Yasuaki Ogawa

Bio: Yasuaki Ogawa is an academic researcher from Takeda Pharmaceutical Company. The author has contributed to research in topics: Glycolic acid & Liposome. The author has an hindex of 34, co-authored 97 publications receiving 4165 citations. Previous affiliations of Yasuaki Ogawa include Wako Pure Chemical Industries, Ltd.

A New Technique to Efficiently Entrap Leuprolide Acetate into Microcapsules of Polylactic Acid or Copoly(Lactic/Glycolic) Acid

Abstract: The aim of this work was to develop injectable microcapsules containing leuprolide acetate, that would deliver that drug at a zero-order rate over a period of about one month. A large amount of leuprolide acetate, a hydrophilic drug, was entrapped into polylactic aicd (PLA) and copoly-(lactic/glycolic) acid (PLGA) microcapsules prepared by an in-water dring method using a (w/o)/w emulsion. The basic techniques were designed to increase the viwcosities of the inner water phase and w/o emulsion. Under the conditions used, it was possible for the drug to be completely entrapped by the microcapsules in the range of 10 to 20% on the basis of the polymer. However, the release profiles of the drug in vitro were inadequate for controlled release for one month.

Prolonged release microcapsules

Abstract: This invention provides a microcapsule designed for zero order release of a physiologically active polypeptide over a period of at least two months, which is produced by preparing a water-in-oil emulsion comprising an inner aqueous layer containing about 20 to 70% (w/w) of said polypeptide and an oil layer containing a copolymer or homopolymer having a weight-average molecular weight of 7,000 to 30,000, wherein the composition ratio of lactic acid/glycolic acid in the copolymer or homopolymer is 80/10 to 100/0, and then subjecting said water-in oil emulsion to microencapsulation.

Preparation of three-month depot injectable microspheres of leuprorelin acetate using biodegradable polymers

Abstract: To obtain a three-month release injection of leuprorelin acetate, microspheres were prepared with copoly(DL-lactic/glycolic acid) or poly(DL-lactic acid) (PLA) using an in-water drying method, and drug release was evaluated. The content of water-soluble oligomers in the polymers was found to strongly affect the initial burst, and reducing the content to less than 0.1% was necessary to keep the first-day release below 10%. Drug loading of more than 15% also increased the initial drug release; the acceptable maximum loading was 12%. Elevation of the glass transition temperature of the microspheres was observed with an increase in drug loading. This suggests formation of a rigid structure, possibly with arrangement of the polymer around the drug cores like in a micelle. This structure provides a hydrophobic barrier against diffusion of the hydrophilic peptide, resulting in high trapping efficiency and long-term sustained release dependent on polymer erosion. The microspheres prepared with PLA having a m.w. of 12,000 to 18,000 provided linear sustained release and persistent serum levels of the drug in rats for over 3 months.

Method for producing microcapsule

Abstract: A microcapsule produced by preparing a water-in-oil emulsion comprising an inner aqueous layer containing said water-soluble drug and a drug retaining substance therefor and an oil layer containing a polymer substance, then thickening or solidifying said inner aqueous layer to a viscosity of not lower than about 5000 centiposes and finally subjecting the resulting emulsion to in water drying gives prolonged release of water-soluble drug.

Controlled-Release of Leuprolide Acetate from Polylactic Acid or Copoly(Lactic/Glycolic) Acid Microcapsules : Influence of Molecular Weight and Copolymer Ratio of Polymer

Abstract: Polylactic acid (PLA) or copoly(lactic/glycolic) acid (PLGA) microcapsules containing leuprolide acetate were prepared by an in-water drying process and the release patterns were examined in vitro. The release rates were extremely small from microcapsules prepared with PLA of average molecular weight 22500, and from microcapsules prepared with PLGA having average molecular weight 21200 and a copolymer ratio of 75/25 (molar ratio of lactic acid to glycolic acid). The release rate of leuprolide acetate from the microcapsules prepared with PLA of average molecular weight 6000 was relatively fast, but was still too slow to give the desired drug level over one month. Several water-soluble compounds were incorporated into microcapsules prepared with PLA of average molecular weight 22500, in an attempt to increase the release rate by the creation of aqueous channels. These compounds only induced a high initial release and failed to increase drug release. The release profile of the drug from microcapsules prepared with PLGA of average molecular weight 14000 and a copolymer ratio of 75/25 was ideal for one month's release. A small initial release was observed followed by a steady release which lasted for 35d, and approximately followed zero-order kinetics.

New methods of drug delivery.

Abstract: Conventional forms of drug administration generally rely on pills, eye drops, ointments, and intravenous solutions. Recently, a number of novel drug delivery approaches have been developed. These approaches include drug modification by chemical means, drug entrapment in small vesicles that are injected into the bloodstream, and drug entrapment within pumps or polymeric materials that are placed in desired bodily compartments (for example, the eye or beneath the skin). These techniques have already led to delivery systems that improve human health, and continued research may revolutionize the way many drugs are delivered.

Bioisosterism: A Rational Approach in Drug Design.

Abstract: Years of cumulative research can result in the development of a clinically useful drug, providing either a cure for a particular disease or symptomatic relief from a physiological disorder. A lead compound with a desired pharmacological activity may have associated with it undesirable side effects, characteristics that limit its bioavailability, or structural features which adversely influence its metabolism and excretion from the body. Bioisosterism represents one approach used by the medicinal chemist for the rational modification of lead compounds into safer and more clinically effective agents. The concept of bioisosterism is often considered to be qualitative and intuitive.1 The prevalence of the use of bioisosteric replacements in drug design need not be emphasized. This topic has been reviewed in previous years.2-5 The objective of this review is to provide an overview of bioisosteres that incorporates sufficient detail to enable the reader to understand the concepts being delineated. While a few popular examples of the successful use of bioisosteres have been included, the George Patani graduated with a B.Pharm. in 1992 from the College of Pharmaceutical Sciences, Mangalore University at Manipal, India. In 1996, he received his M.S. in Pharmaceutical Science at Rutgers University under the direction of Professor Edmond J. LaVoie. He is presently pursuing graduate studies in pharmaceutics. His current research interests are focused on drug design and controlled drug delivery.

Pharmaceutical particle engineering via spray drying.

Abstract: This review covers recent developments in the area of particle engineering via spray drying. The last decade has seen a shift from empirical formulation efforts to an engineering approach based on a better understanding of particle formation in the spray drying process. Microparticles with nanoscale substructures can now be designed and their functionality has contributed significantly to stability and efficacy of the particulate dosage form. The review provides concepts and a theoretical framework for particle design calculations. It reviews experimental research into parameters that influence particle formation. A classification based on dimensionless numbers is presented that can be used to estimate how excipient properties in combination with process parameters influence the morphology of the engineered particles. A wide range of pharmaceutical application examples—low density particles, composite particles, microencapsulation, and glass stabilization—is discussed, with specific emphasis on the underlying particle formation mechanisms and design concepts.