Enabling In Vivo Optical Imaging of an Osmium Photosensitizer by Micellar Formulation

Increasing the Dye Payload of Cetuximab-IRDye800CW Enables Photodynamic Therapy

Cetuximab (Cet)-IRDye800CW, among other antibody-IRDye800CW conjugates, is a potentially effective tool for delineating tumor margins during fluorescence image-guided surgery (IGS). However, residual disease often leads to recurrence. Photodynamic therapy (PDT) following IGS is proposed as an approach to eliminate residual disease but suffers from a lack of molecular specificity for cancer cells. Antibody-targeted PDT offers a potential solution for this specificity problem. In this study, we show, for the first time, that Cet-IRDye800CW is capable of antibody-targeted PDT in vitro when the payload of dye molecules is increased from 2 (clinical version) to 11 per antibody. Cet-IRDye800CW (1:11) produces singlet oxygen, hydroxyl radicals, and peroxynitrite upon activation with 810 nm light. In vitro assays on FaDu head and neck cancer cells confirm that Cet-IRDye800CW (1:11) maintains cancer cell binding specificity and is capable of inducing up to ∼90% phototoxicity in FaDu cancer cells. The phototoxicity of Cet-IRDye800CW conjugates using 810 nm light follows a dye payload-dependent trend. Cet-IRDye800CW (1:11) is also found to be more phototoxic to FaDu cancer cells and less toxic in the dark than the approved chromophore indocyanine green, which can also act as a PDT agent. We propose that antibody-targeted PDT using high-payload Cet-IRDye800CW (1:11) could hold potential for eliminating residual disease postoperatively when using sustained illumination devices, such as fiber optic patches and implantable surgical bed balloon applicators. This approach could also potentially be applicable to a wide variety of resectable cancers that are amenable to IGS-PDT, using their respective approved full-length antibodies as a template for high-payload IRDye800CW conjugation.

Drug Delivery in Photodynamic Therapy

Photodynamic therapy (PDT) has gained prominence as a non-invasive and selective treatment option for solid tumors and non-oncological diseases [...].

Nanoformulation of Lipophilic Osmium Photosensitizers in Liposomes and Micelles as a General Strategy for Improving Reproducibility and Reducing Quenching†

Nanoformulation of an osmium photosensitizer within liposomes and micelles is used to improve the water-solubility of this highly lipophilic molecule. This highlight report describes a recent paper by Cameron, Obaid and McFarland on this topic and discusses the context for this report. Nanoformulation has been explored as a strategy before, but this represents the first usage of this strategy with highly potent metal-based photosensitizers having phototherapeutic indices (PIs) in excess of 104 . The nanoformulation strategy is effective due to reducing aggregation and self-quenching of the photosensitizer molecules.