This is a Phase 1, randomized, double-blind, placebo-controlled, single ascending dose study designed to assess the safety, tolerability, pharmacokinetics and pharmacodynamics of GX-I7 in healthy volunteers.

The subjects who are adequately eligible to attend this clinical trial via screening will be hospitalized one day prior to the injection (Day -1), administered a single dose of GX-I7 solution for subcutaneous injection, and then discharged on Day 3. After completing all scheduled tests at the visit 8 (Day 28), safety-related data of each cohort will be evaluated by Independent Safety Monitoring Committee (SMC). Dose escalation will proceed under the principal investigator, medical monitor, and the sponsor's mutual approval, referring to SMC's evaluation.

Inclusion Criteria:

1. Subject is willing and able to give informed consent after listening character of the clinical trial
2. Must be 19-45 years of age, inclusive
3. Weight 50-100kg, BMI 18-30kg/m2
4. Subject who is adequately able to attend the study based on medical history and physical exam, no clinically significant abnormality from vital sign and clinical laboratory values
5. No clinical abnormality from ECG test
6. Non-smoker (no smoking or no use of any product containing nicotine least for one month and negative from urine test)

Exclusion Criteria:

1. Suspected or confirmed malignancy, or has malignancy history
2. Any clinically significant acute or chronic medical condition requiring care of a physician, in liver, biliary tract, renal, nervous system (CNS or peripheral). respiratory system, endocrine (diabetes, hyperlipidemia etc), cardiovascular (congestive heart failure, coronary artery disease, myocardial infarction etc), hematology, malignancy, urinary disease, mental disorder, musculoskeletal disorder, immune system (rheumatoid arthritis, lupus etc), otorhinolaryngologic diseases
3. Positive to HBsAg, hepatitis C virus (HCV) Ab and HIV Ab
4. Are considering or scheduled to undergo any surgical or dental procedure during the study
5. Administered other Investigational Product (IP) by attending other clinical study or biological equivalent study within recent 3 months
6. Any Serious adverse drug reaction (SAR) against vaccines or antibiotics, any medical history with serious allergic diseases
7. Positive from urine drug screen or respiratory alcohol screen at medical screening or check-in
8. History of alcohol, drug, or substance abuse in the past 12 months
9. Consumption of alcohol within 48 hours prior to hospitalization
10. Medications with antacid, analgesic, herbal treatment, vitamin, mineral (except maximum 4 grams of acetaminophen) hormone, steroids, insulin, hypoglycemic drug or other hormone substitute within 14 days before administration
11. Planning pregnancy or donation of sperm/disagreeing proper contraception during the study and 3 months following IP administration
12. Do not have veins suitable for cannulation or multiple venipunctures
13. Any other factor that the Investigator thinks will increase subject risk with participation