Rhenium-188 can be conveniently obtained from a 188W/188Re generator in high specific activity. The half-life of 188Re (16.9 hr) and �max energy of 2.12 MeV are optimal to match the biological residence time of peptides and fast circulating IgM antibodies. A first step in developing a bifunctional chelate for Re is to evaluate the stability of 188Re chelates at the tracer level. This study evaluates stability of tracer 188Re=ONxS4-x complexes and macroscopic analogs, since behavior seems to be very different at the purified tracer level. The overall objective is to develop bifunctional chelates for conjugation of 188Re to 6D2 and other antibodies, since in Phase 1 clinical trials 188Re-6D2 (where 188Re is introduced into 6D2, an IgM, by direct labeling) has shown no adverse effects and in fact, target tumors were observed to stay stable or decrease in size in nearly all patients. The results from the ligand stability studies indicate that while the Re-N3S complexes are stable at the macroscopic level, the 188Re-N3S complexes decompose quickly at the tracer level. The Re-N2S2 complexes are stable at both the macroscopic and tracer levels.

Stabilities of <sup>188</sup>ReO complexes of nitrogen and sulfur donating ligands

246th National Meeting (2013)

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Stabilities of 188ReO complexes of nitrogen and sulfur donating ligands

Stabilities of ¹⁸⁸ReO complexes of nitrogen and sulfur donating ligands