A phase 2 study of ibrutinib as neoadjuvant therapy in patients with localized prostate cancer

387

Background: Treatment of localized prostate cancer (PCa) with surgery or radiotherapy remains suboptimal with failure rates of 35-40%. Bruton’s Tyrosine Kinase (BTK) is seen elevated in PCa tissues compared to normal prostate tissue. Malignant B-cell density has been correlated with higher risk of aggressive PCa and mitigating that through the BTK has been proposed in mouse models. Ibrutinib is a potent BTK inhibitor which targets B-cell signaling pathways, has an established safety profile, and has been shown to inhibit in vivo prostate tumor growth pre-clinically. Therefore, we hypothesized that ibrutinib will augment anti-tumor immune responses through inhibiting tumor-intrinsic growth via blocking BTK B-cell signaling pathways, while also inducing favorable T-cell profiles in localized PCa. Methods: We performed a neoadjuvant clinical trial (NCT02643667) studying ibrutinib in PCa. Eligible patients had localized PCa with no prior treatment, and deemed suitable for undergoing a radical prostatectomy. Patients received 840mg/day oral ibrutinib for 28 days followed by a radical prostatectomy 7-12 days later. Patients were assessed 4 weeks after surgery. The primary objectives are to assess safety of ibrutinib and characterize B and T cell infiltration. Correlative pre- and post- treatment tissue and blood samples were collected; BTK and PD-L1 expression in tumor and immune-infiltrating immune cells will be examined, and BCR and TCR clonality and diversity will be evaluated. Results: 22 patients were registered and underwent treatment to date. 4 patients had early termination of ibrutinib treatment with 3 due to adverse effects and 1 due to discovery of surgically unresectable disease. A total of 21 of 22 patients received radical prostatectomies. There were no intra-operative complications attributed to ibrutinib. The treatment was generally well tolerated with 7.1% grade 3 treatment related adverse effects. 2% experienced a grade 4 treatment adverse effects of hepatic dysfunction. The most common grade 1-2 adverse effects were diarrhea (8.2%), fatigue (7.1%), and anemia (6.1%). The median follow-up time was 23.9 months. Median overall survival and median failure free survival have not been reached and the two-year milestone is 100%. Sample collection is complete and immune correlative analyses are ongoing. Safety/tolerability, clinical outcomes, and preliminary correlative data will be reported. Conclusions: This is the first clinical trial of ibrutinib in PCa, and lays the foundation for larger future studies. Clinical trial information: NCT02643667 .

Phase 2, randomized, double-blind trial of EC-18 versus placebo to mitigate the development and time course of oral mucositis from concomitant chemoradiation for head and neck cancer

12106

Background: Oral mucositis (OM) is a debilitating side effect of concomitant chemoradiotherapy (CRT) for head and neck cancer (HNC). EC-18 may effectively mitigate OM by minimizing the CRT-induced innate immune response. This Phase II, 2-stage trial evaluated safety, tolerability, and efficacy of EC-18 in reducing the duration, incidence, and trajectory of severe OM (SOM) in HNC patients. Methods: Patients (n = 105) with pathologically confirmed oral cavity, oropharynx, hypopharynx, or nasopharynx squamous cell cancers who received intensity-modulated radiation therapy (IMRT; with ≥ 55 Gy on ≥ 2 oral sites) and weekly or tri-weekly cisplatin were studied. In Stage 1, 24 patients were randomized (n = 6 per arm) to receive 500, 1000, or 2000 mg of EC-18, or placebo. Following independent Data Safety Monitoring Board review, 81 patients in Stage 2 received EC-18 2000 mg (n = 41) or placebo (n = 40) throughout CRT. WHO OM grade was assessed twice weekly during IMRT and then once weekly for up to 6 weeks post-IMRT. The primary efficacy endpoint was duration of SOM during the active and short-term follow-up (STFU) periods in the compliant per-protocol population (PP). Much of Stage 2 was conducted during peak periods of the COVID-19 pandemic which measurably impacted patient compliance relative to test medication dosing and planned radiation. Consequently, to assess efficacy most accurately, the PP population was analyzed (with at least 4 weeks of study drug dosing, minimum cumulative radiation of 55 Gy, 80% study drug compliance in the first 28 days of dosing, and without using not-allowed-therapy). Results: Patient demographics and baseline characteristics were balanced between groups. Adverse events (AEs) were comparable amongst cohorts without drug-related severe AEs. In the PP, the median duration of SOM from baseline through STFU was 0 day in the EC-18 group (n = 22) v 13.5 days in the placebo group (n = 20). SOM incidence through STFU (45.5% v 70%) and opioid use (time to onset: 32.3 v 26.0 days; and duration: 32.8 v 37.5 days) favored EC-18 v placebo. Results of the covariates analyses suggested that EC-18 favorably impacted SOM incidence in patients who experienced SOM treated with weekly low-dose cisplatin (n = 26; 37.5% v placebo 70.0%) and HPV+ tumors (n = 29; 35.3% v placebo 66.7%; Table). One-year long-term follow-up for tumor outcomes is ongoing. Conclusions: EC-18 safely mitigated the development and the time course of SOM in CRT-treated HNC patients. In addition, EC-18 may provide substantial benefits to subpopulations of HPV+ HNC patients treated with low dose cisplatin. Clinical trial information: NCT03200340. [Table: see text]

Phase I study of HFB200301, a first-in-class TNFR2 agonist monoclonal antibody in patients with solid tumors selected via Drug Intelligent Science (DIS)

TPS2670

Background: Tumor necrosis factor receptor-2 (TNFR2) is expressed on effector CD8+ T cells, CD4+ T cells, T regulatory cells, natural killer cells, and myeloid cells. Targeting TNFR2 is anticipated to yield effective anti-tumor immunity by stimulating T-cell and NK-cell activation and proliferation in the tumor microenvironment. HFB200301 is a first-in-class anti-TNFR2 agonistic monoclonal antibody that triggers both innate and adaptive immune stimulation by binding to a specific epitope on TNFR2. HFB200301 has demonstrated dose-dependent anti-tumor activity in human TNFR2 knock-in mice bearing MC38 and Hepa1-6 syngeneic tumors. Methods: HFB200301 is being evaluated in a first-in-human, open-label, multi-center, dose escalation and expansion study in adult patients with advanced solid tumors. A single-cell immune profiling platform, DIS, was deployed to identify unique tumor-infiltrating T cell signatures that could help optimize patient selection for HFB200301 treatment. It is hypothesized that the presence of an effector T cell subpopulation that express both TNFR2 and CD8A in solid tumors may represent a tumor microenvironment favorable to TNFR2 agonism. The following cancer indications have been identified based on the prevalence of a TNFR2 high/CD8 high signature: Epstein-Barr Virus positive (EBV+) gastric cancer, clear cell renal cell carcinoma (ccRCC), cutaneous melanoma, testicular germ cell tumor (TGCT), soft tissue sarcoma (STS), and PD-L1+ cancers: cervical cancer, pleural mesothelioma, lung adenocarcinoma, and head and neck squamous cell carcinoma (HNSCC). The escalation portion of the study explores increasing doses in cohorts of up to six patients, utilizing mTPI-2 design to determine recommended dose(s) for expansion (RDE(s)). Based on pharmacokinetic modeling to maximize HFB200301 activity, 60-minute intravenous infusions of HFB200301 are administered every 4 weeks. Once RDE(s) is determined, expansion into three indication-specific cohorts is planned to determine the recommended phase 2 dose (RP2D). Key eligibility criteria include histologically documented advanced or metastatic solid tumors in the above listed indications. Patient enrollment opened in February 2022 in the USA, with plans for additional clinical sites in Spain and China. The primary objective is to identify the RDE, characterize safety and tolerability of HFB200301, and determine RP2D. Secondary objectives include pharmacokinetic parameters, preliminary evidence of anti-tumor efficacy (e.g., ORR, DCR, DOR) and pharmacodynamic evaluation (e.g., T cell subsets) in the blood and in the tumor. Furthermore, a potential predictive biomarker signature derived based on the DIS single-cell immune profiling approach will be investigated retrospectively. Clinical trial information: NCT05238883.

A randomized phase II trial of cabozantinib combined with PD-1 and CTLA-4 inhibition in metastatic soft tissue sarcoma

TPS11583

Background: Soft tissue sarcomas (STS) are rare malignancies with poor prognosis in the metastatic setting. Current standard therapy includes anthracycline based chemotherapy. Cabozantinib is a multikinase inhibitor that has demonstrated efficacy in solid tumors such as renal cell carcinoma (RCC) and hepatocellular carcinoma (HCC). A phase II study of cabozantinib in advanced STS is underway. Cabozantinib in combination with immune checkpoint blockade has shown clinical benefit in several tumor types including HCC, RCC, non-small cell lung cancer, and urothelial carcinoma. Since cabozantinib may alter PD-1 expression in regulatory T-cells and promote an immune permissive environment, we hypothesize that combining cabozantinib with immune checkpoint inhibition is a therapeutic strategy that will be more effective than cabozantinib alone. Additionally, the design of the trial will allow assessment of whether pretreatment with cabozantinib will enhance the efficacy of nivolumab and ipilimumab alone. Methods: This is an open label, multicenter, randomized phase II clinical trial of cabozantinib (60mg orally daily as a single agent, 40mg in combination) with or without combination Ipilimumab (ipi, 1mg/kg IV every 3 weeks for 4 doses) and Nivolumab (nivo, 3mg/kg IV every 3 weeks for four doses, then 480mg IV every 4 weeks) in patients (pts) with unresectable or metastatic STS refractory to up to two lines of chemotherapy. 105 pts with non-translocation driven sarcomas will be enrolled at three US sites and randomized 2:1 to the combination group. Pts will be stratified by prior pazopanib use and balanced for histologies. Patients who progress on arm A will cross over to combination therapy (arm B). The primary efficacy endpoint is objective response rate (ORR) by RECIST 1.1. 35 patients in Cohort A (cabozantinib alone) and 70 patients in Cohort B (cabozantinib plus ipi/nivo) will be required to detect an increase of the ORR from 10% in cohort A to 30% in cohort B with 81% power with a one-sided alpha level of 10%. Key eligibility criteria include: at least 18 years of age, ECOG performance status of 0 or 1, ≤2 prior lines of therapy and measurable disease. Exclusion criteria include: translocation-driven sarcoma except alveolar soft part sarcoma (ASPS), prior immunotherapy, and chronic use of corticosteroids or other immunosuppression. Secondary endpoints are safety, overall and progression free survival, disease control rate, and response rate to ipilimumab and nivolumab after cabozantinib pretreatment. Mandatory tumor biopsies pre-treatment and at 6 weeks will be obtained. Peripheral blood will be collected for circulating immune phenotyping. Enrollment will occur at 3 participating institutions and is expected to be completed in 2022. Clinical trial information: NCT04551430.

Enhanced pathologic tumor response with two cycles of neoadjuvant pembrolizumab in surgically resectable, locally advanced HPV-negative head and neck squamous cell carcinoma (HNSCC)

6008

Background: We reported that one cycle of neoadjuvant pembrolizumab induced pathologic tumor response in >10% (pTR-any) and in >50% (pTR-2) of the resection bed in 44% and 22% of patients (pts) with surgically resectable HPV-negative, Stage III/IV HNSCC ( Clin Cancer Res 2020). We hypothesized that two cycles of neoadjuvant pembrolizumab would induce pTR-2 in 50% of pts. Increasing the pathologic response rate may favorably impact clinical outcomes. Methods: Multi-institutional phase 2 trial where pts with locally advanced, HPV-negative HNSCC received two cycles of pembrolizumab (200 mg), given 42 and 21 days prior to surgery. Resected tumor was analyzed by two independent pathologists for pTR (tumor necrosis and/or giant cell/histiocytic reaction to keratinous debris) in the resection bed (primary tumor and/or lymph nodes). Additional definitions: pTR-1 (>10-49%) and major pathologic response ( > 90%). The primary endpoint was pTR-2. A sample size of 26 pts was needed to detect a significantly higher pTR-2 rate of 50%, with 80% power using a one-sided alpha level of 0.05. Pts were followed for serious adverse events (AEs) for 30 days after surgery and for AEs of clinical interest for 90 days following the last dose of pembrolizumab. Pts underwent baseline blood collection and tumor biopsies to match with blood and surgical specimens obtained post-pembrolizumab. Planned correlatives included PD-L1 expression, immune function, and molecular signatures of activation in the pre- and post-treatment blood and tumor tissue. Results: Characteristics of 29 enrolled and treated pts were median age 62 (30-82) yrs, smoking history 62% (18 pts); clinical stage T2 (n = 6), T3 (n = 5), T4 (n = 18) and N0/1 (n = 17), N2 (n = 12). All treated patients received two cycles of neoadjuvant pembrolizumab, which was tolerated well with only one (3%) grade 3 AE (rash) and no grade 4 AEs. The primary endpoint was evaluable in 25 pts, and not evaluable in 4 pts (one pt withdrew before surgery and in three pts, pTR review was pending). pTR-2 occurred in 44% (11 of 25 pts), and 4 (16%) of these pts had a major pathologic response including 1 (4%) pathologic CR at the primary site. Conclusions: Two (vs one) cycles of neoadjuvant pembrolizumab resulted in a two-fold increase in the frequency of pTR-2 (44% vs 22%). These data imply that the frequency of pTR to neoadjuvant pembrolizumab can be improved by increasing the number of cycles and the treatment interval. Clinical trial information: NCT02296684.

Phase II trial of pegylated arginine deiminase in combination with gemcitabine and docetaxel for the treatment of soft tissue sarcoma

11508

Background: Soft tissue sarcoma (STS) is dependent on extracellular arginine as it often lacks expression of argininosuccinate synthase 1 (ASS1), the urea cycle enzyme needed to produce intracellular arginine. PEGylated arginine deiminase (ADI-PEG 20) is an extracellular arginine-degrading enzyme that causes ASS1 deficient tumors to enter the starvation state. Preclinical data demonstrated that addition of docetaxel (D) with ADI-PEG20 upregulates expression of the transporter for gemcitabine (G), overcoming transporter level resistance, and causing increased cell death. In vivo modeling demonstrated that the combination of ADI-PEG20 with G+D was superior to G+D alone. Therefore, we performed a phase 2 trial testing the addition of ADI-PEG20 to G+D. Methods: We performed an investigator-initiated, phase 2, multicenter, multi-arm clinical trial of ADI-PEG20 with G (90minute infusion)+D in STS, Ewing’s, osteosarcoma and small cell lung cancer. We are reporting Arm A, the STS arm. Eligible patients had STS that would be standardly treated with G+D that had progressed on at least one prior line of therapy with measurable disease by RECIST1.1 and had adequate organ function Based on a historic median PFS of 6.2 months for G+D, we targeted to enroll N = 75 patients in cohort A to detect a 2.8 month improvement with 80% power at a 5% alpha level. Primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), clinical benefit rate (CBR), safety, tolerability, cancer related mortality, and correlation with ASS1 expression by IHC. We evaluated PFS by Kaplan-Meier method and estimated overall response rate (ORR). Results: 75 patients were treated and deemed evaluable. The trial underwent two dose reductions by the data safety monitoring board due to prolonged neutropenia and thrombocytopenia preventing the use of day 8 G+D, consistent with preclinical mechanism of action data showing that ADI-PEG 20+D enhanced G uptake. Originally, the G dose was 900mg/m2 reduced first to 750mg/m2 then to 600mg/m2. D was dose reduced at the time of the second dose reduction from 75mg/m2 to 60mg/m2. ADI-PEG20 was given at a fixed intramuscular dose (36 mg/m2) weekly. The need for two dose reductions affected the PFS. The PFS/OS (months) were for the 600mg/m2 group (n = 31) was 6.0/N.D., leiomyosarcoma (LMS) (N = 33) 7.2/22.5, liposarcoma 5.1/17.4, and other (N = 36) 2.8/15.0. Responses were 8% complete (6/75) (3 LMS, 1 synovial and 2 angiosarcoma), 17% partial (13/75), and 43% stable disease (32/75), for an ORR of 25% (19/75) and CBR of 68% (51/75). There was a trend for ASS1 negative tumors to benefit more than ASS1 positive tumors. Conclusions: The combination of ADI-PEG20 with G+D can be safely and effectively given at a dose of 600mg/m2 G and 60mg/m2 D. Future randomized trials of ADI-PEG20 with G+D are planned. Clinical trial information: NCT03449901.

A phase II trial of sitravatinib, a multireceptor tyrosine kinase inhibitor, in patients with advanced well-differentiated/dedifferentiated liposarcoma

11513

Background: Well-differentiated/dedifferentiated liposarcoma (WD/DD LPS), a sarcoma of adipocytic origin, lacks effective treatment options for advanced disease. Pazopanib, a receptor tyrosine kinase (RTK) inhibitor active upon angiogenic RTKs, is approved for non-adipocytic sarcomas but failed to show activity in LPS. In a phase 2 study, pazopanib provided a progression-free rate at 12 weeks of 26% in LPS. Our preclinical work implicated IGF1R, MET, and PDGFRα/ß in liposarcomagenesis. Sitravatinib (S) is a novel, orally available, potent, small molecule RTK inhibitor active upon these and related targets. In preclinical WD/DD LPS models, S demonstrated significant activity in vitro and in vivo and appeared superior in efficacy to pazopanib, imatinib and crizotinib. Methods: We performed a phase II, single-arm, multi-center, Simon 2-stage study to evaluate S in adult pts with unresectable/metastatic WD/DD LPS who had received ≥ 1 prior line of systemic therapy and had evidence of disease progression ≤ 12 wks prior to enrollment. Pts received S 120 mg PO daily in continuous 21-day cycles. Primary endpoint was the progression-free rate at 12 wks (PFR12). Secondary endpoints were objective response rate (ORR), progression free survival (PFS) and safety/tolerability. Based upon historical controls, PFR12 ≤ 20% was considered inactive whereas PFR12 ≥ 40% was considered promising. If ≥ 3/13 met PFR12 in stage 1, the study proceeded to full accrual. If ≥ 9/29 met PFR12 overall, S was considered promising. Design provided 85% power with α= 0.10. A subset of pts underwent paired biopsies. Results: 29 pts initiated treatment and are evaluable. Median age was 62 yrs (range: 28-88). 16 (55%) were male. 28/29 had DD LPS. 3 pts remain on treatment and 26 pts have discontinued (22 for disease progression, 2 for adverse events). In the first stage, 5/13 pts met the PFR12 endpoint; therefore, the study proceeded to full accrual. Overall, 12/29 pts (41%) were progression-free at 12 weeks and the study met the primary endpoint. ORR by RECIST was 3.4%. Median PFS was 11.7 weeks (95% CI: 5.9 - 35.9 wks). 12/29 (41%) of pts experienced grade 3 treatment-related adverse events. Common S-related grade 3 AEs were hypertension (24%), fatigue (7%) and hyponatremia (7%). There were 2 grade 4 events (hypertension, reversible posterior leukoencephalopathy syndrome). Hypertension was easily managed with medication. A subset of pts underwent paired tumor biopsies that will be analyzed using next generation sequencing and reverse phase protein array. Conclusions: S met the predefined efficacy endpoint with 12/29 pts (41%) progression-free at 12 weeks, indicating clinically meaningful activity potentially superior to pazopanib. The drug was well tolerated. Further study of S in WD/DD LPS is warranted. Clinical trial information: NCT02978859.

Multicenter, open-label phase II study of daily oral regorafenib for chemotherapy-refractory, metastatic and locally advanced angiosarcoma

11561

Background: Angiosarcoma has a particularly poor prognosis with 5-year overall survival rates of approximately 30-40%. Treatment of locally advanced and metastatic angiosarcoma is inadequate. Data strongly suggest concurrent, potent inhibition of VEGFR and Tie2 represents an attractive therapeutic strategy in angiosarcoma. Regorafenib displays potent VEGFR and Tie2 receptor inhibition and also possesses activity against additional potential targets in angiosarcoma including PDGFRs, RAF, KIT and FGFR, amongst others. Methods: A multicenter phase II study of regorafenib in patients with locally advanced or metastatic angiosarcoma was conducted through the Midwest Sarcoma Trials Partnership. Adequate performance status, organ function, measurable disease (RECIST 1.1) and 1-4 prior therapies were required. Regorafenib 160 mg PO daily was given in 28-day cycles (21 days on, 7 days off) until disease progression (PD) or unacceptable toxicity. The primary endpoint was progression-free survival (PFS), assessed at 16 weeks. Secondary endpoints include overall response rate (ORR), clinical benefit rate (CBR), OS, and safety and tolerability. A Simon 2-stage design was used. Results: After final enrollment of the second stage, a total of 31 pts were enrolled at 6 sites, 23 are evaluable for response. Median age was 65 (range 30-91); 50% were female, 67.7% had metastatic disease. PFS at 4 months is 52.2% with a median PFS and OS of 3.55 and 11.4 months. 1 confirmed CR and 2 PR, 12 SD and 8 PD were observed. ORR and CBR are 14.29 and 65.2%, respectively. No uncommon grade 3-4 adverse events were observed. 6 pts were non-evaluable due to refusal of further therapy and 2 patients progressed prior to first evaluation. Conclusions: Regorafenib was well tolerated in this study of pretreated patients with angiosarcomas and met its primary endpoint with a median PFS > 45% at 4 months. Treatment was feasible and did not reveal any previously unreported toxicities. Efficacy outcomes were complicated by early withdrawals of patients. RECIST responses were encouraging and regorafenib has a clinically meaningful 4-month PFS. Clinical trial information: NCT02048722 .

A phase II study of ADI-PEG 20 in combination with gemcitabine and docetaxel for the treatment of soft tissue sarcoma

TPS11079

Background: The combination of gemcitabine (G) and docetaxel (D) is a standard second line therapy for soft tissue sarcoma (STS) with a modest response rate. Recent studies have looked to add agents to enhance response. We have shown that argininosuccinate synthase 1 (ASS1) expression is silenced in 88% of all sarcomas (n = 708) (Bean et al., 2016, Cell Death and Disease), and that this loss is associated with a reliance on extracellular sources of the amino acid arginine. The arginine depleting enzyme PEGylated arginine deiminase (ADI-PEG 20) depletes extracellular arginine. Preclinical studies have demonstrated that arginine starvation and D administration induce c-Myc-driven hENT1 surface expression overcoming intrinsic cell surface G transporter related resistance. To test this hypothesis, we opened this multi-institutional randomized phase II trial examining the safety and efficacy of ADI-PEG 20 with G + D in STS (NCT03449901) in July of 2018. Methods: Eligible patients are adults with metastatic or unresectable histologically or cytologically confirmed FNCLCC grade 2 or 3 STS that would be standardly treated with G and/or D. Patients are treated with ADI-PEG 20 at a dose of 36 mg/m2 via intramuscular injection on Day -7 of Cycle 1 and then on Days 1, 8, and 15 of each subsequent cycle. G will be given intravenously at a dose of 750 mg/m2 over 90 minutes on Days 1 and 8 and D will be given intravenously at a dose of 75 mg/m2 over 60 minutes on Day 8 of each cycle. The median PFS of metastatic sarcoma patients receiving the standard G + D treatment was estimated to be 6.2 months in a randomized phase II study (Maki et. al., 2007, JCO). With the addition of ADI-PEG 20, we target to improve the median PFS to 9 months, a 45.2% (2.8 months or 12 weeks) improvement in patients treated on G + D + ADI-PEG 20 against the null hypothesis median PFS of 6.2 months to achieve 80% power to detect the improvement in PFS at a 5% alpha level. Tumor specimens (pre- and post-ADI-PEG 20 during week -1) and blood are collected for correlative studies including metabolomics, pharmacodynamics, immunogenicity and ASS1 biomarkers. Quality of life will be measured using FACT-G7. Clinical trial information: NCT03449901.

Neoadjuvant pembrolizumab in surgically resectable, locally advanced HPV negative head and neck squamous cell carcinoma (HNSCC)

6012

Background: Pembrolizumab has efficacy in metastatic HNSCC. We hypothesized that treatment intensification in surgically resectable HPV-negative, Stage III/IV HNSCC with neoadjuvant plus post-operative adjuvant (POA) pembrolizumab would be safe and reduce 1-year locoregional recurrence/distant metastases (LRR/DM) from 35% (historical: Cooper and Bernier NEJM 2004) to 15%. Methods: Phase II trial where all eligible patients received 1 dose of pembrolizumab (200 mg) prior to surgery and only those with high-risk pathologic features (HRPF: extracapsular extension/positive margin) were given POA cisplatin and radiation followed by pembrolizumab. PD-L1 staining was assessed by immunohistochemistry (9A11 antibody). Results: The study continues to enroll. Characteristics of 21 enrolled patients (pts) were median age 59 (32-87) yrs, tobacco use 81% (17 pts), clinical T2 (n = 2), T3 (n = 1), T4 (n = 18), and cN0/1 (n = 8), cN2 (n = 13). Preliminary analyses revealed five important findings: 1) No serious study drug-related AEs or unexpected surgical delays/complications, 2) No LRR/DM events in the first 10 patients with > 1-year follow-up after surgery 3) HRPF rate of 38% (95% CI: 18%-62%) (expected: 80%), 4) 43% of pts (95% CI: 22%-66%) with pathologic treatment response to neoadjuvant pembrolizumab (definition: tumor necrosis and/or giant cell/histiocytic reaction to keratinous debris in > 10% of tumor area), and 5) 48% of pts (95% CI:26%-70%) with clinical-to-pathologic downstaging. Pathologic treatment effect (TE) in ≥ 70% of the resected tumor or lymph node tissue area occurred in 6/21 pts (29%). Baseline tumor biopsies were PD-L1 positive ( > 1% of tumor cells) in 11/19 (58%) evaluable samples and in 7/8 (88%) evaluable pathologic responders. A significant correlation existed between baseline PD-L1 expression on tumor cells and pathologic treatment effect in the tumor (correlation coefficient: 0.72 and p = 0.0005). Conclusions: Neoadjuvant and adjuvant pembrolizumab was safe and well tolerated. We observed several lines of evidence supporting an anti-tumor effect in these pts with a single dose of pre-operative pembrolizumab. Further evaluation of this strategy is warranted. Clinical trial information: NCT02296684.