Synthesis of Inhibitor-Photosensitizer Conjugates for Enhanced hCAIX-targeted Photodynamic Therapy against Hypoxic Tumors

Human Carbonic Anhydrase IX (hCAIX) is involved in key oncogenic processes, including tumor cell proliferation, growth, metastasis, and adhesion.1 The enzyme’s ubiquitous expression in hypoxic tumors and its strategic extracellular localization make hCAIX an attractive biological target for the development of inhibitors designed for hypoxic tumor treatment. In a previous work, compound 1, bearing a benzensulfonamide group, resulted very active in hCAIX inhibition, with a Ki in the low nanomolar range.2 The objective of this study is to investigate hCAIX as a potential therapeutic target for tumor treatment and develop an inhibitor equipped with a photosensitizer (PS) unit, creating a conjugate for enhanced photodynamic therapy (PDT) that should prevent the tumor from compensating through hCAIX activation. For this purpose, three compounds (2, 3, and 4) were synthesized and fully characterized via NMR, MS, UV-VIS and fluorescence spectroscopy. The conjugates incorporate the structure of compound 1, bearing the inhibiting benzensulfonamide group, which is here linked to a BODIPY or ENBS core, known for their high 1O2 and ROS generation, respectively. The inhibitory activity and PDT efficiency are currently under investigation. To study the interaction mechanism and localization under hypoxic conditions, an highly fluorescent Rhodamine-functionalised analogue of compound 1 (5) was synthesized.