The feasibility of 225 Ac as a source of ??-particles in radioimmunotherapy

TLDR

225Ac decays over 10 days into a cascade of short‑lived alpha and beta emitters, and its decay chain can also yield 213Bi, which can be extracted at the bedside, while 225Ac can be produced from 229Th. This paper proposes using 225Ac for alpha‑radioimmunotherapy of cancer. The suitability of alpha‑particle sources depends on their kinetic properties, half‑life, and the characteristics of the target‑selective carrier. The study anticipates that useful therapeutic applications, complementary to or combined with other treatments, will be identified.

Abstract

This paper proposes the utilization of 225Ac for the alpha-radioimmunotherapy of cancer. The isotope decays with a radioactive half-life of 10 days into a cascade of short-lived alpha- and beta-emitting isotopes. In addition, when indicated by the pharmacokinetic requirements of particular clinical applications, 213Bi, with a radioactive half-life of 47 min, can be chosen as an alternative source of alpha-particles in radioimmunotherapy. This isotope is the last alpha emitter in the 225Ac decay-cascade and can be extracted from a 225Ac source at the bedside of the patient. 225Ac can quasi ad infinitum be obtained from one of its precursors, 229Th, which can be made available by various means. The indications for the use of alpha-particles as an alternative to more traditional classes of radiation are derived from the particle-kinetic characteristics and the radioactive half-life of their source isotope, as well as from the properties of the target-selective carrier moiety for the source isotope. It may be expected that useful applications, complementary to and/or in conjunction with other means of therapy will be identified.