Stability of deslorelin injection

The stability of deslorelin, a nonapeptide drug, in an injectable drug formulation was studied for 60 months. An HPLC analytical method was developed to quantify deslorelin and benzyl alcohol in deslorelin injection. The samples containing 500 micrograms/mL of deslorelin were stored at--10, 6, 25, 40 and 50 degrees C. No deslorelin degradation was observed in samples stored at 6 degrees C, but the loss of deslorelin in samples stored at 25, 40 and 50 degrees C was found to increase with temperature. The T90 of the product at 6 degrees C was estimated to be greater than 20 years from the short-term stability data of four lots stored at 25, 40 and 50 degrees C. The long-term stability results confirmed that there was no degradation of deslorelin stored at 6 degrees C for 5 years. Liquid secondary ionization mass spectrometry analysis of aged samples showed hydrolysis of deslorelin and the production of a hexapeptide (< Ser-Tyr-D-Trp-Leu-Arg-Pro-NH-Et) with a molecular weight of 847. A second product resulted from the oxidation of the tryptophan indoylyl ring. The oxyindoyle decapeptide structure had an ion m/z of 1298. The mass spectrum of pure deslorelin also is reported.