This study is a single center, randomized, double-blind, placebo-controlled, single dose, dose escalation Phase I clinical study aimed at evaluating the safety, tolerability, pharmacokinetics, pharmacodynamics, and immunogenicity of CM559 administered intravenously at different doses in healthy male subjects.

Inclusion Criteria:

• Subjects age ≥ 18 years & ≤60 years.
• Subjects voluntarily signed the Informed Consent Form and were able to comply with the provisions of this protocol.

Exclusion Criteria:

• The average number of cigarettes smoked per day is greater than 5 within 3 months prior to screening.
• Drinking heavily within 3 months prior to screening, or unable to guarantee not to drink alcohol during the research period, or positive alcohol breath testing.
• History of drug abuse within 1 year prior to screening, or positive urine drug abuse screening.
• Blood donation or any other form of blood loss exceeding 400mL, or accepting blood transfusion within 12 weeks prior to screening.
• Suspected allergy to Aβ-antibody drugs, humanized monoclonal antibody drugs and their excipients, or other biological agents, or have a history of severe allergic reactions to other drugs.
• Severe trauma or undergo major surgery within 3 months prior to screening,or planned surgery during the research period.