Phase I evaluation of the effects of ketoconazole and rifampicin on cediranib pharmacokinetics in patients with solid tumours

The landscape of tyrosine kinase inhibitors in sarcomas: looking beyond pazopanib

Introduction: Tyrosine kinases are key mediators of intracellular signaling cascades and aberrations in these proteins have been implicated in driving oncogenesis through the dysregulation of fundamental cellular processes including proliferation, migration, and apoptosis. As such, targeting these proteins with small molecule tyrosine kinase inhibitors (TKI) has led to significant advances in the treatment of a number of cancer types.Areas covered: Soft tissue sarcomas (STS) are a heterogeneous and challenging group of rare cancers to treat, but the approval of the TKI pazopanib for the treatment of advanced STS demonstrates that this class of drugs may have broad utility against a range of different sarcoma histological subtypes. Since the approval of pazopanib, a number of other TKIs have entered clinical trials to evaluate whether their activity in STS matches the promising results seen in other solid tumors. In this article, we review the emerging role of TKIs in the evolving landscape of sarcoma treatment.Expert opinion: As our biological understanding of response and resistance of STS to TKIs advances, we anticipate that patient management will move away from a 'one size fits all' paradigm toward personalized, multi-line, and patient-specific treatment regimens where patients are treated according to the underlying biology and genetics of their specific disease.

Clinical Pharmacokinetics and Pharmacodynamics of Cediranib

Cediranib potently and selectively inhibits all three vascular endothelial growth factor receptors (VEGFR-1, -2 and -3), and clinical studies have shown that it is effective in patients with ovarian cancer at a dose of 20 mg/day. Cediranib is absorbed moderately slowly; a high-fat meal reduced the cediranib area under the plasma concentration-time curve (AUC) by 24% and maximum plasma concentration (C _max) by 33%. Cediranib binds to serum albumin and α1-acid glycoprotein; protein binding in human plasma is approximately 95%. The cediranib AUC and C _max increase proportionally with dose from 0.5 to 60 mg, and cediranib has linear pharmacokinetics (PK) over time. Cediranib is metabolized via flavin-containing monooxygenase 1 and 3 (FMO1, FMO3) and uridine 5'-diphospho-glucuronosyltransferase (UGT) 1A4. Cediranib and its metabolites are mainly excreted in faeces (59%), with <1% of unchanged drug being excreted in urine. The apparent oral clearance is moderate and the mean terminal half-life is 22 h. Cediranib is a substrate of multidrug resistance-1 (MDR1) protein (also known as P-glycoprotein [P-gp]). Coadministration with ketoconazole, a potent P-gp inhibitor, increases cediranib AUC at steady-state (AUC_ss) in patients by 21%, while coadministration with rifampicin, a potent inducer of P-gp, decreases cediranib AUC_ss by 39%. Administration of cediranib with chemotherapies demonstrated minimal PK impact on each other. No dose adjustment is recommended for patients with mild or moderate hepatic or renal impairment, and no dose adjustment is needed on the basis of age and body weight. A pooled analysis at doses of 0.5-60 mg showed no significant increase in QTc intervals. Increases in blood pressure and the incidence of diarrhoea were associated with increased cediranib dose and systemic exposure.

Population exposure-safety analysis of cediranib for Phase I and II studies in patients with cancer

AIMS

A multistudy analysis of cediranib, a potent, selective inhibitor of all three vascular endothelial growth factor receptors (VEGFR-1, -2 and -3), was conducted to establish population exposure-safety models for the relationship of cediranib exposure to the safety endpoints, diastolic and systolic blood pressure (DBP and SBP) and diarrhoea in cancer patients. These models were applied to predict safety outcomes for different cediranib dose regimens.

METHODS

Models for hypertension and diarrhoea were constructed based on data from 10 Phase I and three Phase II studies comprising 631 cancer patients following cediranib once-daily oral dosing. Daily DBP and SBP were simultaneously characterized using indirect response models for predicted cediranib concentration-time courses, while daily diarrhoea events were modelled as ordered categorical variables with a proportional odds model with a Markov element for predicted average cediranib concentrations.

RESULTS

For 20 mg cediranib once-daily oral administration, the mean increase in DBP and SBP was predicted to be 7 (95% CI 3-13) and 8 mmHg (95% CI 3-16), respectively, while the probability of mild diarrhoea, but not the severity, was predicted to increase over time. Severe diarrhoea was predicted to be resolved rapidly upon discontinuation of cediranib treatment.

CONCLUSIONS

Maximum blood pressure increase was observed within the first few days of cediranib treatment, consistent with the pharmacokinetic profile of cediranib reaching steady state in about 5 days. The probability of diarrhoea increased with cediranib concentration but was far more dependent on the status of diarrhoea predicted on the previous day.

Pharmacokinetic Interaction of Rifampicin with Oral Versus Intravenous Anticancer Drugs: Challenges, Dilemmas and Paradoxical Effects Due to Multiple Mechanisms

Since many drugs are cytochrome P450 (CYP)-3A4 substrates, it has become common practice to assess drug-drug interaction (DDI) potential with a CYP3A4 inhibitor (ketoconazole) or inducer (rifampicin) in early drug development. Such an evaluation is relevant to anticancer drugs with metabolism governed by CYP3A4. DDIs with rifampicin are complex, involving other physiological mechanisms that may impact overall pharmacokinetics. Our objective was to study and delineate such mechanisms for oral versus intravenous anticancer drugs. We hypothesized that DDIs between anticancer drugs and rifampicin were primarily driven by CYP3A4 induction. This hypothesis was proven for the oral anticancer drugs; however, in some cases, other intrinsic mechanisms such as P-glycoprotein (Pgp)/UDP glucuronosyl transferase (UGT) induction and transporter inhibition may have played an important role alongside the induced CYP3A4 enzymes. The hypothesis that CYP3A4 induction would decrease drug exposure appeared paradoxical for intravenous romidepsin and-to a somewhat lesser extent-for cabazitaxel. In light of this dilemma in the interpretation of the pharmacokinetic data with rifampicin, several questions require further consideration. Given the complexity and paradoxical effects arising with DDIs with rifampicin, the continued preference for rifampicin as CYP3A4 inducer needs immediate re-appraisal.

Population pharmacokinetic and exposure simulation analysis for cediranib (AZD2171) in pooled Phase I/II studies in patients with cancer

AIMS

A population pharmacokinetic (PK) model was developed for cediranib to simulate cediranib exposure for different doses, including comedication with strong uridine glucuronosyl transferase/P-glycoprotein inducers such as rifampicin, in cancer patients.

METHODS

Plasma concentrations and covariates from 625 cancer patients after single or multiple oral cediranib administrations ranging from 0.5 to 90 mg in 19 Phase I and II studies were included in the analysis. Stepwise covariate modelling was used to develop the population PK model. The final model was used to simulate cediranib exposure in cancer patients to evaluate cediranib target coverage and the need for dose adjustment for covariates or coadministration with rifampicin.

RESULTS

A two-compartment model with sequential zero- and first-order absorption and first-order elimination adequately described the cediranib concentration-time courses. Body weight and age were identified as having statistically significant impact on cediranib PK, but only <21% impact on AUC and maximum concentrations. Simulated lower bounds of 90% prediction interval or median of unbound cediranib concentrations after cediranib 15 or 20 mg exceeded the IC₅₀ for vascular endothelial growth factor receptors-1, -2 and -3. Exposures of cediranib 20 or 30 mg with coadministration of rifampicin were comparable to those of 15 or 20 mg, respectively, without coadministration.

CONCLUSIONS

No covariate was identified to require dose adjustment for cediranib. Cediranib exposure following 15 or 20 mg daily dose administration is adequate overall for inhibition of in vitro estimated vascular endothelial growth factor receptor-1, -2 and -3 activities. An increase in cediranib dose may be needed for cediranib coadministered with strong uridine glucuronosyl transferase/P-glycoprotein inducers such as rifampicin.

Impact of cytochrome P450 3A4 inducer and inhibitor on the pharmacokinetics of trabectedin in patients with advanced malignancies: open-label, multicenter studies

PURPOSE

To evaluate the pharmacokinetics, safety and survival of trabectedin, metabolized primarily by cytochrome P450 (CYP)3A4 enzyme, when coadministered with rifampin (CYP3A4 inducer) or ketoconazole (CYP3A4 inhibitor) in adult patients with advanced solid tumors.

METHODS

Two phase 1/2a, 2-way crossover studies were conducted. For rifampin study, 12 patients were randomized (1:1) to sequence of a cycle of trabectedin (1.3 mg/m(2), 3 h, i.v.) coadministered with rifampin (600 mg/day, 6-days), and a cycle of trabectedin monotherapy (1.3 mg/m(2), 3 h, i.v.). In ketoconazole study, eight patients were randomized (1:1) to sequence of a cycle of trabectedin (0.58 mg/m(2), 3 h, i.v.) coadministered with ketoconazole (200 mg, twice-daily, 15-doses), and a cycle of trabectedin monotherapy (1.3 mg/m(2), 3 h, i.v.).

RESULTS

The systemic exposure (geometric means) of trabectedin was decreased [22% (C max) and 31% (AUClast)] with rifampin coadministration and increased [22% (C max) and 66% (AUClast)] with ketoconazole coadministration. This correlated with an increased clearance with rifampin (39.6-59.8 L/h) and a decreased clearance with ketoconazole (20.3-12.0 L/h). Consistent with earlier studies, the most common (≥40%) treatment-emergent adverse events in both studies were nausea, vomiting, diarrhea, hepatic function abnormal, anemia, neutropenia, thrombocytopenia and leukopenia.

CONCLUSIONS

Coadministration of rifampin or ketoconazole altered the pharmacokinetics of trabectedin, but no new safety signals were observed. Coadministration of trabectedin with potent CYP3A4 inhibitors or inducers should be avoided if possible. If coadministration of trabectedin with a strong CYP3A4 inhibitor is required, close monitoring for toxicities is recommended, so that appropriate dose reductions can be instituted as warranted.