Coadministration of cyclosporine strongly enhances the oral bioavailability of docetaxel.

PURPOSE: Oral bioavailability of docetaxel is very low, which is, at least in part, due to its affinity for the intestinal drug efflux pump P-glycoprotein (P-gp). In addition, metabolism of docetaxel by cytochrome P450 (CYP) 3A4 in gut and liver may also contribute. The purpose of this study was to enhance the systemic exposure to oral docetaxel on coadministration of cyclosporine (CsA), an efficacious inhibitor of P-gp and substrate for CYP 3A4. PATIENTS AND METHODS: A proof-of-concept study was carried out in 14 patients with solid tumors. Patients received one course of oral docetaxel 75 mg/m(2) with or without a single oral dose of CsA 15 mg/kg. CsA preceded oral docetaxel by 30 minutes. During subsequent courses, patients received intravenous (IV) docetaxel 100 mg/m(2). RESULTS: The mean (+/- SD) area under the concentration-time curve (AUC) in patients who received oral docetaxel 75 mg/m(2) without CsA was 0.37 +/- 0.33 mg.h/L and 2.71 +/- 1.81 mg.h/L for the same oral docetaxel dose with CsA. The mean AUC of IV docetaxel 100 mg/m(2) was 4.41 +/- 2.10 mg.h/L. The absolute bioavailability of oral docetaxel was 8% +/- 6% without and 90% +/- 44% with CsA. The oral combination of docetaxel and CsA was well tolerated. CONCLUSION: Coadministration of oral CsA strongly enhanced the oral bioavailability of docetaxel. Interpatient variability in the systemic exposure after oral drug administration was of the same order as after IV administration. These data are promising and form the basis for the further development of a clinically useful oral formulation of docetaxel.

Phase II and pharmacological study of oral paclitaxel (Paxoral) plus ciclosporin in anthracycline-pretreated metastatic breast cancer.

Paclitaxel is an important chemotherapeutic agent for breast cancer. Paclitaxel has high affinity for the P-glycoprotein (P-gp) (drug efflux pump) in the gastrointestinal tract causing low and variable oral bioavailability. Previously, we demonstrated that oral paclitaxel plus the P-gp inhibitor cyclosporin (CsA) is safe and results in adequate exposure to paclitaxel. This study evaluates the activity, toxicity and pharmacokinetics of paclitaxel combined with CsA in breast cancer patients. Patients with measurable metastatic breast cancer were given oral paclitaxel 90 mg m-2 combined with CsA 10 mg kg-1 (30 min prior to each paclitaxel administration) twice on one day, each week. Twenty-nine patients with a median age of 50 years were entered. All patients had received prior treatments, 25 had received prior anthracycline-containing chemotherapy and 19 had three or more metastatic sites. Total number of weekly administrations was 442 (median: 15/patient) and dose intensity of 97 mg m-2 week-1. Most patients needed treatment delay and 17 patients needed dose reductions. In intention to treat analysis, the overall response rate was 52%, the median time to progression was 6.5 months and overall survival was 16 months. The pharmacokinetics revealed moderate inter- and low intrapatient variability. Weekly oral paclitaxel, combined with CsA, is active in patients with advanced breast cancer.

Continuous infusion of low-dose topotecan: pharmacokinetics and pharmacodynamics during a phase II study in patients with small cell lung cancer.

Preclinical schedule dependency suggests that prolonged maintenance of low plasma levels of topotecan, a specific inhibitor of the nuclear enzyme topoisomerase I, results in optimal antitumor activity. The pharmacokinetics and pharmacodynamics of topotecan, administered as single agent in second-line therapy as a continuous low-dose infusion for 21 days, were evaluated in nine patients with small cell lung cancer (SCLC). Topotecan was administered i.v. as a 21 day continuous infusion every 28 days via an ambulatory pump. Dosages ranged from 0.4 to 0.6 mg/m2/day. Plasma levels of topotecan, the sum of topotecan, and its hydroxy acid congener and the N-desmethyl metabolite were determined at 1, 7, 14 and 21 days during infusion, using a validated high-performance liquid chromatography method with fluorescence detection. Myelosuppression was the most important toxicity. All patients experienced anemia, being severe (grade 3/4) in 55% of all courses. Other adverse effects were relatively mild and reversible, and included nausea, vomiting, diarrhea and fatigue. Three patients achieved a partial response. Mean steady-state concentrations of topotecan (C(ss)) in the first course were 0.46+/-0.17 and 0.47+/-0.19 ng/ml after doses of 0.4 and 0.5 mg/m2/day, respectively. Steady-state levels of the total of topotecan and hydroxy acid (C(ss,tot)) were 1.28+/-0.25 (range 0.93-1.58) and 1.57+/-0.19 (range 1.43-1.70) ng/ml at doses of 0.4 and 0.5 mg/m2/day, respectively. The percentage of the administered topotecan dose excreted in the urine within 24 h was 40+/-14 and 1.2+/-1.0% for total topotecan and N-desmethyltopotecan, respectively. During the second course, C(ss,tot) was significantly higher (p=0.032, paired t-test), which suggests altered topotecan disposition. A sigmoidal relationship was found between C(ss,tot) and the percent decrease in platelets (r=0.76, p=0.018). We conclude that topotecan administered as a 21 day continuous low-dose infusion has activity as single-agent, second-line therapy in patients with SCLC. There was considerable interpatient and intrapatient variability in systemic exposure to topotecan. Differences in organ function might contribute to this variation. Serum aspartate aminotransferase and albumin levels were predictive of topotecan pharmacokinetics.

The co-solvent Cremophor EL limits absorption of orally administered paclitaxel in cancer patients.

The purpose of this study was to investigate the effect of the co-solvents Cremophor EL and polysorbate 80 on the absorption of orally administered paclitaxel. 6 patients received in a randomized setting, one week apart oral paclitaxel 60 mg m(-2) dissolved in polysorbate 80 or Cremophor EL. For 3 patients the amount of Cremophor EL was 5 ml m(-2), for the other three 15 ml m(-2). Prior to paclitaxel administration patients received 15 mg kg(-1) oral cyclosporin A to enhance the oral absorption of the drug. Paclitaxel formulated in polysorbate 80 resulted in a significant increase in the maximal concentration (C(max)) and area under the concentration-time curve (AUC) of paclitaxel in comparison with the Cremophor EL formulations (P = 0.046 for both parameters). When formulated in Cremophor EL 15 ml m(-2), paclitaxel C(max) and AUC values were 0.10 +/- 0.06 microM and 1.29 +/- 0.99 microM h(-1), respectively, whereas these values were 0.31 +/- 0.06 microM and 2.61 +/- 1.54 microM h(-1), respectively, when formulated in polysorbate 80. Faecal data revealed a decrease in excretion of unchanged paclitaxel for the polysorbate 80 formulation compared to the Cremophor EL formulations. The amount of paclitaxel excreted in faeces was significantly correlated with the amount of Cremophor EL excreted in faeces (P = 0.019). When formulated in Cremophor EL 15 ml m(-2), paclitaxel excretion in faeces was 38.8 +/- 13.0% of the administered dose, whereas this value was 18.3 +/-15.5% for the polysorbate 80 formulation. The results show that the co-solvent Cremophor EL is an important factor limiting the absorption of orally administered paclitaxel from the intestinal lumen. They highlight the need for designing a better drug formulation in order to increase the usefulness of the oral route of paclitaxel

Weekly oral paclitaxel as first-line treatment in patients with advanced gastric cancer.

BACKGROUND: Pharmacokinetic study has shown that co-administration of cyclosporin A (CsA), which acts as a P-glycoprotein (P-gp) and CYP-3A blocker, resulted in an 8-fold increase in the systemic exposure of oral paclitaxel. Two doses of oral paclitaxel on 1 day in combination with CsA resulted in higher systemic exposure than single dose administration. PATIENTS AND METHODS: In this phase II study, chemonaïve patients with advanced gastric cancer received oral paclitaxel weekly in two doses of 90 mg/m(2) on the same day; CsA (10 mg/kg) was given 30 min before each dose of oral paclitaxel. RESULTS: In 25 patients, the main toxicities were: nausea CTC grade 2/3, 10 patients (40%); vomiting grade 2/3, 4 patients (20%); diarrhea grade 2/3, 6 patients (24%); neutropenia grade 3/4, 5 patients (20%). In the 24 evaluable patients, eight partial responses were observed, resulting in an overall response rate (ORR) of 33% [95% confidence interval (CI) 18% to 52%]. Eleven patients had stable disease (46%) and 5 patients showed progressive disease (21%). The ORR in the total population was 32% (95% CI 17% to 50%). The median time to progression was 16 weeks (95% CI 9-22). Pharmacokinetic analyses revealed that the mean area under the plasma concentration-time curve (AUC) of orally administered paclitaxel (+/- standard deviation) was 3757.6 +/- 939.4 ng.h/ml in week 1 and 3928.4 +/- 1281 ng.h/ml in week 2. The intrapatient variability in the AUC was 12%. CONCLUSIONS: Oral paclitaxel in combination with CsA is both active and safe in chemonaïve patients with advanced gastric cancer. Toxicities were mainly gastrointestinal.