To evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of SHR-1707 in patients with mild cognitive impairment (MCI) due to Alzheimer's disease (AD) and mild AD for 26 weeks.

Inclusion Criteria:

1. Ability to understand the trial procedures and possible adverse events, voluntarily participate in the trial,
2. Male or female aged between 55 years and 85 years (inclusive) at the date of signed consent form.
3. Total body weight of 45~100 kg (inclusive), with a body mass index (BMI) of 19~32 kg/m2 (inclusive)at screening or baseline.
4. The subjects must meet the following clinical criteria for Mild cognitive impairment (MCI) due to Alzheimer's Disease (AD) or criteria for mild AD.
5. The subjects should have a stable caregiver who will help the patients to participate in the whole study process.

Exclusion Criteria:

1. Cognitive impairment due to other medical or neurological factors (non-AD).
2. History of stroke or transient ischemic attack, seizures, or other unexplained loss of consciousness within the past 1 year.
3. Any psychiatric diagnosis that may interfere with the subject's cognitive assessment.
4. Inability to tolerate MRI examination or have contraindications to MRI examination.

6. Exclusion criteria related to previous or concomitant diseases, as listed in the protocol.

7. Exclusion criteria related to general or laboratory tests, as listed in the protocol.

8. The subject is suicidal according to the investigator's judgment or has committed suicidal behaviour within 6 months prior to the screening period.

9. Severe visual or hearing impairment, unable to cooperate in the scale examination.

10. Patients suspected to be allergic to Aβ antibody drugs and their excipients.

11. Women who are pregnant, or women of childbearing age with positive pregnancy test results or are lactating.

12. History of drug abuse and/or drug addiction within 1 year prior to screening.

13 Use of dual antiplatelet or anticoagulant drugs within 3 months prior to the randomization period or planned during the trial.

14.Have had prior treatment with an anti-amyloid immunotherapy within 1 year prior to randomization.

15. Those who have participated in a clinical trial of any drug or medical device within 3 months prior to screening.

16. Investigators and site-related personnel or other persons directly involved in the implementation of the protocol.

17. Other unspecified reasons that, in the opinion of the investigator or sponsor, make the subject unsuitable for enrolment.