Lactic acid polymer and process for producing the same

Abstract

A process for producing a lactic acid polymer of 15,000 to 50,000 in weight-average molecular weight, the content of polymeric materials having not more than about 5,000 in weight-average molecular weight therein being not more than about 5% by weight, characterized by hydrolyzing a high molecular weight lactic acid polymer, placing the resultant solution comprising the hydrolyzed product under a condition capable of precipitating the objective lactic acid polymer, separating the precipitated lactic acid polymer and collecting them. The lactic acid polymer is useful as a matrix for sustained-release preparations. The sustained-release microcapsule preparation encapsulating a physiologically active substance can fully prevent the initial excessive release of the physiologically active substance from the microcapsules and keep a stable release rate over a long period of time.

1 - 18 . (canceled)  
   
   
       19 . A pharmaceutical composition, which comprises a lactic acid polymer of 15,000 to 50,000 in weight-average molecular weight, the content of other polymers having not more than about 5,000 in weight-average molecular weight in the lactic acid polymer being not more than about 5% by weight.  
   
   
       20 . The pharmaceutical composition according to  claim 19 , wherein the content of other polymers having not more than about 3,000 in weight-average molecular weight in the lactic acid polymer being not more than about 1.5% by weight.  
   
   
       21 . The pharmaceutical composition according to  claim 20 , wherein the content of other polymers having not more than about 1,000 in weight-average molecular weight in the lactic acid polymer being not more than about 0.1% by weight.  
   
   
       22 . The pharmaceutical composition according to any one of  claims 19  to  21 , wherein the lactic acid polymer has 15,000 to 30,000 in weight-average molecular weight.  
   
   
       23 . The pharmaceutical composition according to any one of  claims 19  to  21 , wherein the lactic acid polymer has 20,000 to 25,000 in weight-average molecular weight.  
   
   
       24 . The pharmaceutical composition according to any one of  claims 19  to  21 , which is a sustained-release preparation.  
   
   
       25 . The pharmaceutical composition according to any one of  claims 19  to  21 , which is a microcapsule.  
   
   
       26 . The pharmaceutical composition according to  claim 19 , which comprises a physiologically active peptide or a salt thereof.  
   
   
       27 . The pharmaceutical composition according to  claim 26 , wherein the physiologically active peptide or the salt thereof is a luteinizing hormone releasing hormone (LH-RH) derivative or a salt thereof.  
   
   
       28 . The pharmaceutical composition according to  claim 26 , wherein the physiologically active peptide or the salt thereof is leuprorelin or a salt thereof.  
   
   
       29 . The pharmaceutical composition according to  claim 27  or  28 , which is used for treatment or prevention of prostatic cancer, prostatic hyperplasia, endometriosis, fibroid, precocious puberty or breast cancer.  
   
   
       30 . The pharmaceutical composition according to  claim 27  or  28 , which is a sustained-release preparation retaining a stable release rate of a physiologically active peptide or a salt thereof over six months or more.  
   
   
       31 . A method for treatment or prevention of prostatic cancer, prostatic hyperplasia, endometriosis, fibroid, precocious puberty or breast cancer in a mammal, which comprises administering an effective amount of the pharmaceutical composition according to  claim 27  or  28  to the mammal.  
   
   
       32 . The method according to  claim 31 , wherein the pharmaceutical composition is a sustained-release preparation.  
   
   
       33 . The method according to  claim 31 , wherein the pharmaceutical composition is a microcapsule.  
   
   
       34 . The method according to  claim 31 , wherein the pharmaceutical composition is a sustained-release preparation retaining a stable release rate of a physiologically active peptide or a salt thereof over six months or more.