Dabrafenib With or Without Trametinib in Treating Patients With Recurrent Thyroid Cancer

PRIMARY OBJECTIVES:

I. To screen two different regimens (GSK2118436 [BRAFi] [dabrafenib] as a single agent versus
the combination regimen of GSK2118436 [BRAFi] and GSK1120212 [MEKi] [trametinib]) and
identify which regimen is more promising for subsequent testing in a phase III trial in
radioiodine refractory BRAF-mutated differentiated thyroid cancer (DTC) patients.

SECONDARY OBJECTIVES:

I. To understand duration of objective response, progression-free survival and overall
survival for each treatment group.

II. To assess tolerability and adverse events of GSK2118436 (BRAFi) as a single agent and the
tolerability and adverse events of GSK2118436 (BRAFi) and GSK1120212 (MEKi) in combination,
in patients with DTC.

III. To evaluate impact of experimental drugs on serum tumor marker thyroglobulin and its
correlation with overall response rate.

IV. To understand pharmacokinetic, pharmacogenetics and pharmacodynamics of experimental
drugs using serial tumor biopsies, tumor blocks and peripheral blood.

OUTLINE: Patients are randomized to 1 of 2 treatment arms.

ARM I: Patients receive dabrafenib orally (PO) twice daily (BID) on days 1-28. Patients with
disease progression may cross-over to arm II.

ARM II: Patients receive dabrafenib PO BID and trametinib PO once daily (QD) on days 1-28.

In both arms, courses repeat every 28 days in the absence of disease progression or
unacceptable toxicity.

After completion of study treatment, patients are followed up for 4 weeks.

Inclusion Criteria:

- Patients must have histologically or cytologically confirmed papillary thyroid cancer,
follicular thyroid cancer (tall cell variant, insular thyroid cancer, follicular
variant of papillary thyroid cancers, poorly differentiated thyroid cancer or any of
the above mixed histology will be allowed)

- Presence of BRAF mutation in tumor tissue

- Patients must have measurable disease, defined as at least one lesion that can be
accurately measured in at least one dimension (longest diameter to be recorded for
non-nodal lesions and short axis for nodal lesions) as >= 20 mm with conventional
techniques or as >= 10 mm with spiral computed tomography (CT) scan, magnetic
resonance imaging (MRI), or calipers by clinical exam; malignant lymph nodes will be
considered measurable if they are >= 15 mm in short axis

- Patients must have progressive disease within the thirteen months prior to study
entry; progressive disease is as defined in Response Evaluation Criteria in Solid
Tumors (RECIST) 1.1, which is at least a 20% increase in the sum of diameters of
target lesions and the sum must also demonstrate an absolute increase of at least 5
mm; the appearance of one or more new lesions is also considered progressive disease

- Patients are willing to have tumor biopsy pre-study and at 4 weeks on study (fine
needle aspiration or core biopsy) if patient has biopsy-accessible tumors as
determined by investigator

- Patients must have disease that is refractory (unresponsive) to radioactive iodine
(RAI) treatment as defined by one of the following:

- One or more measurable lesions that do not demonstrate RAI uptake

- One or more measurable lesions progressive by RECIST 1.1 within 12-months of
prior RAI therapy

- Cumulative RAI dose of > 600 mCi

- Prior therapy allowed:

- Patients may have been previously treated with up to three regimens of oral
multikinase inhibitors, including sorafenib, sunitinib and pazopanib

- Patients may have been previously treated with external beam radiation or
cytotoxic chemotherapy therapy

- Eastern Cooperative Oncology Group (ECOG) performance status =< 2 (Karnofsky >= 60%)

- Absolute neutrophil count >= 1,500/mcL

- Platelets >= 100,000/mcL

- Total bilirubin =< 1.5 X institutional upper limit of normal

- Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase
[SGOT])/alanine aminotransferase (ALT) (serum glutamic pyruvate transaminase [SGPT])
=< 2.5 X institutional upper limit of normal

- Serum creatinine =< 1.5 X institutional upper limit of normal

- Left ventricular ejection fraction (EF) >= institutional lower limit of normal

- Patient must have a calcium phosphate product (CPP) =< 4.0 mmol^2/L^2 (50 mg^2/dL^2)

- Female patients of childbearing age are required to have a negative serum pregnancy
test within 14 days prior to the first dose of study medication

- Females are required to use an effective method of contraception from the time of
negative serum pregnancy test, throughout the study duration, and until 4 weeks
after the last dose of study medication; should a woman become pregnant or
suspect she is pregnant while she or her partner is participating in this study,
she should inform her treating physician immediately; men treated or enrolled on
this protocol must also agree to use adequate contraception prior to the study,
for the duration of study participation, and for 16 weeks after completion of the
last dose of study drug

- Specific contraception requirements for females: female subjects of childbearing
potential must not become pregnant and are required to be sexually inactive by
abstinence or use contraceptive methods with a failure rate of < 1%; sexual
inactivity by abstinence must be consistent with the preferred and usual
lifestyle of the subject; periodic abstinence (e.g. calendar, ovulation,
symptothermal, post ovulation methods) and withdrawal are not acceptable methods
of contraception; contraceptive methods with a failure rate of < 1% include the
following:

- Intrauterine device (IUD) or intrauterine system (IUS) that meets the < 1%
failure rate as stated in the product label

- Male partner sterilization (vasectomy with documentation of azoospermia)
prior to the female subject's entry into the study, and this male is
patient's sole sexual partner; for this definition, "documented" refers to
the outcome of the investigator's/qualified physician designee's medical
examination of the subject or review of the subject's medical history for
study eligibility, as obtained via a verbal interview with the subject or
from the subject's medical records

- Double barrier method: condom and occlusive cap (diaphragm or cervical/vault
caps) plus spermicidal agent (foam/gel/film/cream/suppository); these
allowed methods of contraception are only effective when used consistently,
correctly and in accordance with the product label; the investigator is
responsible for ensuring subjects understand how to properly use these
methods of contraception

- Specific contraception requirements for males: to prevent pregnancy in a female
partner or to prevent exposure of any partner to the investigational product from
a male subject's semen, male subjects must use one of the following contraceptive
methods during the study and for a total of 16 weeks following the last dose of
study drug (based upon the lifecycle of sperm):

- Abstinence, defined as sexual inactivity consistent with the preferred and
usual lifestyle of the subject for 14 days prior to first dose of study
drug, through the dosing period, and for at least 16 weeks after the last
dose of study drug; periodic abstinence (e.g. calendar, ovulation,
symptothermal, post-ovulation methods) and withdrawal are not acceptable
methods of contraception

- Condom (during non-vaginal intercourse with any partner - male or female) OR

- Condom and occlusive cap (diaphragm or cervical/vault caps) plus spermicidal
agent (foam/gel/film/cream/suppository) (during sexual intercourse with a
female)

- Ability to understand and the willingness to sign a written informed consent document

Exclusion Criteria:

- Patients had external beam radiotherapy, cytotoxic chemotherapy, or oral multikinase
inhibitors within 4 weeks prior to entering the study

- Patients who have been treated with radioactive iodine within 24 weeks prior to
entering the study (radioactive iodine within 4 weeks will be allowed if negative
post-treatment scan)

- Patients have not recovered from adverse events related to prior chemotherapy,
radiation therapy or multikinase inhibitors to Common Terminology Criteria for Adverse
Events (CTCAE) 4.0 grade 1 or less except for alopecia

- Patients have been previously treated with potent BRAF inhibitor or MEK inhibitor,
including PLX4032/vemurafenib, ARQ 736; previous treatment with sorafenib is permitted

- Patients are receiving any other investigational agents

- Patients are on any medication that is on the list of prohibitive medications;
patients on therapeutic dose of warfarin; this is due to potential for significant
interactions between warfarin and study agents

- Patients with a known history of infection with hepatitis B virus (HBV) or hepatitis C
virus (HCV)

- Patients with a history of other malignancy; patients who have been disease-free from
other malignancy for 5 years or greater, or patients with a history of resected
non-melanoma skin cancer, or patients with a history of treated in situ carcinoma will
be allowed

- Patients with uncontrolled brain metastases; patients who are on a stable dose of
corticosteroids for more than 1 month or off corticosteroids for 2 weeks can be
enrolled; enzyme-inducing anti-epileptic drugs are not permitted

- Patients with a known history of retinal vein occlusion or central serous retinopathy,
or predisposing factors to retinal vein occlusion (RVO) or central serous retinopathy
(CSR) (e.g. uncontrolled glaucoma or ocular hypertension, uncontrolled systemic
disease such as hypertension, 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

- Evidence of new visual field defects

- Intraocular pressure > 21 mm Hg as measured by tonography

- Patients with a known history of glucose-6-phosphate dehydrogenase (G6PD) deficiency

- Patients with class II, III, or IV heart failure as defined by the New York Heart
Association (NYHA) functional classification system

- Abnormal cardiac valve morphology (subjects with minimal abnormalities, can be
entered on study with approval)

- Corrected QT (QTc) interval greater than or equal to 480 msecs (>= 500 msec for
subjects with bundle branch block)

- Patients with 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

- Pregnant women and nursing women are excluded from this study

- Human immunodeficiency virus (HIV)-positive patients on combination antiretroviral
therapy are ineligible

- Subjects with a history of pneumonitis or interstitial lung disease

- History of acute coronary syndromes (including myocardial infarction and unstable
angina), coronary angioplasty, or stenting within the past 6 months

- History of uncontrolled arrhythmias; subjects with controlled atrial fibrillation for
> 1 month prior to study day 1 are eligible