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Abdel-Rahman S.M.,Childrens Mercy Hospital | Amidon G.L.,University of Michigan | Kaul A.,Cincinnati Childrens Hospital Medical Center | Kaul A.,University of Cincinnati | And 4 more authors.
Clinical Therapeutics

Background: The Biopharmaceutics Classification System (BCS) allows compounds to be classified based on their in vitro solubility and intestinal permeability. The BCS has found widespread use in the pharmaceutical community to be an enabling guide for the rational selection of compounds, formulation for clinical advancement, and generic biowaivers. The Pediatric Biopharmaceutics Classification System (PBCS) Working Group was convened to consider the possibility of developing an analogous pediatric-based classification system. Because there are distinct developmental differences that can alter intestinal contents, volumes, permeability, and potentially biorelevant solubilities at different ages, the PBCS Working Group focused on identifying age-specific issues that need to be considered in establishing a flexible, yet rigorous PBCS. Objective: We summarized the findings of the PBCS Working Group and provided insights into considerations required for the development of a PBCS. Methods: Through several meetings conducted both at The Eunice Kennedy Shriver National Institute of Child Health, Human Development-US Pediatric Formulation Initiative Workshop (November 2011) and via teleconferences, the PBCS Working Group considered several high-level questions that were raised to frame the classification system. In addition, the PBCS Working Group identified a number of knowledge gaps that need to be addressed to develop a rigorous PBCS. Results: It was determined that for a PBCS to be truly meaningful, it needs to be broken down into several different age groups that account for developmental changes in intestinal permeability, luminal contents, and gastrointestinal (GI) transit. Several critical knowledge gaps were identified, including (1) a lack of fully understanding the ontogeny of drug metabolizing enzymes and transporters along the GI tract, in the liver, and in the kidney; (2) an incomplete understanding of age-based changes in the GI, liver, and kidney physiology; (3) a clear need to better understand age-based intestinal permeability and fraction absorbed required to develop the PBCS; (4) a clear need for the development and organization of pediatric tissue biobanks to serve as a source for ontogenic research; and (5) a lack of literature published in age-based pediatric pharmacokinetics to build physiologically- and population-based pharmacokinetic (PBPK) databases. Conclusions: To begin the process of establishing a PBPK model, 10 pediatric therapeutic agents were selected (based on their adult BCS classifications). These agents should be targeted for additional research in the future. The PBCS Working Group also identified several areas where greater emphasis on research was needed to enable the development of a PBCS. © 2012 Elsevier HS Journals, Inc. Source

Samant T.S.,University of Florida | Mangal N.,University of Florida | Lukacova V.,Simulations Plus Inc. | Schmidt S.,University of Florida
Journal of Clinical Pharmacology

The establishment of drug dosing in children is often hindered by the lack of actual pediatric efficacy and safety data. To overcome this limitation, scaling approaches are frequently employed to leverage adult clinical information for informing pediatric dosing. The objective of this review is to provide a comprehensive overview of the different scaling approaches used in pediatric pharmacotherapy as well as their proper implementation in drug development and clinical use. We will start out with a brief overview of the current regulatory requirements in pediatric drug development, followed by a review of the most commonly employed scaling approaches in increasing order of complexity ranging from simple body weight-based dosing to physiologically-based pharmacokinetic (PBPK) modeling approaches. Each of the presented approaches has advantages and limitations, which will be highlighted throughout the course of the review by the use of clinically-relevant examples. The choice of the approach employed consequently depends on the clinical question at hand and the availability of sufficient clinical data. The main effort while establishing and qualifying these scaling approaches should be directed towards the development of safe and effective dosing regimens in children rather than identifying the best model, ie models should be fit for purpose. © 2015, The American College of Clinical Pharmacology. Source

De Zordi N.,University of Trieste | Moneghini M.,University of Trieste | Kikic I.,University of Trieste | Grassi M.,University of Trieste | And 3 more authors.
European Journal of Pharmaceutics and Biopharmaceutics

The 'classical' loop diuretic drug Furosemide has been used as a model compound to investigate the possibility of enhancing the dissolution rate of poorly water-soluble drugs using supercritical anti-solvent techniques (SASs). In the present study we report upon the in vitro bioavailability improvement of Furosemide through particle size reduction as well as formation of solid dispersions (SDs) using the hydrophilic polymer Crospovidone. Supercritical carbon dioxide was used as the processing medium for these experiments. In order to successfully design a CO 2 antisolvent process, preliminary studies of Furosemide microparticles generation were conducted using Peng Robinson's Equation of State. These preliminary studies indicated using acetone as a solvent with pressures of 100 and 200 bar and a temperature of 313 K would yield optimum results. These operative conditions were then adopted for the SDs. Micronization by means of SAS at 200 bar resulted in a significant reduction of crystallites, particle size, as well as improved dissolution rate in comparison with untreated drug. Furosemide recrystallized by SAS at 100 bar and using traditional solvent evaporation. Moreover, changes in polymorphic form were observed in the 200 bar samples. The physicochemical characterization of Furosemide:crospovidone SDs (1:1 and 1:2 w/w, respectively) generated by SAS revealed the presence of the drug amorphously dispersed in the 1:2 w/w sample at 100 bar still remaining stable after 6 months. This sample exhibits the best in vitro dissolution performance in the simulated gastric fluid (pH 1.2), in comparison with the same SD obtained by traditional method. No interactions between drug and polymer were observed. These results, together with the presence of the selected carrier, confirm that the use of Supercritical fluids antisolvent technology is a valid mean to increase the dissolution rate of poorly soluble drugs. Theoretical in vivo-in vitro relation was predicted by means of a pharmacokinetics mathematical model. © 2012 Elsevier B.V. All rights reserved. Source

Woltosz W.S.,Simulations Plus Inc.
Journal of Computer-Aided Molecular Design

In the early days, airplanes were put together with parts designed for other purposes (bicycles, farm equipment, textiles, automotive equipment, etc.). They were then flown by their brave designers to see if the design would work-often with disastrous results. Today, airplanes, helicopters, missiles, and rockets are designed in computers in a process that involves iterating through enormous numbers of designs before anything is made. Until very recently, novel drug-like molecules were nearly always made first like early airplanes, then tested to see if they were any good (although usually not on the brave scientists who created them!). The resulting extremely high failure rate is legendary. This article describes some of the evolution of computer-based design in the aerospace industry and compares it with the progress made to date in computer-aided drug design. Software development for pharmaceutical research has been largely entrepreneurial, with only relatively limited support from government and industry end-user organizations. The pharmaceutical industry is still about 30 years behind aerospace and other industries in fully recognizing the value of simulation and modeling and funding the development of the tools needed to catch up. © 2011 The Author(s). Source

Clark R.D.,Simulations Plus Inc.
Journal of Medicinal Chemistry

Developing a viable new drug candidate is difficult. Developing one that is a small molecule kinase inhibitor that binds competitively with respect to ATP with superb selectivity is even more difficult, which makes the design and optimization work described by Jimenez et al. (J. Med. Chem., DOI: 10.1021/jm301465a) particularly remarkable. They took a lead from a high-throughput screen against protein kinase C θ (PKCθ) through a series of optimization steps, culminating in the demonstration of in vivo activity in mice. Having identified and improved the hinge-binding "warhead" at one end of their lead molecule, they proceeded to use structure-based design tools to guide modification of the other end to enhance selectivity over a closely related isoform of the kinase. With that accomplished, they used a series of protection and deprotection maneuvers to modify the central portion of the series scaffold to further enhance potency against the target while also improving pharmacokinetic properties. The project was a success at the preclinical level: oral administration of the ultimate analogue obtained was effective at suppressing interleukin-2 induction in mice. © 2013 American Chemical Society. Source

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