Evaluation of real-time pharmacokinetics using fluorescence imaging system in Near-infrared photoimmunotherapy for head and neck cancer

Objective

Near-infrared photoimmunotherapy (NIR-PIT) is a molecular targeted therapy that utilizes an antibody-photoabsorber conjugate and excitation light. Herein, excitation of antibody-bound IR700 with near-infrared light at 690 nm causes IR700 to undergo a photochemical ligand reaction. IR700’s hydrophilic side chain is released, and the remaining molecules became hydrophobic and lost fluorescence.

NIR-PIT targeting the epidermal growth factor receptor using cetuximab sarotalocan sodium, and a laser system has been used to treat patients with unresectable head and neck cancers in Japan since 2021. Light irradiates planned treatment area based on preoperative diagnostic imaging; however, the actual drug accumulation and response status during treatment have not been confirmed.

This study aimed to investigate NIR-PIT’s fluorescence intensity and antitumor effects on head and neck cancer in humans using real-time fluorescence imaging system.

Methods

In this single-center prospective observational study, patients with lesions that could be monitored fluorescence were enrolled. Fluorescence intensity during NIR-PIT and tumor characteristics before and after treatment were examined.

Results

Seven patients were included. The fluorescence intensity of the irradiated area showed a rapid decrease in the early stage of treatment, followed by a gradual decrease, almost reaching a plateau before the end of light irradiation. The irradiated areas demonstrated no fluorescence following re-irradiation, and areas irradiated in duplicate tended to lose fluorescence more rapidly than the non-overlapping areas.

Conclusion

We observed and measured the drug accumulation and responses during treatment in humans using real-time fluorescence imaging. This information is expected to be applied to evaluate efficacy of NIR-PIT.