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.