We are also concerned with the development of new therapeutic agents, and particularly molecules active against circulating cancers. For this, we have investigated the possibility of chelating a large cation such as bismuth(III). 213Bi is an α-emitting radionuclide of great interest in line with the development of α-immunotherapy. However, 213Bi is characterized by a short life-time (45 min only!), which implies a fast kinetic process for the binding to a transporting agent. Thus, to be applicable in medicine, a porphyrin-based drug has to complex this cation very rapidly!
In that respect, we have synthesized new porphyrins that are able to complex the bismuth cation almost instantaneously under very mild conditions. They possess carboxylic groups in either a picket or a strapped fashion, and can be further functionalized by a reactive group for the bio-conjugation with an anti-body (see selected examples below).
Recently, the discovery of a molecule capable to bind bismuth(III) cation but also lead(II) cation paved the way for the design of an in-situ generator.