1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelator (DOTA)

The Gallium-68 coordination site on the DOTA chelator within IMP-288 is a chemical structure designed to sequester the Ga-68 radioisotope for positron emission tomography (PET) imaging (Schoffelen et al., 2013, J Nucl Med). IMP-288 is a divalent hapten peptide (DOTA-D-Tyr-D-Lys(HSG)-D-Glu-D-Lys(HSG)-NH2) used in pretargeting strategies, where it binds to a bispecific antibody like TF2 that is already localized to a tumor-associated antigen such as Carcinoembryonic Antigen (CEA) (Goldenberg et al., 2012, J Clin Oncol). The DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) moiety acts as a macrocyclic chelator, providing a stable environment for the trivalent Gallium-68 cation (PubChem CID 67635). This coordination is essential for maintaining the integrity of the radiopharmaceutical in vivo, ensuring that the radioactive signal remains associated with the peptide as it targets the antibody-bound tumor (Lütje et al., 2014, Bioconjug Chem). While this site is critical for the diagnostic and therapeutic efficacy of the IMP-288 system, it is a chemical component of the drug molecule rather than a biological receptor or enzyme. Consequently, it does not participate in endogenous biological signaling but serves as a vehicle for targeted radionuclide delivery. The use of this coordination site allows for high-contrast imaging due to the rapid clearance of the small peptide from non-target tissues compared to directly labeled antibodies (Boddeti et al., 2012, J Nucl Med). Safety concerns primarily involve the radiation dose to the kidneys, where the peptide is cleared, and the potential for off-target effects if the metal-chelate complex is unstable.

Other names

DOTATetraxetan1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acidDOTA-hapten peptide component

The DOTA chelator functions by forming a stable coordination complex with the Gallium-68 radioisotope, allowing the IMP-288 peptide to carry the radioactive signal to a pre-localized bispecific antibody at the tumor site (Schoffelen et al., 2013).