Inclusion Criteria:
1. Understand the study and voluntarily sign the informed consent form.
2. Age ≥18 and ≤80 years old, male or female, weight ≥40 kg.
3. The subject has been diagnosed with asthma for at least 1 year.
4. Pre-bronchodilator FEV1 measured ≤80% of the normal predicted value.
5. A positive bronchodilation test within 24 months before informed consent or at screening.
6. The subject has received medium-to-high dose ICS combined with at least one control drug, such as LABA, LAMA, LTRA, Oral corticosteroids, theophylline, for at least 3 months before signing the informed consent, and maintained stable treatment regimen and dosage for at least 1 month before signing the informed consent.
7. Asthma Control Questionnaire-5 (ACQ-6) score ≥1.5.
8. Subjects must have experienced at least one severe asthma exacerbation event within 12 months before informed consent, and have not experienced a severe asthma exacerbation event within 30 days before informed consent.
9. ≥ 80% compliance with usual asthma controller therapy in subjects during the screening phase
10. Voluntarily use highly effective contraception from the time of signing the informed consent form until 3 months after the last dose.
Exclusion Criteria:
1. Chronic obstructive pulmonary disease (COPD) without asthma or other lung disease that may impair lung function, as judged by the investigator.
2. Have systemic diseases other than asthma that result in an elevated peripheral blood eosinophil count or other diseases such as helminth parasitic infections for which standard treatment is not received or does not respond.
3. Prior autoimmune disease or inflammatory treatment with biologic agents/systemic immunosuppressive agents within 8 weeks or 5 half-lives (whichever is longer) prior to informed consent.
4. Previous history of known or suspected immunosuppression, including a history of invasive opportunistic infection, even if the infection has resolved; or the presence of unusual frequent, recurrent, or prolonged infections.
5. History of malignancy.
6. The presence of any severe and/or uncontrolled medical condition that in the judgment of the investigator may affect the evaluation of the drug, including but not limited to: severe neurological disease, history of severe mental disorder, diabetes mellitus poorly controlled by intensive treatment.
7. Active infection or acute infection requiring systemic anti-infective therapy from 4 weeks before enrollment to the time of randomization.
8. A history of severe cardiovascular disease or clinically significant abnormalities identified by 12-lead electrocardiogram (ECG) during the screening phase.
9. Major surgery within 8 weeks prior to informed consent requiring general anesthesia or hospitalization for \> 1 day .
10. Received biological agents with the same therapeutic purpose within 4 months or 5 half-lives (whichever is longer) before signing the informed consent.
11. Have been enrolled in a clinical trial of any drug or medical device within 3 months before signing informed consent, or are within the follow-up period of a clinical study or the five half-lives of the trial drug (whichever is longer) before signing informed consent.
12. Received immune globulin or blood products within 30 days before informed consent.
13. Subjects treated with systemic corticosteroids other than for the treatment of asthma from 8 weeks before signing the informed consent to the date of randomization.
14. Received live or attenuated vaccine within 3 months before informed consent.
15. Initiation of desensitization therapy within 3 months before informed consent.
16. Underwent bronchial thermoplasty within 12 months before informed consent.
17. Current smokers or former smokers who quit smoking less than 6 months or former smokers who quit smoking more than 6 months with a smoking history of more than 10 pack-years.
18. At screening, any infectious disease screening indicator meets one of the following criteria: a. HBsAg positive b. HBsAg negative , HBcAb positive, HBV DNA exceed the lower limit of quantitation (LLOQ) or 1000 copies/mL (500 IU/mL)(whichever is lower) c. HCV antibody positive, HCV RNA exceed the LLOQ or 1000 copies/mL(whichever is lowerd). d.HIV antibody positive. e.Treponema pallidum antibody positive
19. At screening, aspartate aminotransferase (AST) or alanine aminotransferase (ALT) \> 2 × upper limit of normal (ULN), or serum creatinine (Cr) \> 1.5 × ULN.
20. Allergy or intolerance to components of CM326 injection or placebo or history of severe drug allergy or anaphylactic shock.
21. Subjects who have used heavy alcohol within 3 months before screening.
22. History of drug abuse within 5 years before signing informed consent.
23. Females with a positive pregnancy test, pregnant females, or lactating females.
24. The investigator considers that there are any conditions that may prevent the subject from completing the study.
