High Specific Activity Sm-153 by Post Irradiation Isotope Separation

When the stable samarium-152 (Sm-152) isotope is irradiated, radioactive samarium-153 (Sm-153) is produced through a neutron capture reaction in yields of only about 2%, and this radioactive, therapeutic isotope (Sm-153) cannot be separated from the much more abundant (~98%) non-radioactive isotope (Sm-152) by chemical methods. Successful development of a new process using electromagnetic mass separation will allow isolating the Sm-153 from the Sm-152 and other unwanted impurities, yielding high specific activity Sm-153 applicable for multiple therapeutic uses as well as recovering the target material Sm-152 for further irradiation and Sm-153 production. The radioisotope 153Sm (t1/2=46.3 h), produced through a neutron capture (n,) reaction, is used in radiopharmaceuticals and other nuclear medicine applications. The nuclear reactor at the University of Missouri has demonstrated that it can make large quantities of Sm-153; however the specific activity (SA, radioactivity per gram) is low relative to the large amount of target material152Smplus very small quantities of other unwanted europium contaminants. Chemical separation cannot be used to perform isotopic separation and the only approach that can be applied to increase the specific activity significantly (~50% or higher) is electromagnetic mass separation, i.e., performing isotopic purity by removing the unwanted isotopes. Further, with mass separation, not only can one collect the product of interest153Smimplanted on a material of choice for any necessary post-chemical processing, but the target isotope 152Sm can be collected for recycling in the irradiation step (see Figure 1). In addition, this approach is potentially applicable to other needed radiolanthanides. Phase I of the work will demonstrate the feasibility of this approach to increase the specific activity of the 153Sm based upon a thorough literature study and some experimental measurements, and will develop the concept of an appropriate facility from beginning to final product. In a subsequent Phase II project, a facility based upon the design concepts determine in Phase I will be constructed and installed at the MURR facility at the University of Missouri to produce high levels of 153Sm to be used in subsequent radiopharmaceutical studies by IsoTherapeutics Group, LLC (ITG). The final specifications of all facilities must meet the needs of the final commercial usage. The actual mass spectrometer facility is planned for positioning at the MURR facility, which is the nations sole supplier of 153Sm, and the MURR group plays an essential role in determining the final detailed specifications. The Advanced Applied Physics Solutions (AAPS) team will provide necessary technical expertise under appropriate documentation to protect their intellectual property provided to the collaborating groups. Commercial Applications and Other Benefits: IsoTherapeutics Group, LLC has applications for the final productradioisotopes of high specific activity. A current radiopharmaceutical using Sm-153 is Quadramet, a bone pain palliation agent. Sales of Quadramet in 2007 were $9.3 million, which was deemed to represent about 10% of its market potential (1). The limited use of Quadramet in part may be due to its limited availabilityTuesday through Thursdaydue to its low specific activity and the presence of long-lived europium contaminants that take the radiochemical out of specification after two half-lives. If successful the purified, high specific activity Sm-153 should increase and extend its shelf-life, making it available throughout the week. The higher specific activity Sm-153 will have greater applications in targeted radiotherapy, such as with peptides and antibody fragments, where tumor cell receptors for the drug are limited