The purpose of this study is to evaluate the safety, tolerability, and pharmacokinetics of a single subcutaneous dose of UB-621 in healthy volunteers.

This is a phase I, open-label, single dose, dose escalation study in healthy volunteers. Eligible volunteers will be sequentially enrolled into four escalating-dose cohorts at a study site. After administration of a single subcutaneous dose of UB-621, subjects will be followed for 70 or 112 days and monitored for safety, tolerability, and pharmacokinetics parameters.

Inclusion Criteria:

• With age between 20 and 55 years.
• With no clinically relevant abnormalities in vital signs, and clinical laboratory tests at screening visit judged by investigator.
• Body weight: <85 kg.
• Subject has signed the written informed consent form.

Exclusion Criteria:

• With significant active infection (acute or chronic) within 28 days prior to the screening visit.
• Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurologic or allergic diseases, or clinical findings within 3 months prior to the screening visit.
• Positive serology for HIV antibody, HCV antibody or HBV surface antigen.
• Female subjects who are breastfeeding, pregnant, and planning to become pregnant during the study period.
• The clinical investigator considers that the subject is not in the condition to participate in this study.