This is a multi-center, open label, Phase 1b study of NXP900 in combination with osimertinib in subjects with advanced, progressing, EGFR-mutated non-small cell lung cancer (NSCLC)

Inclusion Criteria:

1. Provide written informed consent.
2. 18 years old or older.
3. Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.
4. Unresectable, metastatic or locally advanced EGFR-mutated NSCLC.
5. Prior treatment with osimertinib as first or second line, as single agent or in combination with chemotherapy, in the metastatic or locally advanced setting.

Exclusion Criteria:

1. Subject's cancer has a known oncogenic driver alteration other than EGFR.
2. Known EGFR mutations that cause resistance to osimertinib
3. Known human epidermal growth factor receptor 2 (HER2) overexpression
4. Any contraindications to treatment with osimertinib