Cyclotron produced <sup>132</sup>La as a PET imaging surrogate of therapeutic <sup>225</sup>Ac
Eduardo Aluicio‐Sarduy, Todd E. Barnhart, Jamey P. Weichert, Reinier Hernandez, Jonathan W. Engle
Abstract
The aim of this work was to explore <sup>132</sup>La as a PET imaging surrogate for <sup>225</sup>Ac using a DOTA-based, tumor-targeting alkylphosphocholine (NM600). <b>Methods:</b><sup>132</sup>La was produced on a biomedical cyclotron. For in vivo experiments, mice bearing 4T1 tumors were administered <sup>132</sup>La-NM600, and PET/CT scans were acquired up to 24 h after injection. After the last time point, the ex vivo tissue distribution was measured to corroborate the in vivo PET data. The ex vivo tissue distribution in mice was determined at 4 and 24 h after injection of <sup>225</sup>Ac-NM600. <b>Results:</b> PET/CT images showed elevated, persistent <sup>132</sup>La-NM600 uptake in the tumor. Low bone accumulation confirmed the in vivo stability of the conjugate. Ex vivo biodistribution studies validated the image-derived quantitative data, and the comparison of the <sup>132</sup>La-NM600 and <sup>225</sup>Ac-NM600 tissue distributions revealed a similar biodistribution for the 2 radiotracers. <b>Conclusion:</b> These findings suggest that <sup>132</sup>La is a suitable imaging surrogate to probe the in vivo biodistribution of <sup>225</sup>Ac radiotherapeutics.