Study to Evaluate Safety and Tolerability of GX-I7 in Patients With Locally Advanced or Metastatic Solid Tumors

Inclusion Criteria: * Signed Informed Consent Form (ICF) * Age ≥ 19 years * Able to comply with the study protocol, in the investigator's judgment * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 * Life expectancy ≥ 12 weeks * Adequate hematologic and end organ function, defined by the following laboratory results obtained within 14 days prior to the first study treatment (Cycle 1, Day 1) * Serum pregnancy test for women of childbearing potential (including women who have had a tubal ligation) must be performed and documented as negative within 14 days prior to Cycle 1, Day 1 * For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive measures, and agreement to refrain from donating sperm * Patients with histologic documentation of locally advanced, recurrent, or metastatic incurable solid tumors that has progressed after at least one available standard therapy; or for whom standard therapy has proven to be ineffective or intolerable, or is considered inappropriate * Patients with measurable disease per RECIST v1.1 Exclusion Criteria: * Inability to comply with study and follow-up procedures * Pregnancy, lactation, or breastfeeding * Significant cardiovascular disease, such as New York Heart Association cardiac disease (Class II or greater), myocardial infarction within the previous 3 months, unstable arrhythmias, and/or unstable angina * Known clinically significant liver disease, including active viral, alcoholic, or other hepatitis, cirrhosis, and inherited liver disease or current alcohol abuse * Poorly controlled Type 2 diabetes mellitus defined as a screening hemoglobin A1C ≥ 8% or a fasting plasma glucose ≥ 160 mg/dL (or 8.8 mmol/L) * Major surgical procedure within 28 days prior to Cycle 1, Day 1, or anticipation of need for a major surgical procedure during the study * Any anti-cancer therapy, whether investigational or approved, including chemotherapy, hormonal therapy, and/or radiotherapy, within 3 weeks prior to initiation of study treatment * Adverse events from prior anti-cancer therapy that have not resolved to Grade ≤ 1 except for alopecia, vitiligo, or endocrinopathy managed with replacement therapy * History of autoimmune disease, including but not limited to systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, vascular thrombosis associated with antiphospholipid syndrome, Wegener's granulomatosis, Sjögren's syndrome, Bell's palsy, Guillain-Barre syndrome, multiple sclerosis, vasculitis, or glomerulonephritis * Primary CNS malignancy, untreated CNS metastases, or active CNS metastases (progressing or requiring corticosteroids for symptomatic control) * History of severe allergic, anaphylactic, or other hypersensitivity reactions to chimeric or humanized antibodies or fusion proteins