A Study to Learn About Study Medicine ALTA3263 in Adults With Advanced Solid Tumors With KRAS Mutations

Inclusion Criteria:

• Histologically confirmed diagnosis of a solid tumor malignancy harboring a KRASmutation identified through molecular testing (NGS- or PCR-based) with a ClinicalLaboratory Improvement Amendments-certified (or equivalent) diagnostic test.

• Unresectable or metastatic disease.

• Progressed on, intolerant to, or declined prior standard-of-care therapy (includingtargeted therapy, if applicable) appropriate to tumor type and stage

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

• Adequate organ function

Exclusion Criteria:

• Prior treatment with a KRAS inhibitor, certain exceptions are described in the fullstudy protocol

• Known condition that prohibits the ability to swallow or absorb an oral medication.

Other inclusion/exclusion criteria may apply.