Inclusion Criteria - Asthma cohort
* Body weight of ≥40 kg and BMI ≤45 kg/m2 at SV1a.
* Physician-diagnosed asthma
* Currently receiving treatment with low, medium, to high dose ICS in combination with at least 1 additional asthma controller medication.
* Must have experienced at least 1 asthma exacerbation requiring the use of systemic corticosteroids.
* Participants in a stable condition, must have a historical peripheral blood eosinophil count of ≥250 cells/μL and/or FeNO ≥ 25 ppb.
* Current acute asthma exacerbation requiring an urgent healthcare visit for treatment.
* Peripheral blood eosinophil count of ≥300 cells/µL as part of the assessment of an index acute asthma exacerbation.
* Requires systemic corticosteroid as SoC in the urgent healthcare setting to treat the current acute asthma exacerbation.
* FEV1 ≥30% predicted.
Exclusion Criteria - Asthma cohort
* Regular use of immunosuppressive medication.
* Unstable ischemic heart disease, cardiomyopathy, heart failure, uncontrolled hypertension.
* Current or former smoker, with a smoking history of ≥5 pack-years if \<30 years old or ≥10 pack-years if ≥30 years old
* COPD and other clinically significant pulmonary disease other than asthma.
* Known or suspected history of immunosuppression.
* History of known immunodeficiency disorder or hepatitis B or C.
* History of alcohol abuse and/or drug abuse.
* Recent history of cancer except basal cell carcinoma or in situ carcinoma of the cervix or other malignancies treated with apparent success with curative therapy.
* Female participant who is pregnant, lactating or breast-feeding.
* Recent receipt of any marketed nonbiologic drug that modulates type 2 cytokines.
* Recent receipt of any marketed biologic drug or any investigational biologic for asthma or other diseases.
* Recent live, attenuated vaccinations or planned live, attenuated vaccinations during the trial.
* Participants that have been recently treated with bronchial thermoplasty.
* Recent receipt of any investigational nonbiologic drug.
* A recent chest X-ray or computed tomography with findings that are inconsistent for an asthmatic population.
Inclusion Criteria - COPD cohort
* Body weight of ≥45 kg and BMI ≤45 kg/m2
* Physician-diagnosed COPD
* Must have experienced at least 1 COPD exacerbation requiring the use of systemic corticosteroids.
* Participants in a stable condition must have a historical peripheral blood eosinophil count of ≥250 cells/μL and/or FeNO ≥ 25 ppb.
* Current or former smoker with a history of smoking of ≥10 pack-years.
* Current acute COPD exacerbation requiring an urgent healthcare visit for treatment.
* Peripheral blood eosinophil count of ≥300 cells/μL as part of the assessment of the index acute COPD exacerbation.
* Requires systemic corticosteroids as standard of care treatment in the urgent healthcare setting for the current acute COPD exacerbation.
Exclusion Criteria - COPD cohort
* Regular use of immunosuppressive medication 12 weeks or 5 half-lives prior to approximately 12 weeks or 5 half-lives, whichever is longer.
* Current diagnosis or a history of asthma, according to the Global Initiative for Asthma; or participants with a current diagnosis or history of Asthma COPD Overlap Syndrome.
* Other respiratory disorders that might compromise the safety of the participant or affect the interpretation of the results.
* Unstable ischemic heart disease, cardiomyopathy, heart failure, uncontrolled hypertension. Cardiac arrhythmias including paroxysmal atrial fibrillation.
* Transient ischemic attack or stroke \<6 months from Screening Visit; hospitalization for any cardiovascular or cerebrovascular event \<6 months from Screening Visit.
* Known or suspected history of immunosuppression.
* History of known immunodeficiency disorder or hepatitis B or C.
* History of alcohol abuse and/or drug abuse.
* Recent history of cancer except basal cell carcinoma or in situ carcinoma of the cervix treated with apparent success.
* Chronic treatment with long-term oxygen therapy or nocturnal oxygen therapy required for \>15 hours a day.
* Participants on long-term macrolide.
* Current acute COPD exacerbation for which SoC was started \>48 hours prior to Screening.
* A recent chest X-ray or computed tomography scan reveals evidence of clinically significant abnormalities or pulmonary infection.
* Female participant who is pregnant, lactating or breast-feeding.
* Receipt of any marketed nonbiologic drug that modulates type 2 cytokines 30 days or 5 half-lives prior to SV1b, whichever is longer.
* Receipt of any marketed or any investigational biologic for COPD or other diseases within 16 weeks or 5 half-lives, whichever is longer.
* Live, attenuated vaccinations within 4 weeks prior to screening or planned live, attenuated vaccinations during the trial.
The above inclusion and exclusion criteria are not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.
