This study will have two parts:
Phase I - During this part, also called the dose de-escalation part, an initial group of 6 participants will receive a certain planned dose of binimetinib in addition to a standard dose of pembrolizumab. If this combination is found to be safe during the first 28 days of receiving the study drugs, this will be considered the most appropriate dose of the study drug combination (the highest dose of binimetinib that can be given with pembrolizumab without causing serious side effects).
Phase Ib - Once the appropriate dose of binimetinib is confirmed in Phase I (as described above), additional participants will be enrolled in the Phase Ib to further test how safe, tolerable, and effective the study drugs at that dose level. Phase Ib will also evaluate the anti-tumour activity of binimetinib and pembrolizumab in participants with advanced non-small cell lung cancer.