The construction of the antibody radionuclide conjugates (ARCs) is similar to that of ADCs. Here, 2 chelator drug bundles are conjugated to each antibody molecule. Thus, homogeneous ARCs with 6, 8, or 10 chelator groups are prepared. The product (antibody-chelator conjugates, before the loading of radionuclides) will be delivered to clinical centers, where an ARC therapy is scheduled. The loading with radioactive nuclide is carried out in a radiopharmacy associated with the clinical center. The shipping of the radionuclide to the radiopharmacy and the timing of the loading reaction are tightly coordinated with the administration of the ARC to a patient, due to the short half-life of the radionuclide. In general, ARCs are much more potent than ADCs on a “cytolytic activity per antibody molecule” basis. The use of an ARC for targeting a specific antigen on tumor is not affected by the shed antigen in the blood. The advancement of the preparation of 177Lu, which emits b particles of moderate energy and decays with t1/2 of 6.7 days, has shed new light on the development of radiotherapeutics.
Here is an example of an ARC.