A Phase III Randomized, Open-label Study Comparing GSK1120212 to Chemotherapy in Subjects With Advanced or Metastatic BRAF V600E/K Mutation-positive Melanoma

Inclusion Criteria:

- ≥18 years of age

- Stage III unresectable (Stage IIIc) or metastatic (Stage IV) cutaneous melanoma which
is also determined to be BRAF V600E/K mutation-positive by the central laboratory

- Received no prior treatment or up to one prior regimen of chemotherapy for advanced
or metastatic melanoma. Prior treatment with immunotherapy (with the exception of
prior ipilimumab, which is only allowed if given in the adjuvant setting), cytokine
therapy, biological or vaccine regimen is permitted. Prior use of sorafenib is
allowed

- Measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST
1.1)

- Women of childbearing potential and men with reproductive potential must agree to use
effective contraception during the study. Additionally women of childbearing
potential must have a negative serum pregnancy test within 14 days prior to
randomization

- Eastern Cooperative Oncology Group (ECOG) Performance Status of 0-1

- Adequate screening organ function

Exclusion Criteria:

- Any prior use of BRAF inhibitors or MEK inhibitors.

- Subjects who have received dacarbazine or paclitaxel prior to randomization will not
be eligible to receive the same chemotherapy as study medication (i.e. a subject who
received prior dacarbazine cannot receive dacarbazine on this trial and would thus
receive paclitaxel if randomized to the control arm)

- History of another malignancy. Exception: Subjects who have been disease-free for 3
years, or subjects with a history of completely resected non-melanoma skin cancer or
successfully treated in situ carcinoma are eligible. Subjects with second
malignancies that are indolent or definitively treated may be enrolled. Consult GSK
Medical Monitor if unsure whether second malignancies meet requirements specified
above

- Known Human Immunodeficiency Virus (HIV), Hepatitis B Virus (HBV), or Hepatitis C
Virus (HCV) infection (with the exception of chronic or cleared HBV and HCV infection
which will be allowed)

- Brain metastases with the following exceptions that are ALL confirmed by the GSK
Medical Monitor:

All known lesions must be previously treated with surgery or stereotactic radiosurgery,
and Brain lesion(s), if still present, must be confirmed stable (i.e. no increase in
lesion size) for ≥90 days prior to randomization (must be documented with two consecutive
MRI or CT scans using contrast), and asymptomatic with no corticosteroids requirement for
≥ 30 days prior to randomization, and no enzyme-inducing anticonvulsants for ≥ 30 days
prior to randomization

- History or evidence of cardiovascular risk including any of the following:

- QTcB ≥ 480 msec.

- History or evidence of current clinically significant uncontrolled arrhythmias.
Exception: Subjects with controlled atrial fibrillation for >30 days prior to
randomization are eligible

- History of acute coronary syndromes (including myocardial infarction and
unstable angina), coronary angioplasty, or stenting within 6 months prior to
randomization.

- History or evidence of current ≥ Class II congestive heart failure as defined by
New York Heart Association

- History of interstitial lung disease or pneumonitis

- History or current evidence / risk of retinal vein occlusion (RVO) or central serous
retinopathy (CSR):

- History of RVO or CSR, or predisposing factors to RVO or CSR (e.g. uncontrolled
glaucoma or ocular hypertension, uncontrolled hypertension, uncontrolled
diabetes mellitus, or history of hyperviscosity or hypercoagulability
syndromes).

- Visible retinal pathology as assessed by ophthalmic exam that is considered a
risk factor for RVO or CSR such as:

- Evidence of new optic disc cupping.

- Intraocular pressure > 21 mm Hg as measured by tonography