THE FIRST INTERNATIONAL STANDARD FOR SOMATROPIN - REPORT OF AN INTERNATIONAL COLLABORATIVE STUDY

Following an earlier decision to move away from the in vivo bioassay f or determination of the potency of therapeutic somatropin (recombinant DNA human growth hormone), 18 laboratories in 12 countries participat ed in an international collaborative study designed to establish an in ternational standard for somatropin, calibrated both by bioassay and b y physicochemical assays of somatropin content. The mean in vivo biolo gical potency of preparation studied, coded 88/624, was 6.75 IU/ampoul e (fiducial limits 6.30-7.23). Determination of the protein content by quantitative amino-acid analysis yielded a mean estimate of 1.98 mg p rotein per ampoule. (Relative standard deviation = 2.88%). Data from t he study also yielded mean values of 97.2% +/- 0.8% for the monomer co ntent of the preparation, and 8.18 (RSD = 4.00%) for A(1%) at 276 mm. At its 45th meeting, in October 1994, the ECBS of WHO formally establi shed the preparation 88/624 as the First International Standard for So matropin, with a defined content of 2.0 mg protein per ampoule, and a defined specific activity of 3.0 International Units per milligram.