Abstract Purpose: We evaluated whether IDO-inhibitor BMS986205 (IDOi) + PD-1 inhibitor nivolumab enhanced T-cell activity and augmented immune-mediated antitumor responses in untreated, resectable HNSCC. We employed response-adaptive surgical timing to identify responders to immunotherapy and enhance their response. Patients and Methods: Patients with HNSCC were 3:1 randomized to receive nivolumab with or without BMS986205 PO daily (NCT03854032). In the combination arm, BMS986205 was initiated 7 days prior to nivolumab. Patients were stratified by HPV status. Response-adaptive surgical timing involved response assessment by radiographic criteria 4 weeks after nivolumab in both arms. Non-responders underwent surgical resection, while responders received 4 more weeks of randomized therapy before surgery. Biomarker analysis utilized pathologic treatment response (pTR) and RNA sequencing. Results: Forty-two patients were enrolled, and the addition of IDOi to nivolumab did not result in greater rate of radiographic response (p=0.909). Treatment was well-tolerated with only 2 (5%) patients experiencing grade 3 immune-related adverse events. The addition of IDO-inhibitor augmented rates of pTR in patients with high baseline IDO RNA expression (p&amp;lt;0.05). Response-adaptive surgical timing demonstrated reliability in differentiating pathologic responders versus non-responders (p=0.009). A pretreatment NK cell signature, PD-L1 status, and IFN-g expression in the HPV– cohort correlated with response. HPV+ cohort found B-cell and CAF signatures predictive of response/non-response. Conclusions: Response-adaptive surgical timing enhanced treatment response. IDO-inhibitor BMS986205 augmented pTR in patients with high IDO1-expression in baseline samples, indicating a need for identifying and targeting resistant nodes to immunotherapy. HPV-status-dependent signatures predicting response to immunotherapy in HNSCC warrant further study.

Response-Adaptive Surgical Timing in neoadjuvant immunotherapy demonstrates enhanced pathologic treatment response in Head and Neck Squamous Cell Carcinoma