Preclinical analysis of the analinoquinazoline AG1478, a specific small molecule inhibitor of EGF receptor tyrosine kinase.

The tyrphostin 4-(3-chloroanilino)-6,7-dimethoxyquinazoline (AG1478) is a potent and specific inhibitor of EGFR tyrosine kinase whose favourable preclinical profile supports progression towards clinical trials. Microphysiometric evaluation revealed a short (<24 min) effective inhibition of cellular receptor response to EGF challenge in BaF/ERX cells indicating a need to maintain sustained levels of inhibitor. Initial pharmacokinetic evaluation in mice of novel AG1478 formulations in a beta-cyclodextrin (Captisol) showed monoexponential elimination from plasma (half-life 30 min) following subcutaneous administration. A two-fold dose escalation gave a 2.4-fold increase in the total AUC. Bolus i.v. and 6 h continuous infusion were investigated in rats to mimic a more clinically relevant administration regimen. Drug elimination following bolus i.v. administration was biphasic (terminal elimination half-life 30-48 min). The linear relationship between dose and AUC(0-->infinity) (r2=0.979) enabled the prediction of infusion rates and doses for sustained delivery using continuous 6 h infusions, where steady state was reached in 120 min. Plasma levels of AG1478>10 microM were achieved over the duration of the infusion. At the lowest dose, plasma drug levels after the cessation of infusion declined with a half-life of approximately 43 min. EGFR activity, measured both by autophosphorylation and downstream signalling, was inhibited in a dose-dependent manner by injection of AG1478 in mice bearing xenografts of the human glioblastoma cell line U87MG.delta2-7, which expresses a constitutively active variant of the EGF receptor. Taken together, these experiments provide essential data to assess the anti-tumour efficacy of AG1478 and will assist in the rational design of dose regimens for clinical studies.

Cremophor pharmacokinetics in patients receiving 3-, 6-, and 24-hour infusions of paclitaxel.

BACKGROUND: Paclitaxel (Taxol) is a new drug with efficacy against a variety of malignant tumors. The clinical formulation of paclitaxel contains 50% Cremophor EL, a polyethoxylated castor oil vehicle (carrier) that can reverse multidrug resistance (MDR) mediated by P-glycoprotein. Three-hour intravenous infusions of paclitaxel can yield end-of-infusion plasma Cremophor concentrations of 1 microL/mL or more, which are sufficient to reverse MDR in vitro by at least 50%. Despite extensive clinical use, the pharmacokinetics of Cremophor have not been described. PURPOSE: We studied the pharmacokinetics of Cremophor in patients with ovarian cancer who were undergoing treatment with paclitaxel to determine whether plasma Cremophor concentrations achieved during and following 3-, 6-, and 24-hour drug infusions were similar to those shown to modulate MDR in vitro. METHODS: Eleven patients with previously treated (i.e., with platinum-containing chemotherapy regimens) ovarian cancer were randomly assigned to receive one 3-hour, one 6-hour, and one 24-hour infusion of paclitaxel in varied sequences during their first three cycles of treatment with this drug. Blood samples were collected both during and following the three infusion periods, and Cremophor concentrations in these samples were measured by use of a bioassay based on the ability of Cremophor in plasma samples to reverse cellular resistance to daunorubicin in vitro. RESULTS: Ten patients were treated with paclitaxel at a dose level of 175 mg/m2, and one patient was treated at a dose level of 135 mg/m2. At the 175-mg/m2 dose level, peak plasma Cremophor concentrations of 1 microL/mL or more were achieved in eight of 10 patients during both the 3-hour and the 6-hour infusions; with the 24-hour infusion, only one patient achieved a peak plasma Cremophor concentration of 1 microL/mL or more. The eight patients who achieved plasma Cremophor concentrations of 1 microL/mL during the 3-hour infusion were above this level 30 minutes into the infusion; the total time that the plasma concentration was greater than 1 microL/mL was 8.9 +/- 5.0 hours (mean +/- standard deviation; range, 4.1-15.6 hours). For the eight patients who achieved plasma Cremophor concentrations of 1 microL/mL during the 6-hour infusion, the total time that the concentration was greater than 1 microL/mL was 10.2 +/- 9.0 hours (range, 0.3-21.9 hours). The patient who received paclitaxel at a dose of 135 mg/m2 achieved a peak plasma Cremophor concentration of 1 microL/mL or more only during the 3-hour infusion. CONCLUSIONS: Paclitaxel infusions of 3 and 6 hours can result in sustained plasma Cremophor concentrations sufficient for substantial reversal of P-glycoprotein-mediated MDR in vitro. These plasma Cremophor concentrations are not achieved during 24-hour infusions of paclitaxel.

Phase I trial of docetaxel and cisplatin in previously untreated patients with advanced non-small-cell lung cancer.

PURPOSE: To determine the maximum-tolerated doses (MTDs), principal toxicities, and pharmacokinetics of the combination of docetaxel and cisplatin administered every 3 weeks to patients with advanced non-small-cell lung cancer (NSCLC) who have not received prior chemotherapy and to recommend a dose for phase II studies. PATIENTS AND METHODS: Patients with advanced NSCLC and performance status 0 to 2 who had not received prior chemotherapy received docetaxel over 1 hour followed by cisplatin over 1 hour with hydration. Dose levels studied were (docetaxel/cisplatin) 50/75, 75/75, 75/100, and 100/75 mg/m2 repeated every 3 weeks. Colony-stimulating factor (CSF) support was not used. Pharmacokinetics of docetaxel and cisplatin were studied in the first cycle of therapy. Most patients (79%) had metastatic disease or intrathoracic recurrence after prior radiation and/or surgery. RESULTS: Of 24 patients entered, all were assessable for toxicity and 18 for response. The MTD schedules were docetaxel 75 mg/m2 with cisplatin 100 mg/m2 (dose-limiting toxicities [DLTs] in five of six patients), and docetaxel 100 mg/m2 with cisplatin 75 mg/m2 (DLTs in two of two patients, including one fatal toxicity). Limiting toxicities were febrile neutropenia and nonhematologic, principally diarrhea and renal. Two patients had neutropenic enterocolitis. Pharmacokinetics of both drugs were consistent with results from single-agent studies, which suggests no major pharmacokinetic interaction. Neutropenia was related to docetaxel area under the plasma concentration-versus-time curve (AUC). An alternative schedule was investigated, with cisplatin being administered over 3 hours commencing 3 hours after docetaxel, but toxicity did not appear to be less. Independently reviewed responses occurred in eight of 18 patients (44%; 95% confidence interval, 22% to 69%), most following 75 mg/m2 of both drugs. CONCLUSION: Docetaxel 75 mg/m2 over 1 hour followed by cisplatin 75 mg/m2 over 1 hour is recommended for phase II studies. The responses seen in this phase I study suggest a high degree of activity of this combination in previously untreated advanced NSCLC.

Optimal sampling strategies for bayesian estimation of docetaxel (Taxotere) clearance.

Docetaxel activity has been documented in many solid tumors, including metastatic breast cancer and non-small cell lung cancer. However, as clinical studies in other tumor types are now being conducted, the validation of an optimal sampling strategy would allow the performance of pharmacokinetics/pharmacodynamics studies with minimum inconvenience for the patient. Six optimal sampling strategies with one to six sampling times were computed, based on the D-optimality theory, using population pharmacokinetic parameters estimated from a large pharmacokinetic database of 547 patients treated in previous Phase II studies. Validation of these sampling strategies was performed on a set of 35 patients, from two Phase I studies, who received docetaxel as a 1-h infusion at doses ranging from 50 to 100 mg/m2. Validation consisted of comparing clearance assessed by maximum likelihood estimation obtained using complete plasma concentration-time data (considered as the reference) and clearance determined by Bayesian estimation with an optimal design. For all of the optimal sampling strategies tested, clearance was found to be well estimated when at least two samples were taken. Bayesian estimation with two measured levels (at the end of infusion and at 6 h after the start of infusion) can be selected, because it allows adequate estimation of clearance with a nonsignificant bias of +1.37% and a precision of 12.3%.

Phase I trial of cremophor EL with bolus doxorubicin.

Cremophor EL (cremophor), a component of the paclitaxel formulation, can potentially reverse P-glycoprotein-associated multidrug resistance. A Phase I trial of cremophor as a 6-h infusion every 3 weeks was performed with bolus doxorubicin (50 mg/m2). The cremophor dose was escalated from 1 to 60 ml/m2. A standard paclitaxel premedication was given before cremophor. Using a bioassay, potentially active cremophor levels (> or = 1 microl/ml) were measured in plasma from patients receiving cremophor doses of 30, 45, and 60 ml/m2. A cross-over design was used to assess the influence of cremophor 30 ml/m2 on the pharmacokinetics of doxorubicin and doxorubicinol. The plasma area under the concentration versus time curve (AUC) of doxorubicin increased from 1448 +/- 350 to 1786 +/- 264 ng/ml x h (P = 0.02) in the presence of cremophor, whereas the AUC of doxorubicinol increased from 252 +/- 104 to 486 +/- 107 ng/ml x h (P = 0.02). This pharmacokinetic interaction was associated with significantly increased neutropenia. With reduction of the doxorubicin dose to 35 mg/m2, the cremophor dose was increased to 60 ml/m2. Dose-limiting toxicities occurred in two of six patients after 45 ml/m2 and two of four patients after 60 ml/m2, which included febrile neutropenia and grade III cremophor-related toxicities of rash, pruritus, headache, and hypotension. All patients who received 45 ml/m2 cremophor reached plasma levels > or = 1.5 microl/ml, but at 60 ml/m2, only two of four reached this level, and the calculated plasma clearance of cremophor was significantly faster at this dose. One patient with hepatoma resistant to epirubicin achieved a near-complete response. Cremophor 45 ml/m2 over 6 h with 35 mg/m2 doxorubicin is recommended for further studies. The pharmacokinetic interaction between cremophor and doxorubicin is quantitatively similar to that described in trials of paclitaxel with doxorubicin and suggests that the cremophor in the paclitaxel formulation is responsible.

Carboplatin dosing: gender bias and inaccurate estimates of glomerular filtration rate.

The aim was to compare doses of carboplatin calculated using the Calvert formula and Chatelut formula and also to compare doses calculated using Calvert formula, modified with non-isotopic estimation of GFR, using the Cockcroft and Gault formula or the Jelliffe formula. For formulae comparison, doses were calculated to target an AUC of 7 mg/ml x min. When compared with the dose derived from the Calvert formula, the doses calculated in 122 adult cancer patients using the Chatelut formula were significantly higher for males and significantly lower for females. There was a statistically significant difference between the dose per kg calculated for males and females (P<0.0001). The mean percentage difference in dose calculated with substituted measures of renal function with the Cockcroft and Gault formula and Jelliffe formula was -8% (standard deviation (S.D.) 17%) and -14% (S.D. 16%), respectively. Further prospective evaluation of the Chatelut formula is required before it can be recommended for routine clinical application.

Preparation, characterization, cytotoxicity, and mutagenicity of a pair of enantiomeric platinum(II) complexes with the potential to bind enantioselectively to DNA.

The synthesis of a pair of enantiomeric Pt(II) complexes, [Pt(R,R-eap)Cl2] and [Pt(S,S-eap)Cl2] (eap = N,N-diethyl-2,4-pentanediamine), designed to bind enantioselectively to GpG and ApG sequences of DNA is described. The in vitro cytotoxicity of each of the enantiomers toward murine leukemia and human bladder tumor cells has been measured. The R,R enantiomer was found to be more active in the leukemia cells, but the difference was not as great as expected (IC50; R,R 14 microM, S,S 33 microM). In the bladder tumor cell line, no significant difference in activity was found. The two enantiomers had similar mutagenicity in the Salmonella reversion assay, but the R,R enantiomer was more cytotoxic in the bacterial cells. A structural analysis of the R,R enantiomer revealed that the ligand adopted an unexpected configuration, and a strain energy minimization analysis showed that this was a consequence of interactions between the diamine ligand and the dichloro ligands. The significance of the structural preferences with respect to the lower than expected enantiospecificity is discussed. Crystals of [Pt(R,R-eap)Cl2] are monoclinic; space group, P2(1)2(1)2(1); a = 7.909(5), b = 12.972(9), and c = 13.269(12) A; Z = 4; and the structure was refined to R = 0.025 (1657F).

cis-bis(pyridine)platinum(II) organoamides with unexpected growth inhibition properties and antitumor activity.

The platinum(II) organoamides [Pt(NRCH2)2L2] (L = pyridine (py), R = p-HC6F4, C6F5,p-IC6F4,p-CIC6F4,p-C6F5C6F4; L = 4-methylpyridine, R = p-HC6F4) and [Pt(NRCH2CH2NR')(py)2] (R = p-HC6F4, R' = C6F5, p-BrC6F4, or p-MeC6F4) inhibit the growth of murine L1210 leukemia cells in culture with ID50 values for continuous exposure in the range 0.6-2.7 microM. Representative complexes are also active against L1210 cells in 2-h pulse exposures, as well as against the cisplatin-resistant variant L1210/DDP and human colonic carcinoma cell lines HT 29 and BE. Three complexes [Pt(NRCH2)2L2] (R = p-HC6F4, C6F5, or p-IC6F4) have good activity (T/C greater than or equal to 180%) against P388 leukemia in mice, and all other compounds tested are active except when R = p-C6F5C6F4, L = py. Although the molecular basis of the biological activity of these complexes is not known, the observation of good activity for amineplatinum(II) compounds with no hydrogen substituents on the nitrogen donor atoms introduces a new factor in the anticancer behavior of platinum(II) complexes.

Metabolism and biliary excretion of trimetrexate by the isolated perfused rat liver.

The metabolism and biliary excretion of trimetrexate (TMTX), a lipid soluble antifolate, were examined using a recirculating isolated perfused rat liver system. Elimination of TMTX into perfusate was biphasic and dose-independent, with distribution and elimination half-lives of 2 and 13 min. Two metabolites, M1 and M2, both known to inhibit dihydrofolate reductase activity, were present in perfusate only in small concentrations. However, of the total TMTX dose, approximately 50% was excreted in bile as M1, and 20% as M2. Up to 75% of the total dose was accounted for as TMTX, M1, or M2 in perfusate and bile.

Effect of hypoxia on oxidative and reductive pathways of omeprazole metabolism by the isolated perfused rat liver.

The effect of hypoxia on the elimination of omeprazole, a potent inhibitor of gastric acid secretion, was studied in the isolated perfused rat liver. During normal oxygenation, a 10 mg bolus dose was eliminated rapidly (T 1/2 beta = 8.0 +/- 1.1 min; mean +/- S.E.M., N = 4), while under hypoxic conditions T 1/2 beta was increased to 81.6 +/- 5.4 min (P less than 0.01). Upon reoxygenation, T 1/2 beta returned to 9.6 +/- 1.3 min. During hypoxia, perfusate concentrations of an oxidative metabolite (the sulphone) were reduced by 68%, while those of the reductively-generated sulphide increased 4-fold. With reoxygenation, both formation and elimination of the sulphone were increased, while the sulphide, which had accumulated during the hypoxic period, was eliminated rapidly. These findings were duplicated in steady-state experiments, in which omeprazole clearance during hypoxia fell by at least 70%, and sulphide concentrations in perfusate rose from undetectable levels to 200 ng/ml (at least a 10-fold increase). Sulphone concentrations did not change with hypoxia, consistent with a reduction in both its formation and elimination rates. We conclude that the hepatic elimination of omeprazole is severely retarded by hypoxia, but that this effect is promptly reversed by reoxygenation. The increased formation of reductive metabolite during hypoxia is not of sufficient magnitude to sustain the normal hepatic elimination of omeprazole.

Inhibition of paclitaxel elimination in the isolated perfused rat liver by Cremophor EL.

PURPOSE: Cremophor can alter the pharmacokinetics of cytotoxic drugs, including doxorubicin and etoposide. In view of its presence in the formulation of paclitaxel, the aim of this study was to investigate the influence of Cremophor on the hepatobiliary elimination of paclitaxel. METHODS: In a recirculating isolated perfused rat-liver system the elimination of 1.7 mg paclitaxel given as a bolus into the perfusate reservoir was monitored in perfusate and bile in controls and after the administration of either 80 or 800 microl Cremophor. The higher dose of Cremophor yields clinically relevant perfusate concentrations. Paclitaxel was measured in perfusate, bile, and liver tissue by high-performance liquid chromatography. RESULTS: Cremophor caused a dose-dependent inhibition of the elimination of paclitaxel, with a statistically significant mean value +/-SD, n=3; (P < 0.05 versus controls Bonferroni t-test) 9-fold increase in AUC (2227+/-106 versus 245+/-40 microg ml(-1) min), 9-fold decrease in total clearance (0.8+/-0.1 versus 7.0+/-1.1 ml/min), and 5-fold increase in elimination half-life (92+/-14 versus 18+/-4 min) being observed after a dose of 800 microl Cremophor. With the addition of Cremophor the amount of paclitaxel remaining after 3 h increased in perfusate from none to 20%, increased in liver tissue from 4% to 18%, and remained constant in bile at 11-13%. In the control group, 86% of the paclitaxel dose was recovered in bile as five putative metabolites, which were measured in paclitaxel equivalents, with the major metabolite. M3 co-eluting with 3'-p-hydroxypaclitaxel. This decreased to 45% of the dose on the addition of Cremophor, and the ratio of M3 to paclitaxel in bile decreased. CONCLUSIONS: Cremophor inhibits the hepatic elimination of paclitaxel in the isolated perfused rat liver, primarily by preventing the drug from reaching sites of metabolism and excretion. The presence of Cremophor in the paclitaxel formulation may therefore contribute to the nonlinear pharmacokinetics and pharmacodynamics of paclitaxel.

Effect of toremifene on antipyrine elimination in the isolated perfused rat liver.

Toremifene is a triphenylethylene antioestrogen with significant antitumor activity. It is structurally very similar to tamoxifen. Both drugs undergo extensive hepatic metabolism, and tamoxifen is known to inhibit hepatic mixed-function oxidases (MFO). Using the isolated perfused rat-liver model, we investigated the effect of toremifene on the elimination of antipyrine, a standard marker of MFO activity. Perfusate consisted of 20% red cells in a modified Krebs-Henseleit buffer, and 80 ml was recirculated at 14 ml/min for 3 h. High but clinically relevant steady-state toremifene levels of 3 and 10 micrograms/ml were achieved using bolus plus constant infusion into the reservoir. Elimination of 2.5 mg antipyrine was not inhibited by steady-state toremifene, but methanol (maximal perfusate concentration, 1.29%), the vehicle used for toremifene administration, caused a statistically significant increase in the antipyrine elimination half-life (mean, 1.4 +/- 0.2 h for controls vs 2.2 +/- 0.3 h for methanol; P < 0.05, n = 4). Whereas the methanol had no apparent effect on liver viability as assessed by bile flow and perfusate back-pressure, toremifene at a steady-state concentration of 10 micrograms/ml caused a statistically significant decrease in bile flow (value at 180 min, 0.22 +/- 0.05 ml/h as compared with 0.52 +/- 0.06 ml/h in the methanol control; P < 0.05) and a statistically significant increase in perfusate back-pressure (value at 180 min, 17.5 +/- 1.8 cm vs 11.0 +/- 2.6 cm in the methanol control; P < 0.05). Therefore, toremifene used at high doses can impair liver function in the isolated perfused rat liver, but it does not have any effect on antipyrine elimination.

Inhibition of etoposide elimination in the isolated perfused rat liver by Cremophor EL and Tween 80.

Cremophor EL, a surfactant used in the clinical formulation of cyclosporine and paclitaxel, will reverse the multidrug resistance (MDR) phenotype in vitro. As other MDR modulators can alter the pharmacokinetics of cytotoxic drugs, the aim of this study was to examine the effect of Cremophor and another MDR-reversing surfactant, Tween 80, on the hepatic elimination and biliary excretion of etoposide. Using the isolated perfused rat-liver model with 80 ml recirculating perfusate containing 20% red blood cells and 4% bovine serum albumin, etoposide (1.6 mg) with and without Cremophor (800 or 80 mg) or Tween 80 (80 mg) was given into the perfusate reservoir, and perfusate and bile samples were collected for 3 h. Etoposide was measured by high-performance liquid chromatography (HPLC) and Cremophor was measured using a bioassay. Both surfactants changed the etoposide elimination profile from biphasic to monophasic. High-dose Cremophor increased the AUC (from 334 +/- 23 to 1540 +/- 490 microgram min ml(-1), P<0.05) and decreased the total clearance (from 4.8 +/- 0.3 to 1.1 +/- 0.3 ml/min, P<0.05) and biliary clearance (from 2.6 +/- 1.1 to 0.5 +/- 0.2 ml/min, p<0.05) but decreased the elimination half-life (from 62 +/- 17 to 40 +/- 5 min, P<0.05) and volume of distribution (from 424 +/- 85 to 65 +/- 19 ml, P<0.05). Low-dose Cremophor and Tween 80 caused intermediate effects on these parameters that were statistically significant for total clearance, half-life, and volume of distribution. Cremophor had no adverse effect on liver function, whereas Tween 80 caused haemolysis and cholestasis. The initial high-dose Cremophor perfusate concentration was 0.8 mg/ml, which previous studies have shown to be clinically relevant and close to the optimal level for MDR reversal in vitro (1.0 mg/ml). Cremophor may be a clinically useful MDR modulator, but it may alter the pharmacokinetics of the cytotoxic drug.

A phase I and pharmacokinetics study of prolonged ambulatory-infusion carboplatin.

A total of 18 patients received 6-week ambulatory infusions of carboplatin in groups at dose levels of 14, 28, 35 and 42 mg/m2 per day. The dose-limiting toxicity was myelosuppression. At 42 mg/m2, three of four patients had WHO grade 4 and one of four had grade 3 neutropenia, whereas two patients had grade 3 thrombocytopenia. At 35 mg/m2, two of five patients had grade 3 neutropenia, whereas one had grade 4 and two had grade 3 thrombocytopenia. Non-hematological toxicities were predominantly gastrointestinal, with 3 of 18 patients experiencing grade 3 emesis. Total and ultrafiltrable platinum (UFPt) were assayed by flameless atomic absorption spectrometry in weekly and post-infusion plasma and urine samples. In plasma, levels of total platinum increased throughout the infusion, and the protein binding slowly increased from 60% platinum bound at week 1 to 90% bound by week 4. Although the UFPt level reached a steady state within 1 week, the concentration did not increase with the dose level, remaining at a mean value of 0.58 +/- 0.24 microM. Renal excretion of platinum accounted for 70 +/- 12% of the dose at steady state. There was a high inter-patient variability in both total body clearance of UFPt (range, 83-603 ml/min) and renal clearance (range, 67-390 ml/min). A terminal elimination half-life of 13-27 h was noted for post-infusion UFPt. Neutropenia was linearly related to the total daily carboplatin dose, but neither neutropenia nor thrombocytopenia could be related to steady-state UFPt or the UFPt area under the concentration-time curve (AUC). The recommended dose for phase II studies is 28 mg/m2 per day.

Plasma alcohol concentrations in patients following paclitaxel infusion.

Paclitaxel is formulated in 50% Cremophor El and 50% ethanol such that patients receiving paclitaxel also receive a significant amount of each of these solvents. The aim of this study was to measure the plasma alcohol levels in patients treated with paclitaxel. A total of 12 patients who were enrolled in phase II trials of non-small-cell lung cancer, breast cancer or ovarian cancer received 175 mg/m2 paclitaxel given as a 3-h infusion. Blood samples were obtained prior to and immediately following the infusion, and plasma ethanol concentrations were measured enzymatically. The dose of ethanol delivered with the paclitaxel ranged from 20.0 to 28.9 ml. No alcohol was detected in pre-dose plasma, but 8 of 12 patients had detectable levels in post-infusion plasma, with 0.033 g/dl being the highest concentration. The elimination rate of alcohol approximates the infusion rate when paclitaxel is given over 3h, resulting in low or undetectable levels in most patients. However, in patients receiving an equivalent dose of paclitaxel given as a 1-h infusion, the plasma alcohol levels will likely be high enough for significant pharmacological effects to occur.

A phase I and pharmacokinetic study of 12-h infusion of flavone acetic acid.

This phase I study investigated flavone acetic acid (FAA) given as a 12-h intravenous infusion every 3 weeks in the absence of urinary alkalinisation. Cohorts of three patients were treated at doses of 7, 10 and 13 g/m2. One subject had colon cancer; 5, renal cancer; and 3, lung cancer. The Eastern Cooperative Oncology Group (ECOG) performance status was 0 in four patients, 1 in two subjects and 2 in three cases. The maximum tolerated dose was 13 g/m2. The dose-limiting toxicities were WHO grade 3 hypotension and grade 3 diarrhoea. Other toxicities included lethargy and dizziness, nausea, temperature fluctuation, myalgia and dry mouth, but no significant myelosuppression was encountered. One patient receiving 10 g/m2 for renal cancer showed a partial response that lasted for 3 months and included the resolution of pulmonary and cutaneous metastases. The pharmacokinetics showed large interpatient variability. At 12-16 h post-infusion, the plasma elimination profile entered a plateau phase, with frequent increases in concentration suggesting enterohepatic recycling. Neither peak FAA levels nor AUC values were dose-dependent at the doses studied. Peak plasma levels were 101-402 micrograms/ml and AUC (0-48 h) values were 75-470 mg ml-1 min. Plasma protein binding varied with total concentration. Two metabolites were detected in the plasma, and both also underwent apparent enterohepatic recycling. Repeat dosing resulted in decreases of up to 48% in peak levels and AUC values for FAA in three of six patients. Of the total FAA dose, 39%-77% was excreted in the urine as FAA or metabolites within 2 days. The dose recommended for further phase II studies is 10 g/m2.

Plasma concentrations of polysorbate 80 measured in patients following administration of docetaxel or etoposide.

Docetaxel (Taxotere, Rhone-Poulenc Rorer) and etoposide are water-insoluble drugs formulated with polysorbate 80 for intravenous administration. We have previously reported that surfactants, including polysorbate 80 and Cremophor EL, can reverse the multidrug resistance (MDR) phenotype in an experimental system and that plasma Cremophor EL concentrations measured following a 3-h infusion of paclitaxel were > or = 1 microliter/ml, sufficient to modulate MDR in vitro. The purpose of this study was to measure polysorbate 80 plasma concentrations in patients following intravenous administration of etoposide or docetaxel using a bioassay in which MDR-expressing cells are incubated with daunorubicin (DNR) plus 50/50 growth medium/plasma and equilibrium intracellular DNR fluorescence is measured by flow cytometry. In vitro experiments show maximal reversal of MDR at concentrations of 1.0-2.0 microliters/ml and 50% reversal at 0.2-0.3 microliter/ml. Patients received docetaxel at 75 mg/m2 (five patients) or 100 mg/m2 (four patients) (total dose 125-178 mg, containing 3.12-4.45 ml polysorbate 80) over 60 min. The median end-infusion polysorbate 80 concentration was 0.1 microliter/ml (range 0.07-0.41 microliter/ml). Only one patient had a level of > 0.2 microliter/ml. Five patients received intravenous etoposide at 120 mg/m2 over 45-120 min (total dose 180-250 mg, containing 0.67-0.93 ml polysorbate 80). In the end-infusion plasma sample, polysorbate 80 was not detectable (< 0.06 microliter/ml) in any patient. Plasma polysorbate 80 levels following an intravenous infusion of 120 mg/m2 etoposide or of docetaxel at doses used in Phase II trials, are insufficient to show modulation of MDR in vitro.

A pharmacokinetic and phase II study of gallium nitrate in patients with non-small cell lung cancer.

This study investigated the pharmacokinetics and activity of gallium nitrate in non-small cell lung cancer when 700 mg/m2 was given as a 30-min infusion with prehydration every 2 weeks. Gallium was measured in plasma and urine using flameless atomic absorption spectrophotometry, and pharmacokinetics of total and ultrafilterable gallium were calculated. Twenty-five patients with non-small cell lung cancer received 1-12 (median 2) courses of gallium nitrate every 2 weeks. Of 21 patients evaluable for response, 1 partial response was recorded, 4 patients had stable disease. and 16 had progressed. The most serious toxicities were renal impairment and optic neuritis. Hypocalcaemia was recorded in 3 patients. The mean C(max) was 15.2 +/- 3.1 microg/ ml (range 9.5-21.2). Most gallium remained ultrafilterable for the first 10 h, after which plasma protein binding increased, and at 48 h only 11% was present as ultrafilterable gallium. The elimination profiles of both total and ultrafilterable gallium were biphasic, and the distribution phase consisted of ultrafilterable gallium, with a distribution half-life of 1.4 h. Total gallium plateaued at 1.9 microg/ml at between 8 and 12 h, and the estimated elimination half-life was 63 h. The elimination half-life of ultrafilterable gallium was 16.5 h. Inter- and intra-patient variability in pharmacokinetics was minimal. A mean of 50 +/- 14% of the gallium dose was excreted in the urine within 48 h. A short infusion of gallium nitrate achieving high peak plasma concentrations results in little efficacy in non-small cell lung cancer.

Radioenhancement by cisplatin with accelerated fractionated radiotherapy in a human tumour xenograft.

The aim of the present study was to investigate whether cisplatin would enhance the radioresponse of a human tumour xenograft when given in different schedules combined with accelerated fractionated radiation therapy. A human squamous carcinoma of the hypopharynx, FaDu, was grown in the thigh of athymic nude mice. Tumours were exposed to twice-daily 2-Gy fractions, applied 6 h apart over 2 weeks, 5 days a week, alone or combined with cisplatin given at maximally tolerated doses in three different schedules: (1) i.p. as a single bolus (SB) or (2) i.p. as a daily bolus at 30 min before the first daily radiation fraction or (3) s.c. as a continuous infusion through a mini-osmotic pump over 13 days, commencing 24 h prior to the first daily radiation fraction. The end point for the study was tumour growth delay (TGD), calculated as the difference between the delay in regrowth to 200% of the initial tumour size in treated versus control mice. SB cisplatin plus radiation showed only an additive effect on TGD, whereas daily-bolus and continuous-infusion cisplatin demonstrated a greater than additive effect when combined with accelerated fractionated radiation in this human tumour model. Cisplatin appears to be especially beneficial as a radiation enhancer when given throughout the course of radiation.

The preparation and in vivo activity of L- and D-O-methyl-methioninedichloroplatinum(II). The crystal structure of the L-enantiomer.

The L and D enantiomers of O-methylmethioninedichloroplatinum(II), chosen for their potential to bind to the GpA sequence of DNA, were prepared and their in vivo activities were measured. Against P388 leukemia both enantiomers showed moderate activity, T/C 128 and 147% for L and D, respectively. Both were inactive against L1210 leukemia and B16 melanoma. The crystal structure of [Pt(O-methyl-L-methionine)Cl2] has been determined by x-ray diffraction methods and refined to a residual of 0.021 for 1299 independent observed reflections. The crystals are monoclinic, space group P2(1); a, 8.698(2); b, 7.124(1); c, 9.198(3) A; beta, 96.71(2) degrees.