Inclusion Criteria:

          -  Patients must have advanced or metastatic NSCLC or cutaneous melanoma

          -  Presence of KRAS or BRAF mutation (NSCLC) or NRAS mutation (cutaneous melanoma) in
             tumor tissue

          -  All patients participating in this clinical trial must have progressed following
             standard therapy or, in the opinion of the Investigator, no effective standard therapy
             exists, is tolerated, appropriate or is considered equivalent to study treatment.

          -  ECOG (Eastern Cooperative Oncology Group) performance status ≤ 2

        Exclusion Criteria:

        -Dose expansion - KRAS or NRAS mutant patients groups: Prior treatment with a RAFi
        (including any BRAFi and pan-RAFi), MEKi and/or ERKi. (Patients with KRAS mutant NSCLC with
        prior G12C inhibitor treatments are also excluded in the LXH254+trametinib expansion part).
        BRAF mutant patients group: Prior treatment with any EGFR, ALK, ROS1, KRAS, RAF (both
        BRAFV600 selective and pan-RAF), MEK1/2 and/or ERK1/2 inhibitors (for patients with BRAF
        V600 mutant NSCLC, prior treatments with BRAF and MEK1/2 inhibitors are allowed).

        Patients who have received more than 3 lines of anti-cancer therapy are excluded.

          -  History or current evidence of retinal vein occlusion (RVO) or current risk factors
             for RVO.

          -  Any medical condition that would, in the investigator's judgment, prevent the
             patient's participation in the clinical study due to safety concerns or compliance
             with clinical study procedures.

          -  Patients receiving proton pump inhibitors (PPI) which cannot be discontinued 3 days
             prior to the start study treatment and for the duration of the study.

          -  Patients with Gilbert's syndrome or other heritable diseases of bile processing.

        Other protocol-defined inclusion/exclusion criteria may apply