• Age ≥18 years.

• Histologically or cytologically documented NSCLC.

• Stage III or IV NSCLC or recurrent NSCLC that is not potentially curable by radiotherapy or surgery.

• The NSCLC must be epidermal growth factor receptor (EGFR) mutation positive-positive based on results from most recent tissue biopsy or most recent evaluation of circulating tumor DNA.

• Achieved clinical response to osimertinib for ≥4 months, which can be a response of stable disease. Must have a minimum of a 10-day osimertinib washout completed at the time of enrollment.

• Must have radiological progression on osimertinib treatment and can have either asymptomatic disease or symptomatic disease. In addition:

∙ Must have measurable disease per RECIST 1.1.

‣ Must have progression on osimertinib treatment as a single agent or in combination with other anti-cancer agents as their most recent treatment.

• Notes:

⁃ Patients may have had treatment with other EGFR inhibitors as single agents prior to osimertinib.

⁃ Patients may have progression on osimertinib treatment being used for adjuvant therapy after surgery.

• Eastern Cooperative Oncology Group performance status (ECOG PS) score from 0 to 1.

• Must be ≥28 days beyond major surgical procedures such as thoracotomy, laparotomy, or joint replacement and must not have evidence of wound dehiscence, active wound infection, or comparable major residual complications of the surgery per Investigator assessment.

• Asymptomatic brain metastases must meet ALL criteria of the following (a-d):

∙ No history of seizures in the preceding six months.

‣ Definitive treatment must be completed ≥21 days.

‣ Must be off steroids administered because of brain metastases or related symptoms for ≥7 days.

‣ Post-treatment imaging must demonstrate stability or regression of the brain metastases.

⁃ Must have and be willing to submit a prior tumor biopsy or undergo a biopsy during Screening to obtain tumor tissue for submission to a central laboratory for IHC analysis and FISH or qPCR testing.

⁃ Absolute neutrophil count (ANC) \>1500/mm3, platelet count \>100,000/mm3 within ≤28 days.

⁃ Adequate renal function documented by serum creatinine of ≤1.5 mg/dL or calculated creatinine clearance \>50 ml/min within ≤28 days.

⁃ Adequate hepatic function as documented by serum bilirubin \<1.5 mg/dL and aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5 X upper limit of normal (ULN) within ≤28 days.

⁃ Stable cardiac condition with a left ventricular ejection fraction ≥40% within ≤28 days.

⁃ If female of childbearing potential (FOCBP), must have negative serum pregnancy test (serum beta-human chorionic gonadotropin \[β-hCG\]) within ≤7 days.

⁃ FOCBP and non-sterile male patients with female partner(s) of childbearing potential must agree to use two forms of contraception including one highly effective and one effective method beginning ≥2 weeks prior to enrollment through four months following the last dose of study treatment.

⁃ If male, must agree to no sperm donation during study treatment and for an additional four months following the last dose of study treatment.

⁃ Must have voluntarily signed an informed consent in accordance with institutional policies.