Phase I clinical and pharmacokinetic trial of docetaxel and irinotecan administered on a weekly schedule

Individualization of Irinotecan Treatment: A Review of Pharmacokinetics, Pharmacodynamics, and Pharmacogenetics

Since its clinical introduction in 1998, the topoisomerase I inhibitor irinotecan has been widely used in the treatment of solid tumors, including colorectal, pancreatic, and lung cancer. Irinotecan therapy is characterized by several dose-limiting toxicities and large interindividual pharmacokinetic variability. Irinotecan has a highly complex metabolism, including hydrolyzation by carboxylesterases to its active metabolite SN-38, which is 100- to 1000-fold more active compared with irinotecan itself. Several phase I and II enzymes, including cytochrome P450 (CYP) 3A4 and uridine diphosphate glucuronosyltransferase (UGT) 1A, are involved in the formation of inactive metabolites, making its metabolism prone to environmental and genetic influences. Genetic variants in the DNA of these enzymes and transporters could predict a part of the drug-related toxicity and efficacy of treatment, which has been shown in retrospective and prospective trials and meta-analyses. Patient characteristics, lifestyle and comedication also influence irinotecan pharmacokinetics. Other factors, including dietary restriction, are currently being studied. Meanwhile, a more tailored approach to prevent excessive toxicity and optimize efficacy is warranted. This review provides an updated overview on today’s literature on irinotecan pharmacokinetics, pharmacodynamics, and pharmacogenetics.

Drug-Drug Interactions in Prostate Cancer Treatment

Polypharmacy is associated with an increased risk of drug-drug interactions (DDIs), which can cause serious and debilitating drug-induced adverse events. With a steadily aging population and associated increasing multimorbidity and polypharmacy, the potential for DDIs becomes considerably important. Prostate cancer (PCa) is the most common cancer in men and occurs mostly in elderly men in the Western world. Therefore, the aim of this review is to give an overview of DDIs in PCa therapy to better understand pharmacodynamic and pharm kinetic side effects as well as their interactions with other medications. Last, we explore potential future strategies, which might help to optimize treatment and reduce adverse events patients with polypharmacy and PCa.

The dual EGFR/HER-2 tyrosine kinase inhibitor lapatinib sensitizes colon and gastric cancer cells to the irinotecan active metabolite SN-38

Members of the human epidermal receptor (HER) family are frequently associated with aggressive disease and poor prognosis in multiple malignancies. Lapatinib is a dual tyrosine kinase inhibitor targeting the epidermal growth factor receptor (EGFR) and HER-2. This study evaluated the therapeutic potential of lapatinib, alone and in combination with SN-38, the active metabolite of irinotecan (CPT-11), in colon and gastric cancer cell lines. Concentration-dependent antiproliferative effects of both lapatinib and SN-38 were observed in all colon and gastric cancer cell lines tested but varied significantly between individual cell lines (lapatinib range 0.08-11.7 muM; SN-38 range 3.6-256 nM). Lapatinib potently inhibited the growth of a HER-2 overexpressing gastric cancer cell line and demonstrated moderate activity in gastric and colon cancer cells with detectable HER-2 expression. The combination of lapatinib and SN-38 interacted synergistically to inhibit cell proliferation in all colon and gastric cancer cell lines tested. Cotreatment with lapatinib and SN-38 also resulted in enhanced cell cycle arrest and the induction of apoptosis with subsequent cellular pharmacokinetic analysis demonstrating that lapatinib promoted the increased intracellular accumulation and retention of SN-38 when compared to SN-38 treatment alone. Finally, the combination of lapatinib and CPT-11 demonstrated synergistic antitumor efficacy in the LoVo colon cancer mouse xenograft model with no apparent increase in toxicity compared to CPT-11 monotherapy. These results provide compelling preclinical rationale indicating lapatinib to be a potentially efficacious chemotherapeutic combination partner for irinotecan in the treatment of gastrointestinal carcinomas.

Tumor, tissue, and plasma pharmacokinetic studies and antitumor response studies of docetaxel in combination with 9-nitrocamptothecin in mice bearing SKOV-3 human ovarian xenografts

PURPOSE

We evaluated the antitumor activity of two different schedules of docetaxel and 9-nitrocamptothecin (9NC) in mice bearing human SKOV-3 ovarian carcinoma xenografts and evaluated the plasma, tissue, and tumor disposition of each agent alone and in combination.

EXPERIMENTAL DESIGN

The following treatment groups were evaluated: (1) docetaxel 10 mg/kg IV on days 0 and 7; (2) 9NC 0.67 mg/kg PO qdx5dx2wk; (3) 9NC 0.67 mg/kg PO qdx5dx2wk in combination with docetaxel 10 mg/kg IV on days 0 and 7; and (4) 9NC 0.67 mg/kg PO qdx5dx2wk in combination with docetaxel 10 mg/kg IV on days 4 and 11; (5) vehicle controls for each agent; and (6) no treatment controls.

RESULTS

All treatment regimens produced significant antitumor activity as compared with control groups (P < 0.05). Docetaxel administered on days 0 and 7 or on days 4 and 11 in combination with 9NC resulted in similar antitumor activity (P > 0.05). High docetaxel concentrations in tumor were maintained at late time points as compared with plasma and tissues with the retention of docetaxel at 24 h being 132-fold and 15-fold higher in tumor than in plasma and liver, respectively. After administration of 9NC alone, the ratio of the 9-aminocamptothecin (9AC) area under the concentration versus time curve (AUC) to 9NC AUC in plasma and tumor was 0.15 and 1.34, respectively.

CONCLUSIONS

The combination of docetaxel and 9NC was effective against SKOV-3 xenografts. The lack of a difference in sequence-dependent antitumor activity may reflect the sensitivity of the SKOV-3 xenograft to 9NC. The factors associated with tumor-specific retention of docetaxel and the ratio of 9NC to 9AC in tumors is unknown.

Clinical pharmacokinetics of docetaxel : recent developments

Docetaxel belongs to the class of taxane antineoplastic agents that act by inducing microtubular stability and disrupting the dynamics of the microtubular network. The drug has shown a broad spectrum of antitumour activity in preclinical models as well as clinically, with responses observed in various disease types, including advanced breast cancer and non-small cell lung cancer. The pharmacokinetics and metabolism of docetaxel are extremely complex and have been the subject of intensive investigation in recent years. Docetaxel is subject to extensive metabolic conversion by the cytochrome P450 (CYP) 3A isoenzymes, which results in several pharmacologically inactive oxidation products. Elimination routes of docetaxel are also dependent on the presence of drug-transporting proteins, notably P-glycoprotein, present on the bile canalicular membrane. The various processes mediating drug elimination, either through metabolic breakdown or excretion, impact substantially on interindividual variability in drug handling. Strategies to individualise docetaxel administration schedules based on phenotypic or genotype-dependent differences in CYP3A expression are underway and may ultimately lead to more selective chemotherapeutic use of this agent.