A Study to Compare the Combination of Navlimetostat (BMS-986504) With Pembrolizumab and Chemotherapy Versus Placebo Plus Pembrolizumab and Chemotherapy in First-line Metastatic Non-small Cell Lung Cancer Participants With Homozygous MTAP Deletion

Inclusion Criteria

* Participants must have Metastatic (Stage IV or recurrent) non-small cell lung cancer (NSCLC) (as defined by the American Joint Committee on Cancer, Ninth Edition) with no prior systemic anti-cancer therapy for metastatic disease.
* Participants must have histologically confirmed diagnosis of NSCLC and homozygous methylthioadenosine phosphorylase (MTAP) deletion or MTAP loss.
* Participants must have an Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.
* Participants must have at least 1 measurable lesion as per RECIST v1.1.

Exclusion Criteria

* Nonsquamous participants must not have documented targetable oncogenic mutation or actionable genetic alterations (AGAs) for which there is a standard of care (SoC) available as first-line (1L) therapy.
* Participants must not have symptomatic brain metastases or spinal cord compression.
* Participants must not have any prior systemic therapy (chemotherapy, immunotherapy, targeted therapy, or biological therapy) for metastatic non-small cell lung cancer (mNSCLC).

Note: One cycle of SoC treatment prior to randomization will be allowed for participants who require immediate treatment if clinically indicated.

* Participants must not have any known or suspected impairment of gastrointestinal function that may prohibit the ability to absorb or swallow an oral medication without chewing or crushing.
* Other protocol-defined Inclusion/Exclusion criteria apply.