Biodistribution Studies

[¹⁷⁷Lu]- PSMA-617 (7.5 μCi, 2.75 MBq) containing 0, 5, 100, 500, 1000 and 2000 pmoles of PSMA-11 was administered via tail vein to different cohorts (n = 4) of athymic nude mice bearing PC3-PIP xenografts. Activity and weights of the syringes were measured pre- and post-injection to calculated amount of administered radioactivity. The mice were sacrificed by CO₂ asphyxiation 1 h post-administration. Blood was collected immediately post-sacrifice by cardiac puncture and collected in a pre-weighed tubes. Necropsy was performed to collect tumor (PC3-PIP), heart, lungs, liver, spleen, stomach, small intestine, large intestine, kidney, muscle bone, tail and salivary glands. The organs were washed with water, air dried, transferred into pre-weighed tubes and counted for radioactivity on gamma counter. For calculating administered dose, several standards were prepared and counted along with the organs. Total administered counts were determined based on the difference in weight before and after injection of the activity. The counts from the gamma-counter were divided by injected counts. For each sample obtained, count data was background- and decay-corrected and the tissue uptake was measured in units of percent injected dose per gram (%ID/g) by dividing tissue counts to total administered counts normalized to the weight of the tissue multiplied by 100.