This is a multi-part, open-label, non-randomized phase Ib/II clinical trial designed to evaluate the safety, tolerability, pharmacokinetics, and preliminary antitumor activity of atamparib, an investigational agent, in patients with advanced or metastatic non-small cell lung cancer (NSCLC) adenocarcinoma. The study comprises dose escalation (phase Ib) and expansion (phase II).

Inclusion criteria:

1. Subject must be ≥18 years of age.
2. Histologically confirmed diagnosis of unresectable advanced or metastatic NSCLC adenocarcinoma.
3. Documented KRAS mutation status at study entry.
4. Have received at least one line of standard therapy and experienced radiographic tumor progression to the last administered treatment and have failed institutional standards of care.
5. Have measurable tumor lesions
6. ECOG 0-1
7. Adequate organ functions

Exclusion criteria:

1. Non-adenocarcinoma histology of NSCLC. Patients whose tumors have a mixed histology are ineligible.
2. Wtih oncogenic driver mutation other than KRAS for which an approved therapy is available but not adequately treated.
3. Known active GI disease that would impact the absorption
4. Clinically significant cardiac disease
5. Requiring the administration of strong inhibitors or inducers of CYP3A4, P-gp or BCRP.
6. Symptomatic, or untreated CNS lesions.