Methylation array data of baseline and on-treatment samples from 8 HNSCC patients who received the combination of low dose of 5AZA and immune checkpoint blockade in a clinical trial
Background Immune checkpoint blockade (ICB) is an effective treatment in a subset of patients diagnosed with head and neck squamous cell carcinoma (HNSCC); however, most patients are refractory.  Methods In a non-randomized, open-label phase 1b clinical trial, participants with recurrent and/or metastatic (R/M) HNSCC were treated with low-dose 5'azacytidine (5'aza) daily for either 5- or 10-days in combination with fixed doses of durvalumab and tremelimumab after progression on ICB therapy. The primary objective was to assess the biologically effective dose of 5'aza as determined by molecular changes in paired baseline and on-treatment tumor biopsies; the secondary objective was safety.   Results Thirty-eight percent (3/8) of participants with evaluable paired tissue samples had a greater than 2-fold increase from baseline in interferon-gamma (IFN-?) signature and CD274 (programmed cell death protein 1 ligand, PD-L1) expression within the tumor microenvironment (TME), which was associated with increased CD8+ T cell infiltration and decreased infiltration of CD4+ T regulatory cells. The mean neutrophil-to-lymphocyte ratio (NLR) decreased by greater than 50%, from 14.2 (SD 22.6) to 6.9 (SD 5.2). Median overall survival (OS) was 16.3 months (95% CI 1.9, NA) and 2-year OS rate was 24.7% (95% CI: 4.5%, 53.2%) with 58% (7/12) of treated participants demonstrated prolonged OS of greater than 12 months.   Conclusion Our findings suggest that low-dose 5'aza can reprogram systemic host immune responses and the local TME to increase IFN-? and PD-L1 expression. The increased expression of these established biomarkers correlated with prolonged OS upon re-challenge with ICB.