A phase I/IB trial of binimetinib in combination with erlotinib in NSCLC harboring activating KRAS or EGFR mutations

Activating mutations in EGFR or KRAS are highly prevalent in NSCLC, share activation of the MAPK pathway and may be amenable to combination therapy to prevent negative feedback activation.In this phase 1/1B trial, we tested the combination of binimetinib and erlotinib in patients with advanced NSCLC with at least 1 prior line of treatment (unless with activating EGFR mutation which could be treatment-naïve). A subsequent phase 1B expansion accrued patients with either EGFR- or KRAS-mutation using the recommended phase 2 dose (RP2D) from Phase 1. The primary objective was to evaluate the safety of binimetinib plus erlotinib and establish the RP2D.43 patients enrolled (dose-escalation = 23; expansion = 20). 17 harbored EGFR mutation and 22 had KRAS mutation. The RP2D was erlotinib 100 mg daily and binimetinib 15 mg BID × 5 days/week. Common AEs across all doses included diarrhea (69.8%), rash (44.2%), fatigue (32.6%), and nausea (32.6%), and were primarily grade 1/2. Among KRAS mutant patients, 1 (5%) had confirmed partial response and 8 (36%) achieved stable disease as best overall response. Among EGFR mutant patients, 9 were TKI-naïve with 8 (89%) having partial response, and 8 were TKI-pretreated with no partial responses and 1 (13%) stable disease as best overall response.Binimetinib plus erlotinib demonstrated a manageable safety profile and modest efficacy including one confirmed objective response in a KRAS mutant patient. While clinical utility of this specific combination was limited, these results support development of combinations using novel small molecule inhibitors of RAS, selective EGFR- and other MAPK pathway inhibitors, many of which have improved therapeutic indices.NCT01859026.