239-Plutonium is among the extrapolated tightest known binders (poisons) of thiol (sulfhydryl) compounds.
Vitalethine (a disulfide or VSSV), cycles in the body through vitaletheine (its thiol form or VSH), and its sulfenic acid form (VSOH).
Vitalethine appears to stimulate the humoral immune system to stop cancer at a concentration just incrementally larger than concentrations of Plutonium (239-Pu) reported to cause cancer.
http://www.vitaletherapeutics.org/vtlrefab.htm
http://www.vitaletherapeutics.org/vtlmntox.htm
http://www.vitalethine.org/WAPFMetlTox.html