PLGA microparticles, a sustained release formulation thereof and a production method thereof

A method of producing approximately spherical lactic acid-glycolic acid copolymer (PLGA) microparticles comprising a biologically active substance, using a processing apparatus in which microparticle forming is performed between the processing surfaces being capable of approaching to and separating from each other at least one of which rotates relative to the other,

• which comprises a step of forming microparticles in which the approximately spherical PLGA microparticles are formed by continuously introducing into the processing apparatus, a PLGA solution obtained by dissolving or dispersing PLGA and the biologically active substance in a good solvent of PLGA and a solution containing a poor solvent of PLGA, are continuously introduced into a minute distance of 1 mm or less between processing surfaces of a processing apparatus in which pulverization is performed between the processing surfaces being capable of approaching to and separating from each other at least one of which rotates relative to the other;
• and the approximately spherical PLGA microparticles are formed in the thin film fluid formed in the space between the processing surfaces without a classification step, and
• wherein the good solvent of PLGA is a solvent which dissolves 0.1 g or more of PLGA in 100 g of the solvent at 25° C., and the poor solvent of PLGA is a solvent which dissolves 0.05 g or less of PLGA in 100 g of the solvent at 25° C., wherein
• an average volume-based particle diameter of the PLGA microparticles is 1 μm or more and 150 μm or less, and
• a Reactive Span Factor (R.S.F.) of the PLGA microparticles is satisfied with formula (1):
• 0.1
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• wherein an R.S.F. means (D90−D10)/D50,
• D90 is a particle diameter (μm) corresponding to the cumulative 90% by volume of the cumulative particle diameter distribution from the small particle side,
• D50 is a particle diameter (μm) corresponding to the cumulative 50% by volume of the cumulative particle diameter distribution from the small particle side, and
• D10 is a particle diameter (μm) corresponding to the cumulative 10% by volume of the cumulative particle diameter distribution from the small particle side.