A functional precision medicine strategy to guide patient selection for oncolytic vaccination in <i>NRAS</i> -mutant melanoma.

Abstract

e21508 Background: The NRAS-mutant melanoma subtype represents one of the major challenges in melanoma treatment, as it is associated with aggressive disease biology, reduced overall survival (OS), heterogeneous responses to immune checkpoint inhibitors (ICIs), and the absence of approved targeted therapies. Methods: This is a single-center, prospective translational study enrolling metastatic NRAS-mutant melanoma patients (pts) undergone to standard clinical practice treatment with ICIs. Blood samples, longitudinally collected at baseline and during treatment, were employed with the aim to develop a patient-specific, functional 3D based platform capable of stratifying pts as potential responders or non-responders, ultimately improving selection for oncolytic cancer vaccination and personalizing therapy. The investigational vaccine leverages an oncolytic adenovirus (Ad5/3-D24-ICOSL-CD40L) designed to selectively replicate in tumor cells and enhance antitumor immunity via costimulatory molecules expression. To further strengthen immune activation, the viral vector was combined with melanoma-associated antigens targeting NRAS-mutant melanoma. Results: The preliminary analysis included 7 pts, 100% male, with ECOG 0 PS and a median age of 65 years. Most pts had poor prognostic features, including visceral disease, multiple metastatic sites (≥3) or elevated lactate dehydrogenase levels. Three pts were ICI-naïve, while 4 had primary resistance. Best overall response included stable disease in 2 pts, while 5 experienced progressive disease. Median progression-free survival was 3.1 months; mOS was not reached. To functionally assess vaccine activity and patient-specific immune responsiveness, we established a 3D co-culture system using patient-derived NRAS-mutant melanoma spheroids and autologous, HLA-matched peripheral blood mononuclear cells. This platform recapitulates key features of the tumor microenvironment and enables dynamic evaluation of immune-mediated antitumor effects, including tumor growth control and regrowth kinetics. Treatment of patient-derived melanoma spheroids with the oncolytic vaccine resulted in enhanced antitumor activity compared to relative control conditions, with a significant reduction in spheroid area and attenuation of tumor regrowth over time. Notably, under control co-culture conditions, spheroid growth dynamics qualitatively reflected the aggressive clinical course observed in pts with poor response to standard immunotherapy, whereas vaccine treatment promoted effective immune-mediated tumor control in vitro . Conclusions: These findings support the feasibility of a functional 3D model to capture differential therapeutic responsiveness and to inform future strategies for early stratification and personalized immunotherapeutic interventions in NRAS-mutant melanoma pts.