IBI306 is a fully human monoclonal antibody that binds proprotein convertase substilisin/kexin type 9 (PCSK9), preventing its interaction with the low-density lipoprotein cholesterol receptor (LDL-R) and thereby restoring LDL-R recycling and low-density lipoprotein cholesterol（LDL-C）uptake. This is a randomized, double-blind, placebo-controlled,single ascending dose study to evaluate the safety, tolerability, pharmacokinetics/pharmacodynamics and immunogenicity of IBI306 in healthy adults.

Ascending dose design includes 6 dose levels （25 mg, 75 mg, 150 mg, 300 mg, 450 mg and 600 mg). Tolerance and safety data up to 14 days after dosing from all subjects of the previous cohort will be reviewed before proceeding to the next dose. Total duration of the study per subject is 12 weeks.

Inclusion Criteria:

• Chinese healthy men or women aged 18 to 55 years old at screening (inclusive）;
• Serum LDL-C concentration between 1.8 mmol/L and 4.9 mmol/L (inclusive）at screening;
• Body mass index between 19 and 28 kg/m2 (inclusive);
• Willing to maintain the current regular diet and physical activity;
• Female subjects and male subject's partner who could become pregnant should take effective contraceptions during the treatment period and 6 months after dosing;
• Without any medical history of serious diseases;
• Willing to comply with protocol required visit schedule and visit requirements and provide written informed consent.

Exclusion Criteria:

• Breast-feeding or pregnant women;
• History of allergic reaction;
• Previously received any anti-PCSK-9 treatment;
• Vital signs, physical examination, clinical laboratory test, 12-lead ECG, and chest X-ray are abnormal with clinical significance;
• Not willing to stop intense physical activities (such as weight lifting or long-distance running) before 72 hours of the scheduled visits;
• Any hospitalization within one month before screening, or major surgery within six months before screening, or any other unstable medical condition;
• Received an investigational chemical agent within 30 days before dosing；
• Received an investigational biological agent within 90 days before dosing；
• Use of medications including over-the-counter medication within 14 days or less than 5 half-lifes of the agent;
• Use of herb,vitamins or nutraceutical in order to alter serum lipids;
• Positive screen of hepatitis B surface antigen, hepatitis C virus, human immunodeficiency virus or syphilis infection at screening；
• History or clinical evidence of alcohol or drugs of abuse within 12 months before screening;
• With any consumption of alcohol and caffeinated beverages within 72 hours prior to and during the trial;
• Blood donations or blood loss 200 ml and more within 2 months before screening;
• History of organ transplantation or malignant tumor;
• Any conditions which, in the opinion of the Investigator, would make the subject unsuitable for enrollment.

Qualified researchers may request access to patient level data and related study documents including the study protocol with any amendments and statistical analysis plan. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants.