Effect of enzalutamide on PK of P-gp and BCRP substrates in cancer patients: CYP450 induction may not always predict overall effect on transporters

Drug‐drug interaction (DDI) is an important consideration for clinical decision making in prostate cancer treatment. The objective of this study was to evaluate the effect of enzalutamide, an oral androgen receptor inhibitor, on the pharmacokinetics (PK) of digoxin (P‐glycoprotein [P‐gp] probe substrate) and rosuvastatin (breast cancer resistance protein [BCRP] probe substrate) in men with metastatic castration‐resistant prostate cancer (mCRPC). This was a phase I, open‐label, fixed‐sequence, crossover study (NCT04094519). Eligible men with mCRPC received a single dose of transporter probe cocktail containing 0.25 mg digoxin and 10 mg rosuvastatin plus enzalutamide placebo‐to‐match on day 1. On day 8, patients started 160 mg enzalutamide once daily through day 71. On day 64, patients also received a single dose of the cocktail. The primary end points were digoxin and rosuvastatin plasma maximum concentration (C_max), area under the concentration‐time curve from the time of dosing to the last measurable concentration (AUC_last), and AUC from the time of dosing extrapolated to time infinity (AUC_inf). Secondary end points were enzalutamide and N‐desmethyl enzalutamide (metabolite) plasma C_max, AUC during a dosing interval, where tau is the length of the dosing interval (AUC_tau), and concentration immediately prior to dosing at multiple dosing (C_trough). When administered with enzalutamide, there was a 17% increase in C_max, 29% increase in AUC_last, and 33% increase in AUC_inf of plasma digoxin compared to digoxin alone, indicating that enzalutamide is a “mild” inhibitor of P‐gp. No PK interaction was observed between enzalutamide and rosuvastatin (BCRP probe substrate). The PK of enzalutamide and N‐desmethyl enzalutamide were in agreement with previously reported data. The potential for transporter‐mediated DDI between enzalutamide and digoxin and rosuvastatin is low in men with prostate cancer. Therefore, concomitant administration of enzalutamide with medications that are substrates for P‐gp and BCRP does not require dose adjustment in this patient population.

Population Pharmacokinetics of Sunitinib and its Active Metabolite SU012662 in Pediatric Patients with Gastrointestinal Stromal Tumors or Other Solid Tumors

BACKGROUND AND OBJECTIVE

Population pharmacokinetic analysis explored the pharmacokinetics of sunitinib and its primary active metabolite, SU012662, in children and evaluated the sunitinib dose(s) that produce comparable plasma exposures to adults receiving the approved daily dose.

METHODS

Data were from 65 children with gastrointestinal stromal tumors (GIST) or solid tumors. Pharmacokinetic models of sunitinib and SU012662 were developed using a systematic multi-step approach employing nonlinear mixed-effects modeling. The effect of predefined covariates on pharmacokinetic parameters was assessed. Final models were validated using visual predictive check and statistical techniques.

RESULTS

The final dataset comprised 439 sunitinib and 417 SU012662 post-baseline plasma observations. Base models were characterized by two-compartment models with first-order absorption and lag time. Body surface area (BSA) was the only covariate that affected (P < 0.001) pharmacokinetic parameters for sunitinib and SU012662 and was incorporated into the final models. Bootstrap results indicated that the final models represented the final dataset adequately. Based on the final models, a sunitinib dose of ~ 20mg/m²/day in children with GIST aged 6-17 years would be expected to lead to similar total plasma exposures of sunitinib and SU012661 as a dose of 50 mg/day in an adult with GIST on schedule 4/2.

CONCLUSIONS

In children with GIST or solid tumors receiving sunitinib, population pharmacokinetic analysis identified BSA as the only covariate that affected pharmacokinetic parameters and predicted a dose of ~ 20 mg/m²/day as achieving equivalent exposure to 50 mg/day in adults with GIST on schedule 4/2.

TRIAL REGISTRATION

ClinicalTrials.gov identifiers (date registered): NCT01396148 (July 2011); NCT01462695 (October 2011); NCT00387920 (October 2006).

Extrapolation of pharmacokinetics and pharmacodynamics of sunitinib in children with gastrointestinal stromal tumors

Purpose

The starting dose of sunitinib in children with gastrointestinal stromal tumors (GIST) was extrapolated based on data in adults with GIST or solid tumors and children with solid tumors.

Methods

Integrated population pharmacokinetics (PK), PK/pharmacodynamics (PD), and exposure–response analyses using nonlinear mixed-effects modeling approaches were performed to extrapolate PK and PD of sunitinib in children with GIST at projected dose(s) with plasma drug exposures comparable to 50-mg/day in adults with GIST. The analysis datasets included PK/PD data in adults with GIST and adults and children with solid tumors. The effect of covariates on PK and safety/efficacy endpoints were explored.

Results

Two-compartment models with lag time were successfully used to describe the PK of sunitinib and its active metabolite SU012662. PK/PD models were successfully built to describe key continuous safety and efficacy endpoints. The effect of age on sunitinib apparent clearance (CL/F) and body surface area on SU012662 CL/F was statistically significant (P ≤ 0.001): children who were younger or of smaller body size had lower CL/F; however, age and body size did not appear to negatively affect safety or efficacy response to plasma drug exposure.

Conclusion

Based on PK, safety, and efficacy trial simulations, a sunitinib starting dose of ~ 25 mg/m²/day was predicted to provide comparable plasma drug exposures in children with GIST as in adults with GIST treated with 50 mg/day. However, in the absence of a tumor type effect of sunitinib on CL/F in children, the projected equivalent dose for this population would be ~ 20 mg/m²/day.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00280-020-04221-x.

Population pharmacokinetics-pharmacodynamics of sunitinib in pediatric patients with solid tumors

Purpose

The safety profile of sunitinib in children, including the impact of sunitinib exposure on safety endpoints, was assessed using population pharmacokinetic (PK) and pharmacokinetic–pharmacodynamic (PK–PD) models.

Methods

Data were from two clinical studies in 59 children with solid tumors (age range 2–21 years, 28 male/31 female, body weight range 16.2–100 kg, body surface are [BSA] range 0.7–2.1 m²). Analysis of covariates that affected PK and PD parameters was conducted using a nonlinear mixed-effects model. Safety and tolerability endpoints were absolute neutrophil count, hepatic transaminases, diastolic blood pressure, hemoglobin, lymphocyte count, platelet count, white blood cell count, hand-foot syndrome, fatigue, nausea, intracranial hemorrhage, and vomiting.

Results

The models well described the time courses of concentrations of sunitinib and its primary active metabolite SU012662, as well as safety and tolerability endpoints. In PK models for sunitinib and SU012662, BSA was the only covariate that statistically significantly affected apparent clearance (CL/F) and apparent central volume of distribution (Vc/F). Higher BSA was associated with greater CL/F and Vc/F. No statistically significant covariates were identified in the PK–PD models. For safety endpoints that had a sufficient number of adverse events, a higher probability of adverse events was associated with higher average plasma sunitinib concentrations.

Conclusion

In PK models, BSA was the only covariate that affected major PK parameters of sunitinib and SU012662. Based on analysis of safety and tolerability endpoints, the PK–PD relationships were mainly driven by sunitinib plasma exposures and were not affected by age, sex, respective baseline safety endpoint values, baseline Eastern Cooperative Oncology Group performance status, or body size.

Trial registration

ClinicalTrials.gov: NCT00387920 (registered October 13, 2006), NCT01462695 (registered October 31, 2011).

Electronic supplementary material

The online version of this article (10.1007/s00280-020-04106-z) contains supplementary material, which is available to authorized users.

Physiologically Based Pharmacokinetic Modeling and Simulation of Sunitinib in Pediatrics

Using physiologically based pharmacokinetic (PBPK) modeling and simulations, this study estimated the exposure of sunitinib and its active metabolite SU012662 in pediatric patients. A PBPK simulator, SimCYP, was used to develop and validate the pharmacokinetic models. Model development employed a combined "bottom-up" and "top-down" approach to fully utilize the available in vitro or in silico experimental data and in vivo observed clinical data. First, the PBPK model for sunitinib was established, then the cytochrome P450 3A4-mediated metabolism of sunitinib was used as the input for SU012662. PBPK models were validated using pharmacokinetics of sunitinib and SU012662 from one study in adult patients with solid tumors and three clinical trials in pediatric patients with solid or gastrointestinal stromal tumors. The models were further used to predict the exposure of sunitinib and SU012662 by pediatric age groups. The PBPK models for sunitinib and SU012662 developed based on pharmacokinetic characteristics in adults successfully predicted the observed in vivo pharmacokinetics of sunitinib and SU012662 in both adults and pediatric patients. Based on the SimCYP model predictions, a daily dose of 20 mg/m² will produce sunitinib and SU012662 total exposures in pediatric patients similar to those in adults with gastrointestinal stromal tumor treated with a clinical dose of 50 mg once daily.

Sunitinib in pediatric patients with advanced gastrointestinal stromal tumor: results from a phase I/II trial

BACKGROUND

Sunitinib is approved for treatment of adults with imatinib-resistant gastrointestinal stromal tumor (GIST) or imatinib intolerance.

METHODS

This single-arm, multicenter, multinational phase I/II clinical trial (NCT01396148) enrolled eligible patients aged 6 to < 18 years with advanced, unresectable GIST with non-mutant KIT, or who demonstrated disease progression or intolerance to imatinib. Patients received sunitinib 15 mg/m² per day, 4-weeks-on/2-weeks-off (schedule 4/2), for ≤ 18 cycles over 24 months. Intra-patient dose escalation to 22.5 and subsequently 30 mg/m² were permitted based on individual patient tolerability and supported by real-time pharmacokinetics (PK). Primary objective was PK characterization. Secondary objectives included safety, antitumor activity and PK/pharmacodynamic relationships.

RESULTS

Six patients were enrolled with median (range) age of 14 (13-16) years. All six patients completed at least three treatment cycles, with one completing all 18 cycles. Five patients had a dose increase to 22.5 mg/m²; two of them had a further dose increase to 30 mg/m². The average daily dose at cycle 3 was 21.1 mg/m² (n = 6). Steady-state plasma concentrations were reached by day 15, cycle 1. No tumor responses were observed, but three patients had stabilization of the disease (50%). Median progression-free survival was 5.8 months (95% CI 2.3-not reached). There were no serious adverse events.

CONCLUSIONS

The tolerable dose of sunitinib in chemotherapy-naïve pediatric patients is at least 20 mg/m² on schedule 4/2. The safety profile and PK of sunitinib in pediatric patients with GIST are comparable to those in adults.

Efficacy and Safety of Sunitinib in Patients with Well-Differentiated Pancreatic Neuroendocrine Tumours

BACKGROUND

In a phase III study, sunitinib led to a significant increase in progression-free survival (PFS) versus placebo in patients with pancreatic neuroendocrine tumours (panNETs). This study was a post-marketing commitment to support the phase III data.

METHODS

In this ongoing, open-label, phase IV trial (NCT01525550), patients with progressive, advanced unresectable/metastatic, well-differentiated panNETs received continuous sunitinib 37.5 mg once daily. Eligibility criteria were similar to those of the phase III study. The primary endpoint was investigator-assessed PFS per Response Evaluation Criteria in Solid Tumours v1.0 (RECIST). Other endpoints included PFS per Choi criteria, overall survival (OS), objective response rate (ORR), and adverse events (AEs).

RESULTS

Sixty-one treatment-naive and 45 previously treated patients received sunitinib. By March 19, 2016, 82 (77%) patients had discontinued treatment, mainly due to disease progression. Median treatment duration was 11.7 months. Investigator-assessed median PFS per RECIST (95% confidence interval [CI]) was 13.2 months (10.9-16.7): 13.2 (7.4-16.8) and 13.0 (9.2-20.4) in treatment-naive and previously treated patients, respectively. ORR (95% CI) per RECIST was 24.5% (16.7-33.8) in the total population: 21.3% (11.9-33.7) in treatment-naive and 28.9% (16.4-44.3) in previously treated patients. Median OS, although not yet mature, was 37.8 months (95% CI, 33.0-not estimable). The most common treatment-related AEs were neutropenia (53.8%), diarrhoea (46.2%), and leukopenia (43.4%).

CONCLUSIONS

This phase IV trial confirms sunitinib as an efficacious and safe treatment option in patients with advanced/metastatic, well-differentiated, unresectable panNETs, and supports the phase III study outcomes. AEs were consistent with the known safety profile of sunitinib.

Clinical Implications of the Pharmacokinetics of Crizotinib in Populations of Patients with Non-Small Cell Lung Cancer

PURPOSE

We assessed the effect of baseline patient demographic and disease characteristics on the crizotinib pharmacokinetic parameters oral clearance (CL/F), volume of distribution (V2/F), and area under the curve at steady state (AUC_ss) following multiple crizotinib 250-mg twice-daily dosing in patients with ALK-positive cancer.

EXPERIMENTAL DESIGN

A pharmacokinetic model was fit to data from 1,214 patients. We identified statistically significant covariates (P ≤ 0.001) by evaluating their effects on CL/F and V2/F and estimated their magnitudes.

RESULTS

Age, Eastern Cooperative Oncology Group performance status, aspartate aminotransferase (AST) levels, albumin levels, and smoking status had no effect on CL/F or V2/F. Statistically significant covariates were Asian race and female sex for CL/F and V2/F and body weight, creatinine clearance (CLcr), and total bilirubin for CL/F only. The model predicted that CL/F would be 9% lower or higher in a 40-kg or a 100-kg patient, respectively; 16% lower in patients with CLcr 30 mL/minute; 23% lower in Asians; and 11% lower in females than the reference patient (65-kg non-Asian male; baseline CLcr, 91.6 mL/minute; total bilirubin, 0.41 mg/dL). The effect of total bilirubin on CL/F was small. V2/F was 23% lower in Asians than non-Asians and females than males. Effects of all significant covariates on AUC_ss were not predicted to be clinically relevant.

CONCLUSIONS

Crizotinib at a 250-mg twice-daily starting dose appears to be appropriate for all patients irrespective of age, sex, race, body weight, mild or moderate renal impairment, or hepatic function (in the range evaluated: bilirubin ≤ 2.1 mg/dL or AST ≤124 U/L). Clin Cancer Res; 22(23); 5722-8. ©2016 AACR.

Effect of gastrointestinal resection on sunitinib exposure in patients with GIST

Background

GIST patients often undergo GI-surgery. Previous studies have shown that imatinib and nilotinib exposures were decreased in GIST patients with prior major gastrectomy. We investigated whether major gastrectomy influences the exposure to sunitinib and its active metabolite SU12662.

Methods

Pharmacokinetic data from 305 GIST patients included in 4 phase I-III trials were analyzed. Patients were subdivided into 6 groups according to their prior GI-surgery. Apparent clearance (CL/F) and dose-corrected steady-state plasma exposures (AUC_24,ss) of sunitinib and SU12662 were estimated using a population PK approach. ANCOVA was performed to test for differences in AUC_24,ss and CL/F between each surgery subgroup and controls.

Results

Major gastrectomy did not influence sunitinib or SU12662 exposure. The geometric mean of sunitinib and SU12662 AUC_24,ss was decreased by 21% and 28% in patients with both gastrectomy and small bowel resection (n = 8) compared to controls (n = 63) for sunitinib (931 ng*hr/mL (95%-CI; 676–1283) versus 1177 ng*hr/mL (95%-CI; 1097–1263); p < 0.05) and SU12662 (354 ng*hr/mL (95%-CI; 174–720) versus 492 ng*hr/mL (95%-CI; 435–555); p < 0.05). No significant differences in exposure were observed in each of the other subgroups versus controls.

Conclusion

In contrast to previous results for imatinib and nilotinib, gastrectomy alone does not influence sunitinib or SU12662 exposure. This should be taken into account for the treatment of gastrectomized GIST patients with TKIs. In patients who had undergone both gastrectomy and small bowel resection, sunitinib and SU12662 exposures are significantly, although clinically not relevantly, decreased.

Sunitinib in combination with trastuzumab for the treatment of advanced breast cancer: activity and safety results from a phase II study

Background

This phase II study evaluated the efficacy and safety/tolerability of sunitinib plus trastuzumab in patients with HER2-positive advanced breast cancer (ABC).

Methods

Eligible patients received sunitinib 37.5 mg/day and trastuzumab administered either weekly (loading, 4 mg/kg; then weekly 2 mg/kg) or 3-weekly (loading, 8 mg/kg; then 3-weekly 6 mg/kg). Prior trastuzumab and/or lapatinib treatment were permitted. The primary endpoint was objective response rate (ORR).

Results

Sixty patients were enrolled and evaluable for safety; 57 were evaluable for efficacy. The majority of patients (58%) had received no prior chemotherapy in the metastatic setting. The ORR was 37%; the clinical benefit rate (CBR; percent objective response plus stable disease ≥ 24 weeks) was 56%. Among patients who were treatment-naïve or had received only adjuvant therapy, the ORR was 44% and the CBR was 59%. Overall, median overall survival had not been reached and the 1-year survival rate was 91%. The majority of adverse events (AEs) were mild to moderate in severity. Forty percent of patients experienced AEs related to measured left ventricular ejection fraction (LVEF) declines, which occurred more frequently in patients who had received prior anthracycline treatment. Ten percent of patients exhibited symptoms related to LVEF declines. One patient died on study from cardiogenic shock. Antitumor response and several safety parameters appeared to correlate with sunitinib exposure.

Conclusions

Sunitinib plus trastuzumab demonstrated antitumor activity in patients with HER2-positive ABC, particularly those who were treatment-naïve or had only received prior adjuvant treatment. Sunitinib plus trastuzumab had acceptable safety and tolerability in patients with HER2-positive ABC who had not received prior anthracycline therapy.

Trial registration

NCT00243503

Phase I study of sunitinib plus capecitabine/cisplatin or capecitabine/oxaliplatin in advanced gastric cancer

BACKGROUND

We evaluated the maximum tolerated dose (MTD) and safety of sunitinib plus capecitabine/cisplatin (XP) or capecitabine/oxaliplatin (XELOX) in Korean patients with advanced gastric cancer (GC).

METHODS

Sunitinib (37.5 or 25 mg/day) was administered on a 2-week-on/1-week-off schedule with chemotherapy. Assessments included dose-limiting toxicity (DLT), safety, pharmacokinetics, and antitumor activity.

RESULTS

Twenty-eight patients received sunitinib/XP; 48 received sunitinib/XELOX. The MTDs were: sunitinib 25 mg/day, cisplatin 80 mg/m(2), and capecitabine 1,000 mg/m(2); sunitinib 37.5 mg/day, oxaliplatin 110 mg/m(2), and capecitabine 800 mg/m(2); and sunitinib 25 mg/day, oxaliplatin 110 mg/m(2), and capecitabine 1,000 mg/m(2). DLTs at the MTDs comprised grade (G) 4 febrile neutropenia plus G3 diarrhea (n = 1; sunitinib/XP), dose delays due to hematologic toxicity (n = 2; both sunitinib/XP), G3 bleeding (menorrhagia; n = 1; sunitinib/XELOX), and G3 increased alanine aminotransferase levels (n = 1; sunitinib/XELOX). There was a high frequency of G3/4 hematologic adverse events observed with both treatment regimens, particularly with sunitinib/XP. Frequent non-hematologic, G3/4 adverse events were nausea, stomatitis, and hypophosphatemia with sunitinib/XP and hypophosphatemia and pulmonary embolism with sunitinib/XELOX. No drug-drug interactions were apparent. At the MTDs, median progression-free survival was 6.4 months and 5.5-8.0 months for sunitinib/XP and sunitinib/XELOX, respectively; and the objective response rate was 46.7% and 43.5-45.5% for sunitinib/XP and sunitinib/XELOX, respectively.

CONCLUSIONS

At the MTD, sunitinib/XELOX had an acceptable safety profile in patients with advanced GC.

Randomized phase II study of sunitinib versus standard of care for patients with previously treated advanced triple-negative breast cancer

PURPOSE

This randomized, open-label phase II study compared the efficacy of sunitinib monotherapy with that of single-agent standard-of-care (SOC) chemotherapy in patients with previously treated advanced triple-negative breast cancer (TNBC).

METHODS

Patients with advanced TNBC, relapsed after anthracycline- and taxane-based chemotherapy, were randomized to receive either sunitinib (37.5 mg/day) or the investigator's choice of SOC therapy. Progression-free survival was the primary endpoint.

RESULTS

Median progression-free survival was 2.0 months with sunitinib and 2.7 months with SOC chemotherapy (one-sided P = 0.888). Median overall survival was not prolonged with sunitinib (9.4 months) compared with SOC chemotherapy (10.5 months; one-sided P = 0.839). The objective response rate was 3% with sunitinib and 7% with SOC chemotherapy (one-sided P = 0.962).

CONCLUSIONS

Sunitinib monotherapy did not improve efficacy compared with SOC chemotherapy in patients with previously treated advanced TNBC, for which identification of effective treatments and therapeutic targets remains an urgent need.

TRIAL REGISTRATION

NCT00246571.

The influence of gastrointestinal resection on sunitinib exposure in GIST patients

10547

Background: GIST patients often have an altered anatomy of the GI tract due to either primary resection of the tumor or palliative surgery. It is unknown whether such GI resections affect the exposure to sunitinib and its active metabolite SU12662. Previous studies showed that the exposure to imatinib and nilotinib was decreased in GIST patients with prior major gastrectomy. Therefore, we postulated that GI resections might similarly affect sunitinib exposure. Methods: A retrospective analysis was performed to assess the effect of GI resections on sunitinib exposure. Pharmacokinetic data from 305 GIST patients included in 4 phase I-II trials were analyzed. Patients were subdivided into 6 groups according to prior GI surgery: 1)Major gastrectomy: 2)Partial gastrectomy: 3)Small bowel resection: 4)Combination of gastrectomy and small bowel resection: 5)Colon resection and 6)Controls with no prior GI surgery. Patients with uncertain GI resections were excluded. Dose normalized exposure (AUC0-24hr) of sunitinib and SU12662 was estimated with a population PK approach using NONMEM. Analysis of covariance was performed to test for significant differences in AUC between each of the subgroups and controls. Results: The geometric mean of total exposure to sunitinib and SU12662 was decreased by 21% and 28% in subgroup 4, (n=8; sunitinib: 931 ng*hr/mL (95%CI;676-1283) and SU12662: 354 ng*hr/mL (95%CI;174-720)) compared to controls (n=63; sunitinib: 1177 ng*hr/mL (95%CI;1097-1263) and SU12662: 491 ng*hr/mL (95%CI;435-555)), with the differences being significant (p<0.05) on the log scale. However, no significant differences in total exposures were observed between each of the other subgroups and control. Conclusions: In patients with a combined gastrectomy and small bowel resection, sunitinib and SU12662 exposure is significantly decreased as compared to subjects with no prior GI surgery. Contrary to previous results for imatinib, gastrectomy alone does not appear to influence sunitinib exposure. This should be taken into consideration for the treatment of GIST patients who had a gastrectomy. In theory, such patients might have better outcomes if treated with sunitinib, given the risk of subtherapeutic exposure to imatininb.

A phase I study of sunitinib combined with modified FOLFOX6 in patients with advanced solid tumors

PURPOSE

This phase I study assessed the safety, tolerability, maximum tolerated dose (MTD), pharmacokinetics, and preliminary antitumor effects of sunitinib combined with modified FOLFOX6 (mFOLFOX6).

METHODS

Patients with advanced solid malignancies received mFOLFOX6 in 2-week cycles with escalating sunitinib doses (25, 37.5, and 50 mg/day) on three schedules: 2 weeks on, 2 weeks off (2/2); 4 weeks on, 2 weeks off (4/2); or continuous daily dosing (CDD). Patients received up to 8 treatment cycles (Schedule 2/2 and CDD schedule) or 6 cycles (Schedule 4/2). An expansion cohort enrolled patients with metastatic colorectal cancer at the Schedule 2/2 MTD.

RESULTS

Overall, 53 patients were enrolled, with 43 evaluable for dose-limiting toxicity (DLT). On Schedule 2/2 (n = 18), DLTs occurred in three patients at 50 mg/day (grade 4 neutropenia [n = 1]; grades 3 and 4 thrombocytopenia [n = 2]) and two patients achieved partial responses (PRs). On Schedule 4/2 (n = 13), 37.5 mg/day exceeded the MTD with two DLTs (febrile neutropenia and grade 4 hypokalemia, respectively). On the CDD schedule (n = 12), the MTD was 25 mg/day; one DLT (grade 3 stomatitis) was reported and two patients achieved PRs. The most common adverse events were neutropenia, fatigue, and thrombocytopenia. No clinically significant drug-drug interactions were apparent between sunitinib, its metabolite SU12662, and mFOLFOX6.

CONCLUSIONS

Sunitinib combined with mFOLFOX6 had acceptable tolerability. The MTDs were sunitinib 50 mg/day on Schedule 2/2 and 25 mg/day on the CDD schedule. A MTD for Schedule 4/2 was not established.

A retrospective analysis of data from two trials of sunitinib in patients with advanced renal cell carcinoma (RCC): Pitfalls of efficacy subgroup analyses based on dose-reduction status

363

Background: Patients requiring sunitinib dose reduction who received a novel dose/schedule modification scheme had longer progression-free survival (PFS) than patients who did not require dose reduction and remained on 50 mg Schedule 4/2 (4 weeks on, 2 weeks off) (Bjarnason 2011). Our analysis compared sunitinib efficacy in advanced RCC patients with/without dose reduction using the label-approved, dose-reduction scheme (ie, 50 mg/37.5 mg/25 mg) and schedule (Schedule 4/2) and explored potential causes of any differences.

Methods: Data from a Phase 3 and a Phase 2 trial, sunitinib Schedule 4/2 arms only (N=375 and 146, respectively), were retrospectively analyzed, and pharmacokinetics and baseline characteristics of patients with/without dose reduction compared.

Results: In the Phase 3 trial, median (95% CI) PFS was 14.0 (13.1–16.2) months (mos) and 8.1 (6.3–10.6) mos with (n=194) and without (n=181) dose reduction, respectively. In the Phase 2 trial, corresponding PFS values were 13.4 (9.8–19.8) mos and 5.8 (3.9–8.5) mos (n=51 and 95, respectively). In the Phase 2 trial, steady-state mean (SD) total drug trough concentrations were 96.0 (42.2) ng/mL and 85.8 (43.4) ng/mL on Day 29 of Cycle 1 in patients with/without dose reduction, respectively. In both studies, the percent of patients with baseline Memorial Sloan-Kettering Cancer Center risk factors of 0 (favorable), 1–2 (intermediate), and 3 (poor) were 37–47%, 53–57% and 0–6% with dose reduction vs. 25–28%, 65–72%, and 0–10% without dose reduction. The mean (range) time to dose reduction was 7.2 (0.03–40.4) mos in the Phase 3 trial and 4.5 (0.4–22.6) mos in the Phase 2 trial.

Conclusions: Patients with dose reduction remaining on Schedule 4/2 appeared to have longer PFS than patients with no dose reduction. The differences were not caused by differences in plasma drug exposures; they appeared to be due, at least in part, to 1) differences in patients’ baseline prognostic factors and 2) patients’ PFS or longevity affecting their dose-reduction status. Thus, efficacy subgroup analysis based on patients’ dose-reduction status appears to be confounded, leading to biased results.

Effect of hydrochlorothiazide on the pharmacokinetics and pharmacodynamics of febuxostat, a non-purine selective inhibitor of xanthine oxidase

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Hyperuricaemia and gout frequently coexist with cardiovascular disorders such as hypertension and heart failure. The use of diuretics has been re-established as a first-line treatment for patients with hypertension and the effects of diuretics on serum uric acid may diminish the urate-lowering effects of febuxostat, a novel, potent, non-purine selective inhibitor of xanthine oxidase.

WHAT THIS STUDY ADDS

Co-administration of febuxostat 80 mg and hydrochlorothiazide 50 mg had no effect on the pharmacokinetics and did not have a clinically significant effect on the pharmacodynamics of febuxostat. Dose adjustment for febuxostat is not necessary when it is administered with hydrochlorothiazide.

AIM

This study examined the effect of co-administration of febuxostat, an investigational urate lowering therapy, and hydrochlorothiazide on the pharmacokinetics and pharmacodynamics of febuxostat.

METHODS

Healthy subjects (36 healthy men and women) received single doses of febuxostat 80 mg alone and febuxostat 80 mg + hydrochlorothiazide 50 mg, separated by 7 days in an open-label, randomized, crossover fashion. Plasma concentrations of febuxostat and urinary and serum concentrations of uric acid were assessed.

RESULTS

Mean febuxostat C(max), AUC((0-t)), AUC((0-infinity)), t(1/2,z), CL/F and V(ss)/F values for regimens co-administration/febuxostat alone were 2.9/2.9 microg ml(-1), 9.3/9.1 microg ml(-1) h, 9.6/9.3 microg ml(-1) h, 6.5/6.1 h, 8.8/9.3 l h(-1) and 45/44 l, respectively. Geometric mean ratios (co-administration : febuxostat alone) and their 90% confidence intervals for febuxostat plasma C(max), AUC((0-t)), and AUC((0-infinity)) were 1.00 (0.86, 1.17), 1.03 (0.98, 1.09), and 1.04 (0.98, 1.10), respectively; all of the 90% CIs were within the no effect range of 0.8 to 1.25. Serum uric acid C(mean,24h), C(mean,48h) and CL(R) for both regimens co-administration/febuxostat alone were 216/203 micromol l(-1), 218/202 micromol l(-1) and 9.1/10.1 ml min(-1), respectively. Although serum uric acid C(mean,24h) and C(mean,48h) values were higher and CL(R) values lower after co-administration compared with dosing of febuxostat alone, with the differences being statistically significant (P < 0.003), none of the differences (6.5%-9.5%) was considered clinically significant.

CONCLUSION

Dose adjustment for febuxostat is not necessary when it is administered with hydrochlorothiazide.

Metabolism and excretion of [14C] febuxostat, a novel nonpurine selective inhibitor of xanthine oxidase, in healthy male subjects

Absorption, metabolism, and excretion of one 80 mg oral dose of [(14)C] febuxostat ([thiazole-4-(14)C] 2-[3-cyano-4-isobutoxyphenyl]-4-methyl-5-thiazolecarboxylic acid) were studied in 6 healthy subjects. Mean cumulative recovery in excreta was 94% (49% urine and 45% feces) of the dose over 9 days; 87% of the dose was profiled. Seventeen radioactive peaks were observed in urine and fecal chromatograms. Unchanged febuxostat contributed to a combined total in excreta of 10% to 18% of the dose, indicating that it was extensively metabolized and well absorbed. Metabolites were 67M-1 (10%) and 67M-2 (11%) hydroxylated febuxostat, febuxostat acyl-glucuronide (30%), 67M-4 di-carboxylic acid (14%), 67M-1 sulfate conjugate (3%), and dehydrated 67M-1/67M-2 acyl-glucuronide (0.5%). Febuxostat and these metabolites accounted for 82% of profiled dose; unidentified peaks individually contributed <1.3% of the dose. Febuxostat and total radioactivity plasma C(max) values were observed at 0.5 hour postdose, suggesting that febuxostat was quickly absorbed. At 4 hours postdose, plasma chromatographic profiles contained 6 peaks: febuxostat (85%), 67M-1 (4%), 67M-2 (5%), febuxostat acyl-glucuronide (4%), 67M-4 (1%), and 67M-1 sulfate (0.5%). Compared to total radioactivity, febuxostat accounted for 94% at C(max) and 83% of the area under the concentration-time curve (AUC) values. Based on the whole blood to plasma total radioactivity, little radioactivity was associated with red blood cells.

Pharmacokinetics and safety of sunitinib malate in subjects with impaired renal function

This phase I, open-label, single-dose study evaluates the effects of severe renal impairment and end-stage renal disease (ESRD) requiring hemodialysis on the pharmacokinetics, safety, and tolerability of sunitinib and its primary active metabolite, SU12662. Subjects with normal renal function (creatinine clearance > 80 mL/min), severe renal impairment (creatinine clearance < 30 mL/min), and ESRD requiring hemodialysis receive a single dose of sunitinib 50 mg. Serial blood samples are collected for quantification of plasma concentrations using a validated liquid chromatography with tandem mass spectrometry assay. Safety is monitored. Twenty-four subjects complete the study. Pharmacokinetics in subjects with severe renal impairment appear similar to those with normal renal function. Plasma exposure to sunitinib and SU12662 appears lower in subjects with ESRD compared with subjects with normal renal function or severe renal impairment. Single-dose sunitinib 50 mg is well tolerated regardless of renal function. The currently approved starting dose of sunitinib 50 mg on Schedule 4/2 is expected to be appropriate for patients with renal impairment; any subsequent dose modifications should be based on patients' ability to tolerate treatment.

The effect of age and gender on pharmacokinetics, pharmacodynamics, and safety of febuxostat, a novel nonpurine selective inhibitor of xanthine oxidase

Febuxostat is a novel nonpurine selective inhibitor of xanthine oxidase, which is currently being developed for the management of hyperuricemia in patients with gout. The effect of age and gender on the pharmacokinetics, pharmacodynamics, and safety of once-daily oral febuxostat 80 mg was assessed in healthy male and female subjects after 7 days. Following multiple dosing with febuxostat, there were no statistically significant differences in the plasma or urinary pharmacokinetic or pharmacodynamic parameters between subjects aged 18 to 40 years and >or=65 years. Although unbound peak concentration (C(max,u)) and area under the concentration-time curve (AUC(24,u)) for febuxostat were higher in women as compared with men (31.5 vs 23.6 ng/mL, P <or= .01, and 62.8 vs 53.9 ng x h/mL, P <or= .05, for C(max,u) and AUC(24,u), respectively), the differences were not considered clinically significant and could be largely accounted for by weight differences between male and female subjects. For pharmacodynamic parameters, even though the percentage decrease in serum uric acid 24-hour mean concentration was slightly greater in women than in men (59% vs 52%, P <or= .01), this difference was not considered clinically meaningful. Febuxostat was well tolerated in male and female subjects in both age groups. Age or gender had no clinically significant effect on the pharmacokinetics, pharmacodynamics, or safety of febuxostat. Therefore, febuxostat does not require any dose adjustments based on age or gender.

Effect of food or antacid on pharmacokinetics and pharmacodynamics of febuxostat in healthy subjects

What is already known about this subject. Febuxostat is a novel nonpurine selective inhibitor of xanthine oxidase. What this study adds. This is the first manuscript to address the effect of food and antacid on the pharmacokinetics and/or pharmacodynamics of febuxostat. The study will determine whether the drug can be administered regardless of food or antacid. It will therefore influence how the drug should be administered.

AIMS

To evaluate the effects of food or antacid on the pharmacokinetics and/or pharmacodynamics of febuxostat.

METHODS

Four Phase I, two-period, crossover studies were performed in healthy male and female subjects. Subjects either received single 40-mg (n = 24), multiple 80-mg (n = 24) and single 120-mg (n = 20) doses of febuxostat in fasting and nonfasting conditions, or received single 80-mg (n = 24) doses alone or with antacid.

RESULTS

Food caused a decrease in C(max) (38-49%) and AUC (16-19%) of febuxostat at different dose levels following single or multiple oral dosing with febuxostat. However, a slightly greater percent decrease in serum uric acid concentrations (58% vs. 51%) after multiple dosing with 80 mg of febuxostat under nonfasting conditions was observed, which was statistically (P < 0.05) but not clinically significant. Antacid caused a decrease in C(max) (32%), but had no effect on AUC of febuxostat. Febuxostat was safe and well tolerated in all studies.

CONCLUSIONS

Even though food caused a decrease in the rate and extent of absorption of febuxostat, this decrease was not associated with a clinically significant change in febuxostat pharmacodynamic effect. Despite a decrease in the absorption rate of febuxostat, antacid had no effect on the extent of febuxostat absorption. Therefore, febuxostat can be administered regardless of food or antacid intake.

Pharmacokinetic interactions of concomitant administration of febuxostat and NSAIDs

To evaluate the effect of febuxostat on the pharmacokinetics of indomethacin and naproxen and vice versa, 2 multiple-dose, 3-period crossover studies were performed in healthy subjects. In study 1, subjects received febuxostat 80 mg once daily, indomethacin 50 mg twice daily, or both. In study 2, subjects received febuxostat 80 mg, naproxen 500 mg twice daily, or both. Twenty-four-hour blood samples were collected on day 5 in study 1 and day 7 in study 2. In study 1, 90% confidence intervals of geometric mean ratios for maximum plasma concentration (Cmax) and area under the curve (AUC) were within the 0.80 to 1.25 no-effect range for febuxostat and indomethacin. In study 2, 90% confidence intervals for febuxostat C(max) and AUC extended above that range, with increases of 28% and 40% in Cmax and AUC24, respectively. However, 90% confidence intervals for naproxen C(max) and AUC were within the 0.80 to 1.25 range. Febuxostat had no effect on the plasma pharmacokinetics of indomethacin and naproxen. Similarly, indomethacin had no effect on the plasma pharmacokinetics of febuxostat. Although naproxen caused an increase in plasma exposure to febuxostat, this increase is not expected to be clinically significant. Therefore, based on the plasma pharmacokinetic data in healthy subjects, febuxostat may be administered with indomethacin or naproxen with no dose adjustments for febuxostat, indomethacin, or naproxen.

The effect of mild and moderate hepatic impairment on pharmacokinetics, pharmacodynamics, and safety of febuxostat, a novel nonpurine selective inhibitor of xanthine oxidase

To assess the effect of hepatic impairment on the pharmacokinetics, pharmacodynamics, and safety of febuxostat at steady state, multiple once-daily 80-mg oral doses of febuxostat were administered to subjects with normal hepatic function and to subjects with mild or moderate hepatic impairment. There were no statistically significant differences in the plasma pharmacokinetic parameters for unbound febuxostat and its active metabolites between subjects with mild or moderate hepatic impairment and those with normal hepatic function. The percentage decrease in serum uric acid appeared to be lower in hepatic impairment groups (49% [mild] and 48% [moderate]) as compared to the normal hepatic group (62%). This lower percentage decrease was minimal and not considered clinically significant. Febuxostat 80 mg once daily appears to be generally safe and well tolerated in mildly and moderately impaired hepatic function groups, and dose adjustment is not required in subjects with mild to moderate hepatic impairment.

Quantification of uric acid, xanthine and hypoxanthine in human serum by HPLC for pharmacodynamic studies

A simple HPLC method was developed and validated for the determination of uric acid (UA), xanthine (X) and hypoxanthine (HX) concentrations in human serum to support pharmacodynamic (PD) studies of a novel xanthine oxidase inhibitor during its clinical development. Serum proteins were removed by ultrafiltration. The hydrophilic analytes and the I.S. were eluted by 100% aqueous phosphate buffer mobile phase. The hydrophobic matrix components (late peaks) were eluted with a step gradient of a higher organic mobile phase. Validation on linearity, sensitivity, precision, accuracy, stability, and robustness of the method for PD biomarkers (UA, X, and HX) was carried out in a similar manner to that for pharmacokinetic (PK) data where applicable. Issues of selectivity for endogenous biomarker analytes and individual concentration variations were addressed during method validation. Standards were prepared in analyte-free phosphate buffer. Quality control samples were prepared in control serum from individuals not dosed with the xanthine oxidase inhibitor. The method was simple and robust with good accuracy and precision for the measurement of serum UA, X, and HX concentrations.

Pharmacokinetics, Pharmacodynamics and Safety of Febuxostat, a Non-Purine Selective Inhibitor of Xanthine Oxidase, in a Dose Escalation Study in Healthy Subjects

BACKGROUND

Febuxostat is a novel non-purine selective inhibitor of xanthine oxidase currently being developed for the management of hyperuricemia in patients with gout.

OBJECTIVE

To investigate the pharmacokinetics, pharmacodynamics and safety of febuxostat over a range of oral doses in healthy subjects.

METHODS

In a phase I, dose-escalation study, febuxostat was studied in dose groups (10, 20, 30, 40, 50, 70, 90, 120, 160, 180 and 240 mg) of 12 subjects each (10 febuxostat plus 2 placebo). In all groups, subjects were confined for 17 days and were administered febuxostat once daily on day 1, and days 3-14. During the course of the study, blood and urine samples were collected to assess the pharmacokinetics of febuxostat and its metabolites, and its pharmacodynamic effects on uric acid, xanthine and hypoxanthine concentrations after both single and multiple dose administration. Safety measurements were also obtained during the study.

RESULTS

Orally administered febuxostat was rapidly absorbed with a median time to reach maximum plasma concentration following drug administration of 0.5-1.3 hours. The pharmacokinetics of febuxostat were not time dependent (day 14 vs day 1) and remained linear within the 10-120 mg dose range, with a mean apparent total clearance of 10-12 L/h and an apparent volume of distribution at steady state of 33-64 L. The harmonic mean elimination half-life of febuxostat ranged from 1.3 to 15.8 hours. The increase in the area under the plasma concentration-time curve of febuxostat at doses >120 mg appeared to be greater than dose proportional, while the febuxostat maximum plasma drug concentration was dose proportional across all the doses studied. Based on the urinary data, febuxostat appeared to be metabolised via glucuronidation (22-44% of the dose) and oxidation (2-8%) with only 1-6% of the dose being excreted unchanged via the kidneys. Febuxostat resulted in significant decreases in serum and urinary uric acid concentrations and increases in serum and urinary xanthine concentrations. The percentage decrease in serum uric acid concentrations ranged from 27% to 76% (net change: 1.34-3.88 mg/dL) for all doses and was dose linear for the 10-120 mg/day dosage range. The majority of adverse events were mild-to-moderate in intensity.

CONCLUSION

Febuxostat was well tolerated at once-daily doses of 10-240 mg. There appeared to be a linear pharmacokinetic and dose-response (percentage decrease in serum uric acid) relationship for febuxostat dosages within the 10-120 mg range. Febuxostat was extensively metabolised and renal function did not seem to play an important role in its elimination from the body.

Febuxostat (TMX-67), a novel, non-purine, selective inhibitor of xanthine oxidase, is safe and decreases serum urate in healthy volunteers

In order to evaluate the safety, pharmacological properties, and urate-lowering efficacy of febuxostat, a non-purine, selective inhibitor of xanthine oxidase, a Phase 1, 2-week, multiple-dose, placebo-controlled, dose-escalation study was conducted in 154 healthy adults of both sexes. Daily febuxostat doses in the range 10 mg to 120 mg resulted in proportional mean serum urate reductions ranging from 25% to 70% and in proportional increases in maximum febuxostat plasma concentrations and area under plasma concentration versus time curves. Accompanying the hypouricemic effect were increases in serum xanthine concentrations, decreases in urinary uric acid excretion, and increases in urinary xanthine and hypoxanthine excretion, confirming inhibition of xanthine oxidase activity by febuxostat. Hepatic conjugation and oxidative metabolism were the major pathways of elimination of febuxostat from the body, and renal elimination did not appear to play a significant role. Although not uncommon, adverse events were mild and self-limited, and no deaths or serious adverse events were observed. Febuxostat is a safe and potent hypouricemic agent in healthy humans.

Pharmacokinetics and Pharmacodynamics of Febuxostat, a New Non-purine Selective Inhibitor of Xanthine Oxidase in Subjects with Renal Impairment

To assess the safety, pharmacokinetics, and pharmacodynamics of febuxostat in subjects with normal renal function or renal impairment, febuxostat (80 mg/d) was orally administered for 7 days to subjects with normal renal function (n = 11, CLcr >80 mL/min/1.73 m) or to subjects with mild (n = 6, CLcr 50-80 mL/min/1.73 m), moderate (n = 7, CLcr 30-49 mL/min/1.73 m), or severe renal impairment (n = 7, CLcr 10-29 mL/min/1.73 m). The pharmacokinetics of febuxostat and its active quantifiable metabolites 67M-1, 67M-2, and 67M-4 as well as the pharmacodynamics of uric acid, xanthine, and hypoxanthine were determined in plasma (or serum) and urine. Febuxostat was safe and well tolerated. Regression analyses indicated that febuxostat tmax and Cmax,u values were not affected by CLcr. However, for AUC24,u, CLu/F, and t1/2z, regression analyses indicated a statistically significant relationship with CLcr. With the exception of 67M-1 Cmax, regression analyses for 67M-2 and 67M-4 Cmax, and for AUC24 for all 3 metabolites indicated a statistically significant linear relationship with CLcr. Irrespective of renal function group, the mean serum uric acid concentrations decreased by 55% to 64% by day 7. Although plasma exposure to febuxostat and its metabolites was generally higher in subjects with increasing degrees of renal impairment, the percentages of decrease in serum uric acid were comparable regardless of the renal function group. A once-daily 80-mg dose of febuxostat appears to be safe and well tolerated in different renal function groups and does not appear to require any dose adjustment based on differences in renal function.

Transbuccal permeation of a nucleoside analog, dideoxycytidine: effects of menthol as a permeation enhancer

The use of a safe and effective permeation enhancer is paramount to the success of a buccal drug delivery system intended for systemic drug absorption. The enhancing effects of menthol (dissolved in an aqueous buffer in the absence of co-enhancers) on buccal permeation of a model hydrophilic nucleoside analog, dideoxycytidine (ddC), were investigated. In vitro transbuccal permeation of ddC was examined using freshly obtained porcine buccal mucosa. The experiments were carried out in side-bi-side flow through diffusion cells. Permeation enhancement studies were performed with varying concentrations of l-menthol dissolved in Krebs buffer solutions containing ddC. Partition coefficient experiments were carried out to probe into the mechanism of permeation enhancing properties of l-menthol and DSC studies were conducted to determine if there is a eutectic formation between ddC and l-menthol at various concentrations. Permeation of ddC increased significantly (P<0.05) in the presence of l-menthol independent of the concentration of the terpene. The apparent 1-octanol/buffer partition coefficient (log K(p)) of ddC was significantly (P<0.05) increased in presence of l-menthol and was also independent of the enhancer concentration. However, the tissue/buffer partition coefficient (log K'(p)) data showed a concentration dependent increase of log K'(p) in presence of l-menthol. Since log K'(p) is a measure of drug binding to the tissue in addition to drug partitioning, binding of ddC to the buccal tissue may provide an explanation for the concentration dependent increase in these values.