This is a randomized, double-blind, placebo-controlled, single ascending dose and multiple ascending dose phase I clinical study to evaluate the safety, tolerability, PK and immunogenicity of SSGJ-627 in healthy adult subjects after single subcutaneous injection.

Seven dose groups are planned for dose escalation in SAD of this study. Subjects in all dose groups will receive a single subcutaneous injection. Group S1 follows open-labeled, single-arm design, Groups S2 to S7 follow randomized, double-blinded, placebo-control design. Blood samples will be collected for PK, immunogenicity, biomarkers, laboratory tests, etc. according to the study schedule throughout the study.

Inclusion Criteria:

• Able to understand protocol requirements and sign a written ICF.
• Male or female subjects aged 18-45 years when signing the ICF.
• Male subjects with body weight ≥ 50 kg, and female subjects with body weight ≥ 45 kg. Subjects with BMI between 18 and 28 kg/m2.
• Subjects whose test results are normal, or abnormal without clinical significance as determined by the investigator.
• Female subjects with childbearing potential and male subjects (and their female partners) must agree to take highly effective contraceptive measures.

Exclusion Criteria:

• History of severe allergy, or with a history of allergy to the study treatment or related excipients.
• History of of significant alcohol abuse.
• History of significant drug abuse.
• Subjects who have positive result for urine nicotine test at screening.
• Pregnant, or nursing females.