CLIO-8221 Dosing in Advanced Solid Tumors

Study start date: February 28, 2026

Inclusion Criteria: * Patients with advanced solid tumors * Patients must have metastatic or unresectable disease not suitable for further local treatment and should have received prior beneficial therapies unless ineligible, unwilling, or lacking access. * LVEF ≥50% by echocardiogram (ECHO) or multigated acquisition (MUGA) scan. * An Eastern Cooperative Oncology Group (ECOG) Performance Status score of 0 or 1 * Measurable disease per RECIST version 1.1 at baseline Exclusion Criteria: * Prior anti-tumor treatment with an ATRi. * Prior or concurrent malignancy whose natural history or treatment has the potential to interfere with the safety or efficacy assessment of the investigational regimen. Exceptions are malignancies with a negligible risk of metastasis or death (e.g., 5-year OS ≥90%), including, but not limited to, adequately treated carcinoma in situ of the cervix, non-melanoma skin carcinoma, localized prostate cancer, ductal carcinoma in situ, and Stage I uterine cancer. * History of uncontrolled seizure disorders or clinically significant neurodegenerative disorders, including progressive peripheral neuropathy. Stable Grade ≤ 2 peripheral neuropathy is allowed. * Clinically significant autoimmune disease, either currently present or present within the previous 2 years, including a current requirement for systemic immunosuppressive therapy equivalent to \>10 mg/prednisone daily (local immunosuppressive therapy such as inhaled or topical corticosteroids is allowed). * Any uncontrolled Grade ≥ 3 (per NCI CTCAE version 6.0) viral, bacterial, or fungal infection within 2 weeks prior to Cycle 1 Day 1. Routine antimicrobial prophylaxis is permitted. * History of hepatic cirrhosis, autoimmune hepatitis, or drug-associated hepatitis within the past 12 months. * Uncontrolled diabetes mellitus, defined as Hgb A1c ≥8% or Hgb A1c between 7% and \<8% with associated diabetes symptoms (polyuria or polydipsia) that are not otherwise explained. * Any other medical, social, or psychosocial factors that, in the opinion of the investigator, could impact safety or compliance with study procedures. Additional protocol defined inclusion/exclusion criteria may apply