Mesothelin (MSLN) has been found to be overexpressed in several human malignancies: 100% of epithelial mesotheliomas, the majority of pancreatic and ovarian adenocarcinomas, more than 50% of lung adenocarcinomas and 34 to 67% of triple negative breast cancer (TNBC). The limited expression of mesothelin in normal human tissues and its overexpression in several aggressive human cancers make MSLN an attractive candidate for therapy. The objective of the inventors was to perform the nuclear imaging of TNBC xenografts with anti-MSLN single domain antibodies radiolabeled with 99mTc (99mTc-A1 and 99mTc-C6). They showed that 99mTc-A1 represent a good candidate for targeting mesothelin positive tumors. Accordingly, the present invention to an anti-mesothelin single domain antibody which is labelled with a radionuclide and its uses for imaging and/or treating cancer.
