Validation of a spectrophotometric method for free thiols quantification in filgrastim

Disulfide bonds are post-translational modifications that provide conformational stability to proteins relevant to perform their biological functions. In this study, the quantification of free thiols by using Ellman’s reagent was validated to demonstrate, that the Filgrastim contained in the Filatil® exhibits the same amount of disulfide bonds than its reference product under both native and denaturing-reducing conditions. The validation exercise demonstrated to be suitable for its intended use. The comparability exercise for this attribute showed no significant differences (p=1.000; α , 0.05) in free cysteines content among the two evaluated products. These results provide evidence of similitude for this attribute, which along with an extended comparability exercise for other physicochemical characteristics, contribute to the demonstration of similarity among the physicochemical and functional properties set as critical quality attributes for Filgrastim according to the regulatory guidelines.