Biodistribution and pharmacokinetics of variously molecular sized 117mSn(II)-polyethyleneiminomethyl phosphonate complexes in the normal primate model as potential selective therapeutic bone agents.

In the search for a cure for metastatic bone cancer, 117mSn with its conversion electrons and low energy photons both of discrete energies shows little bone marrow toxicity, providing the opportunity to increase the administered dose. Selective accumulation in lesions would capitalise on this advantage. The 10-30 kDa fraction of the water-soluble polymer polyethyleneimine, functionalised with methyl phosphonate groups (PEI-MP) and labelled with 99mTc, has shown selective uptake into bone tumours. Furthermore using speciation calculations it was predicted that the Sn(II)-PEI-MP complex would remain intact in the blood plasma. Because of this positive indication animal experiments were carried out to test this prediction. This paper relates the labelling, biodistribution and pharmacokinetics of various fractions of 117mSn-(II) PEI-MP in the normal primate model, and points to promising therapeutic possibilities.