The mice were separated into 4 groups: 6 received no further injection (control group), 6 received 5 µg of rituximab, 4 received 300 µg of rituximab, and 10 received 5 µg of rituximab labeled with radioactive 149Tb with a decay rate of 5.5 × 106 decays per second. These second injections were administered 2 days after the Daudi cell inoculation. Rituximab is a monoclonal antibody that targets CD20 antigens, which are expressed in large numbers by the Daudi cells.
The dramatic results of the study are shown in Figure E.1, which indicates the mice’s survival in days in terms of the percentage surviving. All of the mice except those receiving the 149Tb-labeled rituximab had perished by 120 days, and approximately half had developed macroscopic tumors. In the group treated with the 149Tb-labeled rituximab, only one of the nine had died; the remainder showed no pathological changes upon further examination.
The low-energy alpha particles and longer lifetime properties of 149Tb made it the best isotope available for performing this research. Rare-isotope facilities can examine many more isotopes and can be expected to discover more particular isotopes with the ideal chemical and radiological characteristics for the treatment of disease.