Three Is Better than One: A Multimetal Complex that Triggers Immunogenic Cell Death

Area of Science:

• Metal-based therapeutics
• Cancer immunotherapy
• Regulated cell death

Background:

• Immunogenic cell death (ICD) stimulates adaptive immunity via damage-associated molecular patterns (DAMPs).
• Metal complexes show potential as ICD inducers, but multi-metal conjugates are underexplored.
• Existing ICD inducers often lack multimodal therapeutic integration.

Purpose of the Study:

• To design, synthesize, and evaluate a novel tri-metallic prodrug (Au^I-Pt^IV-Ru^II) for enhanced ICD induction.
• To investigate the prodrug's mechanism of action, including DAMP release and immune cell activation.
• To assess the in vivo efficacy and safety of the tri-metallic prodrug in a colorectal cancer model.

Main Methods:

• Synthesis of a single scaffold tri-metallic prodrug (Au^I-Pt^IV-Ru^II) codelivering oxaliplatin, Ru^II arene, and Au(I) species.
• In vitro assessment of prodrug-induced thioredoxin reductase inhibition, reactive oxygen species (ROS) production, and DAMP release.
• In vivo evaluation in a colorectal cancer mouse model, including tumor growth suppression, metal accumulation analysis, and immune memory assessment via tumor challenge.
• Peripheral white blood cell (WBC) profiling to analyze innate and adaptive immune activation.

Main Results:

• The tri-metallic prodrug effectively released cytotoxic species upon reduction, enhancing TrxR1&2 inhibition and ROS production.
• In vitro studies showed significant DAMP release, indicating ICD induction.
• In vivo studies demonstrated superior tumor growth suppression compared to a mixture of individual agents.
• Reduced off-target metal accumulation and enhanced immune memory were observed in the tri-metallic prodrug group.
• WBC profiling confirmed activation of both innate and adaptive immune compartments.

Conclusions:

• The tri-metallic prodrug represents an integrated chemo-immunotherapeutic strategy, unifying multiple ICD triggers.
• This single-scaffold approach offers a promising platform for developing multimodal metal-based anticancer therapies.
• The study highlights the potential of combining different metal-based cytotoxic agents within a single prodrug for enhanced anti-tumor immunity.