Characterization of recombinant human growth hormone variants from sodium hyaluronate-based sustained release formulation of rhGH under heat stress

This study provides the findings of investigations of potential product-related variants on recombinant human growth hormone (rhGH) in a once-weekly sustained release formulation (SR–rhGH) of sodium hyaluronate microparticles and on the rhGH bulk solution used as the active ingredient for SR–rhGH under extreme stress conditions of 24 h at 60 °C. The extent of rhGH degradation was much higher in solution (33%) than in SR–rhGH (10%). The degradation products, especially Met14 sulfoxide and deamidated rhGH variants, were separated and quantified by a modified reversed-phase high-performance liquid chromatography (RP–HPLC) method at reduced flow rate. The primary degradation product of rhGH was found to be deamidated rhGH, although an unknown peak was also detected. In contrast, the primary degradation product of SR–rhGH was Met14 sulfoxide rhGH, with no unknown peaks. Using a cell proliferation assay, the biological activities of the isolated products of SR–rhGH degradation were found to be equivalent to those of native hGH, as determined by comparison with a National Institute for Biological Standards and Control standard. In conclusion, SR–rhGH is structurally and functionally stable and maintains the intactness of rhGH.