Long-Lived Immunogenic Cell Death Induced by a Water-Soluble Redox Active Au(I) Bis-N-Heterocyclic Carbene

Immunogenic cell death (ICD) is a form of regulated cell death that engages the immune system by releasing damage-associated molecular patterns, making it a promising target for cancer immunotherapy. Presented here is the synthesis and evaluation of a series of asymmetric redox-active water-soluble Au(I) bis-N-heterocyclic carbenes (Au(I) bis-NHCs). We explore the structure-activity relationships between redox activity, water solubility and ICD induction, building on our previous work with a redox-active Au(I) bis-NHC (1) that effectively induced ICD but suffered from poor water solubility. To overcome this limitation, we synthesized several water-soluble redox-active Au(I) bis-NHCs, derivatives 2-4, by modifying the imidazole moiety. Compound 2 was identified as the lead, balancing water solubility and ICD induction efficacy. This compound, featuring a naphthoquinone moiety, and was found to generate reactive oxygen species (ROS) and trigger key ICD biomarkers, including calreticulin (CRT) translocation, ATP release, and high mobility group box 1 (HMGB1) secretion. A control compound lacking the redox active naphthoquinone failed to elicit these ICD markers or promote ROS production. Across the series 1-4 a correlation was observed between ROS generation and ICD biomarker expression. In vivo studies in syngeneic immunocompetent mice demonstrated that compound 2 not only prevents CT26 colorectal cancer tumor growth upon challenge with live cancer cells but also elicits a long-lived immune response upon rechallenge 12 months later.