Study of Mepolizumab Autoinjector in Asthmatics

Inclusion Criteria

• Age: At least 12 years of age inclusive, at the time of signing the informed consent. For those countries where local regulations permit enrolment of adults only, subject recruitment will be restricted to those who are >=18 years of age.
• Asthma: A physician diagnosis of asthma for >=2 years that meets the National Heart, Lung and Blood Institute guidelines or Global Initiative for Asthma guidelines.
• Mepolizumab treatment:

a. Not receiving mepolizumab treatment at Visit 1. These subjects must also meet following inclusion criteria related to eosinophilic asthma, inhaled corticosteroid, controller medication and exacerbation history):

• Eosinophilic asthma: A high likelihood of eosinophilic asthma as per the required 'Continuation to Treatment'-criterion,
• Inhaled corticosteroid: A well-documented requirement for regular treatment with high dose inhaled corticosteroid (ICS) in the 12 months prior to Visit 1 with or without maintenance oral corticosteroids (OCS), for subjects >=18 years old, ICS dose must be >=880 micrograms (mcg)/day fluticasone propionate (FP) (ex-actuator) or equivalent daily, For ICS/long-acting-beta-2-agonist (LABA) combination preparations, the highest approved maintenance dose in the local country will meet this ICS criterion, for subjects >=12 to =440 mcg/day FP (ex-actuator) or equivalent daily, for ICS/LABA combination preparations, the mid-strength approved maintenance dose in the local country will meet this ICS criterion. (Subjects will be permitted to be enrolled without continuous high dose ICS providing the subject was receiving continuous ICS and the Investigator attest that the subject should have been treated with high dose ICS to mitigate the risk of exacerbations, or the subject has financial or tolerance issues that prevent the use of high-dose ICS. Such subjects should be discussed with GSK Medical Monitor prior to enrolment)
• Controller medication: Current treatment with an additional controller medication, besides ICS, for at least 3 months or a documented failure in the past 12 months of an additional controller medication (e.g., LABA, leukotriene receptor antagonist [LTRA], or theophylline) for at least 3 successive months.
• Exacerbation history: Previously confirmed history of one or more exacerbations requiring treatment with systemic corticosteroid (CS) [intramuscular (IM), intravenous, or oral] in the 12 months prior to Visit 1, despite the use of high-dose ICS. For subjects receiving maintenance CS, the CS treatment for an exacerbation must have been a two-fold dose increase or greater.

or, b. Receiving 100 mg SC mepolizumab administered for the treatment of severe eosinophilic asthma every 4 weeks for at least 12 weeks prior to Visit 1.

• Body weight: A minimum body weight >=40 kilograms (kg) at Visit 1
• Gender: Male or female. A female subject is eligible to participate if she is not pregnant (as confirmed by a negative urine human chorionic gonadotrophin [hCG)]test), planning to become pregnant during the time of study participation (and up to 16 weeks after the last dose), not lactating, and at least one of the following conditions applies: Non-reproductive potential defined as: pre-menopausal females with documented tubal ligation or documented hysteroscopic tubal occlusion procedure with follow-up confirmation of bilateral tubal occlusion or hysterectomy or documented bilateral oophorectomy, postmenopausal female, reproductive potential and agrees to follow highly effective methods for avoiding pregnancy in females of reproductive potential from 30 days prior to the first dose of study medication and until 16 weeks after the last dose of study medication and completion of the end of study/early withdrawal visit. The investigator is responsible for ensuring that subjects understand how to properly use these methods of contraception.
• Informed consent: Capable of giving signed informed consent.

Exclusion Criteria

• Concurrent respiratory di