Preformulation Studies on Imexon

Abstract

Imexon is an aziridine containing iminopyrrolidone that, through aziridine ring opening, is able to induce oxidative stress resulting in apoptosis. The main objective of this research was to conduct extensive preformulation studies on Imexon in order to understand the factors that affect its stability. The results obtained indicate that the stability of Imexon is dependant on pH, ionic strength, temperature, buffer species, and initial concentration. Degradation of Imexon follows apparent first-order degradation kinetics with the primary degradation product resulting from opening of the aziridine ring. In order to maximize stability, ionic strength, temperature, and initial concentration should be minimized, with an optimal range pH between 7.2 and 9.0. Experimentation with other aqueous solutions indicates that Imexon has increased stability in D5W as opposed to normal saline, while it undergoes rapid degradation in 6% H₂O₂. Imexon is not ionizable between pH 5.0 to 8.5 and has an aqueous solubility of approximately 25 mg/mL over this range. Solid-state characterization has concluded that Imexon is a crystalline solid that begins decomposition at 165°C, prior to melting.

KEYWORDS:

• Imexon
• Preformulation studies
• General acid/base catalysis
• pH stability
• Solubility