Heterogeneity of commercial recombinant human growth hormone (r-hGH) preparations containing a thioether variant.

The objective of the present study was to assess (I) the potential presence of a recently discovered thioether variant in commercially available recombinant human growth hormone (r-hGH) preparations, and (II) the impact of the thioether modification on the in-vivo bioactivity and the receptor binding kinetics. Samples were tested employing European (EP) and US Pharmacopeia (USP) Somatropin monograph and mass spectrometry methods. None of the international standards contained this variant.