Phase I study of pegylated liposomal doxorubicin and the multidrug-resistance modulator, valspodar

Valspodar, a P-glycoprotein modulator, affects pharmacokinetics of doxorubicin when administered in combination, resulting in doxorubicin dose reduction. In animal models, valspodar has minimal interaction with pegylated liposomal doxorubicin (PEG-LD). To determine any pharmacokinetic interaction in humans, we designed a study to determine maximum tolerated dose, dose-limiting toxicity (DLT), and pharmacokinetics of total doxorubicin, in PEG-LD and valspodar combination therapy in patients with advanced malignancies. Patients received PEG-LD 20–25 mg m⁻² intravenously over 1 h for cycle one. In subsequent 2-week cycles, valspodar was administered as 72 h continuous intravenous infusion with PEG-LD beginning at 8 mg m⁻² and escalated in an accelerated titration design to 25 mg m⁻². Pharmacokinetic data were collected with and without valspodar. A total of 14 patients completed at least two cycles of therapy. No DLTs were observed in six patients treated at the highest level of PEG-LD 25 mg m⁻². The most common toxicities were fatigue, nausea, vomiting, mucositis, palmar plantar erythrodysesthesia, diarrhoea, and ataxia. Partial responses were observed in patients with breast and ovarian carcinoma. The mean (range) total doxorubicin clearance decreased from 27 (10–73) ml h⁻¹ m⁻² in cycle 1 to 18 (3–37) ml h⁻¹ m⁻² with the addition of valspodar in cycle 2 (P=0.009). Treatment with PEG-LD 25 mg m⁻² in combination with valspodar results in a moderate prolongation of total doxorubicin clearance and half-life but did not increase the toxicity of this agent.

Phase I study of rubitecan and gemcitabine in patients with advanced malignancies

BACKGROUND

Rubitecan (9-nitrocamptothecin, 9-NC, Orathecin) and gemcitabine have single-agent activity in pancreatic and ovarian carcinoma. We conducted a phase I trial to evaluate the maximum tolerated dose (MTD) and toxicities of this combination in advanced malignancies.

PATIENTS AND METHODS

Twenty-one patients with refractory or recurrent malignancies were enrolled in this dose escalation trial. Dose escalation proceeded from a starting level of rubitecan at 0.75 mg/m(2)/day administered orally on days 1-5 and 8-12 in combination with gemcitabine 1000 mg/m(2) administered intravenously on days 1 and 8 of a 21-day cycle.

RESULTS

The MTD was defined as rubitecan 1 mg/m(2) administered orally days 1-5 and 8-12, and gemcitabine 1000 mg/m(2) administered intravenously over 30 min days 1 and 8, given every 21 days. Dose-limiting toxicity was myelosuppression including neutropenia and thrombocytopenia. Other side effects included diarrhea, nausea, vomiting and fatigue. Five patients with stable disease were observed among 18 evaluable patients.

CONCLUSIONS

The recommended phase II dose is rubitecan 1 mg/m(2) given orally on days 1-5 and 8-12 in combination with gemcitabine 1000 mg/m(2) as a 30-min intravenous infusion on days 1 and 8 of a 21-day cycle.

Phase I study of paclitaxel in combination with a multidrug resistance modulator, PSC 833 (Valspodar), in refractory malignancies

PURPOSE

To determine the maximum-tolerated dose (MTD), dose-limiting toxicity (DLT), and pharmacokinetics of paclitaxel when given with PSC 833 (valspodar) to patients with refractory solid tumors.

PATIENTS AND METHODS

Patients were initially treated with paclitaxel 175 mg/m(2) continuous intravenous infusion (CIVI) over 3 hours. Subsequently, 29 hours of treatment with CIVI PSC 833 was started 2 hours before paclitaxel treatment was initiated. In this combination, the starting dose of paclitaxel was 52.5 mg/m(2). Paclitaxel doses were escalated by 17.5 mg/m(2) increments for four subsequent cohorts. Each cohort consisted of three patients with the exception of the last cohort, which consisted of six patients. Data for the pharmacokinetics of paclitaxel with and without concurrent PSC 833 administration were obtained.

RESULTS

All 18 patients completed at least one course of concurrent treatment (median, two courses; range, one to six) and were evaluable for toxicity. The MTD for paclitaxel with PSC 833 was 122.5 mg/m(2). Neutropenia was the DLT. All patients had PSC 833 blood concentrations greater than 1, 000 ng/mL before, during, and 24 hours after the paclitaxel infusion. PSC 833 produced small increases in the paclitaxel peak plasma concentrations and areas under the concentration-time curve. However, PSC 833 greatly prolonged the terminal phase of paclitaxel, resulting in plasma paclitaxel concentrations of more than 0.05 micromol/L for much longer than expected. As a result, myelosuppression was comparable to that produced by full-dose paclitaxel given without PSC 833. Of the 16 patients who were assessable for response, one patient experienced a partial response and an additional nine patients experienced disease stabilization after paclitaxel treatment alone.

CONCLUSION

Treatment with paclitaxel 122.5 mg/m(2) as a 3-hour CIVI concurrent with a 29-hour CIVI of PSC 833 results in acceptable toxicity. The addition of PSC 833 alters the pharmacokinetics of paclitaxel, which explains the enhanced neutropenia experienced by patients treated with this drug combination.