Inclusion Criteria:  Voluntary signed and dated written informed consent prior to any specific study procedure. Male or female with age ≥ 18 years. Eastern Cooperative Oncology Group (ECOG) performance status (PS) ≤ 1. Life expectancy > 3 months. Pathologically confirmed diagnosis of advanced solid tumors [except for primary central nervous system (CNS) tumors], for which no approved therapy exists. Recovery to grade ≤ 1 from drug-related adverse events (AEs) of previous treatments, excluding alopecia and grade ≤2 asthenia or fatigue, according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE v.5).  Laboratory values within fourteen days prior to registration: a) Absolute neutrophil count (ANC) > 2.0 x 109/L, platelet count > 120 x 109/L and hemoglobin > 9.0 g/dL (patients may be transfused as clinically indicated prior to study entry). b) Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5 x upper limit of normal (ULN). c) Serum total bilirubin ≤ 1.0 x ULN. If total bilirubin is > 1.0 x ULN, but ≤ 1.5 x ULN, direct bilirubin must be ≤ 1.0 x ULN. d) Albumin ≥ 3.5 g/dL. e) Creatinine clearance (CLcr) >= 30 mL/min (using Cockcroft and Gault's formula).  f) Creatine phosphokinase (CPK) ≤ 2.5 x ULN.  Left ventricular ejection fraction (LVEF) by echocardiography (ECHO) or multiple-gated acquisition (MUGA) within normal range (according to institutional standards). Evidence of non-childbearing status for women of childbearing potential (WOCBP). WOCBP must agree to use a highly effective contraceptive measure up to six months after treatment discontinuation. As bosentan may render hormonal contraceptives ineffective, and taking into account the teratogenic effects observed in animals, hormonal contraceptives cannot be the sole method of contraception during treatment with bosentan. Fertile male patients with WOCBP partners should use condoms during treatment and for four months following the last investigational medicinal product (IMP) dose.  Exclusion Criteria:  Concomitant diseases/conditions: a) History or presence of unstable angina, myocardial infarction, congestive heart failure, or clinically significant valvular disease within last year. b) Symptomatic arrhythmia or any uncontrolled arrhythmia requiring ongoing treatment. c) Known cirrhosis, alcohol induced steatosis, or chronic active hepatitis. For hepatitis B, this includes positive test for both Hepatitis B surface antigen (HBsAg) and quantitative Hepatitis B polymerase chain reaction (PCR or HVB-DNA+). For hepatitis C, this includes positive test for both Hepatitis C antibody and quantitative Hepatitis C by PCR (or HVCRNA+). d) History of obstructive cholestatic liver disease (suitable for stenting procedure) or biliary sepsis in the past 2 months.  e) Active COVID-19 disease (this includes positive test for SARS-CoV-2 in nasopharyngeal/oropharyngeal swabs or nasal swabs by PCR).  Symptomatic, progressive or corticosteroids-requiring documented brain metastases or leptomeningeal disease involvement. Patients with asymptomatic documented stable brain metastases not requiring corticosteroids during the last four weeks are allowed. Use of (strong or moderate) inhibitors or inducers of CYP3A4 activity within three weeks prior to Day 1 of Cycle 1. Use of CYP3A4 substrates for which concomitant administration with moderate CYP3A4 inductor is contraindicated. Treatment with any investigational product within the 30 days before Day 1 of Cycle 1. Women who are pregnant or breast-feeding and fertile patients (men and women) who are not using an effective method of contraception. Psychiatric illness/social situations that would limit compliance with study requirements.