On July 23, the first targeted thorium conjugate patient in the United States was treated at the NIH. This event was the culmination of over 18 months of collaboration with Bayer, the National Cancer Institute (NCI), Clinical Center, and Division of Radiation Safety (DRS).
Targeted thorium conjugates (TTCs) represent a new class of therapeutic radiopharmaceuticals for targeted alpha therapy. They are comprised of the alpha emitter thorium-227 labelled to a chelator which is conjugated to a tumor-targeting monoclonal antibody. The very high energy and very short range of the alpha particles induce complex DNA double strand breaks in the tumor, which helps to shrink the tumor. The alpha radiation is extremely localized, only penetrating a maximum of two to ten cell layers, thus minimizing damage to the adjoining healthy tissue. This therapy shows a lot of promise to help patients with a very limited life expectancy, such as those with mesothelioma.
This being the first use of thorium in humans in the U.S. presented many hurdles to overcome. DRS communicated closely with the Nuclear Regulatory Commission (NRC) to properly classify thorium in a manner appropriate for clinical use. This led to an amendment to the NIH's Broad Scope license for the medical use of Th-227. Interdepartmental logistics needed to be coordinated for: the receipt and prompt delivery of the radiopharmaceutical; collection and off-site shipment of patient samples; and radiation contamination and exposure assessments on the nursing unit. Since this was the first clinical use of an alpha emitter at the NIH, a substantial training initiative was launched for nursing and Clinical Center laboratory staff. Training included lectures and hands-on exercises with live contamination prior to the arrival of Patient #1.
Special recognition is due to: the study's Principal Investigator - Dr. Raffit Hassan; Clinical Authorized User - Dr. Frank Lin; Clinical Research Nurse - Maria Gracia Agra; the entire 5NW nursing staff; and Dr. William Figg's lab in NCI. All partners worked closely with the DRS team to meet all regulatory challenges, and DRS is proud to have collaborated on this important project. If the study proves to have successful clinical outcome, then no doubt it will expand to additional sites – but NIH was a pioneer.
