FOLH1 and neoplasm: [169Er]Er-PSMA-617 was prepared at 10 MBq/nmol concentration with a radiochemical purity > 98% and compared to the clinically-established [177Lu]Lu-PSMA-617 in a tumour cell viability assay using PC-3 PIP tumour cells, where results indicated reduced tumour cell viability of ~ 89% and ~ 69% at 5 MBq/mL and 10 MBq/mL respectively.