Study to Assess GTAEXS617 in Participants With Advanced Solid Tumors

Key Inclusion Criteria:

1. Eastern Cooperative Oncology Group (ECOG) performance status 0-1.
2. Life expectancy > 3 months.
3. One of the following histologically or cytologically confirmed advanced solid tumors: head and neck squamous cell carcinoma (HNSCC), pancreatic adenocarcinoma, non-small cell lung cancer (NSCLC), breast carcinoma (hormone receptor-positive [HR+] and Human Epidermal Growth Receptor 2 negative [HER2-] that has progressed to a prior treatment with Cluster of Differentiation 4 [CD4] / Cyclin-Dependent Kinase 6 [CDK6] inhibitor), or platinum-resistant high-grade epithelial ovarian, primary peritoneal, or fallopian tube cancers (HGSOC).
4. Must have disease that is advanced (ie, surgery or radiotherapy are not considered to be potentially curative), recurrent, or metastatic following SoC treatments.
5. Adequate hematological, liver, and renal function.
6. Must have tumor lesion(s) or metastases amenable to biopsy, excluding bone metastases.

Key Exclusion Criteria:

1. Active and clinically significant (CS) infection.
2. Refractory nausea and/or vomiting, chronic gastrointestinal disease, or previous significant bowel resection, with CS sequelae that would preclude adequate absorption of GTAEXS617.
3. Symptomatic central nervous system (CNS) malignancy or metastases.
4. Concurrent active or previous malignancy.
5. Prior organ or allogeneic stem-cell transplantation.
6. Moderate or severe cardiovascular disease.
7. Received anticancer therapy within 28 days or 5 half-lives (whichever is shorter) before the first dose of the study treatment.
8. Received treatment with known strong/moderate inhibitors and/or strong inducers of cytochrome P450 3A isoform subfamily (CYP3A) within 14 days or 5 half-lives before the first dose of study treatment.
9. Received treatment with known inhibitors or inducers of P-glycoprotein (P-gp) or breast cancer resistance protein (BCRP) within 14 days or 5 half-lives before the first dose of study treatment.
10. Received treatment with known substrates of organic anion transporting peptide 1B3 (OATP1B3) or BCRP within 14 days or 5 half-lives before the first dose of study treatment.
11. Unresolved or unstable serious toxic side-effects of prior chemotherapy or radiotherapy
12. Has had or is scheduled to have major surgery <28 days prior to the first dose of study treatment.

Note: Other protocol Inclusion/Exclusion criteria may apply.