A Study Evaluating the Safety, Pharmacokinetics (PK), and Preliminary Efficacy of ABBV-399 in Subjects With Advanced Solid Tumors.

Inclusion Criteria:

1. Subject must have advanced Non-Small Cell Lung Cancer (NSCLC) that is not amenable to
surgical resection or other approved therapeutic options that have demonstrated
clinical benefit.

2. Subject has an Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 to 2.

3. Subject must have measurable disease per Response Evaluation Criteria In Solid Tumors
(RECIST) version 1.1.

4. Subject has one archived diagnostic formalin-fixed paraffin embedded (FFPE) tumor
tissue confirmed available for analyses.

5. Subject has adequate bone marrow, renal, and hepatic function.

6. Women of childbearing potential must have a negative serum pregnancy test within 14
days prior to initiation of treatment.

7. Subjects in the combination therapy arms must be eligible to receive erlotinib, or
nivolumab per most current prescribing information, or at the discretion of the
Investigator.

Exclusion Criteria:

1. Subject has received anticancer therapy including chemotherapy, radiation therapy,
immunotherapy, biologic, or any investigational therapy within a period of 21 days or
herbal therapy within 7 days prior to the first dose of ABBV-399.

2. Subject has uncontrolled metastases to the central nervous system (CNS) based on head
CT or MRI. Subjects with brain metastases may be eligible 2 weeks after definitive
therapy to all known sites of CNS disease provided they are asymptomatic and either
off or on a non-increasing dose (in last 2 weeks) of systemic steroids and not on
anticonvulsants for seizure activity directly related to progressive CNS metastases.

3. Subject has history of interstitial lung disease or pneumonitis that required
treatment with systemic steroids.

4. Subject has unresolved adverse events >= Grade 2 from prior anticancer therapy, except
for alopecia or anemia.

5. Subject has had major surgery within 21 days prior to the first dose of ABBV-399.

6. Subject has a clinically significant uncontrolled condition(s) s described in the
protocol.

7. Subject has history of major immunologic reaction to any Immunoglobulin G (IgG)
containing agent.

8. Subjects enrolled on the combination therapy phase must satisfy the above exclusion
criteria and also the following:

- Subjects may not receive ABBV-399 in combination with erlotinib or nivolumab if
they have any medical condition which in the opinion of the Investigator places
the subject at an unacceptably high risk for toxicities from the combination.