Inclusion Criteria: - Participant must have histologically confirmed diagnosis of advanced and/or metastatic solid tumor malignancy with homozygous deletion of the MTAP gene detected in tumor tissue. - Depending on the cohort enrolled, participants must have received standard therapies appropriate for their tumor type and stage with disease progression on or after the most recent treatment (there must be no available treatment with curative intent or participant is ineligible or declines treatment) or be treatment-naïve with no prior systemic anticancer therapy for their unresectable or metastatic disease. - Participant must have presence of at least one measurable tumor lesion per RECIST v1.1 or mRECIST at baseline. - Coagulation function: International normalized ratio (INR) and activated partial thromboplastin time (APTT) must be ≤ 1.5 × ULN; subjects with liver metastasis or liver cancer must be ≤ 2 × ULN. - Participant must have Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. Exclusion Criteria: - Participants must not have prior treatment with a PRMT5 or Methionine adenosyl transferase 2A (MAT2A) inhibitor. - Participants must not have active brain metastases or carcinomatous meningitis. Participants are eligible if brain metastases are adequately treated, and participants are neurologically stable for at least 2 weeks prior to enrollment without the use of corticosteroids or are on a stable or decreasing dose of ≤ 10 mg daily prednisone (or equivalent). - Participants must not have history of gastrointestinal disease or other gastrointestinal conditions within 6 months prior to enrollment (including uncontrolled nausea, vomiting, malabsorption syndrome or non-gastrointestinal fistula, gastrointestinal perforation, or intra-abdominal abscess) likely to alter absorption of study treatment or result in inability to swallow oral medications. - Participants must not have inadequate organ function, as determined by laboratory testing within the screening period. - Participants must not have active viral HBV or HCV hepatitis. - Other protocol defined inclusion/exclusion criteria applies.