Stuart Oliver

Pharmacokinetics of Vandetanib: Three Phase I Studies in Healthy Subjects

BACKGROUND Vandetanib is an orally available inhibitor of vascular endothelial growth factor receptor 2 and epidermal growth factor receptor and is rearranged during transfection tyrosine kinase activity. Development has included studies in non-small cell lung cancer and other tumor types. Accurate elimination kinetics were not determined in patient studies, and so the current human volunteer studies were performed to derive detailed kinetic data. OBJECTIVE The aim of this study was to investigate pharmacokinetics, metabolism, excretion, and elimination kinetics after single oral doses of vandetanib in healthy subjects. METHODS Three studies were conducted. In Study A (n = 23), cohorts of 8 subjects were randomized to receive double-blind, ascending doses of vandetanib (300-1200 mg) or placebo (6:2). Study B had a crossover design; subjects (n = 16) received vandetanib 300 mg under fed and fasted conditions. In Study C, subjects (n = 4) received [(14)C] vandetanib 800 mg. Blood samples were collected for pharmacokinetic analysis for up to 28 days after the dose (Studies A and B) and 42 days after the dose (Study C). Plasma (all studies) and urine (Study A only) samples were collected for determination of vandetanib concentrations. In Study C radioactivity was measured in plasma, blood, urine, and feces, and metabolites were identified chromatographically. Tolerability was evaluated by recording of adverse events, clinical chemistry, hematology and urinalysis parameters, vital signs, and ECGs (all studies). RESULTS Study A: mean (SD) age 34.4 (6.9) years; 23/23 male; mean (SD; range) weight 80.6 (8.1; 62-97) kg. Study B: mean (SD) age 35.3 (8.4) years; 15/16 male; mean (SD; range) weight 80.7 (11.2; 57-100) kg. Study C: mean (SD) age 60.3 (7.4) years; 4/4 male; mean (SD; range) weight 78.0 (7.7l; 72-87) kg. Pharmacokinetic parameters were consistent across all studies (Studies A and C, vandetanib 800 mg: geometric mean CL/F, 13.1-13.3 L/h; geometric mean apparent volume of distribution at steady state [V(SS)/F], 3592-4103 L; mean t(½), 215.8-246.6 hours). Vandetanib was absorbed and eliminated slowly after single oral doses. AUC(0-∞) and C(max) were not significantly affected by ingestion of food. Median (range) T(max) was 8 (3-18) hours after food and 6 (5-18) hours after fasting. In plasma, concentrations of total radioactivity were higher than vandetanib concentrations at all time points, indicating the presence of circulating metabolites. Unchanged vandetanib and 2 anticipated metabolites (N-desmethylvandetanib and vandetanib N-oxide) were detected in plasma, urine, and feces. A further trace minor metabolite (glucuronide conjugate) was found in urine and feces. Approximately two thirds of the dose was recovered in feces (44%) and urine (25%) over 21 days, underlining the importance of both routes of elimination. Adverse events were reported by all subjects in Study A apart from 2 at a vandetanib dose of 300 mg; 12/15 (80%) and 14/16 (88%) subjects who took vandetanib under fed and fasted conditions, respectively, in Study B; and 2/4 (50%) subjects in Study C. No serious adverse events were reported. Increasing doses of vandetanib, in Study A, were associated with variable increases in systolic and diastolic blood pressures and variable increases from baseline in QTc interval. Hematuria was reported by 3 subjects (vandetanib 300 mg) in Study A. Small but consistent increases from baseline in serum creatinine were noted in subjects who received vandetanib in these studies. No other clinically important changes were observed in clinical chemistry, hematology and urinalysis parameters, vital signs, and ECGs in any of the studies. CONCLUSIONS The pharmacokinetics of vandetanib after single oral doses to healthy subjects were defined and the metabolic pathway was proposed. Vandetanib was absorbed and eliminated slowly with a t(½) of ∼10 days after single oral doses. The extent of absorption was not significantly affected by the presence of food. Approximately two thirds of the dose was recovered in feces (44%) and urine (25%) over 21 days. Unchanged vandetanib and N-desmethyl and N-oxide metabolites were detected in plasma, urine, and feces. Vandetanib appeared to be was well tolerated in the populations studied.

Phase I Study Assessing the Safety and Tolerability of Barasertib (AZD1152) With Low-Dose Cytosine Arabinoside in Elderly Patients With AML

INTRODUCTION Barasertib is the pro-drug of barasertib-hydroxy-quinazoline pyrazole anilide, a selective Aurora B kinase inhibitor that has demonstrated preliminary anti-AML activity in the clinical setting. PATIENTS AND METHODS This Phase I dose-escalation study evaluated the safety and tolerability of barasertib, combined with LDAC, in patients aged 60 years or older with de novo or secondary AML. Barasertib (7-day continuous intravenous infusion) plus LDAC 20 mg (subcutaneous injection twice daily for 10 days) was administered in 28-day cycles. The MTD was defined as the highest dose at which ≤ 1 patient within a cohort of 6 experienced a dose-limiting toxicity (DLT) (clinically significant adverse event [AE] or laboratory abnormality considered related to barasertib). The MTD cohort was expanded to 12 patients. RESULTS Twenty-two patients (median age, 71 years) received ≥ 1 treatment cycle (n = 6, 800 mg; n = 13, 1000 mg; n = 3, 1200 mg). DLTs were reported in 2 patients (both, National Cancer Institute Common Terminology Criteria for Adverse Events grade 3 stomatitis/mucositis; 1200 mg cohort). The most common AEs were infection (73%), febrile neutropenia (59%), nausea (50%), and diarrhea (46%). Barasertib plus LDAC resulted in an overall response rate (International Working Group criteria) of 45% (n = 10/22; according to investigator opinion). CONCLUSION The MTD of 1000 mg barasertib in combination with LDAC in older patients with AML was associated with acceptable tolerability and preliminary anti-AML activity.

Pharmacokinetic Drug Interactions with Vandetanib during Coadministration with Rifampicin or Itraconazole

AbstractObjective: The aim of this study was to investigate the effects of a potent CYP3A4 inducer, rifampicin (Study A), and a potent CYP3A4 inhibitor, itraconazole (Study B), on the pharmacokinetics of a single 300mg dose of vandetanib in healthy subjects. Study Design and Setting: Two phase I, randomized, open-label, two-way crossover, single-center studies. Participants and Intervention: Study A: 18 healthy male subjects aged 21–44 years were randomized to receive each of the following two regimens, separated by a ≥6-week washout period: (i) oral rifampicin 600mg/day on days 1–31 with a single oral dose of vandetanib 300mg on day 10; and (ii) a single oral dose of vandetanib 300mg on day 1. Study B: 16 healthy male subjects aged 20–44 years were randomized to receive each of the following two regimens, separated by a 3-month washout period: (i) oral itraconazole 200mg/day on days 1–24 with a single oral dose of vandetanib 300mg on day 4; and (ii) a single oral dose of vandetanib 300mg on day 1. Main Outcome Measure: Blood samples for measurement of vandetanib (both studies) concentrations and its metabolites, N-desmethylvandetanib and vandetanib N-oxide (Study A only), were collected before and at various timepoints after vandetanib administration for up to 28 days (Study A) and 37 days (Study B). Pharmacokinetic parameters were determined using noncompartmental methods. The area under the plasma concentration-time curve from time 0 to 504 hours (AUC504) and maximum plasma concentration (Cmax) of vandetanib were compared in the presence and absence of rifampicin, and in the presence and absence of itraconazole. Results: Study A: coadministration of vandetanib with rifampicin resulted in a statistically significant reduction in AUC504 (geometric least square [GLS]mean ratio [vandetanib + rifampicin/vandetanib alone] 0.60; 90% CI 0.58, 0.63). There was no significant difference in Cmax of vandetanib (GLSmean ratio 1.03; 90% CI 0.95, 1.11). AUC504 and Cmax of N-desmethylvandetanib increased by 266.0% and 414.3%, respectively, in the presence of rifampicin compared with vandetanib alone. Exposure to vandetanib N-oxide was very low compared with that of vandetanib, but was increased in the presence of rifampicin. Study B: coadministration of vandetanib with itraconazole resulted in a significant increase in AUC504 (GLSmean ratio [vandetanib + itraconazole/vandetanib alone] 1.09; 90% CI 1.01, 1.18) and no significant change in Cmax (GLSmean ratio 0.96; 90% CI 0.83, 1.11). Vandetanib was well tolerated in both studies. Conclusions: Exposure to vandetanib, as assessed byAUC504 in healthy subjects, was reduced by around 40% when a single dose was given in combination with the potent CYP3A4 inducer rifampicin. Because of this, it may be appropriate to avoid coadministration of potent CYP3A4 inducers with vandetanib. Vandetanib exposure was increased by about 9% when it was taken in combination with the CYP3A4 inhibitor itraconazole. It is unlikely that coadministration of vandetanib and potent CYP3A4 inhibitors will need to be contraindicated.

Pharmacokinetics of Vandetanib in Subjects with Renal or Hepatic Impairment

Background and ObjectiveVandetanib, an oncology drug being evaluated in phase III clinical trials, undergoes significant renal and hepatic excretion. The objective of these two studies was to investigate the single-dose pharmacokinetics of vandetanib in subjects with renal or hepatic impairment in comparison with healthy subjects.Subjects and MethodsTwo open-label, parallel-group studies were conducted at a single centre in Germany. Subjects aged 18-75 years with a body mass index of 18–32 kg/m2 were eligible. The renal impairment study recruited subjects with normal renal function and mild, moderate and severe renal impairment according to creatinine clearance calculated from a 24-hour urine collection pre-dose. The hepatic impairment study recruited subjects with normal hepatic function and mild, moderate and severe hepatic impairment according to the Child-Pugh classification. All subjects received a single 800mg oral vandetanib dose. Blood samples for measurement of vandetanib, N-desmethylvandetanib and vandetanib N-oxide were collected before and at various timepoints after vandetanib administration for up to 63 days. Pharmacokinetic parameters were determined using noncompartmental methods.ResultsThirty-two subjects were recruited for the renal impairment study (ten with normal renal function and six, ten and six with mild, moderate and severe impairment, respectively). Thirty subjects were recruited for the hepatic impairment study (eight with normal hepatic function and eight, eight and six with mild, moderate and severe impairment, respectively). The area under the plasma concentration-time curve from time zero to infinity (AUC∞) values of free vandetanib increased by approximately 46%, 62% and 79% in subjects with mild, moderate and severe renal impairment, respectively. These increases were statistically significant, with the increase in the severe renal impairment group having the possibility of being double the value observed in subjects with normal renal function (geometric least squares [GLS] mean ratio [renal impairment: normal renal function] of 1.79; 90% CI 1.39, 2.31). Peak plasma concentrations of free vandetanib increased slightly by approximately 7%, 9% and 11% in subjects with mild, moderate and severe renal impairment, respectively. Total plasma clearance of free vandetanib decreased with all degrees of renal dysfunction. Hepatic impairment did not have a statistically significant effect on the AUC∞ of total vandetanib. Peak plasma concentrations of total vandetanib were reduced in subjects with all classifications of hepatic impairment compared with normal hepatic function, with a statistically significant effect in the severe hepatic impairment group (GLS mean ratio 0.71; 90% CI 0.53, 0.96). Increased exposure to both metabolites was seen in subjects with renal impairment. Exposure to N-desmethylvandetanib was reduced in subjects with hepatic impairment, while exposure to vandetanib N-oxide was increased in subjects with severe hepatic impairment. Vandetanib was well tolerated and had a similar tolerability profile in subjects with renal or hepatic impairment compared with healthy subjects.ConclusionExposure to vandetanib was increased by about 46%, 62% and 79% in subjects with mild, moderate and severe renal impairment, respectively. A doubling in exposure could be ruled out in subjects with mild or moderate renal impairment but not for those with severe renal impairment. The possibility of dose reductions in patients with severe renal impairment will need to be assessed when the safety and tolerability profile is fully defined. Exposure to vandetanib was not altered in subjects with hepatic impairment, and no dose adjustment would be expected in patients with hepatic impairment.

In vitro metabolism of the specific endothelin-A receptor antagonist ZD4054 and clinical drug interactions between ZD4054 and rifampicin or itraconazole in healthy male volunteers

ZD4054 is an oral specific endothelin-A receptor antagonist in development for the treatment of hormone-resistant prostate cancer. Both renal and metabolic processes contribute to its overall clearance. Two preclinical in vitro studies investigated the metabolism of ZD4054 using human liver microsomes, individual cytochrome P450 (CYP) isozymes, and flavin-containing monooxygenase isoforms. Two Phase I open-label crossover volunteer studies subsequently investigated in vivo drug interactions between ZD4054 and the CYP450 inducer rifampicin or CYP3A4 inhibitor itraconazole. The most abundant metabolite produced in in vitro incubations accounted for 12.8% of radioactivity after ZD4054 was incubated with CYP3A4. No significant flavin-containing monooxygenase metabolism of ZD4054 was observed. In the in vivo studies, rifampicin co-administration reduced the area under the concentration–time curve and maximum plasma concentration of ZD4054 by 68% and 29%, respectively, whilst co-administration with itraconazole was associated with an increase in ZD4054 area under the curve of approximately 28%. While co-administration of CYP450 inducers might be associated with reduced efficacy of ZD4054, dose reduction is unlikely to be required with concomitant administration of CYP3A4 inhibitors.

Pharmacokinetic Properties of Fostamatinib in Patients With Renal or Hepatic Impairment: Results From 2 Phase I Clinical Studies

PURPOSE Phase III trials of fostamatinib, an oral spleen tyrosine kinase inhibitor, in the treatment of rheumatoid arthritis have been completed. Herein, we report the effects of renal and hepatic impairment on the pharmacokinetic (PK) properties of the active metabolite of fostamatinib, R406, in plasma, and on the urinary excretion of R406 and its metabolite N-glucuronide. METHODS Two Phase I, single-center, open-label clinical trials determined the PK properties and tolerability of fostamatinib in subjects with normal or impaired renal or hepatic function. Twenty-four subjects in the study in renal impairment (8 per group: normal renal function, moderate renal dysfunction, or end-stage renal disease [ESRD]), and 32 subjects in the study in hepatic impairment (8 per group: normal hepatic function or mild, moderate, or severe hepatic impairment) received a single 150-mg dose of fostamatinib. Patients with ESRD in the study in renal impairment participated in 2 treatment periods separated by a ≥1-week washout. In these patients, fostamatinib was administered after dialysis or 2 hours before dialysis. FINDINGS Geometric mean R406 Cmax and AUC values were less in the combined renally impaired group than in the group with normal renal function; Tmax was similar across groups. However, renal impairment had no apparent effect considered clinically relevant on unbound R406. In patients with ESRD, R406 exposure was less when fostamatinib was administered after compared with before dialysis. Urinary excretion of R406 N-glucuronide was decreased with increasing severity of renal impairment. Renal elimination of R406 was negligible in all groups. Varying degrees of hepatic impairment had no consistent effects on the PK properties of R406. R406 Cmax values were 10% to 15% less in all hepatically impaired groups than in the group with normal hepatic function. AUC and Tmax values were similar between the groups with normal and severely impaired hepatic function; in the groups with mild or moderate hepatic impairment, AUC was less and Tmax was greater. The geometric mean percentage of unbound R406 ranged from 0.64% to 1.95% and was greatest in the group with severe hepatic impairment. The urinary excretion of R406 was minimal. The amount of R406 N-glucuronide excreted in urine was greater in severely hepatically impaired patients. Fostamatinib 150 mg was generally well tolerated. IMPLICATIONS In these patients, renal or hepatic impairment did not affect exposure to the active metabolite of fostamatinib, R406, to a clinically relevant extent. ClinicalTrials.gov identifiers: NCT01245790 (renal) and NCT01222455 (hepatic).

Effects of Fostamatinib on the Pharmacokinetics of Digoxin (a P-Glycoprotein Substrate): Results From in Vitro and Phase I Clinical Studies

PURPOSE Fostamatinib, a spleen tyrosine kinase inhibitor and prodrug of the active metabolite R406, is being developed as an anti-inflammatory drug for several indications for which polypharmacy is likely. Digoxin, indicated for congestive cardiac failure, may be used for certain supraventricular dysrhythmias. The studies reported herein examined whether fostamatinib and R406 are inhibitors of P-glycoprotein (P-gp) in vitro and evaluated the effect of fostamatinib on the pharmacokinetic parameters of digoxin to understand drug-drug interaction (DDI) potential in the clinic. METHODS Inhibition of P-gp-mediated digoxin transport by fostamatinib and R406 was determined across Caco-2 cell monolayers. Apparent permeability of digoxin was determined and used to calculate efflux ratios and percentage inhibition. Half maximal inhibitory concentrations (IC50) and theoretical gastrointestinal concentration [I2] (dose in moles per 250 mL) were calculated to gauge clinical DDI potential. In a subsequent Phase I study, the plasma concentration-time profiles and resulting pharmacokinetic parameters were examined across 2 treatment periods: (1) oral digoxin loading dose of 0.25 mg BID on day 1 and 0.25 mg once daily on days 2 to 8, and (2) oral digoxin 0.25 mg once daily and oral fostamatinib 100 mg BID on days 9 to 15. FINDINGS Fostamatinib (but not R406) was determined to be a P-gp inhibitor in vitro (IC50 = 3.2 μM). On the basis of a theoretical gastrointestinal concentration (I2)/IC50 ratio of 216 ([I2] = 691 μM), predictions indicated the potential for absorption-based DDI in vivo through inhibition of intestinal P-gp. In the clinical study, when digoxin was co-administered with fostamatinib, digoxin levels were higher before dosing and throughout the dosing interval, and an increase in exposure to digoxin was observed. Co-administration led to a 1.70-fold increase in digoxin maximum plasma concentration at steady state (Cmax,ss) versus digoxin administration alone (2.18 vs 1.32 ng/mL). Median digoxin time of Cmax was earlier when digoxin was co-administered with fostamatinib (1.00 vs 1.48 hours). The digoxin AUC during the dosing interval at steady state was increased 1.37-fold with co-administration. No severe or serious adverse events or deaths were reported. IMPLICATIONS Fostamatinib was confirmed to be a P-gp inhibitor in vitro and in vivo, and a DDI with digoxin was apparent. Co-administration of digoxin and fostamatinib was generally well tolerated. However, continued review of digoxin response and dose is advisable should these agents be prescribed concomitantly. ClinicalTrials.gov identifier: NCT01355354.

An open-label, randomized, single-center, two-period, phase I, crossover study of the effect of zibotentan (ZD4054) on the pharmacokinetics of midazolam in healthy male volunteers.

BACKGROUND Zibotentan (ZD4054) is an oral, specific endothelin A receptor antagonist presently under investigation for the treatment of hormone-resistant prostate cancer. Preclinical in vitro studies suggest that zibotentan has the potential to act as a time-dependent inhibitor of the cytochrome P450 isozyme 3A4 (CYP3A4) metabolic pathway. In clinical practice, it is likely that zibotentan will be coadministered with drugs metabolized by this pathway; the potential exists, therefore, that zibotentan-induced drug interactions could occur. OBJECTIVES The primary objective of this study was to evaluate the effect of zibotentan on the pharmaco-kinetics of a clinically relevant dose of midazolam in healthy volunteers. Secondary objectives were to evaluate exposure to zibotentan, ensure the safety of the healthy volunteers dosed, and investigate the effect of zibotentan on the pharmacokinetics of the midazolam metabolites 1-hydroxy midazolam and 4-hydroxy midazolam. The potency of zibotentan as a CYP3A4 inhibitor was also assessed. METHODS This was an open-label, randomized, singlecenter, 2-period, Phase I, crossover study. Volunteers were randomized in a 1:1 ratio to 1 of 2 cohorts. In cohort 1, volunteers received a single dose of midazolam 7.5 mg on day 1 (treatment A) of a 2-day study period. After a minimum 7-day washout period, volunteers received zibotentan 10 mg once daily on days 1 through 7, plus a single dose of midazolam 7.5 mg on day 6 (treatment B) of a 7-day study period. In cohort 2, volunteers received treatment B followed by treatment A, with a minimum 7-day washout period between treatments. AUC(0-infinity) and C(max) data were expressed as geometric least squares mean ratios and 90% CIs for midazolam + zibotentan:midazolam. A moderate interaction between midazolam and zibotentan was predefined to have occurred if the upper 90% CI of the ratio was >1.5. Adverse events (AEs) were assessed according to the National Cancer Institutes Common Terminology Criteria for Adverse Events version 3. AE data were assessed based on information provided by the volunteer, through open-ended and nonleading verbal questions to the volunteer at each visit, and through observation by the investigational team, other care providers, or relatives. RESULTS Six volunteers (all white) were included in each cohort (cohort 1, mean [SD] age, 48 [7] years; mean weight, 74 [6] kg; cohort 2, mean age, 51 [11] years; mean weight, 75 [13] kg). Steady-state levels of zibotentan, achieved over 7 days, increased the midazolam AUC(0-infinity) by 1.2-fold compared with midazolam alone. The upper limits of the 90% CIs for the AUC(0-infinity) and C(max) ratios were below the predefined level of 1.5 (1.37 and 1.32, respectively). Zibotentan had no apparent effect on the pharmacokinetics of 1-hydroxy midazolam and 4-hydroxy midazolam. Fatigue was reported in 11 volunteers (92%) receiving midazolam monotherapy and 10 (83%) receiving midazolam combined with zibotentan. Headache was reported in all 12 volunteers after zibotentan monotherapy. CONCLUSIONS In this population of healthy male volunteers, once-daily zibotentan 10 mg increased the AUC(0-infinity) of midazolam 1.2-fold; however, the treatment ratio was below the predefined limit for clinical significance. Zibotentan was well tolerated when given alone or in combination with midazolam. The results indicate that once-daily zibotentan 10 mg acted as a weak inhibitor of the CYP3A4 pathway. ClinicalTrials. gov identifier: NCT00709553.

Effects of Fostamatinib on the Pharmacokinetics of the CYP2C8 Substrate Pioglitazone: Results From In Vitro and Phase 1 Clinical Studies.

Fostamatinib is a prodrug that undergoes gastrointestinal tract dephosphorylation to form the active metabolite, R406. Here we report its cytochrome P450–inducing potential. In vitro, R406 3 and 10 μM induced CYP2C8 to levels representing 53% and 75%, respectively, of the level achieved by the positive control, rifampicin. Induction of other enzymes was minor. The effect of fostamatinib (100 mg twice daily) on the pharmacokinetics of a single oral 30‐mg dose of the CYP2C8 substrate pioglitazone and its metabolite, hydroxy pioglitazone, was then investigated (open‐label, nonrandomized, 2‐period phase I study [n = 15]). Coadministration of fostamatinib and pioglitazone (vs pioglitazone alone) was associated with lower mean maximum plasma concentration values for pioglitazone (geometric least‐squares mean ratio, 82.8; 90% confidence interval, 64.2–106.8) and hydroxy pioglitazone (90.9; 78.6–105.1), an increase in pioglitazone AUC (117.8; 108.4–128.0), a decrease in hydroxy pioglitazone AUC(0–t) (89.7; 78.9–101.9), and an increase in pioglitazone geometric mean t1/2λz (9.4–12.8 hours). No tolerability concerns were identified upon coadministration. These data suggest that although clinical significance has not been formally evaluated, fostamatinib is unlikely to have a clinically significant effect on the pharmacokinetics of pioglitazone (which may be extrapolated to other CYP2C8 substrates). However, vigilance is advised should these agents be prescribed together.

Disposition and metabolism of the specific endothelin A receptor antagonist zibotentan (ZD4054) in healthy volunteers

Zibotentan (ZD4054) is a specific endothelin A (ETA) receptor antagonist that is in clinical development for the treatment of castration-resistant prostate cancer (CRPC) and has shown a promising signal for improvement in overall survival compared with placebo in a Phase II study of patients with metastatic CRPC. In this study, the pharmacokinetics, disposition and metabolism of zibotentan were evaluated following administration of a single oral dose of [14C]-zibotentan 15 mg to six healthy subjects. Zibotentan was rapidly absorbed, with the maximum zibotentan plasma concentration being observed 1 hour after administration. Excretion was rapid with the majority of the dose being excreted in the urine (71–94%). Total recovery of radioactivity over the 5 days of the study was high (mean 93%), with 78% of the dose being recovered within 24 hours. Concentrations of radioactivity in the plasma were similar up to 12 hours post dose, and diverged thereafter, indicating the presence of circulating metabolites. The main circulating component was zibotentan with a number of metabolites being identified in excreta. Zibotentan was well absorbed and was cleared via metabolism and urinary excretion with zibotentan-related material predominantly excreted via the urine.