TerraPower Isotopes

TerraPower Isotopes is the radiopharmaceutical arm of TerraPower, the Bellevue, Washington nuclear technology company founded with backing from Bill Gates. The business produces actinium-225, an alpha-emitting isotope used in targeted therapies for advanced cancers, drawing raw material from Cold War-era thorium stockpiles held at Oak Ridge National Laboratory. Global supply of the isotope has been the limiting factor on clinical development for years. The company is building a $450 million, 250,000-square-foot cGMP manufacturing plant in Philadelphia’s Bellwether District, with Gilbane Building Company leading core and shell construction. When the plant opens in 2029 it is expected to increase worldwide production capacity roughly twentyfold and employ about 225 people.

Actinium-225 is not mined and it is not manufactured in any conventional sense. TPI harvests it from the decay of thorium-229, which in turn is recovered from Uranium-233 left over from mid-century United States nuclear programs. The company works with the Department of Energy’s Oak Ridge Office of Environmental Management and with Isotek Systems on that recovery, an arrangement that offsets part of the eventual cost of disposing of the U-233 while giving drug developers a supply route that does not depend on a reactor or an accelerator. Because the extraction relies on natural decay rather than irradiation, the product comes out free of the isotopic impurities that complicate competing methods.

Commercial-scale output began in October 2024, when TPI announced weekly production runs from its laboratory in Everett, Washington. That material is research-grade starting material, not a finished drug, and the company states plainly that it is not made to cGMP standards. It is already inside radiopharmaceuticals given to patients in clinical trials in several countries, aimed at prostate, breast, colon and neuroendocrine cancers along with melanoma and lymphoma. Named partners include Aktis, Advanced Accelerator Applications, Cardinal Health, POINT Biopharma and Isotek.

The Philadelphia decision followed a long search. TPI reviewed more than 350 candidate sites nationally and made 49 site visits across eight metropolitan areas before settling on the Bellwether District, citing the parcel scale available there, proximity to infrastructure, and access to the region’s life sciences and hospital network. Scott Claunch is president of TerraPower Isotopes; Chris Levesque is president and chief executive of parent TerraPower. Corporate offices stay in Bellevue.