received itraconazole, 200 mg, or placebo once daily for 5 days; on day 4, 10 mg (trial A) or 80 mg (trial B) of rosuvastatin was coadministered. Plasma concentrations of rosuvastatin, rosuvastatin-lactone (trial A only), and active and total HMG-CoA reductase inhibitors were measured up to 96 hours after dosing. RESULTS: After coadministration with itraconazole, the rosuvastatin geometric least-square mean for the treatment ratio was increased by 39% for AUC(0-ct) (area under the rosuvastatin plasma concentration-time curve from time 0 to the last common time at which quantifiable concentrations were obtained for both treatments within a volunteer in trial A) and by 28% for AUC(0-t) (area under the rosuvastatin plasma concentration-time curve from time 0 to the time of the last quantifiable concentration in trial B), with the treatment ratio for maximum observed plasma drug concentration increased by 36% in trial A and 15% in trial B compared with placebo. For trial A (but not for trial B), the upper boundary of the 90% confidence interval for the treatment ratios fell outside the preset limits (0.7-1.43). The 95% confidence intervals for all treatment ratios (except maximum observed plasma drug concentration in trial B) did not include 1. These results indicate that itraconazole produces a modest increase in plasma concentrations of rosuvastatin. Rosuvastatin accounted for the majority of the circulating active HMG-CoA reductase inhibitors (> or =87%) and most of the total inhibitors (> or =75%). CONCLUSIONS: Itraconazole produced modest increases in rosuvastatin plasma concentrations, which are unlikely to be of clinical relevance. The results support previous in vitro metabolism findings that CYP3A4 plays a minor role in the limited metabolism of rosuvastatin.

Relative bioavailability and safety profile of gefitinib administered as a tablet or as a dispersion preparation via drink or nasogastric tube: results of a randomized, open-label, three-period crossover study in healthy volunteers.

BACKGROUND: Many patients with head and neck cancer have difficulty swallowing tablet formulations of medications, and use of dispersion preparations may be advantageous. OBJECTIVE: The aim of the present study was to determine the relative bioavailability and safety profile of a single dose of gefitinib, an orally active inhibitor of epidermal growth factor receptor tyrosine kinase, when administered as a whole 250-mg tablet or as a dispersion preparation via drink or nasogastric tube in healthy male volunteers. METHODS: This was a Phase 1, randomized, open-label, 3-period crossover study. Plasma samples obtained before dosing to 240 hours after dosing were analyzed for gefitinib using reverse-phase high-performance liquid chromatography with tandem mass-spectrometric detection. The pharmacokinetic parameters of interest included AUC, C(max), and the relative bioavailability of the dispersion via drink or nasogastric tube compared with the standard tablet. RESULTS: Eighteen healthy white male volunteers were enrolled. They had a mean age of 43 years (range, 21-59 years), mean body weight of 85.1 kg (range, 60-101 kg), and mean height of 180.3 cm (range, 171-187 cm). The geometric mean AUC was 2219 ng.h/mL for a single 250-mg dose of gefitinib administered as a whole tablet, 2233 ng.h/mL for the dispersion preparation administered by drink, and 2007 ng.h/mL for the dispersion preparation administered by nasogastric tube. The corresponding values for the geometric mean C(max) were 95.2, 96.3, and 89.9 ng/mL. The gefitinib dispersion preparation administered by drink had a mean bioavailability of 103.8% relative to the whole tablet; the dispersion preparation administered by nasogastric tube had a mean bioavailability of 99.1% relative to the whole tablet. For the drink-tablet and nasogastric tube-tablet comparisons, the estimate-of-treatment ratios for the AUC were a respective 1.006 and 0.928; for the C(max), they were 1.012 and 0.964. There appeared to be no clinically significant differences in absorption or elimination between the preparations. Three volunteers experienced adverse events (AEs) that were considered possibly related to gefitinib (pruritus and dry skin), and 6 volunteers experienced procedure-related AEs (cannula-site reaction and rhinorrhea); these AEs were mild or moderate. No serious AEs were recorded, and no AEs led to withdrawal of any volunteer. CONCLUSIONS: Administration of a 250-mg dose of gefitinib as a dispersion preparation by drink or nasogastric tube achieved a systemic exposure to gefitinib that was consistent with that achieved when gefitinib was administered as a whole tablet. There was no evidence of tolerability problems associated with the routes of administration studied in these healthy volunteers.

A double-blind, randomized, incomplete crossover trial to assess the dose proportionality of rosuvastatin in healthy volunteers.

BACKGROUND: Rosuvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, has been developed for the treatment of patients with dyslipidemia. OBJECTIVE: This study assessed the dose proportionality and pharmacokinetics of single oral doses of rosuvastatin in healthy volunteers. METHODS: This was a double-blind, randomized, incomplete crossover trial consisting of 3 trial days separated by >/=7-day washout periods. Healthy men were allocated to 1 of 2 treatment regimens: rosuvastatin 10, 20, and 80 mg, or rosuvastatin 10, 40, and 80 mg, administered as single doses on separate trial days in random order. Pharmacokinetic and tolerability assessments were made up to 96 hours after administration. Dose proportionality was tested using the power-law approach. RESULTS: Eighteen healthy white men participated in the trial (mean age, 41.2 years; mean height, 178.4 cm; mean body weight, 81.6 kg). Geometric mean rosuvastatin maximum plasma concentration (C(max)) values of 3.75, 6.79, 10.3, and 30.1 ng/mL were achieved at a median time to C(max) of 5.0 hours after doses of 10, 20, 40, and 80 mg, respectively. The corresponding geometric mean values for rosuvastatin area under the plasma concentration-time curve from time 0 to time of the last measurable concentration (AUC(0-t)) were 31.6, 56.8, 98.2, and 268 ng.h/mL. C(max) and AUC(0-t) were both linearly related to dose. The estimates of the proportionality coefficient (90% CI) for CmaX and AUC(o-t) were 0.999 (0.898-1.099) and 1.024 (0.941-1.107), respectively; all values fell within the prespecified range of 0.847 to 1.153. Rosuvastatin was well tolerated in this group of healthy men when administered orally at doses of 10 to 80 mg. CONCLUSION: Rosuvastatin systemic exposure was dose proportional over the dose range of 10 to 80 mg.

(18)F-FLT-PET for Response Evaluation of MEK Inhibitor Selumetinib (AZD6244, ARRY-142886) in Patients with Solid Tumors.

Selumetinib (AZD6244, ARRY-142886) is a potent, selective, uncompetitive inhibitor of MEK 1 / 2, part of the RAF/MEK/ERK protein kinase signal cascade, which is responsible for tumor. This pilot study was used to explore if (18)F-fluoro-l-thymidine (FLT), a thymidine analogue positron emission tomography (PET) tracer and a surrogate marker for proliferation, can be used as an early predictor of response for patients with solid cancers treated with Selumetinib. FLT-PET scans were performed in four patients at baseline and after 2 weeks of treatment with Selumetinib. FLT uptake in tumors was analyzed qualitatively and quantitatively by measuring standard uptake value (SUV) max in regions of interest (ROI). Results were compared to computed tomography (CT) scans (baseline and after 8 weeks), which were evaluated using the response evaluation criteria in solid tumors (RECIST) 1.0 criteria. One patient with melanoma showed both a qualitative and quantitative decrease in FLT uptake associated with a decrease in sum of longest diameter of 12% RECIST on CT evaluation. Another patient who had colorectal carcinoma (CRC) showed a significant increase in FLT uptake with initially stable, but eventually progressive disease on CT. The other two patients (one with melanoma and one with CRC) showed no significant changes in FLT uptake, whereas CT evaluation showed progressive disease. This is the first report describing changes in FLT-PET in patients receiving Selumetinib. In two patients, changes in FLT uptake as early as after 2 weeks of treatment were consistent with CT results after 8 weeks. Biomarkers to predict and evaluate treatment the outcome of targeted therapies are highly warranted. These initial results need further investigation.

Circulating tumour-derived predictive biomarkers in oncology.

Molecular characterization of tumour material will become increasingly important in selecting patients for clinical trials and offering appropriate treatment for patients in clinical practice. Recent advances in the field have indicated that the molecular characteristics of a tumour can be determined from circulating tumour cells and circulating tumour DNA; thus, a simple blood sample could provide these data in a simple, convenient and efficient manner. This article discusses progress towards guiding treatment decisions through measuring tumour-derived factors in the circulation.

The first-in-human study of the hydrogen sulfate (Hyd-sulfate) capsule of the MEK1/2 inhibitor AZD6244 (ARRY-142886): a phase I open-label multicenter trial in patients with advanced cancer.

PURPOSE: In part A, the aim was to define the maximum tolerated dose (MTD) of the hydrogen sulfate (Hyd-Sulfate) oral capsule formulation of the mitogen-activated protein kinase kinase inhibitor AZD6244 (ARRY-142886). In part B, the aim was to compare the pharmacokinetic profile of the new Hyd-Sulfate capsule with the initial AZD6244 free-base suspension and further characterize the pharmacodynamic profile and efficacy of the new formulation. EXPERIMENTAL DESIGN: In part A, 30 patients received escalating doses of AZD6244 Hyd-Sulfate twice daily. In part B, 29 patients were randomized to a single dose of the Hyd-Sulfate capsule or free-base suspension, followed by a washout, then a single dose of the alternative formulation. Patients received the Hyd-Sulfate capsule twice daily at MTD of part A thereafter. RESULTS: The MTD of the Hyd-Sulfate capsule was 75 mg twice daily. Dose limiting toxicities were Common Terminology Criteria for Adverse Events grade 3 acneiform rash and pleural effusion. Fatigue (65.7%) and acneiform dermatitis (60.0%) were the most frequent adverse events at the MTD. Based on area under curve(0-24), exposure of the 75 mg Hyd-Sulfate capsule relative to the 100 mg free-base suspension was 197% (90% confidence interval, 161-242%). Pharmacodynamic analysis showed that inhibition of 12-O-tetradecanoylphorbol-13-acetate-induced extracellular signal-regulated kinase phosphorylation in peripheral blood lymphocytes was related to plasma concentrations of AZD6244, with an estimated IC(50) of 352 ng/mL and maximum inhibition (E(max)) of approximately 91%, showing target inhibition. A patient with metastatic melanoma bearing a V600E BRAF mutation achieved a complete response persisting after 15 months of therapy. CONCLUSIONS: The AZD6244 Hyd-Sulfate capsule formulation has shown a favorable toxicity, pharmacokinetic, and pharmacodynamic profile, and is being taken forward in ongoing clinical trials.

Effect of oral linezolid on the pressor response to intravenous tyramine.

AIMS: To investigate the effect of monoamine oxidase A inhibition from a single oral dose of linezolid on the pressor response to intravenous (i.v.) tyramine, using positive and negative controls to validate the methodology. METHODS: This placebo-controlled, three-period crossover study was conducted in 12 healthy male volunteers. Each volunteer received either one oral dose of moclobemide (300 mg), linezolid (600 mg), or placebo tablet followed by an i.v. tyramine pressor test until an increase in systolic blood pressure of at least 30 mmHg above baseline occurred. Each study day was separated by a 7-day washout period. The dose of tyramine required to raise the blood pressure by 30 mmHg (TYR30) was calculated for each oral treatment by linear interpolation between log-transformed doses of i.v. tyramine. The influence of body mass index (BMI) on TYR30 was also investigated. RESULTS: The tyramine sensitivity factor (ratio of the geometric least square mean TYR30 for placebo and active oral treatment) was 1.8 [90% confidence interval (CI) 1.6, 2.0, P < 0.0001] for linezolid and 2.1 (90% CI 1.8, 2.4, P < 0.0001) for the positive control moclobemide. BMI had a statistically significant effect on TYR30. CONCLUSIONS: There was a significant difference in the pressor response to i.v. tyramine between linezolid and placebo. Moclobemide (positive control) and linezolid have a similar pressor response to i.v. tyramine. The statistically significant effect of BMI on TYR30 underlines the advantage of within-individual comparisons of treatments in order to reduce variability and provide more accurate treatment estimates.