Mayo Clinic has treated the first patient in the United States with a novel radiopharmaceutical for advanced breast cancer as part of an international multicenter clinical trial.
The investigational drug contains Actinium-225, an alpha-emitting radiopharmaceutical therapy initially developed for a subtype of gastroenteropancreatic neuroendocrine tumors. This therapy is designed to travel through the bloodstream and attach to cancer cells, delivering powerful, precise radiation while aiming to spare healthy tissue.
Researchers at Mayo Clinic are the first in the U.S. to administer this therapy to a patient with metastatic breast cancer. The open-label Phase 1b/2 trial is underway at all three of Mayo’s academic locations in Rochester, Minnesota; Phoenix, Arizona; and Jacksonville, Florida, along with approximately 20 other U.S. sites. The first treatment was administered at Mayo Clinic in Florida.
The principal investigator at Mayo Clinic is Dr. Geoffrey Johnson, a professor of radiology and a leader in the radiopharmaceutical therapy field. Dr. Johnson explains that these are innovative cancer treatments using radioactive drugs designed to target and kill cancer cells with high precision.
Mayo Clinic currently has nearly 20 active radiopharmaceutical therapy clinical trials, with another 10 in preparation, targeting many different cancer types. The Rochester campus treats more patients with modern radiopharmaceuticals, such as Lutetium Lu 177 dotatate for neuroendocrine cancer and Lutetium Lu 177 PSMA for prostate cancer, than any other center in the world.
While therapies like Lutetium Lu 177 dotatate and Lutetium Lu 177 PSMA are beta-emitters, using lower-energy particles, alpha-emitters like Actinium-225 use particles that are 8,000 times more massive. Alpha particles deliver a powerful impact over a very short distance, traveling only about three cell diameters after emission.
Dr. Johnson uses an analogy to explain the difference: knocking down cancer cells is like knocking down a brick wall. Using a beta emitter is like throwing a 10-pound dumbbell at the wall, whereas an alpha emitter is like driving a fully loaded Mack truck into it. The potential of alpha emitters lies in their power and precision to kill individual cancer cells without harming surrounding healthy tissue, representing a next-generation therapy.
Preclinical data suggested that Ac-225 DOTATATE, which targets somatostatin receptor subtype 2 expression, showed feasibility and potential efficacy for treating ER+ metastatic breast cancer in the lab. The drug is developed by RayzeBio Inc., a Bristol Myers Squibb company, which is the sponsor of the ongoing Phase 1b/2 clinical trial.
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