Study of Neratinib +Trastuzumab or Neratinib + Cetuximab in Patients With KRAS/NRAS/BRAF/PIK3CA Wild-Type Metastatic Colorectal Cancer by HER2 Status

The primary aim of this study is to determine the progression-free survival (PFS) in each of these HER2 populations. Secondary aims include overall response rate (ORR) and clinical benefit rate (CBR) defined as the objective tumor decrease and stable disease by RECIST 1.1 criteria; toxicity and safety profile. Exploratory analysis will be performed to assess for molecular predictors of response. The local site will make the primary determination of response and progression based on all radiographic images (e.g., MRI, CT, PET, bone scan, etc.) as well as other relevant reports documenting disease response or progression. For patients identified as quadruple WT with prior cetuximab or panitumumab treatment, a pre-entry blood sample will be required from consenting patients to confirm HER2 amplification for study eligibility. Patients with quadruple WT, HER2 amplified with prior anti-EGRF therapy and/or HER2 mutated colorectal cancer with/or without prior anti-EGRF therapy will receive concurrent therapy with trastuzumab 4 mg/kg IV loading dose followed by 2 mg/kg IV weekly and neratinib 240 mg taken by mouth daily until disease progression, (Arm 1). Patients with quadruple WT, HER2 WT or HER2 amplified with no prior anti-EGRF therapy will be assigned to receive concurrent therapy with cetuximab (400 mg/m2 IV loading dose followed by 250 mg/m2 IV weekly), and neratinib 240 mg taken by mouth daily until disease progression (Arm 2). Approximately thirty-five (35) patients will be accrued to this study; 15 patients with HER2 amplified, 15 patients with HER2 WT, and approximately 5 patients with HER2 mutated colorectal cancer. Patients with HER2 WT or HER2 amplified mCRC who drop out of the study before the first scan (for whatever reason) will be replaced. Patients who drop out of the study after the first scan but before the second scan will be considered to have progressive disease. Toxicity will be graded according to the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events version 4.0 (CTCAE v4.0). Required blood and tissue samples will be collected at entry into the study. A tumor biopsy will be procured from an accessible site of metastasis before study therapy is initiated (after the patient has signed the consent form and has been screened for eligibility). Tissue will be sent to Champions Oncology Laboratory for engraftment into an NOD/SCID mouse to develop a patient-derived xenograft (PDX) model, and to NSABP Pathology Division for correlative science. Tissue samples from PDX models will be sent to Celcuity for functional HER2 signaling assay. Additional blood samples will be collected during the course of treatment. Optional tumor and blood samples will be collected from consenting patients at the time of disease progression.