A Study to Learn About Study Medicine ALTA2618 in Adults With AKT1 E17K-Mutant Solid Tumors

Inclusion Criteria: * Histologically confirmed diagnosis of a solid tumor malignancy harboring AKT1 E17K mutation identified through molecular testing (NGS- or PCR-based) with a Clinical Laboratory Improvement Amendments-certified (or equivalent) diagnostic test. * Unresectable or metastatic disease * Progressed on, intolerant to, or declined prior standard-of-care therapy (including targeted therapy, if applicable) appropriate to tumor type and stage * Evaluable or measurable disease per RECIST v1.1 * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. * Adequate organ function. Exclusion Criteria: * Prior treatment with PI3K and/or mTOR inhibitors * Patients known to have KRAS, NRAS, HRAS, or BRAF genomic alterations in their tumor * Known condition that prohibits ability to swallow or absorb an oral medication Other inclusion/exclusion criteria may apply.