Crystalline Salts of Obeticholic Acid

Abstract

Obeticholic acid is a semi-synthetic bile acid indicated for primary biliary cholangitis/cirrhosis (PBC) and developed for the treatment of other liver conditions such as non-alcoholic steatohepatitis (NASH). The final drug product marketed under the name Ocaliva comprises amorphous obeticholic acid. There is a need for a crystalline salt of obeticholic acid, useful in purification of this acid and suitable for industrial process. So far only few crystalline salts have been found. Set of organic bases, especially amines, were tested in order to obtain a crystalline salt. Out of 39 tested counter-ions, only few provided crystalline salt with obeticholic acid: tetrabutylamonium hydroxide, 3-pentylamine, (S)-aminoquinuclidine a N,N-methylpropylamine. In particular, the salt of obeticholic acid and 3-pentylamine exhibited interesting properties such as a relatively rapid crystallization from chemically impure solution, high degree of crystallinity and solvent-free structure.