technetium Tc-99m tricarbonyl (HE)3-ZCAIX:2

Technetium Tc-99m tricarbonyl (HE)3-ZCAIX:2 is a radiolabeled **Affibody molecule** designed for molecular imaging of carbonic anhydrase IX (CAIX)-expressing tumors. The compound consists of the ZCAIX:2 Affibody scaffold, which specifically binds to CAIX, conjugated with a (HE)3 histidine-glutamate chelating domain and labeled with technetium-99m in its tricarbonyl form [99mTc(CO)3]+. This radiopharmaceutical agent was developed for **diagnostic imaging** of CAIX-positive malignancies, particularly renal cell carcinoma and other hypoxic tumors. The agent demonstrates rapid blood clearance, high tumor uptake, and favorable tumor-to-background ratios, enabling visualization of CAIX-expressing xenografts with high contrast at 4 hours post-injection. The imaging is performed using gamma scintigraphy or single-photon emission computed tomography (SPECT). Among the ZCAIX Affibody variants, [99mTc]Tc(CO)3-(HE)3-ZCAIX:2 showed the most promising preclinical results due to its high tumor uptake characteristics.