90Y-DOTA-biotin
90Y-DOTA-biotin consists of a radioactive substance (yttrium-90) complexed by a chelating agent (DOTA), which in turn is attached to the vitamin biotin via a chemical linker. It is used experimentally in pretargeted radioimmunotherapy. Animal studies have been conducted<ref name="Domingo" /><ref name="Pagel" /> as well as clinical studies in humans.<ref name="Knox" /><ref name="Paganelli" />
In pretargeted radioimmunotherapy, two or three medications are applied in succession. At first, an antibody-drug conjugate is administered, which consists of a monoclonal antibody designed to target the tumour, and a chemical marker which in the case of DOTA-biotin therapy is one of the proteins avidin and streptavidin. After a time of typically one or two days to let the antibody accumulate in the tumour, a clearing agent may be given to eliminate residues of antibody that are still circulating in the bloodstream; this is especially done in humans. After a further waiting time, the radiotherapy (90Y-DOTA-biotin) is administered. Due to the high affinity of biotin to avidin and streptavidin, the radiotherapy accumulates where the antibody is, namely in the tumour, where it delivers its radioactivity.<ref name="Knox" />
