Inclusion Criteria:  Part A (Healthy participants):  Healthy participants aged 18 to 55 years, inclusive:  Japanese participants must be aged 20 to 55 years, inclusive Chinese participants must be aged 18 to 45 years, inclusive Females must have a negative pregnancy test at the Screening Visit and on admission to the Clinical Unit, must not be lactating, and must be of non childbearing potential, confirmed at the Screening Visit Have a body mass index (BMI) between 18 and 30 kg/m^2 inclusive and weigh at least 45 kg. Healthy participant must have a forced expiratory volume in 1 second (FEV1) ≥ 80% of the predicted value regarding age, height, gender, and ethnicity at the Screening Visit. Male participants and their women of childbearing potential partners (WOCPB) should be willing to use highly effective contraception measures and male participants should refrain from donating sperm or fathering a child from the first day of dosing until 3 months after the study Follow up Visit. Part A2 and Part A4 (Chinese population only): Chinese participants must have been born in China, have all parents and grandparents of Chinese origin, and not have lived outside of China for more than 10 years. Part A2 and Part A4 (Japanese population only): Japanese participants must have been born in Japan, have all parents and grandparents of Japanese origin, and not have lived outside of Japan for more than 10 years.  Part B (Participants with Asthma):  Male and female including WOCBP participants with asthma aged 18 to 75 years inclusive, with suitable veins for cannulation or repeated venipuncture. Have a BMI between 18 and 35 kg/m^2 inclusive and weigh at least 45 kg. Confirmed physician-led diagnosis of asthma for > 6 months before the Screening Visit. Bronchodilator reversibility of FEV1 > 12% and at least 200 mL at screening or in their previous history. Pre-bronchodilator FEV1 ≥ 40% and < 85% predicted at the Screening Visit. Have a fractional exhaled nitric oxide (FeNO) of ≥ 35 ppb at the Screening Visit and ≥ 30 ppb at randomisation. Asthma Control Questionnaire -5 score of ≥ 0.75 and ≤ 3.0 at screening.  During 7 consecutive days within screening, immediately prior to randomisation demonstrates ≥ 65% adherence to each of the following:  Once daily home FeNO Twice daily home spirometry measurements Twice daily entries in the eDiary Females must have a negative pregnancy test at the Screening Visit and at Visit 2 (prior to randomisation) and must not be lactating. Male participants and their WOCBP partners should be willing to use highly effective contraception measures and male participants should refrain from donating sperm or fathering a child from the first day of dosing until 3 months after the study Follow-up Visit. WOCBP must be willing to use highly effective contraception measures from the first day of dosing until 3 months after the study Follow up Visit.  Exclusion Criteria:  Part A (Healthy participants)  History of following: any clinically important disease or disorder; any upper or lower respiratory tract infection during screening period; active tuberculosis or current positive result for Interferon gamma release assay at screening; clinically significant history of atopy or allergy to common allergens including house dust mite and pollens, or a history of childhood asthma. Active or previous hepatitis B, hepatitis C, or Human immunodeficiency virus at the Screening Visit, and other latent or chronic infections. History of severe COVID-19 (Coronavirus disease 2019) infection requiring hospitalization SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2) first vaccination within 30 days prior to screening. SARS-CoV-2 second or booster vaccination within 10 days of screening. Unwilling to defer SARS-CoV-2 vaccination during the study period. History of cancer within last 10 years (20 years for breast cancer) except for basal and squamous cell carcinoma of skin or in situ carcinoma of cervix treated and considered cured. Any history of lymphoma is not allowed. Have received live or live attenuated vaccine in 4 weeks prior to randomisation. History of acquired or inherited immunodeficiency disorders including but not limited to HIV, COVID-19, or taking immune replacement therapy. C-reactive protein above upper limit of laboratory reference range Any clinically important abnormalities in clinical chemistry, haematology or urinalysis results and abnormal vital signs at the Screening Visit. Current smokers or those who have smoked or used nicotine products. History of alcohol abuse Use of any prescribed or nonprescribed medication during the 2 weeks prior to the first administration of investigational medicinal product. Has received another new chemical entity. History of severe allergy/hypersensitivity or ongoing clinically important allergy/hypersensitivity, as judged by the investigator, or history of hypersensitivity to drugs with a similar chemical structure or class to AZD8630. History of anaphylaxis to any previous biological therapy. Participants who have previously received AZD8630.  Part B (Participants with Asthma):  History of following: any clinically important disease or disorder; any chronic respiratory disorders (except asthma) such as Chronic obstructive pulmonary disease, bronchiectasis, or IPF; clinically significant lower respiratory tract infection not resolved within 4 weeks prior to screening. Acute exacerbation of asthma requiring hospitalisation and/or attendance at an emergency department and/or systemic corticosteroids within 3 months of randomisation. History of active TB or a current positive result for IGRA at screening. History of severe COVID-19 infection requiring hospitalisation. SARS-CoV-2 first vaccination within 30 days prior to screening. SARS-CoV-2 second or booster vaccination within 10 days of screening. Confirmed COVID-19 infection during screening, by PCR test, prior to randomisation. History of cancer within the last 10 years (20 years for breast cancer) except for basal and squamous cell carcinoma of the skin or in situ carcinoma of the cervix treated and considered cured. Any history of lymphoma is not allowed. Have received live or live attenuated vaccine in the 4 weeks prior to randomisation. C-reactive protein above the upper limit of laboratory reference range at screening. Any clinically important abnormalities in clinical chemistry, haematology or urinalysis results, and abnormal vital signs at the Screening Visit. Current smokers or those who have smoked or used nicotine products. History of alcohol or drug abuse. Positive screen for drugs of abuse or cotinine (nicotine) prior to randomisation. Use of drugs with enzyme inducing properties such as St John's Wort within 3 weeks before first administration of study drug. Use of any prescribed or nonprescribed medication during the 2 weeks prior to the first administration of study drug. Use of following medicines within specified time before Screening: (a) Any biologics for asthma within 6 months prior to Screening; (b) Systemic or intranasal steroids within 4 weeks prior to Screening; (c) Xanthines, anticholinergics, or cromoglycate within 1 week prior to Screening; (d) Short acting bronchodilator other than for rescue and within 12 hours prior to Screening and Day -1 assessments. History of anaphylaxis or ongoing clinically important serious allergy, or history of hypersensitivity or anaphylaxis to drugs with a similar chemical structure or class to AZD8630. History of anaphylaxis to any previous biological therapy. Pregnancy or intention to become pregnant during course of study, breastfeeding, or unwillingness to use a highly effective method of contraception throughout study in female participants of childbearing potential or lactating woman.