Inclusion Criteria:

- Histologically confirmed diagnosis of a solid tumor malignancy with homozygous deletion of the MTAP gene detected in tumor tissue or ctDNA by a sponsor-approved test:

• Phase 1 dose escalation only: solid tumor malignancies with homozygous deletion of the CDKN2A gene may be eligible for enrollment if the CDKN2A assay is approved by the Sponsor. Note: solid tumor malignancies with homozygous deletion of the CDKN2A gene and known wild-type MTAP gene are not eligible.

- Unresectable or metastatic disease.

- Patients must have received standard therapies appropriate for their tumor type and stage with disease progression on or after the most recent treatment.

1. Phase 1 dose escalation, RECIST 1.1 measurable or evaluable disease.

2. Phase 1b and Phase 2 cohorts, RECIST 1.1 measurable disease.

- Presence of a tumor lesion amenable to mandatory biopsy for pharmacodynamic evaluation at baseline and on-study unless Sponsor-confirmed as medically unsafe or infeasible.

- Age ≥ 18 years.

- Recovery from the adverse effects of prior therapy at the time of enrollment to baseline or ≤ Grade 1 (excluding alopecia, peripheral neuropathy, and parameters superseded by other eligibility criteria [eg, hematology parameters]). Note: Patients with prior endocrine adverse effects are permitted to enroll if they are stably maintained on appropriate replacement therapy and are asymptomatic.

- Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.

- Adequate organ function.

Exclusion Criteria:

- Prior treatment with a PRMT5 or MAT2A inhibitor therapy (Phase 2 only).

- Active brain metastases or carcinomatous meningitis.

- History of significant hemoptysis or hemorrhage within 4 weeks of the first dose of
study treatment.

- Major surgery within 4 weeks of first dose of study treatment.

- History of intestinal disease, inflammatory bowel disease, major gastric surgery, or
other gastrointestinal conditions (eg, uncontrolled nausea, vomiting, malabsorption
syndrome) likely to alter absorption of study treatment or result in inability to
swallow oral medications.

- Cardiac abnormalities.

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 11/10/23. Questions regarding updates should be directed to the study team contact.