AC-225 (Actinium-225) is a radioactive isotope used mainly in targeted cancer therapy.
AC-225 emits alpha particles, which are very high energy, able to kill cancer cells efficiently and only travel a very short distance, so they cause less damage to nearby healthy tissue. AC-225 is attached to targeting molecules (like antibodies or ligands) that specifically bind to cancer cells. This allows doctors to deliver radiation directly to tumors and minimizes harm to healthy cells.