A study evaluating the safety, pharmacokinetics (PK), pharmacodynamics, and preliminary efficacy of ABBV-927 with ABBV-368, Budigalimab (ABBV-181) and/or chemotherapy in participants with selected solid tumors. This study consists of 2 main parts, a dose-escalation phase and a dose-expansion phase. The dose-expansion phase can begin once the recommended phase 2 dose/maximum tolerated dose (RP2D/MTD) is determined in the dose-escalation phase.

Inclusion Criteria:

• Adequate liver, kidney and hematology function as demonstrated by laboratory values detailed in the study protocol.
• An Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

Dose-Escalation:

• Arm A: Participants with an advanced solid tumor who have progressed on standard therapies known to provide clinical benefit and/or participants who have refused or are intolerant of such therapy.
• Arm B (non-small-cell-lung-cancer [NSCLC]): Participants with histologically or cytologically confirmed NSCLC who previously progressed during or after an anti-programmed cell death (PD)-1 or PD ligand 1 (PD-L1) therapy and a platinum-based regimen in the recurrent or metastatic setting.

Dose-Expansion:

• Arm 1, 2, and 3 (triple-negative breast cancer [TNBC]): Participants with histologically or cytologically confirmed breast adenocarcinoma that is estrogen receptor/progesterone receptor/human epidermal growth factor receptor (HER)2-negative who must have disease progression during or after at least 1 systemic therapy that included a taxane in the metastatic or recurrent setting and who are treatment-naïve to immunotherapy.
• Arm 4 (TNBC): Participants with histologically or cytologically confirmed TNBC who have received no previous anti-cancer therapy for TNBC, and who are PD-L1 negative on tumor tissue by immunohistochemistry (IHC) assay.
• Arm 5 (NSCLC): Participants with histologically or cytologically confirmed NSCLC who previously progressed either during or after an anti-PD-1 or PD-L1 therapy and a platinum-based regimen in the recurrent or metastatic setting.

Exclusion Criteria:

• Has history of inflammatory bowel disease or pneumonitis.
• Has uncontrolled metastases to the central nervous system.
• Has a concurrent malignancy that is clinically significant, treatment is required, or the participant is not clinically stable.
• Has had a major surgery ≤ 28 days prior to the first dose of study drug or the surgical wound is not fully healed.
• Has previously treated with an anti-PD- or PD-L1-targeting agent and had during the course of their therapy:
• any immune-mediated toxicity of Grade 3 or worse severity
• treatment of the toxicity with systemic corticosteroids
• any hypersensitivity to the PD-1 or PD-L1-targeting agent
• any treatment-related toxicity resulting in discontinuation of the PD-1 or PD-L1 targeting agent