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Astatine is the rarest naturally occurring element on Earth due to its high radioactivity, with the longest-lived isotope having a half-life of 8 hours. Its existence was first inferred in 1871, but it took until 1940 for scientists to produce astatine through alpha bombardment of bismuth.
Medical interest in astatine grew quickly. Astatine-211, with a half-life of just 7.2 hours, emits short-range, high-energy alpha particles that destroy targeted cells while sparing nearby healthy tissue. Each decay releases a single alpha particle and leaves no long-lived, alpha-emitting daughters to drift away from the target, keeping biodistribution predictable and simplifying dosimetry.
As a halogen, astatine shares similar radiochemical properties to iodine. This drove early investigations, including the first recorded human use in 1954, examining free astatine accumulation in the thyroid gland. Chemical stabilisation advances have since led to promising trials of sodium astatide [211At]NaAt for radioiodine-refractory thyroid cancer. More recent programmes have used small molecules, such as meta-[211At]astatobenzylguanidine (MABG), and monoclonal antibodies, broadening the isotope's therapeutic potential.
While chemistry improvements have widened astatine's potential applications, scaling supply to the volume needed for late-phase research and commercialisation will require production innovations. Astatine-211 production demands high-energy alpha particles, and existing cyclotrons are current-limited which significantly constrains yield. A more novel production route uses high-energy lithium particles to produce a radon/astatine generator which will overcome some of the logistical challenges with the short half-life.
StandardX is developing an accelerator that enables high-volume production of both direct and generator routes.