The primary objective of this study is to evaluate the dose response, efficacy and safety of 4 different doses of fluticasone propionate (50, 100, 200, and 400mcg) delivered as Fluticasone Spiromax® Inhalation Powder (Fp Spiromax) when administered twice daily in subjects 12 years of age and older with severe persistent asthma who are uncontrolled on high dose ICS therapy.

Inclusion Criteria:

1. Written informed consent/assent signed and dated by the subject and/or parent /legal guardian before conducting any study related procedure.

2. Male or female 12 years and older, as of the Screening Visit. Male or female 18 years and older, as of the Screening Visit, in countries where local regulations or the regulatory status of study medication permit enrollment of adults only.

3. General good health, and free of any concomitant conditions or treatment that could interfere with study conduct, influence the interpretation of study observations/results, or put the subject at increased risk during the study.

4. Asthma Diagnosis: Asthma as defined by the National Institutes of Health (NIH).

5. Severity of Disease:

   • A best forced expiratory volume in one second (FEV1) of 40%-85% of the predicted normal value during the Screening Visit. NHANES III predicted values will be used for subjects aged ≥12 years and adjustments to predicted values will be made for African American subjects. ATS/ERS 2005 criteria for acceptability, reproducibility, and end of test must be met for spirometry

6. Reversibility of Disease: Demonstrated a ≥12% reversibility of FEV1 within 30 minutes following 2 inhalations of albuterol/salbutamol inhalation aerosol (if required, spacers are permitted for reversibility testing only) at the Screening Visit. If a subject fails to demonstrate an increase in FEV1 ≥12% then the subject is not eligible for the study and will not be allowed to re-screen. Reversibility values of 11.50 - 11.99 will be rounded to 12. Documented historical reversibility of ≥ 12 % within 3 months of the Screening Visit will be accepted.

7. Current Asthma Therapy: Subjects will be required to be on a short acting β2 agonist and inhaled corticosteroid for a minimum of 8 weeks before the Screening Visit and have been maintained on a stable dose of inhaled corticosteroids for four weeks prior to the Screening Visit at one of the following doses:

   • Fluticasone propionate HFA MDI ≥ 880 mcg/day
   • Fluticasone propionate DPI≥ 1000 mcg/day
   • Beclomethasone dipropionate DPI ≥ 2000 mcg/day
   • Beclomethasone dipropionate HFA (QVAR)≥ 640 mcg/day
   • Beclomethasone dipropionate HFA (Clenil Modulite)≥ 2000 mcg/day
   • Budesonide DPI ≥ 1600 mcg/day
   • Budesonide MDI ≥ 1600 mcg/day
   • Flunisolide ≥ 2000 mcg/day
   • Triamcinolone acetonide ≥ 2000 mcg /day
   • Mometasone furoate DPI ≥ 880 mcg/day
   • Ciclesonide HFA MDI ≥ 640 mcg/day

   Exception 1: Based upon the investigator's judgment that there is no inherent harm in changing the subject's current ICS/LABA therapy and the subject provides consent, subjects on inhaled Fluticasone propionate/salmeterol DPI ≥ 1000 mcg/day, or Fluticasone propionate/salmeterol HFA ≥ 880 mcg/day, or Fluticasone propionate/Formoterol ≥ 1000 mcg/day,or Beclomethasone dipropionate/Formoterol ≥ 400 mcg/day, or Budesonide/formoterol HFA ≥ 640 mcg/day, or Budesonide/formoterol DPI ≥ 800 mcg/day, or Mometasone furoate/formoterol MDI ≥ 800 mcg/day or subjects on a qualifying ICS dose plus a long-acting β2-agonists (LABA) administered via separate inhalers, may be switched to a qualifying dose of fluticasone propionate provided the subjects will not participate in the PK portion of the study.

   Exception 2: Subjects on a qualifying dose of fluticasone propionate who wish to participate in the PK portion of the study and who provide consent may have their fluticasone propionate switched to a different qualifying ICS (non-fluticasone propionate) at a pre-screening visit. The subject will be required to return to the clinic to complete the Screening Visit following a 1-week washout period.

8. Short-Acting β2-Agonists: All subjects must be able to replace their current short-acting β2-agonists with albuterol/salbutamol inhalation aerosol at the Screening Visit for use as needed for the duration of the study. The use of spacer devices with the metered dose inhaler (MDI) will not be allowed during the study with exception of it's use during reversibility testing at the Screening Visit. Nebulized albuterol/salbutamol will not be allowed at any time during the study. Subjects must be able to withhold all inhaled short-acting β2 sympathomimetic bronchodilators for at least 6 hours prior to all study visits.

9. If female, is currently not pregnant, breast feeding, or attempting to become pregnant, has a negative serum pregnancy test, and is of

   • Non-childbearing potential, defined as:

     • Before menarche, or
     • 1 year post-menopausal, or
     • Surgically sterile (tubal ligation, bilateral oophorectomy, or hysterectomy), or
     • Congenital sterility, or
     • Diagnosed as infertile and not undergoing treatment to reverse infertility or is of

   • Child-bearing potential, willing to commit to using a consistent and acceptable method of birth control as defined below for the duration of the study:

     • Systemic contraception used for 1 month prior to screening, including birth control pills, transdermal patch (Ortho Evra®), vaginal ring (NuvaRing®), levonorgesterel (Norplant®), or injectable progesterone (Depo-Provera®), or
     • Double barrier methods (condoms, cervical cap, diaphragm, and vaginal contraceptive film with spermicide), or
     • Intrauterine device (IUD) or
     • Monogamous with a vasectomized male partner or is of

   • Child-bearing potential and not sexually active, willing to commit to using a consistent and acceptable method of birth control as defined above for the duration of the study, in the event the subject becomes sexually active

10. Capable of understanding the requirements, risks, and benefits of study participation, and, as judged by the investigator, capable of giving informed consent/assent and being compliant with all study requirements (visits, record-keeping, etc).

Exclusion Criteria:

1. History of life-threatening asthma that is defined for this protocol as an asthma episode that required intubation and/or was associated with hypercapnea, respiratory arrest or hypoxic seizures.

2. Culture-documented or suspected bacterial or viral infection of the upper or lower respiratory tract, sinus, or middle ear that is not resolved within 2 weeks of the Screening Visit. In addition, the subject must be excluded if such infection occurs between the Screening Visit and the Randomization Visit.

3. Any asthma exacerbation requiring oral corticosteroids within 1 month of the Screening Visit. A subject must not have had any hospitalization for asthma within 2 month prior to the Screening Visit.

   Note: An exacerbation of asthma is defined as any worsening of asthma requiring any treatment other than rescue albuterol/salbutamol HFA MDI and/or the subject's regular inhaled corticosteroid maintenance treatment. This includes requiring the use of systemic corticosteroids and/or emergency room visit or hospitalization, a change in the subject's regular inhaled corticosteroid maintenance treatment, or the addition of other asthma medications.

4. Presence of glaucoma, cataracts, ocular herpes simplex, or malignancy other than basal cell carcinoma.

5. Historical or current evidence of a clinically significant disease including, but not limited to: cardiovascular (e.g., congestive heart failure, known aortic aneurysm, clinically significant cardiac arrhythmia or coronary heart disease), hepatic, renal, hematological, neuropsychological, endocrine (e.g., uncontrolled diabetes mellitus, uncontrolled thyroid disorder, Addison's disease, Cushing's syndrome), gastrointestinal (e.g., poorly-controlled peptic ulcer, GERD), or pulmonary (e.g., chronic bronchitis, emphysema, bronchiectasis with the need for treatment, cystic fibrosis, bronchopulmonary dysplasia, chronic obstructive pulmonary disease). Significant is defined as any disease that, in the opinion of the investigator, would put the safety of the subject at risk through participation, or which could affect the efficacy or safety analysis if the disease/condition exacerbated during the study.

6. Have any of the following conditions that, in the judgment of the investigator, might cause participation in this study to be detrimental to the subject, including, but not limited to:

   • Current malignancy excluding basal cell carcinoma; History of malignancy is acceptable only if the subject has been in remission for one year prior to the Screening Visit. (Remission is defined as no current evidence of malignancy and no treatment for the malignancy in the 12 months prior to the Screening Visit)
   • Current or untreated tuberculosis; History of tuberculosis is acceptable only if a subject has received an approved prophylactic treatment regimen or an approved active treatment regimen and has had no evidence of active disease for a minimum of 2 years
   • Uncontrolled hypertension (systolic BP ≥160 or diastolic BP >100)
   • Stroke within 3 months prior to the Screening Visit
   • Immunologic compromise

7. History of a positive test for HIV, hepatitis B or hepatitis C infection.

8. Untreated oral candidiasis at the Screening Visit. Subjects with clinical visual evidence of oral candidiasis and who agree to receive treatment and comply with appropriate medical monitoring may enter the study

9. History of any adverse reaction to any intranasal, inhaled or systemic corticosteroid therapy. Known or suspected sensitivity to the constituents of the dry powder inhalers (Spiromax or Diskus) used in the study (i.e., lactose).

10. History of severe allergy to milk protein.

11. Use of systemic, oral or depot corticosteroids within 4 weeks prior to the Screening Visit

    • Use of topical corticosteroids (≤1% hydrocortisone cream) for dermatological disease is permitted
    • Use of intranasal corticosteroids or ocular corticosteroids at a stable dose for at least 4 weeks prior to the Screening Visit and throughout the study is permitted

12. Use of immunosuppressive medications within 4 weeks prior to the Screening Visit and during the study.

13. Immunotherapy for the treatment of allergy at a stable maintenance dose for at least 90 days prior to the Screening Visit and which will remain at a stable dose without escalation throughout the study is permitted.

14. Use of Cytochrome P450 3A4 (CYP3A4) inhibitors (e.g., ritonavir, ketoconazole, itraconazole) within 4 weeks prior to the Screening Visit. Strong and moderate CYP3A4 inhibitors are prohibited and weak CYP3A4 are allowed.

15. History of alcohol or drug abuse within two years preceding the Screening Visit.

16. Current smoker or a smoking history of 10 pack years or more (a pack year is defined as smoking 1 pack of cigarettes/day for 1 year). A subject may not have used tobacco products within the past one year (e.g., cigarettes, cigars, chewing tobacco, or pipe tobacco).

17. Study participation by clinical investigator site employees and/or their immediate relatives.

18. Study participation by more than one subject from the same household at the same time. However, after the study completion or discontinuation by one subject another subject from the same household may be screened.

19. Participation in any investigational drug study within the 30 days (starting at the final follow-up visit) preceding the Screening Visit or planned participation in another investigational drug study at any time during this study.

20. Pregnancy, nursing, or plans to become pregnant or donate gametes (ova or sperm) for in vitro fertilization during the study period or for 30 days following the subject's last study related visit (for eligible subjects only - if applicable). Eligible female subjects unwilling to employ appropriate contraceptive measures to ensure that pregnancy will not occur during the study will be excluded.