Efficacy of pembrolizumab and vorinostat combination in patients with recurrent and/or metastatic squamous cell carcinomas: a phase 2 basket trial.

Immune checkpoint inhibitors improve the treatment of many solid tumors and have shown encouraging results in advanced squamous cell carcinoma (SCC), yet only a minority of patients respond to immune checkpoint inhibitor monotherapy. We conducted the PEVOsq trial, an open-label, nonrandomized, multicenter, basket phase 2 trial to evaluate the combination of pembrolizumab and vorinostat in recurrent/metastatic SCC of various origins. The primary endpoint was the objective response rate (ORR) in each tumor cohort during treatment as per the investigators' assessment. Secondary endpoints included safety and antitumor activity evaluation in terms of centrally confirmed ORR, progression-free survival, overall survival and duration of response. In the efficacy population (n = 107), the ORR was met in cervical (39%), anal (31%) and vulvar/vaginal (19%) cancer cohorts, but not in head and neck SCC (19%) or penile (18%) cancer cohorts (overall ORR = 26%). Median progression-free survival was 4.0 months (95% confidence interval: 2.6-4.3), and median overall survival was 11.1 months (95% confidence interval: 9.2-17.4). In the safety population, 101 (91%) of 111 patients developed at least one treatment-related adverse event, with 39% and 5.4% of patients experiencing at least one grade 3 and grade 4 treatment-related adverse event, respectively. Vorinostat-related toxicity prompted a dose reduction/interruption in 66% of patients. Whole-exome sequencing analyses revealed several potential predictive biomarkers of response to treatment. Further studies in a larger number of patients are required to validate these findings. ClinicalTrials.gov identifier: NCT04357873 .