This study will assess the efficacy and safety of 610 as an adjunctive therapy in adult subjects with severe eosinophilic asthma.

This is a multicenter, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of 610 in adults with severe eosinophilic asthma. Plan to recruit 120 subjects, and the subjects divided into 3 groups: 610 100mg group, 610 300mg group and placebo group. The study is divided into screening period of 4 weeks, treatment period of 16 weeks and follow-up period of 8 weeks.

Inclusion Criteria:

• Able to understand and follow the protocol requirements, and give written informed consent prior to participation voluntarily in the study
• Female and male aged 18 to 75 years
• Diagnosed with asthma for ≥12 months that meet GINA
• Within 6 months before screening, treatment with medium to high dose inhaled corticosteroid（ICS，inhaled fluticasone at a dosage of at least 500 μg, or equivalent, daily. ICS can be included in In the ICS/LABA combination preparation）and at least one other additional controller medication, such as long-acting β₂ receptor agonist (LABA), leukotriene receptor antagonist (LTRA), theophylline, long-acting Anticholinergic drugs (LAMA), etc. Those medicine must be stable for ≥ 28 days prior to screening and baseline and must continue without dosage changes throughout the study
• Current treatment with maintenance oral corticosteroids (OCS), prednisone dosage must be ≤10 mg, or equivalent, daily, and stable for ≥ 28 days prior to screening and baseline and must continue without dosage changes throughout the study
• In the past 12 months prior to screening， two or more asthma exacerbations history, or at least one time emergency department (ED) visits and/or ICU and/or hospitalization
• Pre-bronchodilator FEV1 <80% predicted value
• Positive of bronchodilator test or positive of bronchial provocation test
• Asthma Control Questionnaire score ≥1.5
• Asthma-related blood eosinophils ≥ 300 cells/μL within 6 months before screening, or asthma-related blood eosinophils ≥ 150 cells/μL at screening
• Male and their partners or female must commit to correct use of one or more effective contraceptive measures of the duration of the trial and for 6 months after the last study drug administration. No fertility, sperm donation, or egg donation plans for at least 6 months after the last study drug administration

Exclusion Criteria:

• With clinically important lung diseases other than asthma that may affect safety or efficacy and evaluated by investigator. This includes lung infection, chronic obstructive pulmonary disease, bronchiectasis, hypersensitivity pneumonitis, pulmonary fibrosis, Allergic bronchopulmonary aspergillosis, etc.
• With other conditions that could lead to elevated eosinophils such as hypereosinophilic syndromes, eosinophilic granulomatosis with polyangiitis (EGPA), or eosinophilic esophagitis
• In past 12 months prior to screening，patients has done bronchial thermoplasty or radiotherapy or plan to do it during of the trial
• with severe cardiac disease or uncontrolled or severe cardiac arrhythmia
• poorly controlled systemic disease
• Active infection that requiring systemic treatment at screening
• Parasitic infection without adequate treatment within 6 months before screening
• Lymphoproliferative disease or any malignancy history within past 5 years prior to screening (Except for received treatment and no recurrence in the past 3 months include basal cell carcinoma, actinic keratosis, carcinoma in situ of cervix, or resected non-invasive malignant colonic polyps.)
• Liver function meets one of the following criteria at screening or before randomization: a) Serum aspartate aminotransferase (AST) or serum alanine aminotransferase (ALT) ≥ 2.0×ULN (upper limit of normal); b) Total bilirubin≥1.5×ULN
• At screening, HBsAg or HCV Ab or HIV Ab or TP Ab positive; HBsAg or HCV Ab positive need to be further tested of HBV DNA titer detection or HCV RNA detection (More than normal value range needs to be excluded)
• Subjects who have received any monoclonal antibody treatment within 3 months or 5 half-lives (whichever is longer) before screening, or with poor treatment effect of anti-IL-5/5R
• Vaccination history with live vaccines (including live attenuated vaccines) within 4 weeks before screening, or plan to receive during of the trial
• Participated in any interventional clinical trial and received intervention within 3 months before screening
• Allergy/intolerance to investigational medicinal product.
• Current smokers with average monthly smoking of ≥10 cigarettes within 6 months before screening, or former smokers with a smoking history of ≥10 pack years (number of pack years = (number of cigarettes per day / 20) x number of years smoked)
• Plan to pregnant during of the trial or pregnant or breastfeeding
• Any other things that are not suitable for participating in this study