SL-28 for Advanced Solid Tumours

Inclusion Criteria: * Ability to provide written informed consent prior to any study-related procedures and to understand the nature, purpose, and potential risks of the study * Adult males and females ≥18 years of age at screening * Life expectancy of at least 3 months * Histologically or cytologically confirmed unresectable advanced solid tumor (recurrent, metastatic, or locally advanced) * Disease refractory to, intolerant of, or refusal of standard therapies, including immunotherapy and molecular/biomarker-directed treatments, as determined by the Principal Investigator (PI) or delegate * Eligible tumor types include: * Head and neck squamous cell carcinoma * Thoracic malignancies (small-cell lung cancer, non-small cell lung cancer, esophageal cancer) * Gastrointestinal malignancies (gastric, liver, colorectal, pancreatic adenocarcinoma) * Genitourinary malignancies (bladder, renal cell, prostate cancer) * Gynecologic malignancies (ovarian, endometrial cancer) * Breast cancer and melanoma * Evaluable disease per RECIST v1.1 * ECOG performance status 0-1 (or up to 2 at PI discretion) * Adequate organ function, defined as: * Total bilirubin ≤1.5 × ULN (≤2.0 × ULN for liver metastases or Gilbert's syndrome) * AST, ALT, alkaline phosphatase ≤2.5 × ULN (≤5 × ULN if liver metastases, at PI discretion) * Creatinine clearance ≥50 mL/min (Cockcroft-Gault) or eGFR ≥50 mL/min (CKD-EPI) * Absolute neutrophil count ≥1,000/mm³ * Platelet count ≥100,000/mm³ * Hemoglobin ≥90 g/L without transfusion within 2 weeks * Prothrombin time and aPTT ≤1.5 × ULN (or stable INR if on anticoagulation) Female patients: -Non-childbearing potential (surgically sterile or postmenopausal), or of childbearing potential with negative pregnancy tests and agreement to effective contraception through 90 days post-dose Male patients: * Agreement not to donate sperm for 90 days post-dose * Agreement to use adequate contraception as applicable * Suitable venous access for blood sampling * Willingness and ability to comply with study procedures and protocol requirements Exclusion Criteria: * Ongoing toxicities ≥ Grade 2 per NCI CTCAE v5.0 (except alopecia, fatigue, sensory neuropathy, or adequately treated endocrine deficiencies) * NYHA Class III or IV heart disease, myocardial infarction within 6 months, unstable arrhythmia, or ischemia on ECG * QTcF \>470 ms (females) or \>450 ms (males) * Active, uncontrolled bacterial, viral, or fungal infection requiring systemic therapy * Requirement for systemic corticosteroids or other immunosuppressive therapy that cannot be discontinued ≥14 days prior to dosing * Prior therapies within restricted timeframes: * Immune checkpoint inhibitors or biologics within 28 days * Antineoplastic therapies, surgery, radiotherapy, or radiopharmaceuticals within 21 days * Unapproved investigational drugs within 5 half-lives * Nitrosoureas or mitomycin C within 6 weeks * Concurrent malignancy within 5 years, except specified low-risk cancers * Pregnancy or breastfeeding * Known HIV, hepatitis B (HBsAg positive), or hepatitis C infection * Inability or unwillingness to comply with protocol procedures * History of anaphylaxis or significant allergy interfering with participation * Clinically significant cardiovascular, pulmonary, hepatic, renal, hematologic, gastrointestinal, endocrine, neurologic, psychiatric, or immunologic disease within 6 months * Conditions affecting drug absorption, distribution, metabolism, or excretion * Receipt of live vaccines within 28 days prior to screening * Participation in another investigational study within 30 days prior to screening