The AAPS Journal

Fish Pharmacokinetics Database Updated

Fri, 31 Aug 2007 00:00:00 -0400

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Basics of US Patents and the Patent System

Elliott G — Fri, 24 Aug 2007 00:00:00 -0400

The patent system plays an important role in stimulating the economy and advancing the quality of life in the United States. It serves as an incentive for innovation by giving inventors an exclusive right to their inventions for a limited period of time. It also increases and hastens the publication of useful knowledge by requiring inventors to disclose their invention to the public. Patents are particularly important in the pharmaceutical and biotechnology industries because they provide a mechanism by which the extremely high product development costs may be recouped. The United States Patent and Trademark Office acts as a gatekeeper in the patent system to prevent patents that do not meet the legal requirements from being thrust on the public. The legal requirements for obtaining a patent are discussed, particularly as they relate to pharmaceutical and biotechnological inventions. The process of examining an application for a patent is briefly described, along with some of the burdens faced by examiners when deciding the patentability of therapy-related inventions.

The Influence of Market Exclusivity on Drug Availability and Medical Innovations

Glover GJ — Fri, 3 Aug 2007 00:00:00 -0400

The interpretation and application of intellectual property laws is enormously complex in the pharmaceutical industry, with companies needing to obtain multiple patents to fully protect their innovations. While patents provide important incentives for biomedical innovation and economic growth, concern has been expressed over the growing number of patents, the granting of patents on basic research tools (eg, genetically engineered animals), and the possibility that these legal protections may ultimately inhibit scientific advancement.

Intellectual Property Policy in the Pharmaceutical Sciences: The Effect of Inappropriate Patents and Market Exclusivity Extensions on the Health Care System

Kesselheim AS — Fri, 3 Aug 2007 00:00:00 -0400

Though patents are effective tools for promoting innovation and protecting intellectual property in the pharmaceutical sciences, there has been growing concern about 2 important ways that patents in this field can have a negative effect on patient care and the practice of medicine. First, inventors can seek and receive patents on pharmaceutical products or research tools that stretch the statutory requirements for patenting. Second, patent holders in the pharmaceutical market can use legal loopholes or aspects of the patent registration system to extend exclusivity for inventions beyond what was anticipated by the Patent Act or subsequent legislation. The monopoly control bestowed by such inappropriate patents or manipulation of the patent system can limit options available to patients, increase the cost of health care delivery, and make cooperative research more difficult. In response, several different government and market-based efforts have emerged to promote more equitable patent policy in health care that encourages dissemination of ideas while still supporting the development of innovative products.

Inactivation of Hepatic Enzymes by Inhalant Nitrite—In Vivo and In Vitro Studies

Turowski SG, Jank KE, Fung H — Fri, 27 Jul 2007 00:00:00 -0400

We examined the effects of acute isobutyl nitrite (ISBN) exposure on the activity of several hepatic enzymes. Two strains of adult male mice (Balb/c and C57BL/6) were exposed to 900 ppm ISBN or ambient air for 45 minutes. The enzyme activity of hepatic cytochrome P450 (CYP)-mediated deethylation, glutathione S-transferase (GST), and carboxylesterase (CBE) was monitored through the substrates 3-cyano-7-ethoxycoumarin (CEC), 1-chloro-2,4-dinitrobenzene, and p-nitrophenyl acetate, respectively. Acute ISBN exposure led to a significant reduction in hepatic CYP-mediated CEC deethylation, GST, and CBE activity in Balb/c mice (of 81.5%, 74.7%, and 25.2%, respectively, vs control mice, each at P < .05) when livers were harvested immediately after inhalant exposure. The corresponding decreases in C57BL/6 mice were smaller (with reductions of 21.8%, 18.8%, and 13.3%, respectively, each at P < .05). This enzyme activity, tested in C57BL/6 mice only, returned to control values after a 24-hour period of nonexposure. Follow-up mechanistic investigations using rat liver GST indicated that ISBN-mediated enzyme inactivation was not caused by its metabolites: inorganic nitrite ion (NO2 –) or nitric oxide. This inactivation could be prevented, but not reversed, by added glutathione, suggesting irreversible protein oxidation. Using different NO donors as comparative agents, we found that GST inactivation by ISBN was not associated with protein S-nitrosylation or disulfide formation, but with tyrosine nitration. Inhalant nitrite exposure, therefore, led to a significant reduction in hepatic enzyme activity in mice, possibly through tyrosine nitration of hepatic proteins. This effect raises the possibility of drug-drug metabolic interactions from inhalant nitrite abuse. However, determining the applicability of these findings to humans will require further study.

Biomarkers, Metabonomics, and Drug Development: Can Inborn Errors of Metabolism Help in Understanding Drug Toxicity?

Vangala S, Tonelli A — Fri, 20 Jul 2007 00:00:00 -0400

Application of “omics” technology during drug discovery and development is rapidly evolving. This review evaluates the current status and future role of “metabonomics” as a tool in the drug development process to reduce the safety-related attrition rates and bridge the gaps between preclinical and clinical, and clinical and market. Particularly, the review looks at the knowledge gap between the pharmaceutical industry and pediatric hospitals, where metabonomics has been successfully applied to screen and treat newborn babies with inborn errors of metabolism. An attempt has been made to relate the clinical pathology associated with inborn errors of metabolism with those of drug-induced pathology. It is proposed that extending the metabonomic biomarkers used in pediatric hospitals, as “advanced clinical chemistry” for preclinical and clinical drug development, is immediately warranted for better safety assessment of drug candidates. The latest advances in mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy should help replace the traditional approaches of laboratory clinical chemistry and move the safety evaluation of drug candidates into the new millennium.

Advanced Pharmacokinetic Models Based on Organ Clearance, Circulatory, and Fractal Concepts

Pang KS, Weiss M, Macheras P — Fri, 29 Jun 2007 00:00:00 -0400

Three advanced models of pharmacokinetics are described. In the first class are physiologically based pharmacokinetic models based on in vitro data on transport and metabolism. The information is translated as transporter and enzyme activities and their attendant heterogeneities into liver and intestine models. Second are circulatory models based on transit time distribution and plasma concentration time curves. The third are fractal models for nonhomogeneous systems and non-Fickian processes are presented. The usefulness of these pharmacokinetic models, with examples, is compared.

Appropriate Calibration Curve Fitting in Ligand Binding Assays

Findlay JWA, Dillard RF — Fri, 29 Jun 2007 00:00:00 -0400

Calibration curves for ligand binding assays are generally characterized by a nonlinear relationship between the mean response and the analyte concentration. Typically, the response exhibits a sigmoidal relationship with concentration. The currently accepted reference model for these calibration curves is the 4-parameter logistic (4-PL) model, which optimizes accuracy and precision over the maximum usable calibration range. Incorporation of weighting into the model requires additional effort but generally results in improved calibration curve performance. For calibration curves with some asymmetry, introduction of a fifth parameter (5-PL) may further improve the goodness of fit of the experimental data to the algorithm. Alternative models should be used with caution and with knowledge of the accuracy and precision performance of the model across the entire calibration range, but particularly at upper and lower analyte concentration areas, where the 4- and 5-PL algorithms generally outperform alternative models. Several assay design parameters, such as placement of calibrator concentrations across the selected range and assay layout on multiwell plates, should be considered, to enable optimal application of the 4- or 5-PL model. The fit of the experimental data to the model should be evaluated by assessment of agreement of nominal and model-predicted data for calibrators.

O-Phospho-L-Serine, Multi-functional Excipient for B Domain Deleted Recombinant Factor VIII

Miclea RD, Purohit VS, Balu-Iyer SV — Fri, 29 Jun 2007 00:00:00 -0400

Factor VIII (FVIII) is an important cofactor in the blood coagulation cascade. A deficiency or dysfunction of FVIII causes hemophilia A, a life-threatening bleeding disorder. FVIII circulates in plasma as a heterodimer comprising 6 domains (heavy chain, A1-A2-B and light chain, A3-C1-C2). Replacement therapy using FVIII is the leading therapy in the management of hemophilia A. However, ~15% to 30% of patients develop inhibitory antibodies that neutralize the activity of the protein. Neutralizing antibodies to epitopes in the lipid binding region of FVIII are commonly identified in patients’ plasma. In this report, we investigated the effect of O-phospho-L-serine (OPLS), which binds to the lipid binding region, on the immunogenicity of B domain deleted recombinant factor VIII (BDDrFVIII). Sandwich enzyme-linked immunosorbent assay (ELISA) studies showed that OPLS specifically bind to the lipid binding region, localized in the C2 domain of the coagulation factor. Size exclusion chromatography and fluorescence anisotropy studies showed that OPLS interfered with the aggregation of BDDrFVIII. Immunogenicity of free- vs BDDrFVIII-OPLS complex was evaluated in a murine model of hemophilia A. Animals administered subcutaneous (sc) injections of BDDrFVIII-OPLS had lower neutralizing titers compared with animals treated with BDDrFVIII alone. Based on these studies, we hypothesize that specific molecular interactions between OPLS and BDDrFVIII may improve the stability and reduce the immunogenicity of BDDrFVIII formulations.

Biodegradable Intraprostatic Doxorubicin Implants

Ortiz R, Au JL, Lu Z, Gan Y, Wientjes MG — Fri, 29 Jun 2007 00:00:00 -0400

Systemic chemotherapy is not effective in the treatment of prostate-confined cancer. We developed biodegradable, doxorubicin-loaded cylinders for intraprostatic implantation and evaluated the feasibility of using regional intraprostatic drug therapy to treat prostate-confined cancer. Cylinders were prepared using poly(lactide-co-glycolide) (PLG) or PLG copolymers. The in vitro and in vivo drug release, intraprostatic pharmacokinetics, and histopathology in dogs implanted with the cylinders were studied. The doxorubicin-loaded cylinders made of PLG polymers of 7.9 to 54 kDa molecular weight (MW) had a diameter of ~800 µm, drug loading of 10% to 30% (wt/wt), and even distribution of crystalline drug throughout the matrix. Burst release varied from 3% to 73%, and 7-day cumulative release from 4% to 90%. Decreasing polymer MW and increasing drug loading were associated with higher initial burst release and overall release rates. The in vivo drug release from cylinders (33-kDa PLG, 30% drug loading) in dog prostates was rapid (~80% in 48 hours). Spatial drug distribution, visualized using confocal fluorescence microscopy, showed high concentrations confined to the lobule containing the implant (referred to as the implanted lobule), with steep concentration gradients over the septa separating the lobules. Concentrations in the implanted lobule were about 8 times higher than concentrations delivered by an intravenous injection. The implants caused necrotic cell death in the implanted lobule, without damage to prostatic nerve bundles or the urethra. These results indicate the feasibility of using biodegradable PLG cylinders as intraprostatic implants to selectively deliver high drug concentrations to prostate tissue.