Gold(I) complexes in anticancer immunotherapy

The 16th International Symposium on Applied Bioinorganic Chemistry brought researchers together in Ioannina, Greece, in June 2023 to examine how coordination compounds could address biological, medical and environmental challenges. Within this setting, gold(I) complexes offer a compelling example of how molecular design can influence both tumour cell destruction and immune recognition.

Au(I) compounds have attracted attention because their soft gold centres interact strongly with biological thiols and can disturb the finely balanced redox environment of cancer cells. Potency alone, however, does not establish therapeutic value. Translation depends on selectivity, stability, pharmacokinetics and evidence that treatment produces a sustained antitumour immune response.

Why gold(I) coordination chemistry matters

Gold(I), commonly written Au(I), is a d10 metal centre that frequently forms linear, two-coordinate complexes with ligands such as phosphines, N-heterocyclic carbenes and sulfur-containing groups. This coordination environment strongly influences solubility, cellular uptake and the ability of the compound to exchange ligands inside cells. Changing the ligand can therefore transform a laboratory-active complex into a compound with a very different biological profile.

The anticancer activity of many gold(I) complexes is associated with thiol binding, inhibition of redox enzymes such as thioredoxin reductase, depletion of glutathione and the generation of reactive oxygen species. These effects can push cancer cells towards apoptosis or other forms of regulated death. Related coordination strategies appear in oxygen-carrier studies, where cobalt Schiff-base complexes illustrate how metal centres, donor atoms and ligand architecture control molecular behaviour.

No single structural feature explains the success of a gold compound. Hydrophobic ligands may improve membrane association, hydrophilic groups can support circulation, and strong gold–sulfur chemistry can assist intracellular delivery. Each feature must be assessed together with chemical stability, since premature ligand exchange or decomposition may compromise both efficacy and experimental interpretation.

From cytotoxicity to immune activation

An anticancer agent must do more than kill tumour cells if it is to support immunotherapy. Treatment can create an immunogenic tumour microenvironment by releasing danger-associated molecular patterns, including ATP, HMGB1 and calreticulin. These signals encourage antigen-presenting cells to engage with dying tumour cells and support cytotoxic T-cell responses. The resulting effect can extend beyond the immediate treatment site.

Not every Au(I) complex produces this outcome. Cytotoxicity, immune activation and suppression of normal immune cells are separate properties, and a dose that damages cancer cells may also impair dendritic cells, T lymphocytes or tissue repair. Studies should consequently measure immune outcomes alongside viability, apoptosis and reactive oxygen species. Useful endpoints include cytokine release, antigen presentation, macrophage and dendritic-cell responses, T-cell proliferation and the persistence of antitumour memory.

The wider ISABC programme provided useful redox and coordination perspectives. Research featured in artificial photosynthesis work, for example, demonstrates how metal clusters and surrounding ligands control electron transfer and reaction selectivity. Although the biological endpoints differ from anticancer research, the shared lesson is clear: activity emerges from the complete molecular architecture rather than from the metal alone.

Designing Au(I) compounds for tumour selectivity

Selectivity is one of the central challenges for metal-based anticancer agents. Au(I) compounds can interact with healthy cells, particularly when they encounter abundant thiol-containing proteins in blood or tissue. Researchers therefore compare ligands, oxidation states and formulations to determine whether a complex can preferentially accumulate in tumours, respond to the tumour microenvironment or release an active species under controlled conditions.

Promising approaches include attaching recognition groups for receptors overexpressed on particular tumours, encapsulating complexes in nanoparticles, or using ligands that remain stable in circulation but exchange inside cancer cells. These strategies must be tested against realistic biological conditions. Dilution by plasma, binding to albumin and non-specific protein interactions may all reduce the available dose long before a tumour is reached.

A rigorous development pathway also demands pharmacokinetic and pharmacodynamic data. Intratumour distribution, clearance, toxicity and the relationship between exposure and immune activation are needed to identify an effective dose. At the same time, assays should distinguish direct effects on cancer cells from effects mediated by the immune system, especially when experiments use both immune-deficient and immunocompetent models.

Australian translation and regulatory context

Australia offers strong clinical and research environments for investigating metal-based therapeutics. Major cancer centres and biotechnology clusters in Sydney, Melbourne, Brisbane, Adelaide and Perth provide access to multidisciplinary teams, while the public hospital system creates pathways for patients who first consult a general practitioner and then enter specialist oncology services. Private hospitals and specialist clinics form another important part of the local treatment market.

Investigational products supplied through Australian trials must meet Therapeutic Goods Administration requirements, applicable human research ethics standards and institutional sponsor oversight. Experimental medicines are not ordinarily listed in the Australian Register of Therapeutic Goods or reimbursed through the Pharmaceutical Benefits Scheme. Trial registration through the ANZCTR, informed consent, adverse-event reporting and pharmacy controls are therefore essential parts of translating promising coordination chemistry.

Funding is another local consideration. The NHMRC and Australian Research Council support many academic collaborations, while universities, hospitals and industry partners contribute equipment, trial infrastructure and staff time. Because the Pharmaceutical Benefits Scheme does not cover investigational therapy, studies need realistic budgets for drug manufacture, quality-control testing, sample handling and monitoring. Travelling from Australia to Ioannina also requires early planning for long-haul flights, connections through Athens, Schengen entry requirements and Australian-dollar exchange-rate changes.

ISABC participation and wider scientific exchange

The Ioannina symposium combined scientific sessions with opportunities for students, early-career researchers and international delegates to exchange results. Young scientist travel awards, poster prizes and scholarships supported participation, while the meeting’s location provided a practical setting for discussion across coordination chemistry, pharmacology and translational medicine. Australian researchers could use these mechanisms to build collaborations and present work involving metal-based therapeutics, immunology or analytical methods.

The event also belonged to a broader international meeting tradition. The earlier AIC 2017 meeting offers historical context for the continuing development of applied bioinorganic chemistry. Comparing meeting themes across years reveals persistent interest in responsive metal complexes, biological imaging, catalysis and therapeutic applications, while newer work places greater emphasis on reproducibility and clinical translation.

Zita Congress & Event Management served as the official symposium secretariat for registration, accommodation and abstract-related enquiries. This central point of contact was particularly useful for overseas participants who needed coordinated travel arrangements, documentation guidance and support with presentation requirements before travelling to Greece.

Priorities for advancing Australian teams

Australian research groups can strengthen the development of Au(I) immunotherapies by combining rigorous coordination chemistry with early consultation from immunology, pharmacy and clinical-trial specialists. The following priorities would help connect promising laboratory findings with evidence that can support regulatory and funding decisions:

• Assemble teams that include coordination chemists, tumour immunologists, pharmacologists, analytical scientists and clinical investigators.
• Test Au(I) compounds for chemical stability, cytotoxicity, immune activity and off-target effects in matched experimental systems.
• Design multicentre studies around Australian ethics, ANZCTR registration, TGA expectations and appropriate informed-consent procedures.
• Collect pharmacokinetic, biodistribution and exposure–response data alongside conventional tumour-growth measurements.
• Engage early with patients, consumer representatives and cancer organisations to ensure that proposed biomarkers and treatment pathways reflect meaningful clinical needs.

The symposium’s interdisciplinary format demonstrates how applied bioinorganic chemistry can connect molecular design with biological response and therapeutic translation. Australian researchers should now review the official ISABC participation information, identify relevant travel-award, scholarship or presentation opportunities, and direct registration, accommodation and abstract questions to Zita Congress & Event Management, the appointed symposium secretariat.