This clinical trial combined pembrolizumab and vorinostat in recurrent/metastatic squamous cell carcinomas of the head and neck (HN), and salivary gland cancer (SGC). Patients with progressing incurable HN and SGC, Eastern Cooperative Oncology Group (ECOG) ≤1, no prior immunotherapy, RECIST1.1 measurable disease, and normal organ function were eligible. Pembrolizumab 200 mg was given intravenous every 21 days, and vorinostat 400 mg given orally 5 days on and 2 days off during each 21-day cycle.

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... Primary endpoints were safety and objective response rates. From November 2015 to August 2017, 25 patients with HN and 25 SGC were enrolled. Median age was 61 (range, 33-86) years, 39 (78%) were male, 21 (62%) were never smokers, and 27 (54%) had ECOG 0. In HN, 13 (52%) were p16+ oropharynx. Most common SGC histologies were adenoid cystic 12 (48%), acinic cell 3 (12%), and mucoepidermoid 3 (12%). Adverse events (AEs) in all patients were: 27 (54%) with grade ≥ 1 and 18 (36%) with grade ≥ 3. The most common AEs in all patients were renal insufficiency in seven, (14%), fatigue in six, (12%), and nausea in three (6%). There were three (12%) deaths on study. Responses in HN were complete response (CR) 0, partial response (PR) eight (32%), and stable disease (SD) five (20%). Efficacy in SGCs was CR 0, PR four (16%) in one lymphoepithelioma-like carcinoma, two acinic cell, one adenoid cystic, and SD 14 (56%). In the HN group, median follow-up (mFUP) was 12.6 months, median overall survival (mOS) was 12.6 months, and median progression-free survival (mPFS) was 4.5 months. In SGC, mFUP was 13.1 months, mOS was 14.0 months, and mPFS was 6.9 months. This combination demonstrated activity in HN, with fewer responses in SGC. Toxicities were higher than reported with pembrolizumab alone.