Studies towards 43Sc, 44Sc and 47Sc - a novel matched pair for theragnostic applications

Abstract:  The concept of personalized medicine, where each patient is treated according to an individually tailored treatment regime, has gained much recognition over the past few years. In nuclear medicine this trend is parallelized by an increased demand for novel radionuclides, fulfilling the characteristics of a “matched pair”. This comprises the use of the same pharmaceutical, labeled either with a diagnostic or a therapeutic radionuclide. Ideally both radioisotopes should belong to the same chemical element and, in this case, the radionuclides 43Sc and 47Sc fit this requirement. The decay characteristics of 43Sc (t1/2= 3.9 h, Eβ+av = 476 keV [88%], Eγ = 372 keV [23%]) are well suited for Positron Emission Tomography imaging, while the low energy β--emitter 47Sc (t1/2= 3.4 d, Eβ-av = 162 keV, Eγ = 159 keV [68%]) could be utilized for targeted tumor therapy. In the course of this work, different production and separation methods for 43Sc and 47Sc were investigated, aiming to obtain the activity in a sufficient quality and quantity for direct radiolabeling. The feasibility of producing 43Sc via proton irradiation of two different target materials (43Ca and 46Ti) was studied so far. Two neutron induced reactions, 46Ca(n,γ)47Ca→47Sc and 47Ti(n,p)47Sc, were investigated towards the generation of 47Sc. After chemical separation and purification, the radionuclidic purity and labeling quality of the obtained nuclides were compared and the in vivo applicability demonstrated in proof-of-concept studies.