• Stage IV or recurrent/metastatic non-squamous NSCLC that harbors an EGFR activating mutation (Exon 21 L858R, Exon 19 deletion, Exon 18 G719X, Exon 21 L861Q, etc). Local testing for EGFR mutations is acceptable provided it was performed in a CLIA certified lab.

• Part I: Progressive disease on at least one prior EGFR TKI

• Part II, Cohort 1: Progressive disease on osimertinib or other prior EGFR TKIs

• Part II, Cohort 2: Receiving osimertinib as front line treatment for less than 12 weeks. Persistent ctDNA with EGFR mutation between weeks 6-12 from the start of osimertinib treatment.

• Age at least 18

• Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) 0-2

• Archival tissue from a biopsy performed after progression of disease on previous EGFR TKI or willing to consent for a fresh tumor biopsy.

• Measurable disease by RECIST 1.1.

• Patients with untreated brain metastases are allowed provided that the patient is clinically asymptomatic and stable.

• Patients must have completed prior chemotherapy ≥ 3 weeks or radiotherapy ≥ 2 weeks prior to receiving study drugs.

• If the subject's most recent line of therapy is treatment with osimertinib, then all adverse events must be resolved to Grade 2 or better

• If the subject's most recent line of therapy is any other treatment than osimertinib, then all Adverse Events must be resolved to grade 1 or better, with the exception of fatigue, alopecia and neuropathy (which must resolve to CTCAE grade 2).

• Adequate organ function

• Women of childbearing potential and men must agree to use adequate contraception while on study.

• Written informed consent obtained from subject and ability for subject to comply with the requirements of the study.