Dry heat stress stability of model peptide: buserelin

Abstract

Buserelin, an gonadotropin hormone releasing agonist peptide implemented in the treatment of prostate cancer, was subjected in its dry powder state to short-term heat exposure to evaluated its potential application in hot melt extrusion processing. Five different temperature and time conditions, ranging from 150°C to 180°C and 10 to 160 min, respectively, were evaluated (4 time points per temperature). Each experimental condition was performed in duplicate. A stability indicating UPLC-DAD (220 nm) method was used both for buserelin assay as degradant quantification. Linear regression, assuming first order degradation kinetics, was employed to calculate the Arrhenius activation energy (Ea) and frequency factor (A). During dry heat stressing, a change from solid to molten state was observed at 165°C. This change is also reflected in the Arrhenius regression curve, which is of sigmoidal nature. Given this change in state, two Arrhenius Ea were calculated, i.e. 217 and 87 kJ/mol for solid and molten state respectively. Three different degradant groups were observed using HPLC ESI/iontrap-MS: [M+H+] 453 amu, [M+H+] 902 amu and busereline diastereoisomers. The apparent degradation mechanisms included hydrolysis, dissociation of the tertiary butyl group on Ser6 and isomerization. Further structure elucidation is ongoing using nanoUPLC ESI/Orbitrap-MS