Open-label Study to Assess Reduction of Background Asthma Medication While Sustaining Asthma Control and Clinical Remission With Tezepelumab in Patients 12-80yrs With Severe Asthma.

Eligibility Criteria

• 1. Any clinically important pulmonary disease other than asthma (eg, active lung infection, chronic obstructive pulmonary disease, bronchiectasis, pulmonary fibrosis, cystic fibrosis, hypoventilation syndrome associated with obesity, lung cancer, alpha 1 anti-trypsin deficiency, and primary ciliary dyskinesia) or pulmonary or systemic diseases, other than asthma, that are associated with elevated peripheral EOS counts (eg, allergic bronchopulmonary aspergillosis/mycosis, Churg-Strauss syndrome, hypereosinophilic syndrome).
• 2. Any disorder, including, but not limited to, cardiovascular, gastrointestinal, hepatic, renal, neurological, musculoskeletal, infectious, endocrine, metabolic, haematological, psychiatric, or major physical impairment that is not stable in the opinion of the investigator and could:
• * Affect the safety of the patient throughout the study
• * Influence the findings of the study or the interpretation
• * Impede the patient's ability to complete the entire duration of study.
• 3. A helminth parasitic infection diagnosed within 6 months prior to Visit 1 that has not been treated with, or has failed to respond to, standard of care therapy.
• 4. Current smokers or patients with smoking history ≥ 10 pack-years and patients using vaping products, including electronic cigarettes. Former smokers with a smoking history of \< 10 pack-years and users of vaping or e-cigarette products must have stopped for at least 6 months prior to Visit 1 to be eligible.
• 5. History of chronic alcohol or drug abuse within 12 months prior to Visit 1.
• 6. Tuberculosis requiring treatment within the 12 months prior to Visit 1.
• 7. History of known immunodeficiency disorder including a positive human immunodeficiency virus test at Visit 1, or the patient taking antiretroviral medications as determined by medical history and/or patient's verbal report.
• 8. Major surgery within 8 weeks prior to Visit 1 or planned surgical procedures requiring general anaesthesia or inpatient status for \> 1 day during the conduct of the study.
• 9. Evidence of COVID-19 within 4 weeks prior to screening or ongoing clinically significant COVID-19 sequelae.
• 10. Receipt of any marketed or investigational biologic agent within 4 months or 5 half-lives (whichever is longer) prior to Visit 1 or receipt of any investigational nonbiologic agent within 30 days or 5 half-lives (whichever is longest) prior to Visit 1.
• 11. OCS-dependent patients (received chronic OCS therapy \[prednisone ≥ 5 mg/day or equivalent\]) for at least 3 months preceding Visit 1.
• 12. Daily use of maintenance corticosteroids for any reason.
• 13. Treatment with systemic immunosuppressive/immunomodulating drugs (eg, methotrexate, cyclosporine, etc.), except for OCS used in the treatment of asthma/asthma exacerbations, within the last 12 weeks or 5 half-lives (whichever is longer) prior to Visit 1.
• 14. Receipt of immunoglobulin or blood products within 30 days prior to Visit 1.
• 15. Receipt of live attenuated vaccines 30 days prior to the date of Visit 1 and during the study.
• 16. Patients that have been treated with bronchial thermoplasty in the last 12 months prior to Visit 1.
• 17. Known history of sensitivity to any component of the tezepelumab formulation or a history of drug or other allergy that, in the opinion of the investigator or medical monitor, contraindicates their participation.
• 18. History of anaphylaxis or documented immune complex disease (Type III hypersensitivity reactions) following any biologic therapy.
• 19. Concurrent enrolment in another clinical study involving an IMP.
• 20. Any clinically meaningful abnormal finding in physical examination, haematology, clinical chemistry at Visit 1 which, in the opinion of the investigator, may put the patient at risk because of his/her participation in the study, or may influence the results of the study, or the patient's ability to complete the entire duration of the study.
• 21. Evidence of active liver disease, including jaundice or AST, ALT, or ALP \> 2 times the ULN at Visit 1.
• 22. Positive hepatitis B surface antigen, hepatitis C virus antibody serology at screening, or a positive medical history for hepatitis B or C. Patients with a history of hepatitis B vaccination without a history of hepatitis B are allowed to participate.
• 23. Involvement in the planning and/or conduct of the study (applies to AstraZeneca staff and/or site staff), or patients employed by or relatives of the employees of the site or AstraZeneca.
• 24. Judgement by the investigator that the patient should not participate in the study if the patient is unlikely to comply with study procedures, restrictions, and requirements.
• 25. For women only: Pregnant, breastfeeding, or lactating women. A serum β-HCG pregnancy test must be drawn for WOCBP at the screening visit. If the results of the serum β-HCG cannot be obtained prior to dosing of the IMP, a patient may be enrolled on the basis of a negative urine pregnancy test, though serum β-HCG must still be obtained. If either test is positive, the patient should be excluded. Since urine and serum tests may miss a pregnancy in the first days after conception, relevant menstrual history and sexual history, including methods of contraception, should be considered. Any patient whose menstrual and/or sexual history suggests the possibility of early pregnancy should be excluded.