Extracellular matrix-myCAF signatures correlate with resistance to neoadjuvant aPD-L1 immune checkpoint inhibition with durvalumab + metformin in HPV+ HNSCC

Background: Immune checkpoint inhibitors (ICI) have demonstrated clinical benefit in head and neck squamous cell carcinoma (HNSCC); however, single-agent efficacy is limited, leaving significant unmet needs. Metformin may synergize with ICI, offering promise to improve response rates. We leveraged multi-omic data from a randomized, presurgical neoadjuvant trial (NCT03618654) evaluating a single infusion of the anti-programmed death ligand 1 (PD-L1) ICI, durvalumab, with or without daily, standard dose metformin in previously untreated, non-diabetic patients with HNSCC to understand predictors of response and the effect of combination therapy. Methods: Clinical, pathological, and correlative data were analyzed to investigate response and resistance mechanisms. We present an in-depth multi-omic analysis of primary tumor specimens to study treatment response/resistance in HPV+ HNSCC. Results: Baseline samples revealed that myofibroblastic cancer-associated fibroblast (MYCAF) and extracellular matrix (ECM) signatures were enriched in durvalumab plus metformin (DM) nonresponders which were localized to the leading tumor edge on spatial transcriptomics. In contrast, baseline responder samples were enriched for the Langerhans-like dendritic cell (DC) state and interferon (IFN) signatures. Treatment increased intratumoral CD8+ T cell and IFN signatures and peripheral blood CCL2 levels. Responders demonstrated macrophage and dendritic cell enrichment and antigen processing and presentation upregulation. Enrichment of cell cycle-related gene sets, specifically the MYC targets V1 Hallmark gene set, correlated with nonresponse. Conclusion: Early response and resistance dynamics for DM in HPV+ HNSCC reveal baseline ECM-MYCAF as predictive of nonresponse. In contrast, responders were distinguished by baseline enrichment in the Langerhans-like DC cell state and post-treatment antigen-presenting gene sets.