Irinotecan pharmacokinetics-pharmacodynamics: the clinical relevance of prolonged exposure to SN-38

We have shown previously that the terminal disposition half-life of SN-38, the active metabolite of irinotecan, is much longer than earlier thought. Currently, it is not known whether this prolonged exposure has any relevance toward SN-38-induced toxicity. Here, we found that SN-38 concentrations present in human plasma for up to 3 weeks after a single irinotecan infusion induce significant cytotoxicity in vitro. Using pharmacokinetic data from 26 patients, with sampling up to 500 h, relationships were evaluated between systemic exposure (AUC) to SN-38 and the per cent decrease in absolute neutrophil count (ANC) at nadir, or by taking the entire time course of ANC into account (AOC). The time course of SN-38 concentrations (AUC500 h) was significantly related to this AOC (P<0.001). Based on these findings, a new limited-sampling model was developed for SN-38 AUC500 h using only two timed samples: AUC500 h=(6.588×C2.5 h)+(146.4×C49.5 h)+15.53, where C2.5 h and C49.5 h are plasma concentrations at 2.5 and 49.5 h after start of infusion, respectively. The use of this limited-sampling model may open up historic databases to retrospectively obtain information about SN-38-induced toxicity in patients treated with irinotecan

Oscillatory surface rheotaxis of swimming E. coli bacteria

Bacterial contamination of biological conducts, catheters or water resources is a major threat to public health and can be amplified by the ability of bacteria to swim upstream. The mechanisms of this rheotaxis, the reorientation with respect to flow gradients, often in complex and confined environments, are still poorly understood. Here, we follow individual E. coli bacteria swimming at surfaces under shear flow with two complementary experimental assays, based on 3D Lagrangian tracking and fluorescent flagellar labelling and we develop a theoretical model for their rheotactic motion. Three transitions are identified with increasing shear rate: Above a first critical shear rate, bacteria shift to swimming upstream. After a second threshold, we report the discovery of an oscillatory rheotaxis. Beyond a third transition, we further observe coexistence of rheotaxis along the positive and negative vorticity directions. A full theoretical analysis explains these regimes and predicts the corresponding critical shear rates. The predicted transitions as well as the oscillation dynamics are in good agreement with experimental observations. Our results shed new light on bacterial transport and reveal new strategies for contamination prevention.Comment: 12 pages, 5 figure

A phase I dose-escalation and pharmacokinetic study of a micellar nanoparticle with entrapped docetaxel (CPC634) in patients with advanced solid tumours

Background: CPC634 is docetaxel entrapped in core-cross linked polymeric micelles. In preclinical studies, CPC634 demonstrated enhanced pharmacokinetics and improved therapeutic index. This phase I dose escalation study is the first-in-human study with CPC634. Methods: adult patients with advanced solid tumours received CPC634 intravenously either 3-weekly (Q3W) (part 1, dose range 15–100 mg/m2 ), 2-weekly (Q2W) (part 2, 45 mg/m2 ) or Q3W with dexamethasone premedication (part 3, 60 mg/m2 ). Results: thirty-three patients were enrolled. Skin toxicity was dose limiting (DLT) at ≥60 mg/m2 in part 1 and at 45 mg/m2 in part 2 and was the most common CPC634 related grade ≥ 3 adverse event (24%). With dexamethasone premedication no DLTs were observed at 60 mg/m2 Q3W. CPC634 exhibited a dose-proportional\ud pharmacokinetic profile. At 60 mg/m2 , the plasma area under the curve was 4067.5 ± 2974.0 ng/h/mL and the peak plasma level 217.3 ± 91.9 ng/mL with a half-life of 39.7 ± 9.4 h for released docetaxel. Conclusion: CPC634 could be administered safely upon pretreatment with dexamethasone. Cumulative skin toxicity was the main DLT. The recommended phase 2 dose was determined at 60 mg/m2 Q3W with dexamethasone premedication

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

Myelosuppression by sunitinib is flt-3 genotype dependent

Personalised Therapeutic

Impact of concomitant administration of gastric acid-suppressive agents and pazopanib on outcomes in soft-tissue sarcoma patients treated within the EORTC 62043/62072 trials

Purpose: Pazopanib is active in soft-tissue sarcoma (STS). Because pazopanib absorption is pH-dependent, coadministration with gastric acid-suppressive (GAS) agents such as proton pump inhibitors could affect exposure of pazopanib, and thereby its therapeutic effects.Experimental Design: The EORTC 62043 and 62072 were single-arm phase II and placebo-controlled phase III studies, respectively, of pazopanib in advanced STS. We first compared the outcome of patients treated with pazopanib with or without GAS agents for ≥80% of treatment duration, and subsequently using various thresholds. The impact of concomitant GAS therapy was assessed on progression-free survival (PFS) and overall survival (OS) using multivariate Cox models, exploring and comparing also the potential effect on placebo-treated patients.Results: Of 333 eligible patients, 59 (17.7%) received concomitant GAS therapy for >80% of pazopanib treatment duration. Median PFS was shorter in GAS therapy users versus nonusers: 2.8 vs. 4.6 months, respectively [HR, 1.49; 95% confidence interval (CI), 1.11-1.99; P = 0.01]. Concomitant administration of GAS therapy was also associated with a shorter median OS: 8.0 vs. 12.6 months (HR, 1.81; 95% CI, 1.31-2.49; P < 0.01). The longer the overlapping use of GAS agents and pazopanib, the worse the outcome with pazopanib. These effects were not observed in placebo-treated patients (HR, 0.82; 95% CI, 0.51-1.34; P = 0.43 for PFS and HR, 0.84; 95% CI, 0.48-1.48; P = 0.54 for OS).Conclusions: Coadministration of long-term GAS therapy with pazopanib was associated with significantly shortened PFS and OS. Withdrawal of GAS agents must be considered whenever possible. Therapeutic drug monitoring of pazopanib plasma concentrations may be helpful for patients on pazopanib and GAS therapy