This is an open-label, non-randomized, dose-escalation trial in patients with advanced solid tumors. The trial comprises 2 stages: a dose escalation stage at 8 dose levels of 2, 5, 10, 20, 40, 60, 80, and 100 mg/day,and possibly additional intermediate doses, to determine the MTD and recommended dose, and a subsequent 2 parts of expansion stage to investigate the safety profile and antitumor effect of OPB-51602 at the recommended dose.

In expansion stage part 1, up to 20 advanced sold tumor subjects will be investigated the safety profiled and antitumor effect of OPB-51602 at the recommended dose for 3 weeks per cycle（2 weeks treatment and 1 week washout). In the expansion stage part 2, a maximum of 20 subjects with Non-small cell lung cancer (NSCLC), Melanoma or Gastrointestinal Stromal Tumor (GIST) will be treated until an investigational Medicinal product (IMP) efficacious case can be found. subject dosing will be started on Day 1 without 2-day treatment free interval and continued until Day 28 at recommend dose (4mg) first in cycle 1. After safety and tolerability are confirmed, same subjects will be treated at the MTD(5mg) from cycle 2 onwards as a once-daily oral dose for 4 weeks per cycle to obtain additional information about safety, tolerability and antitumor activity of OPB-51602

Inclusion Criteria:

• Patients with pathologically confirmed, locally advanced or metastatic solid tumors who are unresponsive to standard therapy or for whom standard therapy is intolerable or unsuitable

• Age: ≥21 years (at time of informed consent)

• ECOG performance status: ≤2 (Appendix 1)

• Life expectancy of longer than 3 months

• Adequate vital organ function as follows:

  1. Bone marrow function Neutrophils: ≥1,500/μL, platelets: ≥75,000/μL, hemoglobin: ≥9.0 g/dL
  2. Hepatic function Aspartate transaminase (AST) and alanine transaminase(ALT): ≤2.5 ×institutional upper limit of normal(ULN) or ≤5.0 × institutional ULN if there is liver metastasis, serum total bilirubin: <2.5 × institutional ULN
  3. Renal function Serum creatinine: <1.5 × institutional ULN

• Capable of swallowing OPB-51602 tablets

• Ability to understand and willingness to sign written informed consent form (ICF) for participation in the trial

• No chemotherapy, radiotherapy, surgery, immunotherapy, or other therapy within 4 weeks prior to start of investigational medicinal product (IMP) administration and recovered from any prior toxicity

• If a subject has received more than 5 regimens of previous chemotherapy, the investigator must discuss with the sponsor regarding subject suitability prior to enrollment.

Exclusion Criteria:

• Uncontrolled central nervous system (CNS) metastasis
• Uncontrolled concurrent illness, including active infection, angina pectoris, cardiac arrhythmia, or heart failure (NYHA class III or IV, Appendix 2 New York Heart Association (NYHA) functional classification)
• Concurrent malignancy of a different type
• Immunocompromised subjects, including those who are known to be infected with human immunodeficiency virus (HIV)
• Psychiatric illness that would limit compliance with trial requirements
• Pregnant or breast-feeding women
• Women of childbearing potential (WOCBP) or male subjects whose partners are WOCBP who cannot or will not use effective contraceptive measures
• Administration of another investigational agent within 6 weeks prior to start of IMP administration
• Use of any of the prohibited medications and other substances listed in Appendix 3 CYP3A4 Inhibitors and Inducers within either 1 week prior to start of IMP administration or a period of at least 5 times the respective elimination halflife, whichever is longer
• Known severe gastrointestinal disorder, including malabsorption (at screening)
• Patients with CTCAE Grade 1 or higher pneumonitis (interstitial pneumonia) or pulmonary fibrosis* * If interstitial lung abnormalities, (e.g. ground-glass or linear opacity) are suspected on chest CT scan (high-resolution CT), regardless of whether or not there are any accompanying symptoms it must be confirmed, such as through consultation with a respiratory or radiology expert if necessary, that the patient dose not fall under this exclusion criterion before the patient can be enrolled in the trial.