Key inclusion criteria for Arm 1,2,3,4:

          -  Histologically confirmed unresectable or metastatic stage IIIB/C/D or IV melanoma
             using AJCC edition 8

          -  Previously treated for unresectable or metastatic melanoma:

          -  Subjects with V600BRAF wild-type disease must have received prior systemic therapy for
             unresectable or metastatic melanoma with anti-PD-1/PD-L1. Additionally, subjects may
             have received anti-CTLA-4 as a single agent or in combination with anti-PD-1/PD-L1,
             irrespective of the sequence. No additional systemic treatment is allowed for advanced
             or metastatic melanoma.

        A maximum of two prior lines of systemic therapies for unresectable or metastatic melanoma
        are allowed.

        The last dose of prior therapy (anti-PD-1, anti-PD-L1 or anti-CTLA-4) must have been
        received more than four weeks before randomization.

          -  Subjects with V600BRAF mutant disease must have received prior systemic therapy for
             unresectable or metastatic melanoma with anti-PD-1/PD-L1, and V600BRAF inhibitor.
             Additionally, subjects may have received anti-CTLA-4 as a single agent or in
             combination with anti-PD-1/PD-L1, or MEK inhibitor (in combination with V600BRAF
             inhibitor or as a single agent), irrespective of the sequence. No additional systemic
             treatment is allowed for advanced or metastatic melanoma .

        A maximum of three prior lines of systemic therapies for unresectable or metastatic
        melanoma are allowed.

        The last dose of prior therapy must have been received more than 4 weeks (for anti-PD-1,
        anti-PD-L1 or anti-CTLA-4) or more than 2 weeks (for V600BRAF or MEK inhibitor) prior to
        randomization.

          -  All subjects (with V600BRAF wild-type disease and with V600BRAF mutant disease) must
             have documented disease progression as per RECIST v1.1 while on/after the last therapy
             received prior to study entry and while on/after treatment with anti-PD1/PD-L1. The
             last progression must have occured within 12 weeks prior to randomization in the
             study.

          -  ECOG performance status 0-2

          -  At least one measurable lesion per RECIST v1.1

          -  At least one lesion, suitable for sequential mandatory tumor biopsies (screening and
             on-treatment) in accordance with the biopsy guidelines specified in protocol. The same
             lesion must be biopsied sequentially.

          -  Screening tumor biopsy must fulfill the tissue quality criteria outlined in the
             protocol, as assessed by a local pathologist

        Key inclusion criteria for Arm 1A:

          -  Histologically confirmed unresectable or metastatic stage IIIB/C/D or IV melanoma
             according to AJCC Edition 8

          -  Previously treated for unresectable or metastatic melanoma:

               -  All subjects must have received anti-PD-1 checkpoint inhibitor therapy (ie.
                  pembrolizumab or nivolumab) either as monotherapy or in combination with
                  ipilimumab as the last systemic therapy prior to enrollment and must have
                  confirmed disease progression as per RECIST v1.1 (confirmed on a subsequent scan,
                  which can be the scan performed during screening) while on or after this therapy
                  prior to enrollment.

               -  Subjects with V600BRAF wild-type disease must have received no more than 2 prior
                  systemic therapies including prior anti-PD-1/PD-L1 (as monotherapy or in
                  combination with ipilimumab)

               -  Subjects with V600BRAF mutant disease must have received no more than 3 prior
                  systemic therapies including anti-PD-1/PD-L1 (as monotherapy or in combination
                  with ipilimumab), and V600BRAF inhibitor (as monotherapy or in combination with a
                  MEK inhibitor)

               -  The last dose of anti-PD-1 based therapy must have been received more than four
                  weeks prior to first dose of study treatment.

               -  The last documented disease progression must have occurred within 12 weeks prior
                  to first dose of study treatment

               -  No additional systemic treatment is allowed for advanced or metastatic melanoma
                  (this includes for example tumor infiltrating lymphocyte therapy)

          -  ECOG performance status 0-1

          -  At least one measurable lesion per RECIST v1.1

          -  Subjects must have baseline tumor sample that is positive for LAG-3 per central
             assessment

        Key exclusion criteria common to all combination arms:

          -  Subjects with uveal or mucosal melanoma

          -  Presence of clinically active or unstable brain metastasis at time of screening.

          -  Use of any live vaccines against infectious diseases within 3 months before
             randomization/enrolment.

          -  Active infection requiring systemic antibiotic therapy at time of
             randomization/enrolment.

          -  Subjects with a condition requiring systemic treatment with either corticosteroids
             (>10 mg daily prednisone equivalent) or other immunosuppressive medications within 14
             days of randomization/enrollment. Inhaled or topical steroids, and adrenal replacement
             steroid doses >10 mg daily prednisone equivalent, are permitted in the absence of
             active autoimmune disease.

          -  Active, known or suspected autoimmune disease or a documented history of autoimmune
             disease.

          -  Prior allogenic bone marrow or solid organ transplant

          -  History of known hypersensitivity to any of the investigational drugs used in this
             study

          -  Prior systemic therapy for unresectable or metastatic melanoma with any
             investigational agent, or with any other agent except anti-PD-1/PD-L1 and anti-CTLA-4
             (and V600BRAF and MEK inhibitors if subject has V600BRAF mutant disease). Prior
             neoadjuvant and/or adjuvant therapy for melanoma completed less than 6 months before
             the start of the study treatment

          -  Medical history or current diagnosis of myocarditis

          -  Cardiac Troponin T (or Troponin I) level > 2 x ULN at screening