A comparative evaluation of Ac-225 and Bi-213 as therapeutic radioisotopes for targeted alpha therapy

This conference presentation covered the relative advantages of Ac-225 and Bi-213 for targeted alpha therapy. Some factors that seem like obvious advantages for one over the other might be ameliorated by various other effects. For example, the Ac-225 decay chain releases four alpha particles whereas Bi213 has only one.

However, the first alpha decay of Ac-225 generates enough recoil for the daughter nucleus to break its bond to the conjugate. This is doubly bad since not only are alphas removed from the target site, but the long-lived daughter is now free to travel throughout the body causing damage to healthy tissue. Maximum tolerated dose and therapeutic gain are other comparison endpoints. Cost considerations for preclinical and clinical trials as well as clinical use are relevant.

Considering all these factors, Ac-225 is still found to have better or equal performance to Bi-213 at much lower cost.

Presented by: William Carithers, Lawrence Berkeley National Laboratory 

at the 10th International Symposium on Targeted Alpha Therapy (TAT-10),  May 31 - June 1, 2017 - Kanazawa, Japan.