In addition, micro-CT showed that repeated NIR-PIT led to repair of metastasis-induced bone destruction and restored bone cortex continuity consistent with healing. Bioluminescence imaging and histological evaluation showed that EGFR-targeted NIR-PIT has a therapeutic effect on bone metastatic lesions in mice. The bone metastatic lesions were treated with NIR-PIT using the anti-EGFR antibody, panitumumab-IR700 conjugate. In this study, the efficacy of NIR-PIT for bone metastases was investigated using a bone metastases mouse model successfully established by caudal artery injection of a human triple-negative breast cancer cell line, MDAMB468-GFP/luc. However, no bone metastases have yet been treated. NIR-PIT using an anti-epidermal growth factor receptor (EGFR) antibody-IR700 conjugate in patients with recurrent head and neck cancer received qualified approval in Japan in 2020 and is now widely used there.

Near-infrared photoimmunotherapy (NIR-PIT) uses antibodies labeled with IRDye700DX (IR700) which is activated by NIR light, resulting in rapid cell membrane damage and immunogenic cell death. Therefore, there is a need to develop new approaches to bone metastases that are effective but minimally invasive. Surgery is often necessary, yet recovery times might exceed life expectancy. Radiotherapy with pain palliation can temporize bone metastases but is generally considered a short-term solution and retreatment is difficult. Chemotherapy, including immunotherapy, is rarely curative. The bones are a common site for metastasis arising from solid tumors such as breast and prostate cancer.

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