A Phase 2 Study to Evaluate the Safety and Efficacy of Intravenously Administered Benralizumab (MEDI-563).

The study will evaluate the effect of two intravenous dose regimens of benralizumab (MEDI-563) on the proportion of adult subjects with asthma exacerbations who required an urgent healthcare visit for treatment of an acute asthma exacerbation.

The study will evaluate the effect of two intravenous dose regimens of benralizumab (MEDI-563) (0.3 milligram per kilogram \[mg/kg\] of body weight and 1.0 mg/kg of body weight) on the proportion of adult subjects with asthma exacerbations (relapse and de novo) who required an urgent healthcare visit for treatment of an acute asthma exacerbation.

Eligibility Criteria:
Inclusion Criteria:

* Male or female subjects aged 18 to 60 years at the time of the administration of investigational product
* Written informed consent and Health Insurance Portability and Accountability Act (HIPAA) authorization (applies to covered entities in the US only) obtained from the subject/legal representative prior to performing any protocol-related procedures, including screening evaluations
* Physician-diagnosed asthma with a duration of greater than or equal to (\>=) 2 years by medical chart or subject report
* Had an asthma exacerbation requiring urgent care in the year prior to screening
* Meets National Heart, Lung, and Blood Institute (NHLBI) for persistent asthma in the 3 months prior to the current urgent healthcare visit
* Current asthma exacerbation that must have lasted \>= 2 hours prior to arrival to the urgent healthcare setting
* Requires at least 2 treatments of inhaled bronchodilators for the current asthma exacerbation in the urgent healthcare setting or within the emergency medical system (EMS) for \>= 1 hour
* Shows an FEV1 or PEF of not more than 70 percent (%) predicted after 1 hour of treatment of the current asthma exacerbation
* Women of child-bearing potential, unless surgically sterile (including tubal ligation) and/or at least 2 years post-menopausal, must have used 2 effective methods of avoiding pregnancy (including oral, transdermal, or implanted contraceptives, intrauterine device, female condom with spermicide, diaphragm with spermicide, cervical cap, abstinence, use of a condom with spermicide by the sexual partner, or sterile sexual partner) from screening through the end of the study (Day 84; Cessation of birth control after this point should be discussed with a responsible physician)
* Men, unless surgically sterile, must likewise practice 2 effective methods of birth control (condom with spermicide or abstinence) and must use such precautions from Day 0 through Day 84
* Otherwise healthy by medical history and physical examination
* A chest x-ray that is normal for an asthmatic population and excludes alternative diagnosis per the investigation
* Ability to complete the follow-up period until Day 168 as required by protocol
* The investigator has determined that the subject is clinically stable and the FEV1, is \>= 30% predicted prior to receiving investigational product on Day 0.

Exclusion Criteria:

* Known history of allergy or reaction to any component of the investigational product formulation
* Acute illness other than asthma at the start of the study
* Fever more than (\>) 38.6 degrees Celsius (C) (\>101.5 degrees Fahrenheit \[F\])
* Current acute asthma attack is due to aspirin-induced asthma
* Current asthma episode is an anaphylactoid/anaphylactic reaction presenting with acute bronchospasm
* Evidence of clinically significant non-respiratory active infection, including ongoing chronic infection
* History or current prolonged diarrhea, abdominal pain, and/or blood and mucus in stools or have minor symptoms and have exposure to stream or lake water, been exposed to someone who has a parasitic infection (like a family member), or study subject has traveled outside the United States of America (USA) and/or Canada within the last year
* Use of immunosuppressive medication (except oral prednisone and inhaled and topical corticosteroids) within 30 days before randomization into the study
* Have received Xolair within 6 months before randomization into the study
* Receipt of immunoglobulin or blood products within 30 days before randomization into the study
* Receipt of any investigational drug therapy within 6 months before the first dose of investigational product in this study through Day 168
* History of primary immunodeficiency
* Previous medical history, or evidence, of an intercurrent illness that may compromise the safety of the subject in the study
* History of clinically significant abnormality on ECG in the opinion of the investigator
* Pregnancy (must have a negative serum pregnancy test prior to the first dose of investigational product)
* Breastfeeding or lactating woman
* History of treatment for alcohol or drug abuse within the past year
* Diagnosis of chronic obstructive pulmonary disease (COPD) by a healthcare professional
* Evidence of any clinically significant systemic disease on physical examination
* History of cancer except basal cell carcinoma or in situ carcinoma of the cervix treated with apparent success with curative therapy \>1 year prior to entry or other malignancies treated with apparent success with curative therapy \>5 years prior to entry
* Known exposure to inhaled occupational agents or fumes with an established diagnosis of occupational asthma
* Any condition (that is, impending ventilatory failure or hemodynamic compromise) that, in the opinion of the investigator, would interfere with evaluation of the investigational product or interpretation of study results
* Any employee of the clinical study site who is involved with the conduct of the study
* History of cigarette smoking \>20 pack years
* Previously received benralizumab (MEDI-563)
* Asthma exacerbation due to acute inhalational exposure.