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Program Number: B055
Session Name: Poster Session

Efficacy, safety, and immune biomarkers in RM-1929 photoimmunotherapy for locoregional, recurrent head and neck squamous cell carcinoma

Takahiro Tsujikawa, MD, PhD¹; Peesit Leelasawatsuk, MD²; Koichi Yoshizawa, MD¹; Ryuhei Okada, MD, PhD³; Mai Mohamed Bedeir, MD¹; Alisa Kimura, MD, PhD¹; Hiroki Morimoto, MD, PhD¹; Sumiyo Saburi, MD, PhD¹; Shigeyuki Mukudai, MD, PhD¹; Hikaru Nagao, MD, PhD¹; Takahiro Asakage, MD, PhD³; Shigeru Hirano, MD, PhD¹; ¹Department of Otolaryngology-Head and Neck Surgery, Kyoto Prefectural University of Medicine; ²Department of Otolaryngology Head and Neck Surgery, Prince of Songkla University; ³Department of Head and Neck Surgery, Institute Science of Tokyo

Background: Locoregional recurrence in head and neck squamous cell carcinoma (HNSCC) is a challenging stage with high morbidity and mortality. RM-1929 photoimmunotherapy, which combines antibody-photoabsorber conjugates with near-infrared light, has shown promise in treating these recurrences and potentially enhancing immunogenicity. However, the clinical and immune factors influencing its efficacy and safety remain unclear.

Design, Setting, and Participants: This retrospective study involved 19 patients who underwent a total of 28 treatment cycles of RM-1929 photoimmunotherapy at Kyoto Prefectural University of Medicine. The treatment utilized cetuximab sarotalocan sodium, an anti-epidermal growth factor receptor (EGFR) monoclonal antibody conjugated with the photoabsorber IR700. Patients received 640 mg/m² intravenously over more than 2 hours, followed by laser application to the lesion 20-28 hours later. These treatments were conducted within the scope of the National Health Insurance approval in Japan. The study assessed clinical profiles, treatment outcomes, safety, and the tumor microenvironment using 14-marker multiplex immunohistochemistry.

Results: Treatment regions included the oral cavity, lymph nodes, oropharynx, nasopharynx, and hypopharynx. Prophylactic tracheostomy was performed in 8 out of 19 cases. The outcomes included 4 complete responses (CR), 17 partial responses (PR), 5 stable diseases (SD), and 2 progressive diseases (PD), resulting in an overall response rate of 75% (21 out of 28 treatment cycles). The median overall survival post-treatment was 341 days. In 12 out of 18 cases, pembrolizumab monotherapy or nivolumab was administered an average of 58 days post-treatment. Adverse events occurred in 20 out of 28 treatment cycles, with Grade 3 edema in four cases, Grade 3 pain in one case, and Grade 3 delirium in one case. The platelet-lymphocyte ratio (PLR) in pretreatment peripheral blood showed a significantly lower trend in responders. In eight cases, the composition and density of 10 types of immune cells in pre-treatment tumor tissue were analyzed. Compared to the remaining six CR/PR cases, a low density of intratumoral T cells was observed in two SD cases, indicating an immunologically cold tumor microenvironment. In two PR cases, comparisons were made with post-treatment tissue. An increase in immune cell density post-treatment was observed, along with an increase in regulatory T cells.

Conclusion: RM-1929 photoimmunotherapy demonstrated favorable local control with manageable adverse events. Ongoing research aims to identify predictive and immune biomarkers to further optimize this therapy.

 

 

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