Mapping MAGE-A4 Expression in Solid Cancers for Targeted Therapies Running header: Mapping MAGE-A4 expression in solid cancers Authors

Christin Habigt ¹ Sylvie Rottey ² Iben Spanggaard ³ Juanita Lopez ⁴ Elena Garralda ⁵ Emiliano Calvo ⁶ Oliver Bechter ⁷ Jayesh Desai ⁸ Rachel Galot ⁹ Leena Gandhi ¹⁰ Florian Heil ¹ Natascha Rieder ¹ Ivan Dimitrov ¹¹ Iris Martinez Quetglas ¹² Christian Heichinger ¹³ Nino Keshelava ¹² Andreas Roller ^14*

• ¹ Pharma Research and Early Development, Roche Innovation Center Munich, Penzberg, Germany
• ² Ghent University Hospital, Ghent, East Flanders, Belgium
• ³ Rigshospitalet, University of Copenhagen, Copenhagen, Capital Region of Denmark, Denmark
• ⁴ Royal Marsden NHS Foundation Trust, London, Westminster, United Kingdom
• ⁵ Vall d'Hebron Institute of Oncology (VHIO), Barcelona, Catalonia, Spain
• ⁶ START Madrid, Centro Integral Oncológico Clara Campal, Madrid, Madrid, Spain
• ⁷ University Hospitals Leuven, Leuven, Brussels, Belgium
• ⁸ Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
• ⁹ Université Catholique de Louvain, Louvain-la-Neuve, Walloon Brabant, Belgium
• ¹⁰ Dana–Farber Cancer Institute, Boston, Massachusetts, United States
• ¹¹ Roche Tissue Diagnostics, Tucson, United States
• ¹² Roche Innovation Center Zurich, Schlieren, Switzerland
• ¹³ Roche Pharma Research and Early Development, Roche Innovation Center, Basel, Switzerland
• ¹⁴ Roche (Switzerland), Basel, Switzerland

Melanoma-associated antigen A4 (MAGE-A4) is a promising target for anti-cancer therapy.However, limited contemporary data is available on the details of MAGE-A4 protein expression in different cancer types. In this study, protein expression of MAGE-A4 is comprehensively studied in patients with unresectable and/or metastatic solid cancers to identify indications of the highest unmet medical need for anti-MAGE-A4 therapy.FFPE tumor sections from 200 patients, predominantly HLA-A*02:01 positive (n = 193), were examined using immunohistochemistry (IHC) to detect MAGE-A4 expression. The patient cohort comprised various cancer types to pinpoint differences in the prevalence and intensity of MAGE-A4 positivity. MAGE-A4 expression was observed in 35% (69 patients) of the overall cohort. Certain cancer types exhibited notably higher frequencies of MAGE-A4 positivity. Specifically, adenoid cystic carcinoma demonstrated the highest prevalence at 82%, followed by liposarcoma at 67%. Ovarian serous/high-grade carcinoma showed a 64% positivity rate, identical to that observed in squamous non-small cell lung cancer (NSCLC).Head and neck squamous cell carcinoma (HNSCC) presented a 60% prevalence, while esophageal cancer had a 54% prevalence of MAGE-A4 expression. This data highlights the variability of MAGE-A4 expression across different cancer types and underscores its relevance as a potential target of novel precision medicines. The significant presence of MAGE-A4 in specific cancers suggests potential for stratified therapeutic approaches and warrants further investigation into its role in oncogenesis and treatment response.