The purpose of this study is to characterize the safety and tolerability of ALTA2618 in adults with AKT1 E17K-mutant advanced solid tumors.

This is an open-label, multicenter, Phase 1/1b study of ALTA2618, a mutant-selective and orally bioavailable AKT1 E17K inhibitor, in adults with AKT1 E17K-mutant solid tumors. This study will evaluate the safety, tolerability, pharmacokinetics (PK), and preliminary clinical activity of ALTA2618, and aims to find the best dose. The study consists of two parts: Part 1 - Dose Escalation and Part 1b - Dose Expansion.

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.