Single cell analysis of recurrent/metastatic, platinum resistant nasopharyngeal cancer patients treated within the POINT trial: Transitional insights for future research.

e18028 Background: POINT trial treated platinum-resistant, recurrent/metastatic (RM) Nasopharyngeal Carcinoma (NPC) patients (pts) with pembrolizumab and olaparib combination. To explore mechanisms of treatment sensitivity/resistance, we performed a translational analysis on selected pts who got opposite treatment response as excellent or poor. Methods: We retrieved baseline FFPE samples of 4 good responders -R- (pts obtaining clinical benefit with partial response or long-lasting stable disease), and 4 non-responders -NR- (progression within 4 months since treatment start), matched-paired for age, ECOG performance status, baseline plasma EBV DNA load, and disease burden/subsites. Samples were processed through Chromium X and libraries were sequenced on NextSeq 2000 platform (Illumina). Single cell data analysis was performed using Seurat (v5.3.1). Results: Patient’s characteristics are reported in Table 1. Immune and stromal cell types, identified based on transcriptomic profile, exhibited distinct proportional differences between R and NR. In R, T cells were enriched for gene signatures associated with migration, cytotoxicity, and active metabolic states; tumor epithelial cells’ phenotype, expressing IDO1 , PROX1 and CXCL14 , was consistent with a microenvironment actively supporting immune response. In contrast, NR T cells showed increased expression of chronic activation state genes, MAP4K1 , ZAP70 , and PIK3CD ; tumor epithelial cells displayed a more aggressive transcriptional profile, marked by signatures of invasion, epithelial–mesenchymal transition, extracellular matrix remodeling and immune suppression. Furthermore, B cells from responders to the treatment express tertiary lymphoid structure’s markers, such as CXCR5. Validation of these findings is ongoing through spatial transcriptomics. Conclusions: We highlighted clear differences in both cellular composition and gene expression profiles between R and NR baseline samples from platinum-resistant NPC pts treated with an immunotherapy-based approach. These preliminary findings provide novel insights on treatment selection of NPC pts and on future improvements in therapeutic strategies for resistant pts. Clinical trial information: NCT04825990 . Patients 1-R 1-NR 2-R 2-NR 3-R 3-NR 4-R 4-NR Plasma EBV DNA (copies/ml) 732 441 181 24 6341 7020 1258 1429 Disease sites Local Local, bone Hepatic Hepatic, bone Local, hepatic Hepatic, bone, nodal Pleural Distant nodal Sex M M F F M M F M Age (years) 51 62 55 51 40 42 69 40 ECOG PS 0 0 0 0 0 0 0 0 PFS (months) 9 4 17 2 15 2 20 4