The Effects of Treatment With Vemurafenib on the Immune System in Advanced Melanoma

Approximately 40-60 % of cutaneous melanomas select for a mutation in the BRAF protein which
is part of a signaling pathway called the Mitogen Activated Protein Kinase (MAPK) pathway.
Over 90% of mutations in BRAF occur at position V600 with the most common being a V600E
mutation. Mutation at position V600 of BRAF activates the MAPK pathway which facilitates
melanoma proliferation and growth. The response rate to treatment with vemurafenib in
patients with stage IV melanoma expressing a V600E BRAF mutation is approximately 50%. A
phase III study comparing first line treatment with vemurafenib compared to standard
dacarbazine chemotherapy demonstrated a statistically significant overall survival benefit
in this patient population. Based on this survival benefit vemurafenib was FDA approved for
treatment of stage IV melanoma expressing a V600E BRAF mutation. Vemurafenib is administered
at a dose of 960 milligrams orally twice daily.

While targeting BRAF can lead to survival benefits in patients with melanoma expressing BRAF
mutation it is becoming increasingly apparent that the immune system is important in
modulating the growth of melanoma. As such there are immune therapies FDA approved for the
treatment of stage IV melanoma including ipilimumab which confers an overall survival
benefit by activating the immune system through inhibition of the CTLA-4 protein expressed
on certain T-cells. Little is known about how the exposure of different classes of immune
cells to vemurafenib modulates the activity of the immune system. We do know that many
melanomas express differentiation antigens which could potentially be recognized by the
immune system. This recognition could potentially be utilized in the development of novel
immunotherapeutic treatment approaches. The pharmacologic inhibition of the MAPK pathway
does lead to increased expression of various melanoma differentiation antigens along with
improved recognition by antigen-specific T-lymphocytes. Evaluation of a limited number of
tumor biopsy specimens suggest that the infiltration of melanomas by CD4+ and CD8+
T-lymphocytes markedly increases following treatment with a BRAF inhibitor. Furthermore the
viability and function (determined using assays for cytokine release assays and cytotoxic
activity) of T-lymphocytes was not negatively affected by exposure to vemurafenib at
concentrations known to cause anti-tumor effects.

The MAPK pathway is a pathway utilized by many cell types including immune cells and cells
in the tumor microenvironment. As such vemurafenib could potentially modulate the activity
of the MAPK pathway in the melanoma cells, immune cells, and components of the tumor
microenvironment. Effects of vemurafenib on tumor cells may directly lead to changes in
antigen presentation and effects on the innate and adaptive immune systems could potentially
alter recognition of tumor cells and modulate positively or negatively immune recognition
and antitumor activity. Therefore, a better understanding of immune modulation induced by
anti-BRAF therapy should provide data to model and develop in a more rational fashion
therapies which combine BRAF targeted and immune modulatory agents potentially using such
agents as ipilimumab or anti-PD1 or anti-PDL1 antibodies.

Inclusion Criteria:

- Histologically confirmed stage IV or unresectable stage III melanoma with documented
BRAF V600 mutation

- Age > 18 years

- ECOG Performance Status 0,1, or 2

- Measurable disease by RECIST v1.1

- Adequate organ function: Hemoglobin > 9 g/dl, ANC> 1.5 x 109/L, platelets > 100 x
109/L, AST and ALT < 2.5 x upper limit of normal, bilirubin < 1.5 x upper limit
normal, Cr < 1.5 x upper limit normal

- Adequate recovery from prior systemic or local melanoma therapy. No systemic
anticancer therapy in the 4 weeks and no ipilimumab in the 6 weeks from planned
vemurafenib administration. No radiation therapy in 2 weeks prior to date plan to
initiate vemurafenib treatment and no surgery in 3 weeks prior to date of planned
vemurafenib administration.

- Agreement for females of childbearing potential use 2 acceptable methods
contraception. Men with female partners of childbearing potential must agree to use
of latex condom and advise female partner to use additional method contraception
during the study and 6 months after discontinuation of vemurafenib

- Negative serum or urine pregnancy test within 7 days prior to and including the
morning of day -7 (first potential day of research blood draw and tumor biopsy)

- Agreement not to donate blood or blood products or to donate sperm during the study
and for at least 6 months after discontinuation of vemurafenib.

Exclusion Criteria:

- Prior vemurafenib treatment

- Use of oral or intravenous corticosteroids or other immunosuppressive medications
such as cyclosporine or azathioprine. Subjects must not have received any systemic
immunosuppressive drug such as corticosteroids for at least 2 weeks prior to study
entry. Maintenance inhaled corticosteroids for controlled asthma or COPD or
maintenance systemic steroids to correct autoimmune endocrinopathy due to prior
ipilimumab treatment is allowed as is the use of topical steroids and
anti-inflammatory eye drops.

- Symptomatic CNS metastases requiring steroid use.

- No active second malignancy

- Pregnant or breast feeding

- Mean QTc interval > 450 (triplicate ECGs) or history congenital prolonged QT interval

- Any of the following within 3 months prior to study drug administration: myocardial
infarction, unstable angina, symptomatic congestive heart failure, cerebrovascular
accident or transient ischemic attack, or pulmonary embolism

- Inability to swallow pills

- Ongoing cardiac dysrhythmia >2 (per NCI CTCAE, v4.0)

- Unwillingness to practice birth control

- Inability to comply with requirements of the protocol

- Uncontrolled medical illness such as infection requiring intravenous antibiotics.

- Known allergy to treatment medication (vemurafenib)

- Known active or chronic infection with HIV.