Lifespan based pharmacokinetic-pharmacodynamic model of tumor growth inhibition by anticancer therapeutics

Model-Based Anticancer Effect of Botulinum Neurotoxin Type A1 on Syngeneic Melanoma Mice

In recent, Botulinum Neurotoxin A1 (BoNT/A1) has been suggested as a potential anticancer agent due to neuronal innervation in tumor cells. Although potential BoNT/A1's mechanism of action for the tumor suppression has been gradually revealed so far, there were no reports to figure out the exposure-response relationships because of the difficulty of its quantitation in the biological matrix. The main objectives of this study were to measure the anticancer effect of BoNT/A1 using a syngeneic mouse model transplanted with melanoma cells (B16-F10) and developed a kinetic-pharmacodynamic (K-PD) model for quantitative exposure-response evaluation. To overcome the lack of exposure information, the K-PD model was implemented by the virtual pharmacokinetic compartment link to the pharmacodynamic compartment of Simeoni's tumor growth inhibition model and evaluated using curve-fitting for the tumor growth-time profile after intratumoral injection of BoNT/A1. The final K-PD model was adequately explained for a pattern of tumor growth depending on represented exposure parameters and simulation studies were conducted to determine the optimal dose under various scenarios considering dose strength and frequency. The optimal dose range and regimen of ≥13.8 units kg^-1 once a week or once every 3 days was predicted using the final model in B16-F10 syngeneic model and it was demonstrated with an extra in-vivo experiment. In conclusion, the K-PD model of BoNT/A1 was well developed to optimize the dosing regimen for evaluation of anticancer effect and this approach could be expandable to figure out quantitative interpretation of BoNT/A1's efficacy in various xenograft and/or syngeneic models.

Delay differential equations based models in NONMEM

Delay differential equations (DDEs) are commonly used in pharmacometric models to describe delays present in pharmacokinetic and pharmacodynamic data analysis. Several DDE solvers have been implemented in NONMEM 7.5 for the first time. Two of them are based on algorithms already applied elsewhere, while others are extensions of existing ordinary differential equations (ODEs) solvers. The purpose of this tutorial is to introduce basic concepts underlying DDE based models and to show how they can be developed using NONMEM. The examples include previously published DDE models such as logistic growth, tumor growth inhibition, indirect response with precursor pool, rheumatoid arthritis, and erythropoiesis-stimulating agents. We evaluated the accuracy of NONMEM DDE solvers, their ability to handle stiff problems, and their performance in parameter estimation using both first-order conditional estimation (FOCE) and the expectation-maximization (EM) method. NONMEM control streams and excerpts from datasets are provided for all discussed examples. All DDE solvers provide accurate and precise solutions with the number of significant digits controlled by the error tolerance parameters. For estimation of population parameters, the EM method is more stable than FOCE regardless of the DDE solver.

Evaluation of Ceiba pentandra (L.) Gaertner bark extracts for in vitro cytotoxicity on cancer cells and in vivo antitumor activity in solid and liquid tumor models

The stem bark of Ceiba pentandra (L.) Gaertner is claimed to be useful in the treatment of tumors in the southern part of India. This plant possesses a number of sesquiterpenoids and isoflavones which are known for their anticancer properties. The present study was designed to scientifically evaluate the cytotoxic potential of bark extracts in in vitro on Ehrlich ascites carcinoma (EAC), MCF-7 and B16F10 cells and in vivo in EAC (Liquid tumor) model and Dalton's lymphoma ascites (DLA or solid tumor) model. The bark was powdered and extracted successively with solvents viz., petroleum ether (PE), benzene, chloroform, acetone (AC), and ethyl alcohol in the sequential order of polarity. Cytotoxicity of dried extracts was screened on EAC cells by trypan blue assay. Three potent extracts namely petroleum ether, acetone, and ethanol were screened for their cytotoxicity on MCF-7 and B16F10 cells by MTT assay and nucleomorphological alteration by propidium iodide staining. Safe doses of these extracts were evaluated by acute toxicity study in mice. Extracts were found to be safe up to 300 mg/kg in acute toxicity study. Dosage of 1/10th and 1/20th of safe dose i.e., 15 and 30 mg/kg were selected for in vivo study. In the EAC model, both doses of the extracts showed a significant (P < 0.05) improvement in mean survival time and a maximum decline in tumor induced increase in body weight (an indirect measure of tumor weight) by the PE and AC treatment at 15 mg/kg compared to control. In the DLA-model, all extracts at both tested dose levels showed >50 % reduction in tumor weight and a significant reduction (P < 0.05) in tumor volume on the 30th day compared to control. It can be concluded that these extracts possess cytotoxic and antitumor activity.