In a recent study jointly authored by Minerva Imaging, two radionuclides (140Nd and 134Ce) were used to trace a urokinase-type plasminogen activator (uPA)-targeting mouse monoclonal antibody. PET imaging was performed 120 h post-injection in the U87 MG xenograft tumor-bearing mouse model. The results gave no indication of redistribution of the positron emitting daughter nuclides 134La and 140Pr from tumor tissue. The lack of redistribution indicates that both 134Ce and 140Nd could be considered as long-lived PET-diagnostic matches to therapeutic radionuclides like 177Lu, 161Tb and 225Ac.

The targeted radionuclide therapy field is rapidly evolving. Long-lived radioisotopes such as 177Lu, 161Tb, and 225Ac are translating into clinical practice. However, there is a potential long-term instability of the targeting vector and radiolabeling constructs.

The data presented in this work are consistent with the hypothesis that the free lanthanide daughters 134La and 140Pr of 134Ce and 140Nd, have a nearly equivalent distribution to the internalized vector-bound parents. These results show promise for short-range targeted radiotherapies using internalizing mAbs as carrier molecules. Additionally, 134Ce/134La and 140Nd/140Pr are promising as theranostic matched pair PET radiolabels for therapies with long-lived lanthanides and actinides like 169Er, 161Tb, 177Lu, and 225Ac.

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