Marta Hamilton

Effects of smoking on the pharmacokinetics of erlotinib.

Purpose: To compare the pharmacokinetic variables of erlotinib in current smokers with nonsmokers after receiving a single oral 150 or 300 mg dose of erlotinib. Experimental Design: This was a single-center, open-label pharmacokinetic study in healthy male subjects. Subjects were enrolled into two treatment cohorts based on smoking status (current smokers and nonsmokers). The pharmacokinetic profile for erlotinib and its metabolite, OSI-420, was determined for each subject following each treatment. Results: Current smokers achieved significantly less erlotinib exposure following a single 150 or 300 mg dose than nonsmokers. Following the 150 mg dose, the geometric mean erlotinib AUC0-∞ in smokers was 2.8-fold lower than in nonsmokers and similar to that of nonsmokers at the 300 mg dose. Cmax in smokers was two-thirds of that in nonsmokers, and C24h in smokers was 8.3-fold lower than in nonsmokers. The median C24h of smokers at the 300 mg dose was slightly less than the C24h of smokers at the 150 mg dose. The median Cmax was greater in smokers at the 300 mg dose than in nonsmokers at the 150 mg dose. Conclusion: This study confirms that the pharmacokinetics of erlotinib is different in current smokers and nonsmokers. The observation that AUC0-∞ and C24h were significantly decreased in smokers compared with nonsmokers, and a smaller decrease in Cmax was observed, is consistent with increased metabolic clearance of erlotinib in current smokers.

Validated assays for the determination of gemcitabine in human plasma and urine using high-performance liquid chromatography with ultraviolet detection

Procedures are described for the determination of gemcitabine, a new anti-tumor agent, and its uridine metabolite in human plasma and in human urine. The sample preparation for the plasma assay involves precipitation of plasma proteins with isopropanol and ethyl acetate. Following this, the solids are discarded and the supernatant is evaporated to dryness. For the urine assay, the sample is diluted with methanol and evaporated to dryness. For both procedures, the residue is reconstituted in mobile phase prior to injection into a normal-phase (amino column) liquid chromatographic system followed by UV detection at 272 nm. The limits of quantitation for both compounds are 50 ng/ml in plasma and 20 micrograms/ml in urine. The procedures were used to provide pharmacokinetic data for both compounds in man following the intravenous administration of a 1000 mg/m2 dose of gemcitabine.

Placental transfer and fetal distribution of fluoxetine in the rat

Previously conducted reproduction and teratology studies in rats (unpublished observations) exposed to fluoxetine have revealed no compound-related adverse effects on fertility and no teratogenic effects. In order to confirm embryonic/fetal exposure to fluoxetine and/or metabolites, dissection and whole-body autoradiographic techniques were utilized to determine the placental transfer and fetal distribution in 12- and 18-day-pregnant Wistar rats 1, 4, 8, and 24 hr following a single oral 12.5 mg/kg dose of [14C]fluoxetine. On gestation Days 12 (organogenesis) and 18 (postorganogenesis), peak concentrations of radiocarbon occurred 4-8 hr after dose administration in the placenta, embryo/fetus, amniotic fluid, and maternal kidney, brain, and lung, and declined slightly at 24 hr postdose. Maternal lung contained the highest tissue concentration of radiocarbon at all time points. Placenta and maternal brain, kidney, and liver contained moderate levels of radioactivity, while embryonic/fetal tissue, amniotic fluid, and maternal plasma contained low levels of radioactivity. Mean fetal concentrations of radiocarbon at 4, 8, and 24 hr on gestation Day 18 were higher than mean embryonic concentrations on Day 12 of gestation. Analytical characterization of radioactivity indicated that combined fluoxetine and norfluoxetine concentrations accounted for 63-80% of the total radiocarbon concentrations in embryonic/fetal tissue. Results indicated that embryonic/fetal and maternal tissue levels of fluoxetine were greatest at early time points and declined with time, while norfluoxetine tissue levels were highest at the 24-hr time point. Whole-body autoradiographic techniques demonstrated that radioactivity associated with [14C]fluoxetine and/or its metabolites traversed the placenta and distributed throughout the 18-day fetus 4 hr following dose administration. Visual and quantitative evaluations of the autoradiograms indicated that the highest fetal concentrations of radiocarbon were associated with brain and thymus. Results from these studies indicate that fluoxetine and norfluoxetine traverse the placenta and distribute within the embryo/fetus during the periods of organogenesis and postorganogenesis and confirm embryonic/fetal exposure of parent and metabolite in previous negative rat teratology and reproductive studies.

Phase I and Pharmacologic Study of Liposomal Lurtotecan, NX 211: Urinary Excretion Predicts Hematologic Toxicity

PURPOSE To determine the maximum-tolerated and recommended dose, toxicity profile, and pharmacokinetics of the liposomal topoisomerase I inhibitor lurtotecan (NX 211) administered as a 30-minute intravenous infusion once every 3 weeks in cancer patients. PATIENTS AND METHODS NX 211 was administered by peripheral infusion. Dose escalation decisions were based on all toxicities during the first cycle as well as pharmacokinetic parameters. Serial plasma, whole blood, and urine samples were collected for up to 96 hours after the end of infusion, and drug levels were determined by high-performance liquid chromatography. RESULTS Twenty-nine patients (16 women; median age, 56 years; range, 39 to 74 years) received 77 courses of NX 211 at dose levels of 0.4 (n = 3), 0.8 (n = 6), 1.6 (n = 3), 3.2 (n = 6), 3.8 (n = 6), and 4.3 mg/m(2) (n = 5). Neutropenia and thrombocytopenia were the dose-limiting toxicities and were not cumulative. Other toxicities were mild to moderate. Nine patients had stable disease while undergoing treatment. The systemic clearance of lurtotecan in plasma and whole blood was 0.82 +/- 0.78 L/h/m(2) and 1.15 +/- 0.96 L/h/m(2), respectively. Urinary recovery (Fu) of lurtotecan was 10.1% +/- 4.05% (range, 4.9% to 18.9%). In contrast to systemic exposure measures, the dose excreted in urine (ie, dose x Fu) was significantly related to the percent decrease in neutrophil and platelet counts at nadir (P <.00001). CONCLUSION The dose-limiting toxicities of NX 211 are neutropenia and thrombocytopenia. The recommended dose for phase II studies is 3.8 mg/m(2) once every 3 weeks. Pharmacologic data suggest a relationship between exposure to lurtotecan and NX 211-induced clinical effects.

Erlotinib 'dosing-to-rash': a phase II intrapatient dose escalation and pharmacologic study of erlotinib in previously treated advanced non-small cell lung cancer

Background:To evaluate the anticancer activity of erlotinib in patients with previously treated, advanced non-small cell lung cancer (NSCLC) whose dose is increased to that associated with a maximal level of tolerable skin toxicity (i.e., target rash (TR)); to characterise the pharmacokinetics (PK) and pharmacodynamics (PD) of higher doses of erlotinib.Methods:Patients initially received erlotinib 150 mg per day. The dose was successively increased in each patient to that associated with a TR. Anticancer activity was evaluated. Plasma, skin, and hair were sampled for PK and PD studies.Results:Erlotinib dose escalation to 200–475 mg per day was feasible in 38 (90%) of 42 patients. Twenty-four (57%) patients developed a TR, but 19 (79%) did so at 150 mg per day. Five (12%) patients, all of whom developed a TR, had a partial response. Median progression-free survival (PFS) was 2.3 months (95% CI: 1.61, 4.14); median PFS was 3.5 months and 1.9 months, respectively, for patients who did and did not experience a TR (hazard ratio, 0.51; P=0.051). Neither rash severity nor response correlated with erlotinib exposure.Conclusion:Intrapatient dose escalation of erlotinib does not appreciably increase the propensity to experience a maximal level of tolerable skin toxicity, or appear to increase the anticancer activity of erlotinib in NSCLC.

Liposomal lurtotecan (NX211): Determination of total drug levels in human plasma and urine by reversed-phase high-performance liquid chromatography

Lurtotecan (GI147211; LRT) is a semisynthetic and water-soluble analogue of the topoisomerase I inhibitor camptothecin. To determine whether the therapeutic efficacy of LRT in patients could be improved, the drug was encapsulated in liposomes (NX211; Gilead Sciences). In order to allow accurate description of the pharmacokinetic behavior of NX211 in cancer patients, we have developed sensitive RP-HPLC assays with fluorescence detection (lambdaex=378 nm; lambdaem=420 nm) for the determination of total LRT levels in human plasma and urine. Sample pretreatment involved deproteinization with 10% (w/v) aqueous perchloric acid-acetonitrile (2:1, v/v), and chromatographic separations were achieved on an Inertsil-ODS 80A analytical column. The lower limit of quantitation (LLQ) was established at 1.00 ng/ml in plasma (200-microl sample) and at 100 ng/ml in urine (200 microl of 40-fold diluted sample). The within-run and between-run precisions were <7.5%. LRT concentrations in urine of <100 ng/ml were determined by a modified procedure comprising a single solvent extraction with n-butanol-diethyl ether (3:4, v/v). In this assay, the fluorescence signal of LRT was increased 14-fold prior to detection by post-column exposure to UV light (254 nm) in a photochemical reaction unit. The LLQ of this assay was 0.500 ng/ml (150-microl sample) and the within-run and between-run precisions were <10%.

Effect of gastric pH on erlotinib pharmacokinetics in healthy individuals: omeprazole and ranitidine.

The aim of this study was to evaluate the effect of coadministration of acid-reducing agents on the pharmacokinetic exposure of orally administered epidermal growth factor receptor inhibitor erlotinib, a drug that displays pH-dependent solubility. Two studies were conducted, the first with the proton pump inhibitor omeprazole and the second with the H2-receptor antagonist ranitidine. Twenty-four healthy male and female volunteers were enrolled in each study. Erlotinib was administered as a single oral 150 mg dose on day 1. After the washout a subsequent study period evaluated 150 mg erlotinib administered with the acid-reducing agent. Omeprazole (40 mg once daily) was given on days 11–14, concomitantly with erlotinib on day 15, and for two additional days (days 16–17). In the ranitidine study, on day 13, participants were randomized to either concomitant dosing (treatment B) or staggered administration (treatment C) of erlotinib and ranitidine and crossed over to the other treatment starting on day 27. For treatment B, ranitidine (300 mg once daily) was administered in the morning for 5 days, 2 h before erlotinib. For treatment C, ranitidine was administered as a divided dose (150 mg twice daily) for 5 days, with erlotinib given 10 h after the previous evening dose and 2 h before the next ranitidine morning dose. Plasma samples were obtained for determination of the concentrations of erlotinib and its metabolite OSI-420, following each erlotinib dose. All participants were monitored for safety and tolerability. The geometric mean ratios of AUC0–∞ and Cmax for erlotinib and AUC0–last and Cmax for OSI-420 were substantially decreased when erlotinib was dosed with omeprazole. The estimated mean ratio (90% confidence interval) for erlotinib was 0.54 (0.49–0.59) for AUC0–∞ and 0.39 (0.32–0.48) for Cmax. For OSI-420, the estimated mean ratio was 0.42 (0.37–0.48) for AUC0–last and 0.31 (0.24–0.41) for Cmax. AUC0–∞ and Cmax for erlotinib were substantially decreased by 33 and 54%, respectively, upon coadministration with ranitidine, but the decrease was only 15 and 17% when ranitidine and erlotinib were given staggered. Similar results were observed for the metabolite OSI-420. Erlotinib was generally well-tolerated alone or in combination with omeprazole or ranitidine. Erlotinib pharmacokinetic exposure was substantially reduced upon coadministration with omeprazole and ranitidine, but not when administered with a staggered dosing approach to ranitidine. Therefore, it is recommended that the concomitant use of erlotinib with proton pump inhibitors be avoided. If treatment with an H2-receptor antagonist such as ranitidine is required, erlotinib must be administered 10 h after the H2-receptor antagonist dosing and at least 2 h before the next dose of the H2-receptor antagonist.

Biodistribution of NX211, liposomal lurtotecan, in tumor-bearing mice.

Prolonging tumor exposure to topoisomerase I inhibitors has been correlated to enhance the efficacy of those agents. Lurtotecan, a water-soluble camptothecin analog, was formulated as a liposomal drug, NX211, to enhance the delivery of drug to tumors. Tumor-bearing mice were treated with either [14C]NX211 containing [14C]lurtotecan, [3H]NX211 containing [3H]phosphatidylcholine or [14C]lurtotecan, euthanized at selected times post-injection, and tissues, plasma, urine and feces were collected. These studies demonstrated that KB tumors of [14C]NX211-treated mice had approximately 70-fold greater concentrations of [14C]lurtotecan at 24 h, respectively, compared to concentrations of [14C]lurtotecan of the KB tumors of [14C]lurtotecan-treated mice. The area under curve (AUC) from 0 to 48 h of [14C]lurtotecan for the KB tumors of [14C]NX211-treated animals was over 17-fold greater than the AUC of [14C]lurtotecan for the tumors of [14C]lurtotecan-treated animals. Treatment with [3H]NX211 demonstrated that the lipid component continually accumulated over 24 h in the tissues. HPLC analysis of extracted material from tumors of [14C]NX211-treated mice showed that more than 95% of the radioactive material was intact [14C]lurtotecan. These findings are one of the keys justifying the development of a liposomal formulation of lurtotecan, which has the intent to increase tumor exposure and increase antitumor efficacy.

Liquid chromatographic determination of pinacidil, a new antihypertensive drug, and its major metabolite, pinacidil N-oxide, in plasma

Two procedures are described, one for the determination of pinacidil, the other for the determination of both pinacidil and its metabolite, pinacidil N-oxide, in plasma. When only parent drug levels are required, the plasma proteins are precipitated with acetonitrile, the solids discarded and the supernatant is evaporated to dryness. The residue is then reconstituted for analysis. For the determination of both drug and metabolite, the analytes are selectively retained from plasma on a solid-phase extraction column and eluted with methanol. After evaporation to dryness, the residue is reconstituted in mobile phase. Both procedures utilize reversed-phase liquid chromatographic separations with ultraviolet detection. The limits of detection are 10 ng/ml pinacidil in plasma and 5 ng/ml each of pinacidil and pinacidil N-oxide in plasma for the two procedures, respectively.

Sensitive method for the quantitation of nortriptyline and 10-hydroxynortriptyline in human plasma by capillary gas chromatography with electron-capture detection

A method for the determination of nortriptyline and 10-hydroxynortriptyline concentrations in human plasma by capillary gas chromatography with electron-capture detection is described. The procedure requires 1.0 ml of plasma and uses maprotiline as an internal standard. The compounds are extracted from alkalinized plasma with hexane-2-butanol (98:2) and back-extracted into hydrochloric acid. The acid solution is then made basic and the compounds are re-extracted into n-butyl chloride. The extract is evaporated to dryness, derivatized with heptafluorobutyric anhydride, and analyzed by gas chromatography on a fused-silica capillary column coated with phenylmethyl silicone. The calibration curves for nortriptyline and 10-hydroxynortriptyline are linear in the ranges 3-40 and 7-90 micrograms/l, respectively, with coefficients of variation for within-day and between-day precision of less than 12%. The quantitation limits for nortriptyline and 10-hydroxynortriptyline are 1 and 3 micrograms/l, respectively. This procedure was used to analyze more than 1400 samples following sub-therapeutic doses of nortriptyline in human subjects. The assay was sufficiently sensitive for use in pharmacokinetic analysis.