This work represents the first published radiosynthesis of [165Er]PSMA-617, a radiopharmaceutical that could serve as a useful in vitro and in vivo tool that can be used to assess the role of AEs in the efficacy of PSMA-targeted radionuclide therapy of prostate cancer using [161Tb]PSMA-617 [11]. The gene discussed is FOLH1; the disease is prostate carcinoma.