Phase I trial of copanlisib, a selective PI3K inhibitor, in combination with cetuximab in patients with recurrent and/or metastatic head and neck squamous cell carcinoma.

Background The phosphatidylinositol-3 kinase pathway is often altered in head and neck squamous cell carcinoma (HNSCC), and is involved in the resistance to EGFR inhibitors. Objective We investigated the dose-limiting toxicities (DLTs), maximum tolerated dose, pharmacokinetics, and preliminary efficacy of the combination of copanlisib, an intravenous, pan-class I PI3K inhibitor, with the anti-EGFR monoclonal antibody cetuximab in recurrent and/or metastatic HNSCC patients in a phase I dose-escalation trial. Patients and methods Copanlisib was given intravenously on days 1, 8, and 15 of 28-day cycles at the dose of 45 mg and 30 mg, in combination with standard doses of weekly cetuximab (400 mg/m2 loading dose followed by 250 mg/m2 on days 8, 15, and 22, and weekly thereafter). Results Three patients received copanlisib 45 mg, of whom two experienced grade 3 hyperglycemia during Cycle 1 that met the DLT criteria. Eight patients were then treated with copanlisib at the dose of 30 mg. Because of the occurrence of hyperglycemia, a premedication with metformine was introduced on the day of the injections. No DLTs were reported at this dose level. The trial was stopped early because of the unfavourable toxicity profile of the combination. Among eight evaluable patients for response, four patients (50%) had disease stabilization according to RECIST1.1 as best response. Conclusion Copanlisib combined with cetuximab demonstrated unfavorable toxicity and limited efficacy in heavily pretreated recurrent and/or metastatic HNSCC patients.Trial registration NCT02822482, Date of registration: June 2016.