Tumour uptake was variable across analogues at 4 h pi ([177Lu]Lu-AU-RM26-M2: 1.5 ± 0.05%IA/g; [177Lu]Lu-AU-RM26-M4: 15 ± 4%IA/g, [177Lu]Lu-AU-SAR-M1: 8 ± 2%IA/g; [177Lu]Lu-AU-SAR-M2: 11 ± 1%IA/g) and GRPR-specific, since co-injection of a 100 × molar excess of NOTA-PEG2-RM26 led to a substantial decrease of tumour uptake (≥ 89% decrease in activity uptake; Tables S1 and S2). Here, GRPR is linked to neoplasm.