Purpose: Patients with resected, local–regionally advanced, head and neck squamous cell carcinoma (HNSCC) have a one-year disease-free survival (DFS) rate of 65%–69% despite adjuvant (chemo)radiotherapy. Neoadjuvant PD-1 immune-checkpoint blockade (ICB) has demonstrated clinical activity, but biomarkers of response and effect on survival remain unclear. Patients and Methods: Eligible patients had resectable squamous cell carcinoma of the oral cavity, larynx, hypopharynx, or oropharynx (p16-negative) and clinical stage T3-T4 and/or two or more nodal metastases or clinical extracapsular nodal extension (ENE). Patients received neoadjuvant pembrolizumab 200 mg 1–3 weeks prior to surgery, were stratified by absence (intermediate-risk) or presence (high-risk) of positive margins and/or ENE, and received adjuvant radiotherapy (60–66 Gy) and concurrent pembrolizumab (every 3 weeks × 6 doses). Patients with high-risk HNSCC also received weekly, concurrent cisplatin (40 mg/m2). Primary outcome was one-year DFS. Secondary endpoints were one-year overall survival (OS) and pathologic response (PR). Safety was evaluated with CTCAE v5.0. Results: From February 2016 to October 2020, 92 patients enrolled. The median age was 59 years (range, 27–80), 30% were female, 86% had stage T3–T4, and 69% had ≥N2. At a median follow-up of 28 months, one-year DFS was 97% (95% CI, 71%–90%) in the intermediate-risk group and 66% (95% CI, 55%–84%) in the high-risk group. Patients with a PR had significantly improved one-year DFS relative to patients without response (93% vs. 72%, hazard ratio 0.29; 95% CI, 11%–77%). No new safety signals were identified. Conclusions: Neoadjuvant and adjuvant pembrolizumab increased one-year DFS rate in intermediate-risk, but not high-risk, HNSCC relative to historical control. PR to neoadjuvant ICB is a promising surrogate for DFS.

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BackgroundImmunotherapy has emerged as a promising treatment modality for head and neck squamous cell carcinoma (HNSCC). Pembrolizumab, an anti-programmed death 1 antibody, is an immunotherapy agent currently approved for metastatic HNSCC and curative intent clinical trials. Although clinical responses to pembrolizumab are promising, many patients fail to respond. However, it is well known that T cell cytotoxicity and chemotaxis are critically important in the elimination of HNSCC tumors. These functions depend on ion channel activity and downstream Ca2+ fluxing abilities, which are defective in patients with HNSCC. The purpose of this study was to elucidate the effects of pembrolizumab on potassium (K+) channel (KCa3.1 and Kv1.3) activity, Ca2+ fluxes, and chemotaxis in the cytotoxic T cells of patients with HNSCC and to determine their correlation with treatment response.MethodsFunctional studies were conducted in CD8+ peripheral blood T cells (PBTs) and tumor infiltrating lymphocytes (TILs) from patients with HNSCC treated with pembrolizumab. Untreated patients with HNSCC were used as controls. The ion channel activity of CD8+ T cells was measured by patch-clamp electrophysiology; single-cell Ca2+ fluxing abilities were measured by live microscopy. Chemotaxis experiments were conducted in a three-dimensional collagen matrix. Pembrolizumab patients were stratified as responders or non-responders based on pathological response (percent of viable tumor remaining at resection; responders: ≤80% viable tumor; non-responders: >80% viable tumor).ResultsPembrolizumab increased K+ channel activity and Ca2+ fluxes in TILs independently of treatment response. However, in PBTs from responder patients there was an increased KCa3.1 activity immediately after pembrolizumab treatment that was accompanied by a characteristic increase in Kv1.3 and Ca2+ fluxes as compared with PBTs from non-responder patients. The effects on Kv1.3 and Ca2+ were prolonged and persisted after tumor resection. Chemotaxis was also improved in responder patients’ PBTs. Unlike non-responders’ PBTs, pembrolizumab increased their ability to chemotax in a tumor-like, adenosine-rich microenvironment immediately after treatment, and additionally they maintained an efficient chemotaxis after tumor resection.ConclusionsPembrolizumab enhanced K+ channel activity, Ca2+ fluxes and chemotaxis of CD8+ T cells in patients with HNSCC, with a unique pattern of response in responder patients that is conducive to the heightened functionality of their cytotoxic T cells.

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6006 Background: Patients with resected HNSCC, with high-risk (positive margins, extracapsular spread [ECE]) or intermediate-risk pathological features have an estimated 1-year DFS of 65% and 69%, respectively. Immune checkpoint blockade improved survival of patients with recurrent/metastatic HNSCC, and preclinical models indicate radiotherapy (RT) synergizes with anti-PD-1. Therefore, we administered the PD-1 inhibitor pembrolizumab (pembro) pre- and post-surgery with adjuvant RT +/- cisplatin in patients with resectable, locoregionally advanced (clinical T3/4 and/or ≥2 nodal metastases) HNSCC (NCT02641093). Methods: Eligible patients received pembro (200 mg I.V. x 1) 1-3 weeks before resection. Adjuvant pembro (q3 wks x 6 doses) was administered with RT (60-66Gy) with or without weekly cisplatin (40mg/m2 X 6) for patients with high-risk and intermediate-risk features, respectively. The primary endpoint was 1-year DFS estimated by Kaplan Meier curves. Safety was evaluated by CTCAE v5.0. Pathological response (PR) to neoadjuvant pembro was evaluated by comparing pre- and post-surgical tumor specimens for treatment effect (TE), defined as tumor necrosis and/or histiocytic inflammation and giant cell reaction to keratinaceous debris. PR was classified as no (NPR, < 20%), partial (PPR, ≥20% and < 90%) and major (MPR, ≥90%). Tumor PD-L1 immunohistochemistry was performed with 22c3 antibody and reported as combined positive score (CPS). Results: Ninety-two patients were enrolled. Seventy-six patients received adjuvant pembro and were evaluable for DFS. Patient characteristics included: median age 58 (range 27 – 80) years; 32% female; 88% oral cavity, 8% larynx, and 3% human papillomavirus negative oropharynx; 86% clinical T3/4 and 65% ≥2N; 49 (53%) high-risk (positive margins, 45%; ECE, 78%); 64% (44/69 available) had PD-L1 CPS ≥1. At a median follow-up of 20 months, 1-year DFS was 67% (95%CI 0.52-0.85) in the high-risk group and 93% (95%CI 0.84-1) in the intermediate-risk group. Among 80 patients evaluable for PR, TE scoring resulted in 48 NPR, 26 PPR and 6 MPR. Patients with PPR/MPR had significantly improved 1-year DFS when compared with those with NPR (100% versus 68%, p = 0.01; HR = 0.23). PD-L1 CPS ≥ 1 was not independently associated with 1-year DFS, but was highly associated with MPR/PPR (p = 0.0007). PPR/MPR in PD-L1 CPS < 1, ≥1 and ≥20, were estimated as 20, 55 and 90%, respectively. Grade ≥ 3 adverse events occurred in 62% patients with most common including dysphagia (15%), neutropenia (15%), skin/wound infections (10%), and mucositis (9%). Conclusions: PR to neoadjuvant pembro is associated with PD-L1 CPS≥1 and high DFS in patients with resectable, local-regionally advanced, HNSCC. Clinical trial information: NCT02641093.

BACKGROUND:The 5-year overall survival (OS) rate remains at 50% for patients with locally advanced head and neck squamous cell carcinoma (LAHNSCC), thereby underscoring the need for improved treatments. An antidiabetic agent, metformin, was found in retrospective studies to improve survival in patients with HNSCC. Therefore, the authors conducted a phase 1 dose escalation study combining metformin with chemoradiotherapy in patients with LAHNSCC. METHODS: Nondiabetic patients with LAHNSCC were enrolled in the current study to receive escalating doses of metformin and CRT based on the modified toxicity probability interval design. Metformin cohort doses included 2000 mg, 2550 mg, and 3000 mg daily in divided doses in addition to cisplatin (at a dose of 100 mg/m 2 on days 1, 22, and 43) and standard radiotherapy (70 grays). Adverse events were categorized as per the National Cancer Institute Common Terminology Criteria for Adverse Events (version 4.03). RESULTS: Twenty patients were enrolled, 2 of whom withdrew consent. The median age of the patients was 56 years and the majority were male (83%), were white (88%), had p16-positive disease (72%), and were tobacco users (61%). The median length of metformin exposure was 28.5 days. The most common grade ≥3 toxicities were nausea (11%), vomiting (11%), mucositis (6%), acute kidney injury (17%), anemia (6%), and leukopenia (11%). Dose-limiting toxicities included diarrhea and acute kidney injury. After a median follow-up of 19 months, the 2-year overall survival and progression-free survival rates were 90% and 84%, respectively. No hypoglycemia events or lactic acidosis were observed. Cisplatin administration did not appear to affect metformin pharmacokinetics. The maximum tolerated dose for metformin could not be determined given the limited number of patients who tolerated metformin during chemoradiotherapy. CONCLUSIONS: To the authors' knowledge, the current study is the first phase 1 trial combining metformin with chemoradiotherapy. Rates of overall survival and progression-free survival were encouraging in this limited patient population, and warrant further investigation in a phase 2 trial. Cancer 2020;126:354-362.

BackgroundMetformin slows tumor growth and progression in vitro, and in combination with chemoradiotherapy, resulted in high overall survival in patients with head and neck cancer squamous cell carcinoma (HNSCC) in our phase 1 clinical trial (NCT02325401). Metformin is also postulated to activate an antitumor immune response. Here, we investigate immunologic effects of metformin on natural killer (NK) and natural killer T cells, including results from two phase I open-label studies in patients with HNSCC treated with metformin (NCT02325401,NCT02083692).MethodsPeripheral blood was collected before and after metformin treatment or from newly diagnosed patients with HNSCC. Peripheral immune cell phenotypes were evaluated using flow cytometry, cytokine expression by ELISA and/or IsoLight, and NK cell-mediated cytotoxicity was determined with a flow-based NK cell cytotoxicity assay (NKCA). Patient tumor immune infiltration before and after metformin treatment was analyzed with immunofluorescence. NK cells were treated with either vehicle or metformin and analyzed by RNA sequencing (RNA-seq). NK cells were then treated with inhibitors of significant pathways determined by RNA-seq and analyzed by NKCA, ELISA, and western blot analyses.ResultsIncreased peripheral NK cell activated populations were observed in patients treated with metformin. NK cell tumor infiltration was enhanced in patients with HNSCC treated with metformin preoperatively. Metformin increased antitumorigenic cytokines ex vivo, including significant increases in perforin. Metformin increased HNSCC NK cell cytotoxicity and inhibited the CXCL1 pathway while stimulating the STAT1 pathway within HNSCC NK cells. Exogenous CXCL1 prevented metformin-enhanced NK cell-mediated cytotoxicity. Metformin-mediated NK cell cytotoxicity was found to be AMP-activated protein kinase independent, but dependent on both mechanistic target of rapamycin and pSTAT1.ConclusionsOur data identifies a new role for metformin-mediated immune antitumorigenic function through NK cell-mediated cytotoxicity and downregulation of CXCL1 in HNSCC. These findings will inform future immunomodulating therapies in HNSCC.

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