Abstract 3882: Translating genotype to immunophenotype in HRAS mutated head and neck squamous cell carcinoma (HNSCC) to identify effective Tipifarnib partners for optimal patient outcomes

Abstract Background: Tipifarnib is a highly selective farnesyltransferase inhibitor that has shown promising activity in HRAS mutant recurrent/metastatic HNSCC. The incidence of HRAS mutations in HNSCC is 4-10%. Since HRAS mutated HNSCC can be successfully targeted with Tipifarnib, we sought to analyze the immune and genomic landscape of these tumors to guide combinatorial strategies. Methods: We identified thirteen patients with HRAS mutant tumors. We included in the analysis 50 patients with HRAS wild-type tumors. Genomic DNA from baseline biopsies of tumors was purified and subjected to targeted sequencing (TruSightTM Oncology 500 panel). PD-L1 expression in formalin-fixed tumor samples was assessed using the PD-L1 IHC 22C3 pharmDx assay (Agilent Technologies, Carpinteria, CA, USA) and characterized by the combined positive score (CPS). Assessment of PD-L1+ cells inside and at the periphery of the tumor was performed. HRAS mutational status was correlated with PD-L1 status. The genomic data derived from the targeted gene panel of HRAS mutant tumors were compared to those with wild-type HRAS. Results: Thirty-seven patients had both genomic and PD-L1 expression data available. The presence of HRAS mutations was associated with higher TPS PD-L1 scores (26% vs 40% vs 100% in TPS <1%, 1-49% and >50% respectively, p=0.043). Similar results were obtained for CPS (28% vs 80% in CPS <10% and =>10%, p=0.047). HRAS mutations were more commonly found with TP53 mutations (16% in WT TP53 and 55.6% in mutated TP53, p=0.073). Higher PD-L1 TPS showed increased survival without reaching significance when measuring either in the margins (64.1 vs 35.8, p=0.066) or the center of the tumor (p=0.097) due to the small sample size. Conclusions: HRAS mutant HNSCC are associated with high PD-L1 expression and co-occurrence of p53 mutations. Combinations of tipifarnib with an anti-PD1 antibody, an anti-PDL1 antibody, or an anti-CTLA-4 antibody warrant clinical investigation in this rare subset of HNSCC. Citation Format: Amanda Psyrri, Miriam Anastasiou, Aris Spathis, Stergios Doumas, Panagiota Economopoulou, Ioannis Kotsantis, Anastasios Pantazopoulos, Anastasios Kyriazoglou, George Kavourakis, Theodoros Rampias, Periklis Foukas. Translating genotype to immunophenotype in HRAS mutated head and neck squamous cell carcinoma (HNSCC) to identify effective Tipifarnib partners for optimal patient outcomes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3882.