This phase II trial tests how well vemurafenib and cobimetinib work in treating patients with high risk differentiated thyroid carcinoma with BRAFV600E mutation, in preparation for radioactive iodine therapy. Vemurafenib and cobimetinib are used in patients whose cancer has a mutated (changed) form of a gene called BRAF. They are in a class of medications called kinase inhibitors. They work by blocking the action of an abnormal protein that signals cancer cells to multiply. This helps slow or stop the spread of cancer cells. Giving vemurafenib and cobimetinib may work better to treat patients with high risk differentiated thyroid carcinoma with BRAFV600E mutation, in preparation for radioactive iodine therapy.

PRIMARY OBJECTIVE:

I. The proportion of BRAF mutated high-risk differentiated thyroid carcinoma patients who achieve excellent or indeterminate response with vemurafenib and cobimetinib treatment prior to initial radioactive iodine (RAI) therapy as defined by American Thyroid Association guideline.

SECONDARY OBJECTIVES:

I. The proportion of patients who had significant change on their I-123 scan before and after the targeted therapy.

II. To evaluate the safety and tolerability as determined by adverse events related to vemurafenib and cobimetinib combination therapy.

III. To evaluate the efficacy of vemurafenib and cobimetinib in enhancing RAI avidity by assessing the progression-free survival.

IV. To evaluate the diagnostic and prognostic value of thyroglobulin level as determined by thyroglobulin changes associated with treatment response.

V. To evaluate the tumor molecular characteristics in treatment responders as compared to non-responders.

OUTLINE:

Patients receive vemurafenib orally (PO) twice per day (BID) for 6 weeks and cobimetinib PO once per day (QD) for 3 weeks, followed by 1 week off, and then continuing for 2 weeks. Patients then receive iodine 131 PO followed by 3 additional days of vemurafenib PO BID and cobimetinib PO QD. Patients receive thyrogen intramuscularly (IM) daily for 2 days followed by I-123 diagnostic scan during screening and on study. Patients also undergo magnetic resonance imaging (MRI) during screening, positron emission tomography (PET) scan or computed tomography (CT) scan and blood sample collection throughout the study and ultrasound imaging and I-131 whole body scan during follow up.

After completion of study treatment, patients are followed up every 3 months for up to 12 months.

Inclusion Criteria:

• Documented informed consent of the participant and/or legally authorized representative

• Willingness to be followed for about 14 months

• Males or females aged ≥ 18 years at the time of informed consent

• Patients with thyroid carcinoma of follicular origin (papillary, follicular or Hurthle cell)

• Known positive BRAFV600E mutation (determined on a previous analysis and/or on a representative formalin-fixed paraffin embedded (FFPE) tumor samples or on a biopsy sample)

• High risk for recurrence according to the American Thyroid Association (ATA) guideline defined as having one or more of the features below:

  • Gross extrathyroidal extension
  • FTC with extensive vascular invasion (> 4), although less likely to have BRAF mutation
  • PTC with vascular invasion
  • Advanced nodal disease of (any node >3 cm, > 4 nodes, or extra-nodal extension)
  • BRAF+TERT promoter mutation
  • Post op thyroglobulin (TG) suggestive of distant metastasis
  • Distant metastatic sites (only for exploratory arm)

• Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1

• Blood pressure (BP) ≤ 140/90 mm Hg at screening with or without antihypertensive medications and no change in antihypertensive medications within 1 week prior to treatment start

• Creatinine clearance ≥ 50 mL/min according to the Cockcroft and Gault formula

• Absolute neutrophil count (ANC) ≥ 1.5 x 109/L

• Hemoglobin ≥ 9.0 g/dL

• Platelet count ≥ 100 x 109/L

• Normal blood coagulation function as evidenced by an International Normalized Ratio (INR) ≤ 1.5

• Bilirubin ≤ 1.5 × upper limit of normal (ULN) except for unconjugated hyperbilirubinemia or Gilbert's syndrome

• Alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) ≤ 3 × ULN (≤ 5 × ULN if subject has liver metastases)

• Women of childbearing potential must have a negative urine or serum β-HCG pregnancy test within 7 days prior to the administration of the first study treatment

• Agreement by women of childbearing potential (WOCBP) and males of childbearing potential* to use an effective** method of birth control** for at least 3 months prior to screening through 1 year of study follow-up.

  • Childbearing potential defined as not being surgically sterilized (men and women) or have not been free from menses for > 1 year (women only)

    • Effective birth control defined as hormonal and/or barrier contraception

• Non-English speaking persons and adults lacking capacity to consent are not excluded from participation

Exclusion Criteria:

• Prior RAI treatment
• Prior anti-BRAF, anti-MEK treatment such as sorafenib, dabrafenib, vemurafenib, encorafenib, binimetinib, cobimetinib, trametinib, d selumitinib and other TKIs like, lenvatinib, sunitinib, axitinib, cabozantenib, vandatinib, pazopanib use
• Low to intermediate risk differentiated thyroid cancer (DTC) cases (not having the high-risk features as described above)
• RAI contraindication
• Undifferentiated or Medullary (MTC) carcinoma of the thyroid
• Major surgery within 4 weeks prior to the first dose of treatment
• Subjects having > 1 + proteinuria on urine dipstick testing will undergo 24 h urine collection for quantitative assessment of proteinuria. Subjects with urine protein ≥ 1 g/24 h will be ineligible
• Need for locoregional treatment such as surgery, external beam radiation or thermoablation at inclusion
• External beam radiation, for thyroid cancer, <4 weeks prior initiation of treatment
• Gastrointestinal malabsorption or any other condition that in the opinion of the investigator might affect the absorption of the drugs
• History of congestive heart failure greater or equal to than New York Heart association (NYHA) Class II, unstable angina, myocardial infarction, or stroke within 6 months of the first dose of treatment, or cardiac arrhythmia associated with significant cardiovascular impairment and uncontrolled hypertension
• Electrocardiogram (ECG) with QT interval (QTc) interval ≥ 480 msec
• Active hemoptysis (bright red blood of at least 0.5 teaspoon) within 2 months prior to the first dose of treatment and any other active bleeding, coagulopathy or pathologic condition that would confer a high risk of bleeding
• Active infection requiring systemic therapy
• Active malignancy (except for DTC, or definitively treated melanoma in-situ, basal or squamous cell carcinoma of the skin, or carcinoma in-situ of the cervix or bladder) within the past 24 months
• Any history of or concomitant medical condition that, in the opinion of the investigator, would compromise subject's ability to safely complete the protocol
• Females who are pregnant or breastfeeding
• Patients with an injection of radio-contrast agent within 12 weeks prior to enrollment (can be enrolled after 12 weeks)
• Previous history of retinal vein occlusion
• Previous history of central serious retinopathy
• Known hypersensitivity to the study drugs or to any of the excipients
• Any other condition (including psychosocial condition) that would, in the Investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns with clinical study procedures
• Any other condition that would confound study results
• Noncompliance
• Prospective participants who, in the opinion of the investigator, may not be able to comply with all study procedures (including compliance issues related to feasibility/logistics)