Study to Assess Adverse Events and Pharmacokinetics in Adult Participants With Non-Small Cell Lung Cancer (NSCLC), Head and Neck Squamous Cell Carcinoma (HNSCC) and Other Solid Tumors, Receiving Intravenous (IV) Infusion of ABBV-514 Alone or in Combination With Budigalimab

Cancer is a condition where cells in a specific part of body grow and reproduce uncontrollably. Non-Small Cell Lung Cancer (NSCLC) is a solid tumor, a disease in which cancer cells form in the tissues of the lung. Head and Neck Squamous Cell Carcinoma (HNSCC) is a solid tumor, a disease in which cancer cells form in the tissues of the head and neck. The purpose of this study is to assess adverse events and pharmacokinetics of ABBV-514 as a monotherapy and in combination with Budigalimab.

Budigalimab and ABBV-514 are investigational drugs being developed for the treatment of NSCLC, HNSCC, and other solid tumors. Study doctors put the participants in groups called treatment arms. The maximum-tolerated dose (MTD)/maximum administered dose (MAD) of ABBV-514 will be explored. Each treatment arm receives a different dose of ABBV-514 in monotherapy and in combination with Budigalimab. Approximately 268 adult participants will be enrolled in the study across approximately 80 sites worldwide.

Participants will receive ABBV-514 as a monotherapy or in combination with Budigalimab as an Intravenous (IV) Infusion for an estimated treatment period of up to 2 years.

There may be higher treatment burden for participants in this trial compared to their standard of care. Participants will attend regular visits during the study at a hospital or clinic. The effect of the treatment will be checked by medical assessments, blood tests, checking for side effects and completing questionnaires.


Eligibility Criteria:
Inclusion Criteria:

* Dose-escalation cohorts only:

  -- Must have an advanced solid tumor who are considered refractory to or intolerant of all existing therapies known to provide a clinical benefit for their condition.
* Relapsed Non-Small Cell Lung Cancer (NSCLC) Head and Neck Squamous Cell Carcinoma (HNSCC) dose-expansion cohorts only:

  * Must have histologically or cytologically confirmed advanced or metastatic NSCLC or HNSCC that is not suitable for surgical resection and / or radiation therapy and has been treated with platinum-based chemotherapy and a programmed cell death (PD)-1 or PD ligand 1 (PD-L1) targeting agent (separately or in combination therapy).
  * Must have failed (or refused) treatment with available therapies known to be active for treatment of their disease.
* Participants enrolled in dose escalation must have disease that is evaluable or measurable per Response Evaluation Criteria in Solid Tumors (RECIST, version 1.1).
* Participants enrolled in dose expansion must have measurable disease per RECIST, version 1.1.
* Eastern Cooperative Oncology Group (ECOG) performance status of \<= 1.
* Laboratory values meeting the criteria outlined in the protocol.

Exclusion Criteria:

- Relapsed Non-Small Cell Lung Cancer (NSCLC) Head and Neck Squamous Cell Carcinoma (HNSCC) dose-expansion cohorts only:

-- Non-Small Cell Lung Cancer (NSCLC) participants with known EGFR mutations or ALK gene rearrangements are ineligible.