(175)Yb-TTHMP as a good candidate for bone pain palliation and substitute of other radiopharmaceuticals

Bone metastasis is one of the most frequent causes of pain in cancer patients. Different radioisotopes such as P-32, Sm-153, Ho-166, Lu-177, and Re-186 with several chemical ligands as ethylenediaminetetramethylene phosphonic acid (EDTMP), 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene phosphonic acid (DOTMP), and propylenediaminetetramethylene phosphonate (PDTMP) are recommended for bone pain palliation. In this work, (175)Yb-triethylenetetraminehexamethylene phosphonic acid (TTHMP) was produced as a proper alternative to other radiopharmaceuticals. Relatively long half-life (T(1/2) = 4.18 days), maximum energy beta particle E(β) =470 keV (86.5%), low abundance gamma emission 396 keV (6.4%), 286 keV (3.01%), 113.8 keV (1.88%) and low cost are considered advantageous of Yb-175 are to wider usage of this isotope; in addition, TTHMP is an ideal carrier moiety for bone metastases. Production, quality control, and biodistribution studies of (175)Yb-TTHMP were targeted. Yb-175 chloride was obtained by thermal neutron bombardment of a natural Yb(2)O(3) sample at Tehran Research Reactor (TRR), radiolabeling was completed in 1 h by the addition of TTHMP at the room temperature and pH was 7.5-8, radiochemical purity was higher than 95%. Biodistribution studies in normal rats were carried out. The results showed favorable biodistribution features of (175)Yb-TTHMP, indicating significant accumulation in bone tissues compared with clinically used bone-seeking radiopharmaceuticals. This research presents (175)Yb-TTHMP can be a good candidate for bone pain palliation and substitute of other radiopharmaceuticals, however, further biological studies in other mammals are still needed.