This is a patient pilot study testing the hypothesis that vemurafenib with the addition of KTN3379 can restore iodine incorporation in BRAF mutant (MUT), radioiodine-refractory (RAIR) thyroid cancer patients.

This is a patient pilot study testing the hypothesis that vemurafenib with the addition of KTN3379 can restore iodine incorporation in BRAF mutant (MUT), radioiodine-refractory (RAIR) thyroid cancer patients. Eligible patients with BRAF MUT, RAIR thyroid cancer will undergo human recombinant TSH (rhTSH or Thyrogen)-stimulated 124I PET/CT lesional dosimetry to quantify the baseline RAI avidity of index metastatic lesion(s). Patients will then receive vemurafenib followed by the addition of KTN3379 after which a second Thyrogen-stimulated 124I PET/CT lesional dosimetry will be performed. For patients whose tumor(s) demonstrate sufficient iodine incorporation warranting 131I therapy, Thyrogen-stimulated standard dosimetry will be performed and therapeutic 131I will be administered concurrently with vemurafenib and KTN3379. Subsequent to discontinuation of vemurafenib, tumor assessments will be conducted with serial radiologic scan(s) and thyroglobulins (scans will be performed at baseline, before 131I, 3 months (+/- 1 month) following 131I, and 6 months after 131I).

Inclusion Criteria:

• Patients must have histologically or cytologically confirmed thyroid carcinoma of follicular origin (including papillary, follicular, or poorly differentiated subtypes and their respective variants).

• Confirmation in a CLIA certified laboratory or in an FDA-approved assay that one of the patient's thyroid tumors (primary tumor, recurrent tumor, or metastasis) possesses a BRAF mutation at V600.

• Patients must have measurable disease defined by RECIST criteria 1.1.

• Tumors in previously irradiated fields may be considered measureable if there is evidence of tumor progression after radiation treatment.

• RAI-refractory disease on structural imaging

• Age ≥ 18 years.

• ECOG performance status ≤ 2

• Patients must have normal organ and marrow function as defined below:

  • Absolute neutrophil count (ANC) > 1500/mcl
  • Hemoglobin ≥ 9 g/dL
  • Platelets ≥ 100,000/mcl
  • Albumin ≥ 2.5 g/dL
  • Total bilirubin ≤ 1.5x institutional ULN
  • Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2x institutional ULN unless it is related to the primary disease
  • Creatinine ≤ 1.5 mg/dL OR calculated creatinine clearance (Cockcroft-Gault formula) ≥ 50 mL/min OR 24-hour urine creatinine clearance ≥ 50 mL/min

Exclusion Criteria:

• Concomitant malignancies or previous malignancies treated within the past 3 years. Exception: Patients who have been disease-free for 3 years, patients with a history of completely resected non-melanoma skin cancer, and/or patients with indolent secondary malignancies, are eligible.

• Use of other investigational drugs within 28 days preceding the first dose of vemurafenib on this study.

• Symptomatic or untreated leptomeningeal or brain metastases or spinal cord compression.

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

  • Corrected QT (QTc) interval ≥ 450 msec at baseline or history of congenital long QT syndrome or uncorrectable electrolyte abnormalities. (Patients with well controlled atrial fibrillation are exempt from this criteria.)
  • History of cerebrovascular attack or transient ischemic attack within 6 months prior to the initiation of therapy on this protocol.
  • Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection or psychiatric illness/social situations that would limit compliance with study requirements.