Synthesis and evaluation of compounds that facilitate the gastrointestinal absorption of heparin

A family of novel compounds (delivery agents) that promote the gastrointestinal absorption of USP heparin in rats and primates has been discovered. The delivery agents in combination with heparin were administered either orally or intracolonically in an aqueous propylene glycol solution and caused dramatic increases in both plasma heparin concentrations (anti-Factor Xa) and clotting times (APTT). Using one of the most effective delivery agents in this series, an estimated relative bioavailability of 8% can be achieved following oral administration to cynomolgus monkeys. To establish a correlation between the in vivo data and an in vitro parameter, immobilized artificial membrane (IAM) chromatography was performed. Log relative k' values were correlated to the efficiency of oral heparin delivery.

4-[4-[(2-Hydroxybenzoyl)amino]phenyl]butyric acid as a novel oral delivery agent for recombinant human growth hormone

A series of N-acetylated, non-alpha, aromatic amino acids was prepared and shown to promote the absorption of recombinant human growth hormone (rhGH) from the gastrointestinal tract. Seventy compounds in this family were tested in vivo in rats. Of the compounds tested, 4-[4-[(2-hydroxybenzoyl)amino]phenyl]butyric acid was identified as a preclinical candidate and was used to demonstrate the oral delivery of rhGH in primates. A significant positive correlation was found between the relative log k' of the delivery agents, as determined by HPLC on an immobilized artificial membrane (IAM) column, and serum rhGH concentrations following oral or colonic dosing in rats. Structure-activity relationships have also been developed on the basis of electronic effects and hydrogen-bonding characteristics of the aromatic amide substituents.

Microsphere formation in a series of derivatized alpha-amino acids: properties, molecular modeling, and oral delivery of salmon calcitonin

A series of benzoylated and phenylsulfonylated amino acids are novel, low molecular weight, self-assembling molecules. At low pH, these compounds form microspheres that dissolve readily under neutral conditions. In a given synthetic series, those molecules with low aqueous solubility formed microspheres more readily than did the molecules possessing high water solubility, suggesting that the hydrophobicity of these compounds contributes to the ability to form microspheres. In addition, molecular modeling studies on selected compounds have shown that microsphere formation may depend also on various aromatic ring and dipole-dipole interactions, which could effect the extent and types of favorable stacking conformations between molecules. The microspheres prepared from these compounds have been used to effect the oral delivery of salmon calcitonin, a model protein drug, in both rodents and primates.