Inclusion Criteria:

          -  All patients participating in this clinical trial must have progressed following
             standard therapy, or for whom, in the opinion of the Investigator, no effective
             standard therapy exists, is tolerated or appropriate.

          -  Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1

          -  Presence of at least one measurable lesion according to RECIST v1.1.

          -  Documented MAPK alteration

        Additional inclusion criteria for the Dose Expansion part: LXH254 in combination with
        PDR001:

          -  Patients with confirmed KRAS-mutated NSCLC

          -  Patients with confirmed NRAS-mutated melanoma (cutaneous melanoma only)

        Exclusion Criteria:

        - Prior treatment with a BRAFi, MEKi and/or pan-RAF inihibitors for patients to be enrolled
        in the dose expansion part.

        Exceptions may be made after documented agreement between Novartis and Investigator.

          -  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 which cannot be discontinued 3 days prior to
             the start study treatment and for the duration of the study.

          -  Pregnant or nursing (lactating) women

        Additional exclusion criteria for LXH254 in combination with PDR001

          -  History of severe hypersensitivity reactions, which in the opinion of the investigator
             may cause in increased risk of serious infusion reaction.

          -  Known human immunodeficiency virus (HIV).

          -  Any positive test for hepatitis B virus or hepatitis C virus indicating acute or
             chronic infection.

          -  Active, known or suspected autoimmune disease.

          -  Active infection requiring systemic antibiotic therapy

          -  Patients requiring systemic steroid therapy or any immunosuppressive therapy
             (≥10mg/day prednisone or equivalent) which cannot be discontinued at least 7 days
             prior to first dose of study treatment.

          -  Use of any live vaccines against infectious diseases within 4 weeks of initiation of
             study treatment.

        Other inclusion/exclusion criteria as per protocol may apply.