Provided is a radiolabeled drug which contains a compound expressed in the following formula (I)； the compound to which polypeptide is bound which is capable of being bound to a target site, or a pharmacologically acceptable salt of the compound； and a complex which includes a complex structure which contains the compound to which the polypeptide is bound which is capable of being bound to the target site, or the pharmacologically acceptable salt thereof, and a radioisotope. (I) Herein, R1 is a hydrogen atom, a methyl group, or a carboxymethyl group； R2 is CH2-CH2-NH-CH2-COOH, CH2-CH2-N(CH2-COOH)2, CH2-CH2-NH2, CH2-CH2-NHR3, the carboxymethyl group, or CH2-CH2-NR3R4； R3 and R4 are alkyl groups which may be different； X, Y, and Z are amino acids which may be different； and F is a functional group which is capable of being bound to the polypeptide. Using the compound according to the present invention, the radiolabeled drug is provided which is prepared through a simple operation, has high accumulation toward the target site, and reduces non-specific renal accumulation.
