Pain response was seen in up to 71% of the patients with a dose response observed 2 weeks after administration. The highly tolerable side-effect profile of radium-223 previously reported was confirmed.

A fetal form of somatomedin (insulin-like growth factor) that crossreacts in the fetal brain radioreceptor assay has been proposed to exist in humans. Using this assay to monitor activity during purification, we have isolated a variant form of insulin-like growth factor I (IGF-I) from human fetal brain tissue. The variant IGF-I showed potent crossreaction in the fetal brain radioreceptor assay and stimulated DNA synthesis in fetal brain cells in vitro. Structural analysis revealed the variant IGF-I to have a truncated NH2-terminal region compared to IGF-I isolated from serum. An additional peptide, which displayed less potent crossreaction in the fetal brain radioreceptor assay, was also isolated from the human fetal brain. Partial amino acid sequence analysis revealed identity to insulin-like growth factor II.

The forms of somatomedin present in the adult human brain have been characterized in this study. Two peptides were purified by acidification, size exclusion chromatography, affinity chromatography, FPLC and HPLC. structural analysis identified these peptides as the variant form of IGF‐1 with a truncated N‐terminal region earlier isolated from human fetal brain and IGF‐2. The presence of the truncated IGF‐1 variant and IGF‐2 in the human CNS suggests their role as neuropeptides.

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