The purpose of this study is to test the safety of dacomitinib and osimertinib, at increasing doses, to find out what effects, if any, this combination of drugs has on people with metastatic EGFR mutant lung cancer that has not been treated with an EGFR TKI.

Inclusion Criteria:

• Written informed consent

• Advanced biopsy-proven metastatic non-small cell lung cancer

• Somatic activating mutation in EGFR in a tumor biopsy

• No prior EGFR inhibitor treatment (gefitinib, afatinib, erlotinib, dacomitinib, osimertinib) however, prior treatment with other chemotherapies are allowed

• Archival tissue available from a pre-treatment tumor biopsy or willing to undergo a tumor biopsy prior to study initiation.

• Measurable (RECIST 1.1) indicator lesion not previously irradiated

• Karnofsky performance status (KPS) ≥ 70%

• Age >18 years old

• Ability to swallow oral medication

• Agree to use effective methods of contraception from the time of screening until 3 months after treatment discontinuation (for males and females of child-bearing potential)

• Adequate organ function

  • AST, ALT ≤ 3 x ULN
  • Total bilirubin ≤1.5x ULN
  • Creatinine ≤ 1.5x ULN OR calculated creatinine clearance ≥ 60ml/min
  • Absolute neutrophil count (ANC) ≥ 1000 cells/mm^3
  • Hemoglobin≥9.0 g/dL
  • Platelets ≥100,000/mm^3

Exclusion Criteria:

• Pregnant or lactating women
• Any radiotherapy within 1 week of starting treatment on protocol.
• Any major surgery within 1 weeks of starting treatment on protocol.
• Any evidence of active clinically significant interstitial lung disease
• A mean QTc >470ms (Fridericia"s correction), clinically important arrhythmia, conduction or morphology of resting ECG (eg complete LBBB, 1st -3rd degree heart block, any factors that increase the risk of QTc prolongation or risk of arrhythmia)
• Cardiovascular disease or cerebrovascular disease, CVA or MI < 6 months prior to study enrollment, unstable angina, NYHA >Grade II CHF, or serious cardiac arrhythmia uncontrolled by medication or with the potential to interfere with protocol treatment
• History of pneumonitis or interstitial lung disease (ILD), drug induced ILD, radiation pneumonitits that required steroid treatment, and any evidence of clinically active ILD
• Serious chronic GI conditions associated with diarrhea
• Symptomatic, unstable brain metastases requiring escalating doses of steroids
• Continue to have unresolved > CTCAE grade 1 toxicity from any previous treatment

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.