Dosage adjustments in pivotal clinical trials with oral targeted therapies in solid tumors conducted in Europe

Effects of CYP2D6 Genetic Polymorphism and Drug Interaction on the Metabolism of Dacomitinib

We aim to study the effects of CYP2D6 variants and drug-drug interaction on the metabolism of dacomitinib. CYP2D6 variants were incubated with 25-1000 μM dacomitinib for 40 min at 37 °C, and the reaction was terminated by cooling to -80 °C immediately. For an in vivo experiment, 18 male Sprague-Dawley rats were randomly divided into three groups (n = 6): a single dose of 5 mg/kg dacomitinib (group A), a single dose of 6 mg/kg trazodone (group B), and a combined group (group C). Processed samples were analyzed by ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS.) The relative clearance of dacomitinib was reduced for most of the variants. Moreover, the inhibitory potency of classic CYP inhibitors on dacomitinib metabolism was significantly different among the main subtypes of CYP2D6. Interestingly, compared with gefitinib, even the same CYP2D6 variants showed significant differences in metabolic activity, suggesting that the activity of CYP2D6 has strong variability. In addition, the interaction between trazodone and dacomitinib was determined both in vitro and in vivo. When dacomitinib was given in combination with trazodone, the blood exposure to these two drugs increased remarkably. The mechanistic study revealed that the interaction followed the noncompetitive inhibition. We demonstrated that the activity of CYP2D6 variants to metabolize dacomitinib was significantly reduced. In combination with the CYP2D6 inhibitor, the degree of activity inhibition of different variants obviously differed. When trazodone and dacomitinib were used in combination, the body exposure to the two drugs increased significantly. This study provides data for the precise use of dacomitinib in clinical settings.

Development and validation of a sensitive liquid chromatography tandem mass spectrometry assay for the simultaneous determination of ten kinase inhibitors in human serum and plasma

A liquid chromatography tandem mass spectrometry method for the analysis of ten kinase inhibitors (afatinib, axitinib, bosutinib, cabozantinib, dabrafenib, lenvatinib, nilotinib, osimertinib, ruxolitinib, and trametinib) in human serum and plasma for the application in daily clinical routine has been developed and validated according to the US Food and Drug Administration and European Medicines Agency validation guidelines for bioanalytical methods. After protein precipitation of plasma samples with acetonitrile, chromatographic separation was performed at ambient temperature using a Waters XBridge® Phenyl 3.5 μm (2.1 × 50 mm) column. The mobile phases consisted of water-methanol (9:1, v/v) with 10 mM ammonium bicarbonate as phase A and methanol-water (9:1, v/v) with 10 mM ammonium bicarbonate as phase B. Gradient elution was applied at a flow rate of 400 μL/min. Analytes were detected and quantified using multiple reaction monitoring in electrospray ionization positive mode. Stable isotopically labeled compounds of each kinase inhibitor were used as internal standards. The acquisition time was 7.0 min per run. All analytes and internal standards eluted within 3.0 min. The calibration curves were linear over the range of 2–500 ng/mL for afatinib, axitinib, bosutinib, lenvatinib, ruxolitinib, and trametinib, and 6–1500 ng/mL for cabozantinib, dabrafenib, nilotinib, and osimertinib (coefficients of correlation ≥ 0.99). Validation assays for accuracy and precision, matrix effect, recovery, carryover, and stability were appropriate according to regulatory agencies. The rapid and sensitive assay ensures high throughput and was successfully applied to monitor concentrations of kinase inhibitors in patients.

New Oral Anti-Cancer Drugs and Medication Safety

BACKGROUND

Many oral anti-cancer drugs have come onto the market in the past 20 years. For example, kinase inhibitors, such as the BCR-ABL and BRAF inhibitors, have markedly improved the treatment of chronic myeloid leukemia and melanoma. In this review, we discuss the special challenges posed by poor adherence, drug-drug interactions with other substances, and side effects, among other problems, and the ways in which these challenges can be met.

METHODS

A selective search was carried out in PubMed for original and review articles on the safety of new oral anti-cancer drugs. Guidelines and current Summaries of Product Characteristics (SmPC) were also considered in the analysis.

RESULTS

Review articles have pointed out numerous safety concerns with oral anti-cancer drugs. One of these is adherence, on which highly variable figures are available (with mean non-adherence rates ranging from 0 to 54%). The absorption of approximately half of these drugs is influenced by the patient's diet, and that of approximately 20% by gastric pH (Caution: proton-pump inhibitors may influence bioavailability). 70% of the active substances are metabolized primarily by CYP3A4, which means that their pharmacokinetics can be altered by grapefruit juice and CYP3A4 modulators. The prevention, detection, and treatment of side effects (which can be gastrointestinal, cutaneous, cardiovascular, or other) is a highly important matter.

CONCLUSION

The increasing use of oral anti-cancer drugs confronts patients and treatment teams with special challenges. To optimize treatment outcomes, a multidisciplinary approach should be taken, involving physicians, pharmacists, and nurses. To improve medication safety, medication and side-effect management should be performed, and adherence should be regularly checked and systematically encouraged.