• Best radiographic response [ Time Frame: Within 6 months of initiation of study treatment ]
  Radiographic response will be defined as a complete response or partial response according to immune-related response criteria (Immune-Modified Response Evaluation Criteria in Solid Tumors) and Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria.
• Incidence of treatment-related grade 3 adverse events [ Time Frame: Up to 28 days ]
  Will assess according to Common Terminology Criteria for Adverse Events version 5.0.

• Progression-free survival [ Time Frame: Up to 5 years ]
  Will be defined according to RECIST 1.1 criteria.
• Overall survival [ Time Frame: Up to 5 years ]
  Will be defined according to RECIST 1.1 criteria.
• Time to response [ Time Frame: Up to 5 years ]
• Duration of response [ Time Frame: Up to 5 years ]

PRIMARY OBJECTIVES:

I. To describe overall response rate (ORR) upon treatment with encorafenib, cetuximab, and nivolumab.

II. To determine the safety and tolerability of nivolumab, encorafenib, and cetuximab.

SECONDARY OBJECTIVES:

I. To estimate median progression-free survival (PFS) upon treatment with encorafenib, cetuximab, and nivolumab.

II. To estimate median overall survival (OS) upon treatment with encorafenib, cetuximab, and nivolumab.

III. To estimate median time to response (TTR) upon treatment with encorafenib, cetuximab, and nivolumab.

IV. To estimate median duration of response (DOR) upon treatment with encorafenib, cetuximab, and nivolumab.

V. To estimate disease control rate (DCR) upon treatment with encorafenib, cetuximab, and nivolumab.

EXPLORATORY OBJECTIVES:

I. To assess genomic and immune changes upon treatment with encorafenib, cetuximab, and nivolumab.

II. To demonstrate feasibility of establishing humanized patient-derived xenograft models in matched patients with BRAFV600E metastatic colorectal cancer (mCRC).

OUTLINE: This is a phase I, dose-escalation study followed by a phase II study.

Patients receive encorafenib orally (PO) once daily (QD) on days 1-28, cetuximab intravenously (IV) over 1 hour on days 1 and 15, and nivolumab IV over 30 minutes on day 1. Cycles repeat every 28 days in the absence of disease progression or unacceptable toxicity.

After completion of study treatment, patients are followed up at 30 and 100 days, at 3 months, and then every 3 months thereafter.

• BRAF NP_004324.2:p.V600E
• Metastatic Colon Adenocarcinoma
• Metastatic Microsatellite Stable Colorectal Carcinoma
• Metastatic Rectal Adenocarcinoma
• Progressive Disease
• Recurrent Colorectal Carcinoma
• Stage III Colorectal Cancer AJCC v8
• Stage IIIA Colorectal Cancer AJCC v8
• Stage IIIB Colorectal Cancer AJCC v8
• Stage IIIC Colorectal Cancer AJCC v8
• Stage IV Colorectal Cancer AJCC v8
• Stage IVA Colorectal Cancer AJCC v8
• Stage IVB Colorectal Cancer AJCC v8
• Stage IVC Colorectal Cancer AJCC v8
• Unresectable Colon Adenocarcinoma
• Unresectable Rectal Adenocarcinoma

• Biological: Cetuximab
  Given IV
  Other Names:

  • Cetuximab Biosimilar CDP-1
  • Cetuximab Biosimilar CMAB009
  • Cetuximab Biosimilar KL 140
  • Chimeric Anti-EGFR Monoclonal Antibody
  • Chimeric MoAb C225
  • Chimeric Monoclonal Antibody C225
  • Erbitux
  • IMC-C225
• Drug: Encorafenib
  Given PO
  Other Names:

  • Braftovi
  • LGX 818
  • LGX-818
  • LGX818
• Biological: Nivolumab
  Given IV
  Other Names:

  • BMS-936558
  • MDX-1106
  • NIVO
  • ONO-4538
  • Opdivo

Inclusion Criteria:

• Provision of signed informed consent prior to any screening procedures being performed
• Histologically (or cytologically) confirmed diagnosis of adenocarcinoma of the colon or rectum, with clinical confirmation of unresectable and/or metastatic disease that is measurable according to Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria
• Confirmation of BRAFV600E tumor as detected by a Clinical Laboratory Improvement Amendments (CLIA)-certified laboratory
• Confirmation of microsatellite stable (MSS) status in a CLIA-certified laboratory
• Prior treatment with at least one, but no more than two, systemic chemotherapy regimen(s) for mCRC, or recurrence/progression with development of unresectable or metastatic disease within 6 months of adjuvant chemotherapy for resected colorectal cancer
• Eastern Cooperative Oncology Group (ECOG) performance status =< to 1
• Absolute neutrophil count (ANC) >= 1.0 x 10^9/L
• Hemoglobin (Hgb) >= 9 g/dL with or without transfusions
• Platelets (PLT) >= 100 x 10^9/L without transfusions
• Aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) =< 2.5 x upper limit of normal (ULN)

• Total bilirubin =< to 1.5 x ULN and < 2 mg/dL

  • Note: Patients who have a total bilirubin level > 1.5 x ULN will be allowed if their indirect bilirubin level is =< 1.5 x ULN
• Serum creatinine =< 1.5 x ULN, or calculated creatinine clearance (determined as per Cockcroft-Gault) >= 50 mL/min at screening
• Corrected QT (QTc) interval =< 480 ms (preferably the mean) from triplicate electrocardiograms (ECGs)
• Able to take oral medications
• Female patients are either postmenopausal for at least 1 year, are surgically sterile for at least 6 weeks, or must agree to take appropriate precautions to avoid pregnancy from screening through follow-up if of childbearing potential. Note: Permitted contraception methods should be communicated to the patients and their understanding confirmed. For all females, the pregnancy test result must be negative within 24 hours of starting treatment with nivolumab. Males to avoid fathering a child from screening through 100 days following the end of therapy

Exclusion Criteria:

• Concurrent corticosteroid therapy or concurrent use of any other immunosuppressive medication (corticosteroid use on study as a pre-medication for IV contrast allergies/reactions is allowed). Subjects who are receiving daily steroid replacement therapy (the equivalent of prednisone =< 10 mg daily) serve as an exception to this rule
• Prior treatment with a BRAF inhibitor, MEK inhibitor, or ERK inhibitor (of note, regorafenib is not considered a BRAF inhibitor for the context of eligibility criteria)
• Prior treatment with anti-EGFR therapies
• Prior immune checkpoint therapy including, but not limited to, an anti-PD-1, anti-PD-L1, anti-PD-L2, anti-CD137, or anti-cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) antibody, or any other prior immune-modulating agent administered with antineoplastic intent (monoclonal antibodies used against VEGF are permitted)
• Prior allogeneic tissue/solid organ transplant
• History of (non-infectious) pneumonitis that has required oral or IV steroids
• Receipt of a live vaccine within 30 days prior to the first administration of study medication. Seasonal flu vaccines that do not contain a live virus are permitted
• History of a grade 3 or 4 allergic reaction attributed to humanized or human monoclonal antibody therapy
• Active infection requiring concurrent antibiotic use
• Any symptomatic brain metastasis. Note: Patients previously treated or untreated for this condition who are asymptomatic in the absence of corticosteroid and anti-epileptic therapy are allowed. Brain metastases must be stable for > or equal to 4 weeks, with imaging (e.g., magnetic resonance imaging [MRI] or computed tomography [CT]) demonstrating no current evidence of progressive brain metastases at screening
• Leptomeningeal disease
• Previous or concurrent malignancy within 3 years of study entry, with the following exceptions: adequately treated basal or squamous cell skin cancer, superficial bladder cancer, prostate intraepithelial neoplasm, carcinoma in-situ of the cervix, or other noninvasive or indolent malignancy; other solid tumors treated curatively without evidence of recurrence for at least 3 years prior to study entry
• History of acute coronary syndromes (including myocardial infarction, unstable angina, coronary artery bypass grafting, coronary angioplasty, or stenting) < 6 months prior to screening, symptomatic chronic heart failure (i.e. grade 2 or higher), history or current evidence of clinically significant cardiac arrhythmia and/or conduction abnormality < 6 months prior to screening except atrial fibrillation and paroxysmal supraventricular tachycardia
• Uncontrolled hypertension defined as persistent elevation of systolic blood pressure >= 170 mmHg or diastolic blood pressure >= 100 mm Hg, despite current therapy
• Known positive serology for HIV (human immunodeficiency virus), active hepatitis B, and/or active hepatitis C infection
• Known history of acute or chronic pancreatitis (history of acute pancreatitis with no recurrent events in the prior 24 months are permitted)
• Patients with a history of inflammatory bowel disease, including ulcerative colitis and Crohn's disease, are excluded from this study, as are patients with a history of symptomatic autoimmune disease (e.g., rheumatoid arthritis, systemic progressive sclerosis [scleroderma], systemic lupus erythematosus, autoimmune vasculitis [e.g., Wegener's granulomatosis]); central nervous system (CNS) or motor neuropathy considered of autoimmune origin (e.g., Guillain-Barre syndrome and myasthenia gravis, multiple sclerosis). Patients with Graves' disease will be allowed
• Impaired gastrointestinal function or disease that may significantly alter the absorption of study drug (e.g., ulcerative diseases, uncontrolled vomiting, malabsorption syndrome, small bowel resection with decreased intestinal absorption)
• Any other condition that would, in the investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns or compliance with clinical study procedures
• Major surgery =< 6 weeks prior to starting study drug or failure to recover from side effects of such procedure at the discretion of the treating investigator
• Pregnant or nursing (lactating) women, where pregnancy is defined as the state of a female after conception and until the termination of gestation, confirmed by a positive human chorionic gonadotropin (hCG) laboratory test
• Medical, psychiatric, cognitive or other conditions, according to investigator judgment, that may compromise the patient's ability to understand the patient information, give informed consent, comply with the study protocol or complete the study