Design and Synthesis of Bendamustine-Carbonic Anhydrase Inhibitors with Antiproliferative Effects in Clear Cell Renal Cell Carcinoma

Human carbonic anhydrase IX (hCA IX) is markedly overexpressed in clear cell renal cell carcinoma and plays a key role in establishing an acidic tumor microenvironment associated with intrinsic chemoresistance. Extracellular acidification limits the uptake and efficacy of several cytotoxic agents, including bendamustine, a bifunctional alkylating agent whose activity depends on intracellular accumulation and DNA cross-link formation. Herein, we report the design and synthesis of novel bendamustine-carbonic anhydrase inhibitor (CAI) hybrids aimed at combining CA IX targeting with DNA-damaging activity. Structural modification of the bendamustine butyric acid side chain enabled the introduction of CAI warheads while preserving the alkylating moiety. The resulting compounds were evaluated against hCA I, II, IX, and XII, displaying preferential inhibition of the tumor-associated isoforms. Selected derivatives (13a and 14c) showed antiproliferative activity in 786-O and CAKI-1 cells, inducing cell-cycle arrest and reducing long-term proliferative capacity more effectively than the reference CA IX inhibitor SLC-0111.