High-performance liquid chromatographic (HPLC) and HPLC-mass spectrometric (MS) analysis of the degradation of the luteinizing hormone-releasing hormone (LH-RH) antagonist RS-26306 in aqueous solution.
The kinetics of the degradation of an LH-RH antagonist, RS-26306,1, in aqueous solution from pH 1 to pH 11 were studied by reverse-phase HPLC. The pH-rate profiles at 50, 60, and 80 degrees C were U-shaped with the rate law of kobs = kHaH + kw + kOHaOH. The predicted 25 degrees C shelf life at the pH of maximum stability, pH approximately 5, is greater than 10 years. The products from the degradation were analyzed by HPLC-MS using thermospray ionization. Below pH 3, the primary product, 2, forms from the acid-catalyzed deamidation of the C-terminal amide. Above pH 7, epimerization of the individual amino acids is the principal reaction. Between pH 4 and pH 6, intramolecular serine-catalyzed peptide hydrolysis becomes important, yielding a tripeptide, 3, and a heptapeptide, 4. At the pH of maximum stability all three pathways for degradation are observed.
Strickley
R G
RG
Institute of Pharmaceutical Sciences, Syntex Research, Palo Alto, California 94304.
Brandl
M
M
Chan
K W
KW
Straub
K
K
Gu
L
L
D055598:Chemical Phenomena; D002621:Chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D013058:Mass Spectrometry / Q000379:methods; D008970:Molecular Weight; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D014867:Water
D012996:Solutions; D014867:Water; D007987:Gonadotropin-Releasing Hormone; C061018:ganirelix