Repurposing pantoprazole in combination with systemic therapy in advanced head and neck squamous cell carcinoma: a phase I/II randomized study.

Pantoprazole decreases the acidity of the tumor microenvironment by inhibiting proton pumps on the cancer cell. This possibly leads to increased sensitivity to cytotoxic therapy. We conducted a phase I/II randomized controlled trial in adult patients with head and neck squamous cell carcinoma (HNSCC) planned for first-line palliative chemotherapy. Patients were randomized to chemotherapy + / - intravenous (IV) pantoprazole. The primary endpoint in phase I was to determine the maximum safe dose of intravenous pantoprazole, whereas it was progression-free survival (PFS) in phase II. The dose of IV pantoprazole established in phase I was 240 mg. Between Nov'18 and Oct'20, we recruited 120 patients in phase II, 59 on pantoprazole and 61 on the standard arm. Median age was 51 years (IQR 43-60), 80% were men. Systemic therapy was IV cisplatin in 22% and oral-metronomic-chemotherapy (OMC) in 78%. Addition of pantoprazole did not prolong PFS, which was 2.2 months (95% CI 2.07-3.19) in the pantoprazole arm and 2.5 months (95% CI 2.04-3.81, HR, 1.14; 95% CI 0.78-1.66; P = 0.48) in the standard arm. Response rates were similar; pantoprazole arm 8.5%, standard arm 6.6%; P = 0.175. Overall survival was also similar; 5.6 months (95% CI 4.47-8.51) in the pantoprazole arm and 5.4 months (95% CI 3.48-8.54, HR 1.06; 95% CI 0.72-1.57; P = 0.75) in the standard arm. Grade ≥ 3 toxicities were similar. Thus, pantoprazole 240 mg IV added to systemic therapy does not improve outcomes in patients with advanced HNSCC.