Inclusion Criteria:
* Males and nonpregnant and non-breastfeeding females, aged ≥ 18 years of age at the time of signing the informed consent.
* Subjects with advanced solid tumors resistant or refractory to standard treatment.
* Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1.
* Measurable disease per RECIST 1.1 criteria.
* Adequate hematological function defined by absolute neutrophil count, ≥ 1.5 × 10\^9/L, platelet count ≥ 100 × 10\^9/L, and hemoglobin ≥ 9 g/dL, and without growth factor treatment or blood transfusion within 2 weeks before the study intervention start.
* Adequate hepatic function defined by total bilirubin level ≤ 1.5 × upper limit of normal (ULN), aspartate aminotransferase (AST) level ≤ 3 × ULN, and an alanine aminotransferase (ALT) level ≤ 3 × ULN.
* Adequate renal function defined by creatinine clearance \> 60 mL/min according to the Cockcroft-Gault equation or creatinine levels \<1.5 mg/dl.
* Adequate coagulation laboratory assessments, as follows: Prothrombin time (PT) or partial thromboplastin time (PTT) \< 1.5 x upper limit of normal (ULN), or international normalized ratio (INR) \< 1.5 or within target range if on prophylactic anticoagulation therapy.
* Life expectancy of \> 3 months, in the opinion of the Investigator.
* Willing to adhere to contraception, egg and sperm donation, the fasting requirement, and other criteria as described in lifestyle restrictions
* Capable of giving signed informed consent.
Exclusion Criteria:
* Clinically significant (i.e., active) uncontrolled intercurrent illness.
* Presence of brain metastases unless clinically stable.
* History or presence of malignancies unless curatively treated with no evidence of disease ≥ 2 years.
* Subjects with known human immunodeficiency virus and/or active viral hepatitis (B and/or C), and subjects on viral hepatitis B therapy are excluded. However, subjects with hepatitis C treated with curative therapy are not considered actively infected.
* Subject received a live vaccine within 30 days prior to the first dose of the study treatment administration.
* Serious gastrointestinal bleeding within 3 months, refractory nausea and vomiting, uncontrolled diarrhea, known malabsorption, significant small bowel resection or gastric bypass surgery, use of feeding tubes, other chronic gastrointestinal disease, and/or other situation that may preclude adequate absorption of oral medications.
* Subjects that have received a strong CYP3A4 inhibitor within 7 days prior to the first dose of TT125-802 or a strong CYP3A4 inducer within 14 days prior to the first dose of TT125-802.
* Hypersensitivity to the active substance or to any of the excipients of TT125-802.
