99mTc-sdAb20

99mTc-sdAb20 is a radiopharmaceutical imaging agent consisting of an AXL-specific single-domain antibody (sdAb) labeled with the radioisotope Technetium-99m (99mTc). Developed by researchers at the Vrije Universiteit Brussel, this agent is designed for non-invasive SPECT/CT imaging of AXL-expressing tumors. AXL is a receptor tyrosine kinase that is overexpressed in approximately 50% of acute myeloid leukemia (AML) patients and is associated with poor prognosis. The sdAb20 component exhibits nanomolar affinity for both human and mouse AXL and effectively blocks the interaction between AXL and its ligand, GAS6. In preclinical studies, 99mTc-sdAb20 demonstrated significant tumor uptake in AML xenograft models, suggesting its utility as a diagnostic tool to identify patients eligible for AXL-targeted therapies and to monitor treatment response.