Phase I trial of bortezomib daily dose: safety, pharmacokinetic profile, biological effects and early clinical evaluation in patients with advanced solid tumors.

Purpose This phase I study investigated bortezomib in solid tumors used as a daily subcutaneous regimen. Previous regimens showed only modest activity in solid tumors which was potentially related to sub-optimal tumor penetration. We aimed at exploring if daily low dose administration of bortezomib may allow a greater and tolerable pharmacokinetic exposure which might be required for antitumor activity in solid tumors. Patients and methods This 3 + 3 design, dose escalation, monocentric study aimed at defining the maximum tolerated dose of daily low dose schedule of bortezomib. Tolerability, pharmacokinetics, pharmacodynamics, antitumor activity, biomarkers for proteasome inhibition, pre- and post-treatment tumor biopsies were also evaluated. Results A total of eighteen patients were dosed in 3 bortezomib cohorts (0.5, 0.6 and 0.7 mg/m2), with 3, 11 and 4 patients respectively. Three patients experienced dose-limiting toxicities: Grade (G) 3 Sweet's syndrome (at 0.6 mg/m2), G3 asthenia and anorexia or ataxia (2 patients at 0.7 mg/m2). The most common study drug-related adverse events (all grades) were thrombocytopenia (72%), fatigue (56%), neuropathy (50%), anorexia (44%) and rash (39%). Dose 0.6 mg/m2 of bortezomib was considered as the recommended phase II dose. A significant tumor shrinkage (-36% according to WHO criteria) was observed in one patient with heavily pre-treated GIST, and 2 minor responses (-20%) were recorded in two patients with melanoma and mesothelioma. Conclusion This daily subcutaneous regimen of bortezomib showed a dose dependent plasma exposure, evidence of target inhibition and preliminary signs of clinical activity. However, cumulative neurological toxicity of this dose-dense daily regimen might preclude its further clinical development.

In Vitro and In Vivo Drug-Drug Interaction Studies to Assess the Effect of Abiraterone Acetate, Abiraterone, and Metabolites of Abiraterone on CYP2C8 Activity.

Abiraterone acetate, the prodrug of the cytochrome P450 C17 inhibitor abiraterone, plus prednisone is approved for treatment of metastatic castration-resistant prostate cancer. We explored whether abiraterone interacts with drugs metabolized by CYP2C8, an enzyme responsible for the metabolism of many drugs. Abiraterone acetate and abiraterone and its major metabolites, abiraterone sulfate and abiraterone sulfate N-oxide, inhibited CYP2C8 in human liver microsomes, with IC50 values near or below the peak total concentrations observed in patients with metastatic castration-resistant prostate cancer (IC50 values: 1.3-3.0 µM, 1.6-2.9 µM, 0.044-0.15 µM, and 5.4-5.9 µM, respectively). CYP2C8 inhibition was reversible and time-independent. To explore the clinical relevance of the in vitro data, an open-label, single-center study was conducted comprising 16 healthy male subjects who received a single 15-mg dose of the CYP2C8 substrate pioglitazone on day 1 and again 1 hour after the administration of abiraterone acetate 1000 mg on day 8. Plasma concentrations of pioglitazone, its active M-III (keto derivative) and M-IV (hydroxyl derivative) metabolites, and abiraterone were determined for up to 72 hours after each dose. Abiraterone acetate increased exposure to pioglitazone; the geometric mean ratio (day 8/day 1) was 125 [90% confidence interval (CI), 99.9-156] for Cmax and 146 (90% CI, 126-171) for AUClast Exposure to M-III and M-IV was reduced by 10% to 13%. Plasma abiraterone concentrations were consistent with previous studies. These results show that abiraterone only weakly inhibits CYP2C8 in vivo.

Food effects on abiraterone pharmacokinetics in healthy subjects and patients with metastatic castration-resistant prostate cancer.

Food effect on abiraterone pharmacokinetics and safety on abiraterone acetate coadministration with low-fat or high-fat meals was examined in healthy subjects and metastatic castration-resistant prostate cancer (mCRPC) patients. Healthy subjects (n = 36) were randomized to abiraterone acetate (single dose, 1000 mg) + low-fat meal, + high-fat meal, and fasted state. mCRPC patients received repeated doses (abiraterone acetate 1000 mg + 5 mg prednisone twice daily; days 1-7) in a modified fasting state followed by abiraterone acetate plus prednisone within 0.5 hours post-low-fat (n = 6) or high-fat meal (n = 18; days 8-14). In healthy subjects, geometric mean (GM) abiraterone area under plasma concentration-time curve (AUC) increased ∼5- and ∼10-fold, respectively, with low-fat and high-fat meals versus fasted state (GM [coefficient of variation], 1942 [48] and 4077 [37] ng · h/mL vs 421 [67] ng · h/mL, respectively). In mCRPC patients, abiraterone AUC was ∼2-fold higher with a high-fat meal and similar with a low-fat meal versus modified fasting state (GM [coefficient of variation]: 1992 [34] vs 973 [58] ng · h/mL and 1264 [65] vs 1185 [90] ng · h/mL, respectively). Adverse events (all grade ≤ 3) were similar, with high-fat/low-fat meals or fasted/modified fasting state. Short-term dosing with food did not alter abiraterone acetate safety.

Pharmacokinetics of abiraterone in healthy Japanese men: dose-proportionality and effect of food timing.

PURPOSE: Abiraterone acetate (AA) was recently approved for castration-resistant prostate cancer in Japan. Two phase 1 studies were conducted to assess the pharmacokinetics of abiraterone after single-dose administration in Japanese healthy men and to evaluate the effects of food timing on abiraterone pharmacokinetics after single-dose administration of AA in Japanese and Caucasian healthy men. METHODS: In the dose-proportionality study, subjects (n = 30 Japanese) were randomly assigned to receive single doses of 250, 500, and 1,000 mg AA, and in the food-timing study, subjects (n = 22 Japanese and n = 23 Caucasian) randomly received single doses of 1,000 mg AA under fasted (overnight) and three different modified fasting conditions. RESULTS: Mean C(max) and AUC(∞) for abiraterone increased dose-dependently in Japanese healthy men; however, 90 % confidential interval (CI) was outside the predefined dose-proportionality criteria. Based on geometric mean ratios and 90 % CIs (versus overnight fasting condition), abiraterone exposure (AUC) increased significantly with dosing 1 h premeal, 2 h postmeal, or in between two meals 4 h apart by 57 %, 595 %, and 649 %, respectively. CONCLUSION: No clinically meaningful difference was observed in the pharmacokinetics of abiraterone between Caucasian and Japanese subjects.

Effect of canagliflozin, a sodium glucose co-transporter 2 inhibitor, on the pharmacokinetics of oral contraceptives, warfarin, and digoxin in healthy participants.

OBJECTIVE: Drug-drug interactions between canagliflozin, a sodium glucose co-transporter 2 inhibitor approved for the management of type-2 diabetes mellitus, and an oral contraceptive (OC), warfarin, and digoxin were evaluated in three phase 1 studies in healthy participants. METHODS: All studies were open-label; study 1 included a fixed-sequence design, and studies 2 and 3 used a crossover design. Regimens were: study 1: OC (levonorgestrel (150 µg) + ethinyl estradiol (30 µg))/day (day 1), canagliflozin 200 mg/day (days 4 - 8), and canagliflozin with OC (day 9); study 2: canagliflozin 300 mg/day (days 1 - 12) with warfarin 30 mg/day (day 6) in period 1, and only warfarin 30 mg/day (day 1) in period 2, or vice versa; study 3: digoxin alone (0.5 mg/day (day 1) + 0.25 mg/day (days 2 - 7)) in period 1, and with canagliflozin 300 mg/day (days 1 - 7) in period 2, or vice versa. Pharmacokinetics (PK) were assessed at prespecified intervals; OC: days 1 and 9, canagliflozin: days 8 - 9 (study 1); warfarin: days 6 (period 1) and 1 (period 2) (study 2); and digoxin: days 5 - 7 (periods 1 and 2) (study 3). Warfarin's pharmacodynamics (PD; International Normalized Ratio (INR)) was assessed on days 6 (period 1) and 1 (period 2). RESULTS: Canagliflozin increased the plasma exposure of OC (maximum plasma concentration (Cmax): 22%, area under the curve (AUC): 6%) and digoxin (Cmax: 36%, AUC: 20%); but did not alter warfarin'€™s PK and PD. No clinically relevant safety findings (including hypoglycemia) were noted. CONCLUSION: Canagliflozin can be coadministered with OC, warfarin, or digoxin without dose adjustments. All treatments were well-tolerated.

Impact on abiraterone pharmacokinetics and safety: Open-label drug-drug interaction studies with ketoconazole and rifampicin.

We evaluated the impact of a strong CYP3A4 inhibitor, ketoconazole, and a strong inducer, rifampicin, on the pharmacokinetic (PK) exposure of abiraterone in two studies in healthy men. All subjects received 1,000 mg of abiraterone acetate on Days 1 and 14. Study A subjects (n = 20) received 400 mg ketoconazole on Days 11-16. Study B subjects (n = 19) received 600 mg rifampicin on Days 8-13. Serial PK sampling was done on Days 1 and 14. Study A: When given with ketoconazole, abiraterone exposure increased by 9% for maximum plasma concentration (Cmax ) and 15% for area under the plasma concentration-time curve from 0 to time of the last quantifiable concentration (AUClast ) and AUC from time 0 to infinity (AUC∞ ) compared to abiraterone acetate alone. Study B: When given with rifampicin, abiraterone exposure was reduced to 45% for Cmax and AUC∞ and to 42% for AUClast compared to abiraterone acetate alone. Ketoconazole had no clinically meaningful impact on abiraterone exposure. Rifampicin decreased abiraterone exposure by half. Hence, strong CYP3A4 inducers should be avoided or used with careful evaluation of clinical efficacy when administered with abiraterone acetate.

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.

Mathematical modeling of tumor growth and tumor growth inhibition in oncology drug development.

INTRODUCTION: Approaches aiming to model the time course of tumor growth and tumor growth inhibition following a therapeutic intervention have recently been proposed for supporting decision making in oncology drug development. When considered in a comprehensive model-based approach, tumor growth can be included in the cascade of quantitative and causally related markers that lead to the prediction of survival, the final clinical response. AREAS COVERED: The authors examine articles dealing with the modeling of tumor growth and tumor growth inhibition in both preclinical and clinical settings. In addition, the authors review models describing how pharmacological markers can be used to predict tumor growth and models describing how tumor growth can be linked to survival endpoints. EXPERT OPINION: Approaches and success stories of application of model-based drug development centered on tumor growth modeling are growing. It is also apparent that these approaches can answer practical questions on drug development more effectively than that in the past. For modeling purposes, some improvements are still needed related to study design and data quality. Further efforts are needed to encourage the mind shift from a simple description of data to the prediction of untested conditions that modeling approaches allow.