Identification and functional evaluation of monoclonal antibodies specifically targeting human Carbonic Anhydrase IX

Introduction Poor vascularisation of solid tumours leads to inadequate nutrient and oxygen supplies which forces tumour cells to reprogram their metabolism. As a consequence the tumour cell’s environment becomes acidic and hypoxic. This, in turn, triggers signalling cascades involving for example heterodimeric hypoxia-inducible factor (HIF). Activation of this hypoxia-induced transcriptional program is crucial for the survival of tumour cells in their hostile microenvironment but also their ability to metastasize. One of the genes upregulated through the HIF pathway is carbonic anhydrase (CA)-IX (CAIX, gene G250/MN-encoded transmembrane protein). CA-IX catalyses carbon dioxide (CO2) thereby generating a proton (H+) and bicarbonate (HCO3-), the latter of which is transported back into the cell and utilised to help safeguard intracellular pH (pHi) stability. Except for the stomach and the gallbladder, CA-IX expression is negligible in normal tissues. In contrast, a broad range of tumours express high levels of CA-IX, where the protein can serve as a biomarker for the early stages of tumour development but also as tumour marker of hypoxia associated with resistance to chemotherapy and radiotherapy. Material and methods Preclinical and clinical studies have shown that CA-IX is a promising therapeutic target for detection and therapy for several cancer types. To date only a limited number of ant-CAIX monoclonal antibodies (mAbs) have been available for clinical testing as therapeutic and imaging agents. In the current study, we generated and functionally categorised a panel of 51 mouse mAbs that specifically bind to human CA-IX. Results and discussions Characterisation of the mAbs revealed that of the mAbs with the best biophysical characteristics, three3 mAbs are suitable as an antibody-drug conjugate (ADC), two2 mAbs inhibit the CA-IX enzyme activity, and one1 mAb that is suitable for CA-IX imaging purposes. Conclusion These preliminary data presented here could thus form the basis for the development of novel CA-IX targeted immunotherapies and diagnostic tools for the treatment of cancer.