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

Patients will be enrolled in two stages:

* Dose-escalation stage: Approximately 15-30 patients will be enrolled.
* Dose-expansion stage: 6-12 patients will be enrolled. Dose-escalation slots will be filled first, then dose-expansion slots.

* Dose-escalation stage : designed as classical 3+3 to determine MTD or RP2D to evaluate approximately GX-I7.
* Dose-expansion stage : designed to enroll additional 6-12 patients to acquire additional safety and pharmacodynamic data to more fully inform the dose selection for RP2D

Eligibility Criteria:
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