Synthesis and immunosuppressive activity of ruthenium complexes

The syntheses and immunosuppressive activity of ruthenium complexes are described. One of the complexes (1a) was shown to be a potent inhibitor of human T-lymphocyte proliferation with an IC50 of 5 nM. The activity of these complexes compares favorably to the well known immunosuppressants Cyclosporin A and Rapamycin.