Development and validation of a cholate binding capacity method for DMP 504, a bile acid sequestrant

DMP 504, a highly cross-linked insoluble polymer, is a bile acid sequestran t developed by the DuPont Pharmaceuticals Company for serum cholesterol red uction. Since DMP 504 is insoluble, it was necessary to develop unique spec ific analytical methods to measure and control the quality of different lot s of the drug. Since the mechanism of action of DMP 504 is believed to be b y sequestration of bile acids, the in-vitro binding capacity of the polymer for cholic acid was chosen as a surrogate of in-vivo performance and used to assess potency of the compound. In this method, individual aliquots of D MP 504 at three different levels were incubated with a cholate solution of known concentration. The residual cholate solution was filtered and analyze d by a reversed-phase HPLC method using refractive index detection. When th e bound cholate was plotted versus the mass of DMP 504, the resulting curve was linear. The slope of this curve is the cholate binding capacity of DMP 504. This method has been shown to be precise and robust. Precision of the method was shown to have an RSD of 2.0% with injection precision of 0.4% a nd stability of cholate solutions up to 73 h. It is also a unique binding c apacity method due to its multi-point determination, and it has been shown to be a suitable quality control method for ensuring lot-to-lot consistency of drug substance. (C) 2001 Dupont Pharmaceuticals Company. Published by E lsevier Science B.V. All rights reserved.