avidin + yttrium-90-DOTA-biotin

This drug combination is a core component of a **pre-targeted radioimmunotherapy (PRIT)** regimen, often referred to as the three-step or PAGET protocol. The system is designed to decouple the slow-circulating antibody from the fast-clearing radioisotope to improve the tumor-to-background radiation ratio. In practice, a biotinylated monoclonal antibody is first administered to localize at the tumor site. Subsequently, **avidin** (or a combination of avidin and streptavidin) is injected to act as a high-affinity molecular bridge. Finally, the therapeutic effector, **yttrium-90-DOTA-biotin**, is administered. The biotin moiety rapidly binds to the localized avidin complex, while the **DOTA** chelator ensures the stable retention of the **yttrium-90** isotope. Yttrium-90 is a high-energy beta-emitter that induces lethal DNA damage through cross-fire effects in the tumor microenvironment. This approach has been primarily investigated for the treatment of high-grade gliomas and ovarian cancer, where it allows for high radiation doses to be delivered to the tumor with significantly reduced systemic toxicity compared to conventional radioimmunotherapy.

Other names

Three-step pretargetingPAGET protocolPretargeted Antibody-Guided RadioimmunotherapyAvidin-biotin pretargeting system