A Trial of Mepolizumab Adjunctive Therapy for the Prevention of Asthma Exacerbations in Urban Children

Inclusion Criteria: Study applicant(s) that fulfill all of the inclusion criteria and none of the exclusion criteria are eligible for the study- * Participant and/or parent guardian must be able to understand and provide informed consent and age-appropriate assent; * Must have a primary place of residence in one of the pre-selected recruitment census tracts as outlined in the study's Manual of Procedures (MOP); * Has had a diagnosis of asthma made \>1 year prior to recruitment; --Those who received an asthma diagnosis by a clinician ≤1 year prior to recruitment must report that their respiratory symptoms were present for more than 1 year prior to recruitment. * Has had ≥2 asthma exacerbations in the prior year (defined as a requirement for systemic corticosteroids and/or hospitalization); * At Visit 0 (Screening), has the following requirement for asthma controller medication: * For those ages 6 to 11 years, treatments with at least fluticasone 250 mcg dry powder inhaler (DPI) one puff twice daily or its equivalent and, * For those ≥12 years of age, treatment with at least Advair 250/50 mcg dry powder inhaler (DPI), one puff twice daily or its equivalent. * Has peripheral blood eosinophils ≥150 cells/µl obtained at Visit 0 (Screening) or in another Inner-City Asthma Consortium (ICAC) clinical research study within 6 months; * Is able to perform spirometry at randomization (Visit for treatment assignment); * Has documentation of current medical insurance with prescription coverage at randomization; and * Has had varicella or the varicella vaccination. Exclusion Criteria: Individual(s) who meets any of the following criteria are not eligible for enrollment or randomization- * Is not able or willing to give written informed consent or comply with the study protocol; * Has concurrent (existing) medical problems that would require systemic corticosteroids or other immunomodulator treatments during the study; * Is currently receiving immunotherapy; * Is currently receiving treatment with omalizumab or has had omalizumab treatment within 6 months prior to planned participant randomization to treatment assignment; * Is currently requiring greater than fluticasone 500 mcg administered twice daily plus a long-acting beta agonist (LABA) one puff twice daily or its equivalent, and/or --Individuals using oral corticosteroids daily or every other day for more than 14 days at the time of Visit 0 (Screening). * Is currently pregnant or lactating, or plans to become pregnant during the time of study participation --Note: Females of child-bearing potential (post-menarche) must be abstinent or use a medically acceptable birth control method throughout the study (e.g. oral subcutaneous, mechanical, or surgical contraception). * Has a known, pre-existing clinically important lung condition other than asthma; * Has a current malignancy or previous history of cancer in remission for less than 12 months prior to randomization; * Has known, pre-existing, unstable liver disease; * Is a current smoker or has a smoking history of 10 or more pack years; * Has a known immunodeficiency disease; * Has other conditions that could lead to elevated eosinophils such as hypereosinophilic syndromes, including eosinophilic granulomatosis with polyangiitis; * Has a known, active pre-existing parasitic infestation or is undergoing treatment for a parasitic infestation --Note: Once the individual has been successfully treated, the interested study applicant may be reevaluated for study eligibility. * Positive for use of investigational drugs within 4 weeks of randomization; * Has a past or current medical problems or findings from physical examination or laboratory testing that are not listed above, which, in the opinion of the study clinician, * May pose additional risks from participation in this study, * May interfere with the participant's ability to comply with study requirements, or * May impact the quality or interpretation of the data obtained from the study. * In the event that the study applicant will not allow the study clinician, an asthma specialist, to manage their disease for the duration of the study or who are not willing to change their asthma medications to follow the protocol; * Has a known history of allergic reaction to previous biologic therapy for asthma; or * Has had a life threatening asthma exacerbation in the last 2 years requiring intubation, mechanical ventilation or resulting in a hypoxic seizure.