Inclusion Criteria:

- ≥ 18 years at time of consent

- If a sexually active male or a sexually active female of child-bearing potential,
agrees to use a highly effective form of contraception (including birth control
pills, barrier device, or intrauterine device)from the time of consent 90 days
following the last dose of study drug

- If female of child-bearing potential, negative pregnancy test

- For Phase 1: must have histologically or cytologically-confirmed advanced cancer that
is BRAF mutation-positive (V600E or V600K) for which there is no remaining standard
therapy with curative potential. Patients must have disease sites amenable to biopsy.
For Phase 2: must have histologically or cytologically-confirmed BRAF
mutation-positive (V600E or V600K) advanced (defined as unresectable Stage IIIC or
IV) melanoma that has not been treated with a selective BRAF inhibitor

- For Phase 1: must have measurable or non-measurable disease. For Phase 2: must have
measurable disease per RECIST 1.1

- For Phase 1: no restriction on number of prior therapy regimens. For Phase 2: the
following restrictions on prior therapy apply: 1) must not have been treated with a
selective BRAF inhibitor and must not have had more than 2 prior treatment regimens
for advanced metastatic disease; 2) must have completed prior cytotoxic chemotherapy
a minimum of 4 weeks prior to starting PX-866 and/or vemurafenib (except for BCNU
and/or mitomycin C, which must have been completed a minimum of 6 weeks prior to
starting therapy). Prior biologic therapy and localized radiation therapy must have
been completed a minimum of 2 weeks prior to starting therapy.

- All toxicities related to prior cancer therapies other than alopecia must have
resolved to Grade 1 or less

- Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

- In the opinion of the clinical investigator, life expectancy > 3 months

- Adequate hematologic function

- Adequate hepatic function

- Serum creatinine < 2.0 mg/dL

- Adequate cardiac function

- Corrected QTc must be <480 milliseconds

Exclusion Criteria:

- May not be receiving any other investigational agents

- Active central nervous system (CNS) metastases are excluded. Patients with a history
of CNS metastasis, who have been treated prior to enrollment, must be stable for
eight weeks after completion of treatment. These patients must have undergone
appropriate imaging studies and currently be on a stable, lowest possible dose of
steroids

- History of allergic reactions attributed to compounds of similar chemical or biologic
composition to PX-866 or vemurafenib

- Uncontrolled intercurrent illness including, but not limited to: ongoing or active
infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac
arrhythmia, or psychiatric illness/social situations that would limit compliance with
study requirements

- Uncorrectable electrolyte abnormalities or long QT syndrome

- Poorly controlled diabetes mellitus

- Pregnant, breastfeeding, or planning to become pregnant

- Known to be human immunodeficiency virus (HIV)-positive

- Inability to swallow pills

- Previous treatment with a phosphatidylinositol-3-kinase (PI-3K) inhibitor

- Any other significant medical or psychiatric condition that in the opinion of the
investigator renders the patient inadequate for participation