This is a phase I study intended to determine the MTD and RP2D of SKI-G-801 monotherapy by assessing the safety and tolerability including dose-limiting toxicity (DLT) at various dose levels and to explore the efficacy and PK in patients with advanced solid tumors.

This is an open-label, monotherapy study in patients with advanced solid tumors, to evaluate the safety, tolerability, and pharmacokinetics (PK) of multiple ascending doses of SKI-O-801(Denfivontinib). A total of 36 subjects are planned to participate in 6 cohorts (traditional 3+3 design). In each cohort, 3 subjects will receive SKI-O-801. Dosing will be initiated with a 100 mg once daily (QD) dose cohort and escalated to 500 mg QD. After 1 cycle (28 days) of treatment if 3 subjects in each cohort have no DLT(Dose Limiting Toxicity), escalate the next dose level by Safety Review Committee decision.

Inclusion Criteria:

• Male and female adults aged 19 years and older

• Subjects with histologically and/or cytologically confirmed, unresectable advanced or metastatic solid tumors that are confirmed as PD after the standard of care currently known to have clinical benefits, or for which no currently available standard therapies exist due to intolerance, ineligibility, refusal, etc.

• At least 1 evaluable lesion based on RECIST version 1.1 (the irradiated area or biopsied lesion will be considered evaluable if PD is demonstrated).

• The Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0-1

• Life expectancy of at least 12 weeks

• The last screening test results obtained within 7 days prior to the first dose of the IP (baseline) meet the following (with no administration of granulocyte colony-stimulating factor [G-CSF] or erythropoietin [EPO], or transfusion within 14 days prior to the laboratory tests)

  1. Hematological function ANC ≥1,500/μL Hemoglobin ≥9 g/dL Platelet count ≥100,000/μL
  2. Renal function: Creatinine clearance (CrCl) ≥45 mL/min (MDRD equation)
  3. Hepatic function AST ≤2.0 × ULN ALT ≤2.0 × ULN (AST/ALT ≤5 × ULN, if hepatic metastasis is confirmed) Total bilirubin ≤1.5 × ULN (<3.0 × ULN, if Gilbert's syndrome is confirmed)
  4. Blood coagulation function: prothrombin time (PT) (international normalized ratio [INR]) and activated partial thromboplastin time (aPTT) ≤1.5 × ULN (with an exception of PT or aPTT in the therapeutic range as per the purpose of anticoagulants if the subject is taking anticoagulants such as warfarin, heparin, or low molecular weight heparin)

• Voluntary written consent to participate in this study

Exclusion Criteria:

• 7th line or greater palliative systemic anti-cancer therapy for advanced or metastatic solid tumors (postoperative adjuvant therapy is considered as a single line of therapy if the disease recurs within 6 months after the last treatment, while endocrine therapy is excluded from the line of therapy)

• History of AXL inhibitors

• Difficulty (e.g., problem swallowing) in oral administration of SKI-G-801 or disease (celiac disease, Crohn's disease, or intestinal resection which is clinically significant or impacts absorption) which impact absorption

• Hypersensitivity to the active ingredient or excipients of SKI-G-801

• Major surgery within 4 weeks prior to IP administration

• Minor surgery within 2 weeks prior to IP administration

• Women who have a positive pregnancy test or are pregnant or breastfeeding at screening, or female subjects of childbearing potential or male subjects who do not agree to remain abstinent or use effective methods of contraception** for at least 27 weeks (female subjects) or 14 weeks (male subjects) after the last dose of the IP

  **Effective forms of contraception are defined as the following:

  1. Hormonal contraceptives (implants, injectables, oral contraceptives, etc.)
  2. Intrauterine device or intrauterine system (copper loop, hormone containing intrauterine system)
  3. Surgical sterilization (vasectomy, tubal ligation, etc.) of a subject or spouse (or partner)
  4. Double-barrier method with spermicide (including condom, diaphragm, vaginal sponge, or cervical cap; a male and a female condom must not be used together)

• Toxicity associated with prior anti-cancer therapy that does not resolve to Grade ≤1 or baseline (with the exceptions of alopecia [any grade], Grade ≤2 neuropathy, and endocrinopathy that is not controlled by hormone replacement therapy)

• History of using another investigational product/device within 4 weeks (or 5 half-lives, whichever is shorter) prior to IP administration

• Ineligibility or inability to participate in the study at the judgement of the investigator