Pharmacokinetics of pazopanib administered in combination with bevacizumab

Pharmacokinetic interaction assessment of an HIV broadly neutralizing monoclonal antibody VRC07-523LS: a cross-protocol analysis of three phase 1 trials in people without HIV

VRC07-523LS is a safe and well-tolerated monoclonal antibody (mAb) targeting the CD4 binding site on the HIV envelope (Env) trimer. Efficacy of VRC07-523LS, in combination with mAbs targeting other HIV epitopes, will be evaluated in upcoming trials to prevent HIV acquisition in adults. However, differences in the pharmacokinetics (PK) of VRC07-523LS when administered alone vs. in combination with other mAbs have not been formally assessed. We performed a cross-protocol analysis of three clinical trials and included data from a total of 146 adults without HIV who received intravenous (n = 95) or subcutaneous (n = 51) VRC07-523LS, either alone ('single'; n = 100) or in combination with 1 or 2 other mAbs ('combined'; n = 46). We used an open, two-compartment population PK model to describe serum concentrations of VRC07-523LS over time, accounting for inter-individual variabilities. We compared individual-level PK parameters between the combined vs. single groups using the targeted maximum likelihood estimation method to adjust for participant characteristics. No significant differences were observed in clearance rate, inter-compartmental clearance, distribution half-life, or total VRC07-523LS exposure over time. However, for the combined group, mean central volume of distribution, peripheral volume of distribution, and elimination half-life were slightly greater, corresponding to slightly lower predicted concentrations early post-administration with high levels being maintained in both groups. These results suggest potential PK interactions between VRC07-523LS and other mAbs, but with small clinical impact in the context of HIV prevention. Our findings support coadministration of VRC07-523LS with other mAbs, and the use of the developed PK models to design future trials for HIV prevention.

Therapeutic Drug Monitoring of Tyrosine Kinase Inhibitors in the Treatment of Advanced Renal Cancer

Seven tyrosine kinase inhibitor compounds with anti-angiogenic properties remain key drugs to treat advanced renal cell carcinoma. There is a strong rationale to develop therapeutic drug monitoring for these drugs. General considerations of such monitoring of the several groups of anticancer drugs are given, with a focus on oral therapy. Pharmacokinetics and the factors of inter- and intraindividual variabilities of these tyrosine kinase inhibitors are described together with an exhaustive presentation of their pharmacokinetic/pharmacodynamic relationships. The latter was observed in studies where every patient was treated with the same dose, and the results of several prospective studies based on dose individualization support the practice of increasing individual dosage in case of low observed plasma drug concentrations. Finally, the benefits and limits of therapeutic drug monitoring as a routine practice are discussed.

Pharmacokinetics and Bioequivalence of a Generic and a Branded Pazopanib Tablet in Healthy Chinese Subjects

This study aimed to evaluate the bioequivalence of two pazopanib tablet formulations in healthy Chinese subjects. A randomized, open-label, single-dose, two-period, two-sequence, crossover study was conducted under fasting conditions. A total of 32 eligible subjects were randomly administered a single dose of a 200-mg generic or branded pazopanib tablet with a 16-day washout period. Blood samples were collected before and up to 72 hours after dosing. Pharmacokinetic parameters were analyzed with noncompartmental analysis. Safety assessments included physical examinations, laboratory tests, and adverse events reporting. Maximum plasma concentration (C_max ), area under the plasma concentration-time curve (AUC) from zero to the last quantifiable concentration (AUC_0-t ), and AUC from zero to infinity (AUC_0-∞ ) were similar between the generic and branded products (all P > .05). The 90% confidence intervals of the geometric mean ratio of the test/reference products for C_max , AUC_0-t , and AUC_0-∞ were 89.1%-117.1%, 81.9%-108.5%, and 82.4%-109.6%, respectively. There were no serious adverse events during the study. The newly developed generic pazopanib tablet was bioequivalent to the reference product under fasting conditions. Both formulations were well tolerated in healthy Chinese volunteers.

Population Pharmacokinetic Analysis of Pazopanib in Patients and Determination of Target AUC

Pazopanib is a potent multi-targeted kinase inhibitor approved for the treatment of advanced renal cell carcinoma and soft tissue sarcoma. The pharmacokinetics of pazopanib is characterized by a significant inter- and intra-patient variability and a target through plasma concentration of 20.5 mg·L^-1. However, routine monitoring of trough plasma concentrations at fixed hours is difficult in daily practice. Herein, we aimed to characterize the pharmacokinetic (PK) profile of pazopanib and to identify a target area under the curve (AUC) more easily extrapolated from blood samples obtained at various timings after drug intake. A population pharmacokinetic (popPK) model was constructed to analyze pazopanib PK and to estimate the pazopanib clearance of a patient regardless of the time of sampling. Data from the therapeutic drug monitoring (TDM) of patients with cancer at Institute Gustave Roussy and a clinical study (phase I/II) that evaluates the tolerance to pazopanib were used. From the individual clearance, it is then possible to obtain the patient's AUC. A target AUC for maximum efficacy and minimum side effects of 750 mg·h·L^-1 was determined. The comparison of the estimated AUC with the target AUC would enable us to determine whether plasma exposure is adequate or whether it would be necessary to propose therapeutic adjustments.

VOTRAGE study: Phase I dose-escalation study of pazopanib in unfit older patients

BACKGROUND

Pazopanib is a tyrosine kinase inhibitor given at the approved dose of 800 mg orally once daily (OD), but often requiring individual dose adjustment due to toxicity. Limited data is available to guide prescription in older patients especially the unfit according to geriatric assessment.

PATIENTS AND METHODS

VOTRAGE is a 3 + 3 dose-escalation, open-label phase I trial of continuous OD oral administration of pazopanib to evaluate safety, PK and PD data in unfit older patients with advanced solid tumors. The primary objective was to determine the maximum tolerated dose (MTD). PK data were compared with those obtained in younger adult patients in a population PK analysis.

RESULTS

Eighteen patients with a median age of 82.5 years (range 75-91) were included in three dosing cohorts (400, 600, and 800 mg daily). Three dose-limiting toxicities (DLT) were observed in five patients at 800 mg and one DLT at 600 mg in six evaluable patients. MTD was defined as level 2 dose (600 mg). Individual oral clearance was not correlated with age. A relationship was observed between the occurrence of DLT and pazopanib plasma exposure. Decreased oral bioavailability of pazopanib when given with proton-pump inhibitors was confirmed in this group of patients.

CONCLUSION

We recommend performing geriatric assessment in patients older than 75 and starting pazopanib at 600 mg per day in unfit older patients. Therapeutic drug monitoring appears very helpful in this population.

Imatinib, sunitinib and pazopanib: From flat-fixed dosing towards a pharmacokinetically guided personalized dose

Tyrosine kinase inhibitors (TKIs) are anti‐cancer drugs that target tyrosine kinases, enzymes that are involved in multiple cellular processes. Currently, multiple oral TKIs have been introduced in the treatment of solid tumours, all administered in a fixed dose, although large interpatient pharmacokinetic (PK) variability is described. For imatinib, sunitinib and pazopanib exposure‐treatment outcome (efficacy and toxicity) relationships have been established and therapeutic windows have been defined, therefore dose optimization based on the measured blood concentration, called therapeutic drug monitoring (TDM), can be valuable in increasing efficacy and reducing the toxicity of these drugs.

In this review, an overview of the current knowledge on TDM guided individualized dosing of imatinib, sunitinib and pazopanib for the treatment of solid tumours is presented. We summarize preclinical and clinical data that have defined thresholds for efficacy and toxicity. Furthermore, PK models and factors that influence the PK of these drugs which partly explain the interpatient PK variability are summarized. Finally, pharmacological interventions that have been performed to optimize plasma concentrations are described. Based on current literature, we advise which methods should be used to optimize exposure to imatinib, sunitinib and pazopanib.

Clinical Pharmacokinetics and Pharmacodynamics of Pazopanib: Towards Optimized Dosing

Pazopanib is an inhibitor of the vascular endothelial growth factor receptor, platelet-derived growth factor receptor, fibroblast growth factor receptor and stem cell receptor c-Kit, and has been approved for the treatment of renal cell carcinoma and soft tissue sarcoma. The pharmacokinetics of pazopanib are complex and are characterized by pH-dependent solubility, large interpatient variability and low, non-linear and time-dependent bioavailability. Exposure to pazopanib is increased by both food and coadministration of ketoconazole, but drastically reduced by proton pump inhibitors. Studies have demonstrated relationships between systemic exposure to pazopanib and toxicity, such as hypertension. Furthermore, a strong relationship between pazopanib trough level ≥20 mg/L and both tumor shrinkage and progression-free survival has been established. At the currently approved daily dose of 800 mg, approximately 20% of patients do not reach this threshold and may be at risk of suboptimal treatment. As a result of this, clinical trials have explored individualized pazopanib dosing, which demonstrate the safety and feasibility of individualized pazopanib dosing based on trough levels. In summary, we provide an overview of the complex pharmacokinetic and pharmacodynamic profiles of pazopanib and, based on the available data, we propose optimized dosing strategies.

High throughput routine determination of 17 tyrosine kinase inhibitors by LC-MS/MS

Several studies have shown that therapeutic drug monitoring of tyrosine kinase inhibitors (TKI) can improve their benefit in cancer. An analytical tool has been developed in order to quantify 17 tyrosine kinase inhibitors and 2 metabolites in human plasma (afatinib, axitinib, bosutinib, crizotinib, dabrafenib, dasatinib, erlotinib, gefitinib, imatinib, lapatinib, nilotinib, ponatinib, regorafenib, regorafenib M2, regorafenib M5, ruxolitinib, sorafenib, sunitinib, vandetanib). Drugs were arranged in four groups, according to their plasma concentration range: 0.1-200ng/ml, 1-200ng/ml, 4-800ng/ml and 25-5000ng/ml. Solid phase extraction was used and separation was performed with HPLC using a gradient system on a solid core particle C18 column (5×2.1mm, 1.6μm). Ions were detected with a triple quadrupole mass spectrometry system. This assay allows rapid determination of 19 TKI in less than 5min per run. This high throughput routine method will be useful to adjust doses of oral anticancer drugs in order to improve treatments efficacy.

Development of a Pharmacokinetic Model to Describe the Complex Pharmacokinetics of Pazopanib in Cancer Patients

BACKGROUND AND OBJECTIVE

Pazopanib is a multi-targeted anticancer tyrosine kinase inhibitor. This study was conducted to develop a population pharmacokinetic (popPK) model describing the complex pharmacokinetics of pazopanib in cancer patients.

METHODS

Pharmacokinetic data were available from 96 patients from three clinical studies. A multi-compartment model including (i) a complex absorption profile, (ii) the potential non-linear dose-concentration relationship and (iii) the potential long-term decrease in exposure was developed.

RESULTS

A two-compartment model best described pazopanib pharmacokinetics. The absorption phase was modelled by two first-order processes: 36 % (relative standard error [RSE] 34 %) of the administered dose was absorbed with a relatively fast rate (0.4 h^-1 [RSE 31 %]); after a lag time of 1.0 h (RSE 6 %), the remaining dose was absorbed at a slower rate (0.1 h^-1 [RSE 28 %]). The relative bioavailability (rF) at a dose of 200 mg was fixed to 1. With an increasing dose, the rF was strongly reduced, which was modelled with an E _max (maximum effect) model (E _max was fixed to 1, the dose at half of maximum effect was estimated as 480 mg [RSE 23 %]). Interestingly, the plasma exposure to pazopanib also decreased over time, modelled on rF with a maximum magnitude of 50 % (RSE 27 %) and a first-order decay constant of 0.15 day^-1 (RSE 43 %). The inter-patient and intra-patient variability on rF were estimated as 36 % (RSE 16 %) and 75 % (RSE 22 %), respectively.

CONCLUSION

A popPK model for pazopanib was developed that illustrated the complex absorption process, the non-linear dose-concentration relationship, the high inter-patient and intra-patient variability, and the first-order decay of pazopanib concentration over time. The developed popPK model can be used in clinical practice to screen covariates and guide therapeutic drug monitoring.

Phase I dose-escalation study of pazopanib combined with bevacizumab in patients with metastatic renal cell carcinoma or other advanced tumors

BACKGROUND

Vascular endothelial growth factor (VEGF) directed therapies are being used in a large number of advanced tumors. Metastatic renal cell carcinoma (mRCC) is highly dependent on the VEGF pathway; VEGF receptor (VEGFR) tyrosine kinase inhibitors (TKI) and humanized VEGF monoclonal antibody have been registered for clinical use in advanced renal cell carcinoma. The VEGFR TKI, pazopanib, with a rather manageable toxicity profile, was preferred to sunitinib by mRCC patients. We investigate the combination of pazopanib and bevacizumab to determine the maximum tolerated dose (MTD) in mRCC and other advanced solid tumors.

METHODS

In this bicentric phase I trial with a 3 + 3 + 3 dose-escalation design, patients received oral pazopanib once daily plus intravenous infusion of bevacizumab every 2 weeks from D15, at one of the four dose levels (DL) planned according to the occurrence of dose limiting toxicities (DLT). 400 and 600 mg pazopanib were respectively combined with 7.5 mg/kg bevacizumab in DL1 and DL2, and 600 and 800 mg pazopanib with 10 mg/kg bevacizumab in DL3 and DL4. Tumor response was evaluated every 8 weeks. Blood samples were assayed to investigate pazopanib pharmacokinetics.

RESULTS

Twenty five patients including seven mRCC were enrolled. Nine patients received the DL1, ten received the DL2. No DLT were observed at DL1, five DLT at DL2, and 3 DLT in the six additional patients who received the DL1. A grade 3 microangiopathic hemolytic anemia syndrome was observed in four (16%) patients. Five (22%) patients achieved a partial response. The mean (range) plasmatic concentrations of 400 and 600 pazopanib were respectively 283 (139-427) and 494 (227-761) μg.h/mL at Day 1, and 738 (487-989) and 1071 (678-1464) μg.h/mL at Day 15 i.e. higher than those previously reported with pazopanib, and were not directly influenced by bevacizumab infusion.

CONCLUSIONS

The combination of pazopanib and bevacizumab induces angiogenic toxicity in patients without any pre-existing renal or vascular damage. Even if a marginal efficacy was reported with five (22%) patients in partial response in different tumor types, the toxicity profile compromises the development of this combination.

TRIAL REGISTRATION

The study was retrospectively registered on ClinicalTrials.gov (number NCT01202032 ) on 2010, Sept 14th.

Pharmacokinetic drug evaluation of pazopanib for the treatment of uterine leiomyosarcomas

INTRODUCTION

Uterine leiomyosarcomas (ULMS) represent 1.3% of all uterine malignant tumors. Surgery is the curative treatment for patients with early stage disease. In case of advanced, persistent or recurrent tumor, chemotherapy represents the standard of care, but these patients have a poor prognosis. As the results with available therapies are far from being satisfactory, research is focusing on identification of new compounds. In 2012 the Food and Drug Administration (FDA) licensed pazopanib for the treatment of advanced soft-tissue sarcomas failing previous chemotherapy. Areas covered: The aim of this article is to review the literature on the pharmacokinetics, pharmacodynamics, clinical efficacy and safety of the tyrosine kinase inhibitor (TKI), pazopanib in the treatment of ULMS. Expert opinion: The discovery of some relevant signalling pathways in LMS cells led to the development of new targeted drugs with promising results in the management of these tumors. Pazopanib is a multi-target second-generation TKI with activity against growth factors involved in angiogenesis. It has shown promising results both in terms of efficacy and safety, as shown in the EORTC 62043 Study and the PALETTE trial. Further studies are awaited to evaluate its efficacy in uterine leiomyosarcomas.

Inventory of oral anticancer agents: Pharmaceutical formulation aspects with focus on the solid dispersion technique

Dissolution from the pharmaceutical formulation is a prerequisite for complete and consistent absorption of any orally administered drug, including anticancer agents (oncolytics). Poor dissolution of an oncolytic can result in low oral bioavailability, high variability in blood concentrations and with that suboptimal or even failing therapy. This review discusses pharmaceutical formulation aspects and absorption pharmacokinetics of currently licensed orally administered oncolytics. In nearly half of orally dosed oncolytics poor dissolution is likely to play a major role in low and unpredictable absorption. Dissolution-limited drug absorption can be improved with a solid dispersion which is a formulation method that induces super-saturated drug dissolution and with that it enhances in vivo absorption. This review discusses formulation principles with focus on the solid dispersion technology and how it works to enhance drug absorption. There are currently three licensed orally dosed oncolytics formulated as a solid dispersion (everolimus, vemurafenib and regorafenib) and these formulations result in remarkably improved dissolution and absorption compared to what can be achieved with conventional formulations of the respective oncolytics. Because of the successful implementation of these three solid dispersion formulations, we encourage the application of this formulation method for poorly soluble oral oncolytics.

Pharmacokinetic interaction between pazopanib and cisplatin regimen

PURPOSE

A phase I study combining daily oral pazopanib and cisplatin (given iv every 3 weeks) was performed in order to determine the maximum tolerated dose of both drugs in combination. Pharmacokinetic interactions were evaluated.

METHODS

Plasma pazopanib and ultrafilterable cisplatin concentrations were obtained in 32 patients treated according to four levels of dose corresponding to 200, 400 or 600 mg daily dose of pazopanib and 60 or 75 mg/m(2) of cisplatin. Two sequences of treatment were performed in order to explore any interaction of cisplatin on pazopanib pharmacokinetics and inversely. Data were analyzed using the NONMEM program.

RESULTS

Maximum tolerated dose was 400 mg of pazopanib and 75 mg/m(2) of cisplatin. Mean (CV % for inter-individual variability) cisplatin clearance was 10.3 L/h (33.2 %) and appeared not to be influenced by pazopanib. However, pazopanib pharmacokinetics was significantly modified by the cisplatin regimen. Mean (CV %) of oral pazopanib clearance was 0.66 L/h (55 %) at Day 0 (before cisplatin administration), 24.8 % lower at Day 1 and 32.9 % lower at Day 2. The interaction is less likely to be due to cisplatin than to a competitive inhibition of pazopanib metabolism and efflux by aprepitant, an antiemetic drug systematically administered with cisplatin. The plasma pazopanib exposures observed at Day 0 with a 400 mg dose were similar to those observed at the recommended dose of pazopanib in monochemotherapy (800 mg) during the first-in-man phase 1 study.

CONCLUSION

The observed pazopanib plasma overexposure probably contributed to the poor tolerance encountered during this phase 1 study.

Determination of unbound fraction of pazopanib in vitro and in cancer patients reveals albumin as the main binding site

INTRODUCTION

Pazopanib exhibits wide inter-patient pharmacokinetic variability which may contribute to differences in treatment outcome. Unbound drug concentrations are believed to be more relevant to pharmacological responses than total concentrations. Thus it is desirable to evaluate pazopanib binding on plasma proteins and different factors potentially affecting this process.

METHODS

An equilibrium dialysis method coupled with UPLC-MS/MS assay has been optimized and validated for the determination of pazopanib unbound fraction (fu%) in human plasma. Pazopanib binding in the plasma of healthy volunteers and in isolated protein solutions was investigated. The unbound fraction was determined for 24 cancer patients treated daily with pazopanib.

RESULTS

We found that pazopanib was extensively bound in human plasma (>99.9 %) with a mean fu% value of 0.0106 ± 0.0013 % at 40 μg/mL. Protein binding was concentration independent over a clinically relevant range of concentrations. In isolated protein solutions, pazopanib at 40 μg/mL was mainly bound to albumin (40 g/L) and to a lesser extent to α1-acid glycoprotein (1 g/L) and low density lipoproteins (1.2 g/L), with a mean fu% of 0.0073 ± 0.0022 %, 0.992 ± 0.44 % and 7.4 ± 1.7 % respectively. Inter-patient variability (CV%) of fu% in cancer patients was limited (27.2 %). A correlation was observed between individual unbound fraction values and albuminemia.

CONCLUSIONS

Pazopanib exhibits extensive binding to plasma proteins in human plasma. Variable albumin concentrations, frequently observed in cancer patients, may affect pazopanib unbound fraction with implications for inter-patient variability in drug efficacy and toxicity.