Doxorubicin in combination with verapamil in advanced colorectal cancer. A phase II trial

Design, synthesis and structure-activity relationships of novel taxane-based multidrug resistance reversal agents

A series of novel taxane-based multidrug resistance (MDR) reversal agents (TRAs) has been designed and synthesized. Structure-activity relationship (SAR) study clearly indicates that modification of the C-7 position with hydrophobic arenecarbonylcinnamoyl groups brings about high potency against drug efflux mediated by P-glycoprotein (P-gp). Six TRAs exhibit ability to modulate a wide range of ATP-binding cassette (ABC) transporters, such as P-gp, multidrug resistance-associated protein 1 (MRP1), and breast cancer resistance protein (BCRP), which may serve as novel broad-spectrum modulators of ABC transporters.

Multidrug resistance (MDR) in cancer. Mechanisms, reversal using modulators of MDR and the role of MDR modulators in influencing the pharmacokinetics of anticancer drugs

In recent years, there has been an increased understanding of P-glycoprotein (P-GP)-mediated pharmacokinetic interactions. In addition, its role in modifying the bioavailability of orally administered drugs via induction or inhibition has been also been demonstrated in various studies. This overview presents a background on some of the commonly documented mechanisms of multidrug resistance (MDR), reversal using modulators of MDR, followed by a discussion on the functional aspects of P-GP in the context of the pharmacokinetic interactions when multiple agents are coadministered. While adverse pharmacokinetic interactions have been documented with first and second generation MDR modulators, certain newer agents of the third generation class of compounds have been less susceptible in eliciting pharmacokinetic interactions. Although the review focuses on P-GP and the pharmacology of MDR reversal using MDR modulators, relevance of these drug transport proteins in the context of pharmacokinetic implications (drug absorption, distribution, clearance, and interactions) will also be discussed.

Treatment of hepatic-metastatic colorectal cancer with a chemotherapeutic emulsion: interim results of a phase I trial

BACKGROUND

Hepatic arterial infusion of 5-fluoro-2-deoxyuridine (FUdR) is associated with a 60% response rate among previously untreated patients who have hepatic-metastatic colorectal cancer. One obstacle to further dose escalation has been concomitant hepatic toxicity. We are evaluating a FUdR-containing chemotherapeutic emulsion to further dose intensify therapy without associated toxicity.

METHODS

The in vitro pharmacokinetics of the emulsion were determined using high-pressure liquid chromatography (HPLC). The rate at which FUdR is released from emulsion into an overlying aqueous phase was determined in static and dynamic assays. Fifteen patients with hepatic-metastatic colorectal cancer were treated with intrahepatic arterial infusions of emulsion on a phase I dose-escalating clinical protocol. Serum collection determined systemic drug levels using HPLC.

RESULTS

In vitro studies demonstrate that FUdR is slowly released from emulsion into overlying aqueous medium. The emulsion serves as a depot for FUdR. Therapy was well tolerated. Emulsion was sequestered in the liver after infusion in all treated patients.

CONCLUSIONS

This Ethiodol-based, oil-in-water emulsion serves as a sustained-release preparation of FUdR. An Ethiodol-based oil-in-water emulsion is a clinically effective vehicle for delivering FUdR to hepatic-metastatic colorectal tumors.

MDR1/P-glycoprotein expression in colorectal cancer

Drug resistance to multiple chemotherapeutic agents is considered a major cause of chemotherapy failure. An extensively studied and relatively well understood type of cellular drug resistance is P-glycoprotein (Pgp)-mediated multidrug resistance (MDR). Pgp acts as an energy-dependent drug efflux pump, thereby decreasing the intracellular drug concentration and causing drug resistance, in in vitro experiments. Colorectal cancer and colorectal mucosa generally express high levels of Pgp, and this may contribute to the general unresponsiveness of colorectal cancer to natural product, anticancer drugs. The controversies concerning the prognostic role of Pgp expression and its contribution to tumour aggressiveness, and possible reasons for the disappointing results of clinical MDR reversal trials in colorectal cancer are discussed.

Oral verapamil with chemotherapy for advanced non-small cell lung cancer: a randomised study

To determine if the chemotherapy resistance of non-small cell lung cancer could be modified by oral verapamil, 72 patients were entered into a randomised trial of verapamil plus chemotherapy vs the same chemotherapy alone. Verapamil 480 mg day-1 was given for 3 days starting 24 h prior to chemotherapy which consisted of bolus vindesine 7 mg followed by ifosfamide/mesna 5 g m-2 over 24 h, followed by mesna alone for a further 8 h. Cycles were repeated every 3 weeks for up to six courses. Sixty-six patients were eligible for tumour response analysis and responses occurred in 41% of those randomised to chemotherapy plus verapamil and in 18% of those randomised to chemotherapy alone (P = 0.057). Median survival from start of treatment was significantly better in the verapamil arm (P = 0.02). Toxicity of the combination of chemotherapy plus verapamil was principally neurological and was manageable. Thus the addition of oral verapamil to vindesine/ifosfamide chemotherapy is feasible and in this study was associated with improved outcome. Further confirmation of these observations is required in non-small cell lung cancer, a tumour characterised by resistance to conventional chemotherapy.