Application of a validated stability-indicating chromatographic method to evaluate the reproducibility between batches of small peptides in solution

A stability-indicating reversed-phase high-performance liquid chromatographic method was developed and validated as per the International Conference on Harmonization (ICH) guidelines to evaluate the reproducibility of batches of synthetic peptides included in a stability program, in particular cholecystokinin (CCK-4) peptide. Both isothermal and nonisothermal approaches were used to determine stability under experimental conditions and the resulting degradation products were identified by liquid chromatography–mass spectrometry (LC–MS). The principal degradation product was the cyclic dimer, although another two products derived from it were also detected, due to the loss of one or two Phe-NH 2 residues. The dimerization follows first-order kinetics, whereas the hydrolytic cleavage implies both consecutive and in-parallel processes. The linear Arrhenius plot indicates that the degradation mechanism and kinetics do not change with temperature or the batch, but the degradation rate does depend on the batch, for example, the shelf-life at 25 °C was 2.54 days for batch 3, which is 13-times lower than batch 2. This variability is caused by a change in the synthesis process introduced by the manufacturer. The combination of these two elements: the analytical and stability-evaluating methods provide enough data to establish a stability-indicating profile, as required by the guideline ICH-Q6B for biotechnological/biological products.