{"entity":{"id":"chelator-term","kind":"term","name":"Chelator (bifunctional chelating agent)","aka":[],"tldr":"A molecular 'cage' that grips a radioactive metal atom tightly so it stays attached to the drug all the way to the tumour, instead of leaking out and going to the wrong part of the body.","summary":"A chelator (or bifunctional chelating agent, BFC/BFCA) is the part of a metal-based radiopharmaceutical that binds the radiometal ion in a stable coordination complex while a second reactive group lets it be covalently attached to a targeting molecule, such as a peptide, antibody or small molecule. The three-part architecture, radiometal plus chelator plus targeting vector (often via a linker), is the standard design of essentially all radiometal radiopharmaceuticals, from diagnostic 68Ga and 64Cu tracers to therapeutic 177Lu, 90Y and 225Ac agents.\n\nDOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) is the dominant macrocyclic chelator in the field, used with 68Ga, 111In, 86Y/90Y, 44Sc/47Sc and 177Lu, among others, because its rigid ring gives very high thermodynamic and kinetic stability once the metal is locked in; the trade-off is that labelling usually needs heating (60-95°C for 30-90 minutes), which limits its use with heat-sensitive biomolecules such as intact antibodies. Acyclic chelators (such as DTPA) and other macrocycles (such as NOTA, which forms a stable gallium-68 complex at room temperature) trade some of that ultimate stability for faster, milder labelling conditions.\n\nA poorly matched chelator-metal pair, or incomplete complexation, shows up as radiochemical impurity: unbound or loosely bound radiometal that redistributes in the body (free gallium-68 to bone, free lutetium-177 to bone and liver) rather than following the targeting vector, degrading image quality and increasing off-target dose. Chelator choice is therefore one of the first decisions in designing any new radiometal agent and is documented in the drug's CMC (chemistry, manufacturing and controls) package.","asOf":"2026-09-22","links":[{"label":"Chemical Society Reviews: matching chelators to radiometals for radiopharmaceuticals","url":"https://pubs.rsc.org/en/content/articlehtml/2014/cs/c3cs60304k"},{"label":"PMC: the chemical scaffold of theranostic radiopharmaceuticals","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC9143622/"}],"tags":[],"related":["specific-activity","radiochemical-purity","ga-68","in-111","cu-64","sc-44","y-86","lu-177","ac-225","y-90"],"indications":[],"sections":[],"technologies":["site-specific-conjugation","radionuclide-generators-kits","pet-tracer-manufacturing"],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"category":"chemistry"},"route":"/terms/chelator-term/","neighbours":{"term":[{"id":"radiochemical-purity","kind":"term","name":"Radiochemical purity (RCP)","route":"/terms/radiochemical-purity/"},{"id":"radiolysis","kind":"term","name":"Radiolysis (self-radiolysis of radiopharmaceuticals)","route":"/terms/radiolysis/"},{"id":"specific-activity","kind":"term","name":"Specific activity and molar activity","route":"/terms/specific-activity/"}],"isotope":[{"id":"ac-225","kind":"isotope","name":"Actinium-225","route":"/isotopes/ac-225/"},{"id":"cu-64","kind":"isotope","name":"Copper-64","route":"/isotopes/cu-64/"},{"id":"ga-68","kind":"isotope","name":"Gallium-68","route":"/isotopes/ga-68/"},{"id":"in-111","kind":"isotope","name":"Indium-111","route":"/isotopes/in-111/"},{"id":"lu-177","kind":"isotope","name":"Lutetium-177","route":"/isotopes/lu-177/"},{"id":"sc-44","kind":"isotope","name":"Scandium-44","route":"/isotopes/sc-44/"},{"id":"y-86","kind":"isotope","name":"Yttrium-86","route":"/isotopes/y-86/"},{"id":"y-90","kind":"isotope","name":"Yttrium-90","route":"/isotopes/y-90/"}],"technology":[{"id":"pet-tracer-manufacturing","kind":"technology","name":"PET tracer manufacturing and distribution","route":"/technologies/pet-tracer-manufacturing/"},{"id":"radionuclide-generators-kits","kind":"technology","name":"Radionuclide generators and cold kits","route":"/technologies/radionuclide-generators-kits/"},{"id":"site-specific-conjugation","kind":"technology","name":"Site-specific conjugation & linker chemistry","route":"/technologies/site-specific-conjugation/"}]}}