BackgroundSingle-agent MEK1/2 inhibition has been disappointing in clinical trials targeting RAS mutant (MT) cancers, probably due to upstream receptor activation, resulting in resistance. We previously found that dual c-MET/MEK1/2 inhibition attenuated RASMT colorectal cancer (CRC) xenograft growth. In this study, we assessed safety of MEK1/2 inhibitor PD-0325901 with c-MET inhibitor crizotinib and determined the optimal biological doses for subsequent clinical trials.MethodsIn this dose-escalation phase I trial, patients with advanced solid tumours received PD-0325901 with crizotinib, using a rolling-6 design to determine the maximum tolerable dose (MTD) and safety/tolerability. Blood samples for pharmacokinetics and skin biopsies were collected.ResultsTwenty-five patients were recruited in 4 cohorts up to doses of crizotinib 200 mg B.D continuously with PD-0325901 8 mg B.D, days 1-21 every 28 days. One in six patients exhibited a dose-limiting toxicity at this dose level. Drug-related adverse events were in keeping with single-agent toxicity profiles. The best clinical response was stable disease in seven patients (29%).ConclusionsPD-0325901/crizotinib can be given together at pharmacologically-active doses. The MTD for PD-0325901/crizotinib was 8 mg B.D (days 1-21) and 200 mg B.D continuously in a 28-days cycle. The combination was further explored with an alternate MEK1/2 inhibitor in RASMT CRC patients.EudraCT-Number2014-000463-40