A Phase 3a, Repeat Dose, Open-label, Long-term Safety Study of Mepolizumab in Asthmatic Subjects

Inclusion Criteria:

- Informed Consent: Prior to commencing any study related activities, subjects must be
able and willing to provide written informed consent.

- Male or Eligible Female Subjects: To be eligible for the study, females of
child-bearing potential must commit to consistent and correct use of an acceptable
method of birth control and for 4 months after the last study drug administration. A
urine pregnancy test is required of all females of childbearing potential at the
initial Baseline Visit (Visit 1).

- French Subjects Only: In France, a subject will be eligible for inclusion in this
study only if either affiliated to or a beneficiary of a social security category.

- MEA115661 Participation: Subjects must have completed Visit 14 of MEA115661.

- Current Anti-Asthma Therapy: The subject's asthma has been treated with an ICS
controller medication for the last 8 months with fluticasone propionate (FP) >=500
mcg/day (or equivalent).

- Disease Severity: Subjects must be assessed as having life-threatening /serious
debilitating asthma in order to enroll, as defined by the following: Subjects enrolled
in MEA115588 must meet one of the following criteria: a) Subject has a history of at
least one intubation during their lifetime; b) >=3 asthma exacerbations in the 12
months prior to screening for MEA115588; c) >=1 or more hospitalization for asthma
exacerbation in the 12 months prior to screening for MEA115588. Subjects enrolled in
MEA115575 must meet one of the following criteria: d) Subject has a history of at
least one intubation during their lifetime; e) Their optimized dose at randomization
in MEA115575 was >=10mg of prednisone; f) >=1 or more hospitalization for asthma
exacerbation in the 12 months prior to screening for MEA115575.

- Clinical Benefit: Subjects must have experienced documented clinical benefit to
enroll. Subjects must meet the following criteria demonstrating clinical benefit:
Subjects enrolled in MEA115588 who received mepolizumab must meet all of the following
criteria: a) Subject must have had a reduction in their exacerbation frequency by
>=50% during MEA115588. The baseline for comparison is the total number of
exacerbations reported in the 12 months prior to screening for MEA115588. b) The
investigator response on the "Clinician-Rated Response to Therapy" questionnaire at
Visit 10 was either: mildly improved, moderately improved or significantly improved.
Subjects enrolled in MEA115588 who received placebo must meet all of the following
criteria: c) Subject must have had a reduction in their exacerbation frequency by
>=50% during the first 8 months of MEA115661. The baseline for comparison is the total
number of exacerbations reported in the 12 months prior to screening for MEA115588; d)
The investigator confirms that the subject demonstrated improvement during MEA115661.
Subjects enrolled in MEA115575 who received mepolizumab must meet all of the following
criteria: e) Subject must have reduced their oral corticosteroid dose by >=50% during
MEA115575. The baseline for comparison is the subject's optimized oral corticosteroid
(OCS) dose at randomization in MEA115575; f) The investigator response on the
"Clinician-Rated Response to Therapy" questionnaire at Visit 9 was either: mildly
improved, moderately improved or significantly improved. Subjects enrolled in
MEA115575 who received placebo must meet all of the following criteria: g) Subject
must have reduced their oral corticosteroid dose at randomization by >=50% in the
first 6 months of MEA115661. The baseline for comparison is the subject's optimized
OCS dose at randomization in MEA115575; h) The investigator confirms that the subject
demonstrated improvement during MEA115661.

Exclusion Criteria

- Health Status: Clinically significant change in health status during MEA115661 which
in the opinion of the investigator would make the subject unsuitable for participation
in this long-term study.

- Pregnancy: Subjects who are pregnant or breastfeeding. Subjects should not be enrolled
if they plan to become pregnanDeart during the time of study participation.

- Exacerbation History: Subjects who received placebo in MEA115588 and had NO
exacerbations during the study.

- Oral Corticosteroid Use: Subjects who received placebo in MEA115575 and were able to
discontinue oral corticosteroid therapy by the end of the study.

- Smoking Status: Current smokers

- Previous Significant Protocol Deviation: Subjects who were excluded from the per
protocol analysis due to significant protocol deviations in either study MEA115575 or
MEA115588.

- Electrocardiogram (ECG) Assessment: A clinically significant ECG abnormality at the
exit visit of MEA115661, as determined by the investigator.