The study is being conducted to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of single intravenous administration of SHR-1707 in healthy young adult and elderly subjects.

Inclusion Criteria:

1. Ability to understand the trial procedures and possible adverse events, be able and willing to provide a written informed consent
2. Male or female aged between 18 years and 45 years (inclusive) at the date of signed consent form in Part 1 and aged between 55 years and 80 years (inclusive) in Part 2
3. Total body weight of 45~100 kg (inclusive), with a body mass index (BMI) of 19~28 kg/m2 (inclusive)
4. Subjects with good general health, no clinically significant abnormalities, or have underlying disease which is believed to have minimal impact on the study treatment in elderly subjects
5. WOCBP agree to take effective contraceptive methods

Exclusion Criteria:

1. Severe injuries or surgeries within 6 months before screening
2. Positive hepatitis B virus (HBsAg), hepatitis C virus (HCV-Ab), or human immunodeficiency virus (HIV-Ab) at screening
3. ALT, or AST or total bilirubin level <1.5x upper limit of normal range (ULN) at screening or baseline visits
4. QTcF > 450msec (Male), QTcF > 470msec (Female) in 12-lead ECG test during screening and baseline
5. Known history or suspected of being allergic to Aβ antibody
6. Use of any medicine within 14 days (including any prescription, or over-the-counter medicine, herbal remedy or nutritional supplement, except for vitamins and acetaminophen with recommended dose [The dose of acetaminophen should be less than 2g/day, and no more than 3 days for continuous use]), or within 5 half-lives
7. Live (attenuated) vaccination within 1 month before screening
8. Blood donation or loss of more than 400 mL of blood within 3 months; or received blood transfusion within 3 months before screening.
9. History of alcohol abuse in the past 12 months of screening
10. History of illicit or prescription drug abuse or addiction within 12 months of screening
11. More than 5 cigarettes daily for 12 months before screening
12. Participation in clinical trials of other investigational drugs (include placebo) or medical devices within 3 months prior to screening
13. Researchers and relevant staff of the research center or other persons directly involved in the implementation of the program
14. The instigators determined that other conditions were inappropriate for participation in this clinical trial