Extension Study to Evaluate the Safety and Tolerability of Tezepelumab in Adults and Adolescents With Severe, Uncontrolled Asthma

Inclusion Criteria: * Provision of signed and dated written informed consent * Negative urine test for female subjects of childbearing potential prior to administration of IP at visit 1 * Females of childbearing potential who are sexually active with a nonsterilized male partner must use a highly effective method of contraception from screening, and must agree to continue using such precautions for 16 weeks after the final dose of IP. * Female or male subjects who have not met investigational product discontinuation criteria and have attended the EOT visit in either study D5180C00007 (NAVIGATOR) or D5180C00009 (SOURCE) To enter the extended follow-up phase of the study, the following inclusion criteria also apply: * Provision of signed and dated Addendum for Extended Follow-up to informed consent, as well as assent by adolescent subjects where applicable, prior to any mandatory study specific procedures, sampling and analyses before Extended Follow Up. * Must have entered DESTINATION from D5180C00007 study and have completed IP dosing to Week 100, have not met IP Discontinuation criteria and have attended the EOT Visit. Exclusion Criteria: * Any clinically important pulmonary disease other than asthma * Any disorder, including, but not limited to cardiovascular, gastrointestinal, hepatic, renal, neurological, musculoskeletal, infectious, endocrine, metabolic, hematological, psychiatric, or major physical impairment that is not stable * History of chronic alcohol or drug abuse within 12 months prior to visit 1 * Current malignancy or malignancy that developed during a predecessor study * Major surgery or planned surgical procedures requiring general anesthesia or inpatient status for \> 1 day during the conduct of the study * Treatment with systemic immunosuppressive/immunomodulating drugs except for OCS used in the treatment of asthma/asthma exacerbations within the last 12 weeks prior to randomization * Concurrent enrolment in another clinical study involving an IP * Any clinically meaningful abnormal finding in physical examination, vital signs, ECG,haematology, clinical chemistry, or urinalysis during the predecessor study * Pregnant, breastfeeding, or lactating To enter the extended follow-up phase of the study (which extends from week 104 to week 140), the following exclusion criteria also apply: * Discontinuation of IP during the treatment period of DESTINATION. * Entered DESTINATION from D5180C00009 (SOURCE) study.