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.

Improved stability of lipiodol-drug emulsion for transarterial chemoembolisation of hepatocellular carcinoma results in improved pharmacokinetic profile: Proof of concept using idarubicin.

OBJECTIVES: To investigate the relationship between the improved stability of an anticancer drug-lipiodol emulsion and pharmacokinetic (PK) profile for transarterial chemoembolisation (TACE) of hepatocellular carcinoma (HCC). METHODS: The stability of four doxorubicin- or idarubicin-lipiodol emulsions was evaluated over 7 days. PK and clinical data were recorded after TACE with the most stable emulsion in eight unresectable HCC patients, after institutional review board approval. RESULTS: The most stable emulsion was the one that combined idarubicin and lipiodol (1:2 v:v). At 7 days, the percentages of aqueous, persisting emulsion and oily phases were 50-0-50, 33-0-67, 31-39-30, and 10-90-0 for the doxorubicin-lipiodol (1:1 v:v), doxorubicin-lipiodol (1:2 v:v), idarubicin-lipiodol (1:1 v:v), and the idarubicin-lipiodol (1:2 v:v) emulsion, respectively. After TACE, mean idarubicin Cmax and AUC0-24h were 12.5 ± 9.4 ng/mL and 52 ± 16 ng/mL*h. Within 24 h after injection, 40% of the idarubicin was in the liver, either in vessels, tumours, or hepatocytes. During the 2 months after TACE, no clinical grade >3 adverse events occurred. One complete response, five partial responses, one stabilisation, and one progression were observed at 2 months. CONCLUSION: This study showed a promising and favourable PK and safety profile for the idarubicin-lipiodol (1:2 v:v) emulsion for TACE. KEY POINTS: • Transarterial chemoembolisation (TACE) regimens that improve survival in hepatocellular carcinoma are needed. • Improved emulsion stability for TACE resulted in a favourable pharmacokinetic profile. • Preliminary safety and efficacy data for the idarubicin-lipiodol emulsion for TACE were encouraging.

Revisiting metronomic vinorelbine with mathematical modelling: a Phase I trial in lung cancer.

BACKGROUND: A phase Ia/Ib trial of metronomic oral vinorelbine (MOV) driven by a mathematical model was performed in heavily pretreated metastatic Non-Small Cell Lung Cancer or Pleural Mesothelioma patients. Disease Control Rate, progression free survival, toxicity and PK/PD were the main endpoints. METHODS: Best MOV scheduling was selected using a simplified phenomenological, semi-mechanistic model with a total weekly dose of 150-mg vinorelbine. Computation of individual PK parameters was performed using population approach. RESULTS: The mathematical model proposed the following metronomic schedule for a 150-mg weekly dose of vinorelbine: 60 mg D1, 30 mg D2, 60 mg D4. A total of 37 heavily pre-treated patients (30 evaluable) were enrolled. Grade III/IV neutropenia was observed in 30% patients. Median PFS was 11 weeks. Disease Control Rate was 73% (i.e.; 13% partial response and 60% stable disease). A large variability in drug exposure (AUC0-24 h: 53%) and PK parameters (Cl: 83%) were observed among patients. Simulated trough levels after D2 and D4 showed similarly 56-73% variability among patients. Drug exposure was not associated with efficacy, but neutropenia was more frequent in patients with AUC > 250 ng/ml.h. Tumor burden, performance status and neutrophils-to-lymphocyte ratio (NLR) were associated with PFS, suggesting that MOV would be indicated in selected patients. We built a composite score to predict efficacy, mixing baseline tumor size and NLR showing 84% selectivity and 75% specificity. CONCLUSIONS: MOV was characterized by important variability in drug exposure among patients. However, and despite being all heavily pre-treated, 73% of disease control rate and 11 weeks PFS were achieved with manageable toxicities. PK/PD relationships yielded conflicting results depending on the initial tumor burden and BSA, suggesting that patients should be carefully selected prior to be scheduled for metronomic regimen. Possible role NLR could play as a predictive marker suggests immunomodulating features with MOV.

Design and Mechanism of Action of a New Prototype of Combi-Molecule "Programed" to Release Bioactive Species at a pH Range Akin to That of the Tumor Microenvironment.

The clinical use of cytotoxic agents is plagued by systemic toxicity. We report a novel approach that seeks to design a "combi-molecule" to behave as an alkylating agent on its own and to undergo acid-catalyzed conversion to two bioactive species at a pH range akin to that of a tumor microenvironment: an AL530 prototype was synthesized and we studied its ability to release a chlorambucil analogue (CBL-A) plus a potent mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK) inhibitor (PD98059) at different pHs in buffered solutions, plasma and tumors. Its potency was compared in vitro with CBL+PD98059 (SRB assay) and in vivo in a xenograft model. Its target modulation was studied by western blotting and immunohistochemistry. AL530 released PD98059+CBL-A at mild acidic pH and in vitro was fivefold more potent than CBL and three-to-fivefold more potent than CBL+PD98059. In vivo it released high levels of PD98059 in tumors with a tumor/plasma ratio of five. It induced γ-H2AX phosphorylation and blocked pErk1,2, indirectly indicating its ability to damage DNA and modulate MEK. It induced significant tumor delay and less toxicity at unachievable doses for CBL and CBL+PD98059. We demonstrated the feasibility of a pH-labile combi-molecule capable of delivering high MEK inhibitor concentration in tumors, damaging DNA therein, and inducing tumor growth delay.

Revisiting Bevacizumab + Cytotoxics Scheduling Using Mathematical Modeling: Proof of Concept Study in Experimental Non-Small Cell Lung Carcinoma.

Concomitant administration of bevacizumab and pemetrexed-cisplatin is a common treatment for advanced nonsquamous non-small cell lung cancer (NSCLC). Vascular normalization following bevacizumab administration may transiently enhance drug delivery, suggesting improved efficacy with sequential administration. To investigate optimal scheduling, we conducted a study in NSCLC-bearing mice. First, experiments demonstrated improved efficacy when using sequential vs. concomitant scheduling of bevacizumab and chemotherapy. Combining this data with a mathematical model of tumor growth under therapy accounting for the normalization effect, we predicted an optimal delay of 2.8 days between bevacizumab and chemotherapy. This prediction was confirmed experimentally, with reduced tumor growth of 38% as compared to concomitant scheduling, and prolonged survival (74 vs. 70 days). Alternate sequencing of 8 days failed in achieving a similar increase in efficacy, thus emphasizing the utility of modeling support to identify optimal scheduling. The model could also be a useful tool in the clinic to personally tailor regimen sequences.

CDA as a predictive marker for life-threatening toxicities in patients with AML treated with cytarabine.

Cytarabine (Ara-C) is the backbone of acute myeloid leukemia (AML) chemotherapy. Little is known about possible risk factors predictive for the frequent (ie, up to 16%) life-threatening or lethal toxicities caused by Ara-C. Ara-C is detoxified in the liver by a single enzyme, cytidine deaminase (CDA), coded by a gene known to be highly polymorphic. In this proof-of-concept study, we particularly investigated the role of the CDA poor metabolizer (PM) phenotype in Ara-C toxicities. CDA phenotyping (measurement of CDA residual activity in serum) and genotyping (search for the CDA*2 allelic variant) were performed in 58 adult patients with AML treated with the standard 7+3 (Ara-C + anthracyclines) protocol. Statistically significantly lower CDA activity was observed in patients experiencing severe/lethal toxicities as compared with patients who did not (1.5 ± 0.7 U/mg vs 3.95 ± 3.1 U/mg; Student t test P < .001). Subsequent receiver operating characteristic analysis identified a threshold in CDA activity (ie, 2 U/mg) associated with PM syndrome and increased risk of developing severe toxicities. Five percent of patients experienced lethal toxicities, all displaying CDA PM status (1.3 ± 0.5 U/mg). In terms of efficacy, a trend toward higher response rates and longer progression-free survival and overall survival were observed in patients with low CDA activity. Taken together, the results of this study strongly suggest that CDA is a predictive marker of life-threatening toxicities in patients with AML receiving induction therapy with standard Ara-C.

Model driven optimization of antiangiogenics + cytotoxics combination: application to breast cancer mice treated with bevacizumab + paclitaxel doublet leads to reduced tumor growth and fewer metastasis.

Bevacizumab is the first-in-class antiangiogenic drug and is almost always administrated in combination with cytotoxics. Reports have shown that bevacizumab could induce a transient phase of vascular normalization, thus ensuring a better drug delivery when cytotoxics administration is adjuvant. However, determining the best sequence remains challenging. We have developed a mathematical model describing the impact of antiangiogenics on tumor vasculature. A 3.4 days gap between bevacizumab and paclitaxel was first proposed by our model. To test its relevance, 84 mice were orthotopically xenografted with human MDA-231Luc+ refractory breast cancer cells. Two sets of experiments were performed, based upon different bevacizumab dosing (10 or 20 mg/kg) and inter-cycle intervals (7 or 10 days), comprising several combinations with paclitaxel. Results showed that scheduling bevacizumab 3 days before paclitaxel improved antitumor efficacy (48% reduction in tumor size compared with concomitant dosing, p < 0.05) and reduced metastatic spreading. Additionally, bevacizumab alone could lead to more aggressive metastatic disease with shorter survival in animals. Our model was able to fit the experimental data and provided insights on the underlying dynamics of the vasculature's ability to deliver the cytotoxic agent. Final simulations suggested a new, data-informed optimal gap of 2.2 days. Our experimental data suggest that current concomitant dosing between bevacizumab and paclitaxel could be a sub-optimal strategy at bedside. In addition, this proof of concept study suggests that mathematical modelling could help to identify the optimal interval among a variety of possible alternate treatment modalities, thus refining the way experimental or clinical studies are conducted.

Mathematical modeling for Phase I cancer trials: A study of metronomic vinorelbine for advanced non-small cell lung cancer (NSCLC) and mesothelioma patients.

INTRODUCTION: Using mathematical modelling allows to select a treatment's regimen across infinite possibilities. Here, we report the phase I assessment of a new schedule for metronomic vinorelbine in treating refractory advanced NSCLC and mesothelioma patients. RESULTS: Overall, 13 patients were screened and 12 were treated (50% male, median age: 68yrs), including 9 NSCLC patients. All patients received at least one week (3 doses) of treatment. At data cut-off, the median length of treatment was 6.5 weeks (1-32+). All the patients presented with at least one adverse event (AE) and six patients with a severe AE (SAE). One partial response and 5 stable diseases were observed. The median OS was 6.4 months (95% CI, 4.8 to 12 months). The median and mean vinorelbine's AUC were 122 ng/ml*h and 159 ng/ml*h, respectively, with the higher plasmatic vinorelbine exposure associated with the best ORR (difference of AUC comparison between responders and non-responders, p-value 0.017). MATERIALS AND METHODS: The mathematical modelling determined the administration of vinorelbine, 60 mg on Day 1, 30 mg on Day 2 and 60 mg on Day 4 weekly until progression, as the best schedule. Advanced NSCLC or mesothelioma patients progressing after standard treatment were eligible for the trial. NCT02555007. CONCLUSIONS: Responses with acceptable safety profile were observed in heavily pretreated NSCLC and mesothelioma patients using oral vinorelbine at this metronomic dosage based on a mathematic modeling. This study demonstrates the feasibility of this new type of approach, as mathematical modeling may help to rationally decide the better regimen to be clinically tested across infinite possibilities.

A simple and rapid LC-MS/MS method for therapeutic drug monitoring of cetuximab: a GPCO-UNICANCER proof of concept study in head-and-neck cancer patients.

Administration of first-in-class anti-EGFR monoclonal antibody cetuximab is contingent upon extensive pharmacogenomic testing. However in addition to tumor genomics, drug exposure levels could play a critical, yet largely underestimated role, because several reports have demonstrated that cetuximab pharmacokinetic parameters, in particular clearance values, were associated with survival in patients. Here, we have developed an original bioanalytical method based upon the use of LC-MS/MS technology and a simplified sample preparation procedure to assay cetuximab in plasma samples from patients, thus meeting the requirements of standard Therapeutic Drug Monitoring in routine clinical practice. When tested prospectively in a pilot study in 25 head-and-neck cancer patients, this method showed that patients with clinical benefit had cetixumab residual concentrations higher than non-responding patients (i.e., 49 ± 16.3 µg/ml VS. 25.8 ± 17 µg/ml, p < 0.01 t test). Further ROC analysis showed that 33.8 µg/ml was the Cmin threshold predictive of response with an acceptable sensitivity (87%) and specificity (78%). Mass spectrometry-based therapeutic drug monitoring of cetuximab in head-and-neck cancer patients could therefore help to rapidly predict cetuximab efficacy and to adapt dosing if required.

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.

A Phase I, Dose-Escalation Trial of Pazopanib in Combination with Cisplatin in Patients with Advanced Solid Tumors: A UNICANCER Study.

INTRODUCTION: To determine the feasibility, maximum-tolerated dose (MTD), and dose-limiting toxicities (DLT) of pazopanib in combination with cisplatin. METHODS: Patients with advanced malignancies were included in a 3 + 3 dose-escalation phase I study. Pazopanib administration started 8 days before the first infusion of cisplatin; some patients were treated according to a reverse sequence (cisplatin first). Five dose levels (DLs) were planned. MTD was based on DLT observed during cycles 1 and 2. RESULTS: Thirty-five patients were enrolled. The MTD was reached at the first DL, (pazopanib 400 mg daily + cisplatin 75 mg/m2 every 21 days). Main DLTs were pulmonary embolism, neutropenia, thrombocytopenia, and elevation of liver enzymes. Overall, most common adverse events were anemia (83%), fatigue (80%), thrombocytopenia (80%), neutropenia (73%), hypertension (59%), neurotoxicity (56%), and anorexia (53%). Sixteen patients (46%) discontinued the study due to toxicity. One patient (sarcoma) had a complete response, and three patients (one with breast cancer and two with ovarian cancers) had a partial response. Pharmacokinetic (PK) analyses showed interactions with aprepitant, resulting in increased exposure to pazopanib, which might explain partly the poor tolerance of the combination. CONCLUSION: Cisplatin and pazopanib could not be administered at their single agent full doses, partly due to a PK interaction between pazopanib and aprepitant. FUNDING: This work was funded by GlaxoSmithKline and by the charity Ligue Nationale de Lutte Contre le Cancer. TRIAL REGISTERED: ClinicalTrials.gov identifier, NCT01165385.

Pharmacokinetics of pazopanib administered in combination with bevacizumab.

A combination of monoclonal antibody that binds and inhibits effects induced by vascular endothelial growth factor and tyrosine kinase inhibitor of vascular endothelial growth factor receptor represents a promising concept to block pathological angiogenesis completely. A phase I study combining daily oral pazopanib and bevacizumab (given iv every 2 weeks) was performed in order to determine the maximum tolerated dose of the two drugs in combination. Pazopanib pharmacokinetics were evaluated to compare pharmacokinetic parameters given alone and those observed on the day of the bevacizumab administration. Plasma pazopanib concentrations were obtained in 25 patients treated at two dose levels (400 or 600 mg) at Day 1 (given alone) and Day 15 (the day of the 7.5 mg/kg bevacizumab infusion), and analyzed using the NONMEM program. The apparent oral clearance (CL/F, mean value of 0.60 L/h) presented an inter-individual variability of 40 %, and an inter-occasion of 27 %. A modest but statistically significant decrease in CL/F was observed from Day 1 to Day 15 (-16.4, 95 % confidence interval of -8.5 to -27.2 %). However, trough pazopanib concentrations observed at Day 16 (24 h after the bevacizumab iv infusion) were not significantly higher than those observed just before the beginning of the bevacizumab iv infusion, suggesting that the pharmacokinetic change between Day 1 and Day 15 was not due to an interaction of bevacizumab. Overall, the mean observed concentrations at the maximum tolerated pazopanib dose (600 mg) at both Day 1 and Day 15 were higher than those observed at 800 mg once daily level (corresponding to the recommended dose when given alone) during the first-in-man phase 1 study of pazopanib in monochemotherapy. This first population pharmacokinetic analysis of pazopanib shows that inter-individual and inter-study pharmacokinetic variability emphasize the need for further evaluation of therapeutic drug monitoring for pazopanib as suggested for other tyrosine kinase inhibitors.