PET in vivo generators 134 Ce and 140 Nd on an internalizing monoclonal antibody probe.

The in vivo-generator radionuclides 140 Nd (t 1/2  = 3.4 d) and 134 Ce (t 1/2  = 3.2 d) were used to trace a urokinase-type plasminogen activator (uPA)-targeting mouse monoclonal antibody, ATN-291, in U87 MG xenograft tumor-bearing mice. ATN-291 is known to internalize on the uPA/uPA-receptor pair, making it an appropriate targeting vector for investigating the fate of in vivo generator daughters on internalizing probes. Ante-mortem and post-mortem PET imaging at 120 h post-injection gave no indication of redistribution of the positron emitting daughter nuclides 134 La and 140 Pr from tumor tissue (p > 0.5). The lack of redistribution indicates that the parent radionuclides 134 Ce and 140 Nd could be considered as long-lived PET-diagnostic matches to therapeutic radionuclides like 177 Lu, 161 Tb and 225 Ac when internalizing bioconjugates are employed.