cardiovascular-agents and roxifiban

In the course of the development of Lumaxistrade mark (roxifiban), the physical state of XP280 (the besylate salt of the active metabolites of roxifiban) and SC887 (the mesylate salt of the free base of roxifiban) were characterized. Powder X-ray diffraction patterns of XP280 were ambiguous in that a high degree of background signal was present and potentially indicative of the existence of an amorphous phase. Herein the results of combined synchrotron X-ray diffraction and electron microscopy (diffraction and imaging) studies on XP280 and SC887 are reported. The combination of these two techniques allowed an unambiguous assessment of the crystallinity, as well as determination of four of the unit cell parameters of XP280 and complete determination of the unit cell parameters for SC887.

Topics: Amidines; Cardiovascular Agents; Crystallization; Isoxazoles; Mesylates; Microscopy, Electron; X-Ray Diffraction

1. The methyl ester prodrug roxifiban is an orally active, potent and selective antagonist of the platelet glycoprotein GPIIb/IIIa receptor and is being developed for the prevention and treatment of arterial thrombosis. 2. Roxifiban was rapidly hydrolyzed to the zwitterion XV459 in vivo and by liver slices from the rat, mouse and human and by intestinal cores from dog. XV459 was metabolized to only a small extent in vitro and in vivo. 3. Studies with rat and dog given radiolabelled roxifiban showed limited oral absorption with the majority of the radiolabel being excreted in faeces. After i.v. doses of 14C-roxifiban, most of the radioactivity was recovered in the urine of rat whereas the dog excreted significant amounts of radioactivity in bile and urine. 4. XV459 could be metabolized extrahepatically by dog gut flora to produce an isoxazoline ring-opened metabolite. In vitro hepatic metabolism of XV459 was mainly by hydroxylation at the prochiral and chiral centres of the isoxazoline ring. These hydroxylated metabolites were not detected in the urine and plasma of human volunteers administered roxifiban. 5. Initial LC/MS identification of metabolites was achieved by dosing the rat with an equimolar mixture of d0:d4 roxifiban and detecting isotopic clusters of pseudomolecular ions. Unequivocal characterization of these metabolites was achieved by LC/MS, LC/NMR and high-field NMR techniques using synthetic standards of the metabolites. 6. The synthesis of one hydroxylated metabolite enabled the assignment of the correct stereochemistry of the substituted hydroxyl group on the isoxazoline ring.

Topics: Amidines; Amino Acids; Animals; Cardiovascular Agents; Chromatography, High Pressure Liquid; Dogs; Feces; Gas Chromatography-Mass Spectrometry; Humans; Isoxazoles; Liver; Magnetic Resonance Spectroscopy; Mass Spectrometry; Mice; Platelet Glycoprotein GPIIb-IIIa Complex; Rats; Thrombosis

Unit cell parameters of two polymorphs of roxifiban have been determined by a combination of transmission electron microscopy (TEM) single-crystal and synchrotron X-ray powder diffraction techniques. While it was difficult to differentiate the two forms by their standard X-ray diffraction patterns, the high-resolution synchrotron patterns clearly showed striking differences. Unit cells for the two forms required the use of cell parameters derived from TEM diffraction patterns. The two unit cells are, not surprisingly, very similar except for a doubling of one of the axes for form II. The combined use of TEM and synchrotron patterns appears to be a good general approach for characterizing complex (low-symmetry, large unit cell) polymorphs.

Topics: Amidines; Cardiovascular Agents; Electrons; Isoxazoles; Microscopy, Electron; Platelet Glycoprotein GPIIb-IIIa Complex; Synchrotrons; X-Ray Diffraction