DDDR-35. HMCD-conjugated therapies: a strategy to repurpose and potentiate drugs for brain tumours

Abstract Glioblastoma (GBM) remains one of the most aggressive and treatment-resistant cancers. Most chemotherapeutic agents fail to penetrate the blood-brain barrier (BBB), and those that do often lack tumour-specific targeting or are rapidly effluxed from the tumour, limiting their clinical effectiveness. Heptamethine cyanine dyes (HMCDs) are a promising drug delivery strategy that could overcome these challenges. HMCDs exhibit BBB permeability, tumour-targeting capabilities, resistance to efflux mechanisms and offer the ability to conjugate drugs. Our team developed a novel HMCD conjugate with crizotinib, a receptor tyrosine kinase inhibitor that predominantly targets ALK and c-MET, which are commonly dysregulated in more than 50% of GBM patients. In vitro screening across both commercial and patient-derived primary GBM cell lines demonstrated that the HMCD-crizotinib conjugate exhibits over a 1000-fold increase in cytotoxic potency compared to the parent drug. This enhanced efficacy was tumour-selective as no cytotoxicity was observed in non-tumour cells at equivalent concentrations. We confirmed prolonged intracellular retention of our compound in GBM cells for up to 96 hours post-treatment via flow cytometry. Additionally, high-performance liquid chromatography (HPLC) was used to characterise the metabolic profile of the compound, revealing sustained stability within tumour cells. Preliminary in vivo data from orthotopic GBM mouse models further support the ability of the HMCD-crizotinib conjugate to cross the BBB and accumulate within tumour tissue after intraperitoneal administration. This was further validated with immunohistochemistry in formalin-fixed paraffin-embedded mouse brain samples. Ongoing studies are focused on evaluating survival outcomes in these models to further assess therapeutic potential. These findings demonstrate the potential of HMCD-based conjugation for improved delivery and retention of drugs into the brain. This approach may enable the repurposing of existing anticancer agents for effective targeted treatment of GBM and other brain malignancies.