A Phase III Parallel Group Study, Comparing the Efficacy, Safety and Tolerability of the Fixed Dose Combination (FDC) of Fluticasone Furoate+Umeclidinium Bromide+Vilanterol (FF/UMEC/VI) With the FDC of FF/VI in Subjects With Inadequately Controlled Asthma

Inclusion Criteria for Screening * Age: 18 years of age or older at the time of signing the informed consent. * Diagnosis: Subjects with a diagnosis of asthma as defined by the National Institutes of Health at least one year prior to Visit 0. * Symptomatic: Subjects with inadequately controlled asthma (ACQ-6 score \>=1.5) despite ICS/LABA maintenance therapy at Visit 1. * Asthma Control: In the 1 year prior to Visit 1 * A documented healthcare contact for acute asthma symptoms or * A documented temporary change in asthma therapy for acute asthma symptoms, according to a pre-specified asthma action plan (or equivalent) * Current Asthma Maintenance Therapy: Subjects are eligible if they have required daily ICS/LABA for at least 12 weeks prior to Visit 0 with no changes to maintenance asthma medications during the 6 weeks immediately prior to Visit 0 (including no changes to a stable total dose of ICS of \>250 mcg/day fluticasone proprionate \[FP, or equivalent\]). * Spirometry: A best pre-bronchodilator morning (ante meridian \[AM\]) FEV1 \>=30% and \<85% of the predicted normal value at Visit 1. Predicted values will be based upon the European Respiratory Society (ERS) Global Lung Function Initiative. * Reversibility of Disease: airway reversibility defined as \>=12% and \>=200 milliliter (mL) increase in FEV1 between 20 and 60 minutes following 4 inhalations of albuterol/salbutamol aerosol at Visit 1. * If the subject does not meet the above reversibility criteria at Visit 1 then the reversibility assessment may be repeated once within 7 days of Visit 1 if either criteria a) or b) are met: a) \>=9% increase in FEV1 between 20 and 60 minutes following 4 inhalations of albuterol/salbutamol aerosol at Visit 1. b) Documented evidence of a reversibility assessment within 1 year prior to Visit 1 which demonstrated a post-bronchodilator increase in FEV1 of \>=12% and \>=200 mL. Should the subject successfully demonstrate airway reversibility (defined as \>=12% and \>=200 mL increase in FEV1 between 20 and 60 minutes following 4 inhalations of albuterol/salbutamol aerosol) at the second attempt then, provided that all other eligibility criteria assessed at Visit 1 are met, the subject may enter the 3-week run-in period. * Short-Acting beta2 Agonists (SABAs): All subjects must be able to replace their current SABA inhaler with albuterol/salbutamol aerosol inhaler at Visit 1 as needed for the duration of the study. Subjects must be judged capable of withholding albuterol/salbutamol for at least 6 hours prior to study visits. * Male or eligible Female, defined as having documentation of non-reproductive potential or reproductive potential as follows: A female subject is eligible to participate if she is not pregnant (as confirmed by a negative serum human chorionic gonadotrophin (hCG) test), not lactating, is not planning on becoming pregnant during the study 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 defined as 12 months of spontaneous amenorrhea with an appropriate clinical profile (e.g., age appropriate, \>45 years, in the absence of hormone replacement therapy). In questionable cases for women \<60 years of age, a blood sample with simultaneous follicle stimulating hormone and estradiol falling into the central laboratory's postmenopausal reference range is confirmatory. Females under 60 years of age, who are on hormone replacement therapy (HRT) and whose menopausal status is in doubt, are required to use a highly effective method to avoid pregnancy if they wish to continue their HRT during the study. Otherwise, they must discontinue HRT to allow confirmation of post-menopausal status prior to study enrolment. For most forms of HRT, at least 2 to 4 weeks will elapse between the cessation of therapy and the blood draw; this interval depends on the type and dosage of HRT. Following confirmation of their post-menopausal status, subjects can resume use of HRT during the study without use of a highly effective method to avoid pregnancy; Reproductive potential and agrees to follow one of the options listed in the Modified List of Highly Effective Methods for Avoiding Pregnancy in Females of Reproductive Potential (FRP) from the screening visit until after the last dose of study medication and completion of the follow-up visit. The Investigator is responsible for ensuring that subjects understand how to properly use these methods of contraception. * Informed Consent: Able to give written informed consent prior to participation in the study, which will include the ability to comply with the requirements and restrictions listed in the consent form and in this protocol. Subjects must be able to read, comprehend, and write at a level sufficient to complete study related materials. Exclusion Criteria for Screening * Pneumonia: Chest X-ray documented pneumonia in the 6 weeks prior to Visit 1. * Asthma Exacerbation: Any asthma exacerbation requiring a change in maintenance asthma therapy in the 6 weeks prior to Visit 1. Note: Subjects requiring a temporary change in asthma therapy (e.g., oral corticosteroids or increased dose of ICS) to treat an exacerbation in the 6 weeks prior to Visit 1 are not explicitly excluded at Visit 1 provided that, at the Investigator's discretion, the subject's condition is stable after they have resumed their pre-exacerbation maintenance asthma therapy (without modification) and they are considered appropriate for enrolment into this study of up to 12 month's duration. * Chronic Obstructive Pulmonary Disease: Subjects with the diagnosis of chronic obstructive pulmonary disease, as per Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines, including history of exposure to risk factors (i.e., especially tobacco smoke, occupational dusts and chemicals, smoke from home cooking and heating fuels) and a post-albuterol/salbutamol FEV1/Forced Vital Capacity (FVC) ratio of \<0.70 and a post-albuterol/salbutamol FEV1 of =\<70% of predicted normal values and onset of disease \>=40 years of age. * Concurrent respiratory disorders: Subjects with current evidence of pneumonia, active tuberculosis, lung cancer, significant bronchiectasis, sarcoidosis, lung fibrosis, pulmonary hypertension, interstitial lung diseases or other active pulmonary diseases or abnormalities other than asthma. * Risk Factors for Pneumonia: Immune suppression (e.g., human immunodeficiency virus, Lupus) or other risk factors for pneumonia (e.g., neurological disorders affecting control of the upper airway, such as Parkinson's Disease, Myasthenia Gravis). * Patients at potentially high risk (e.g., very low body mass index (BMI), severely malnourished, or very low FEV1) will only be included at the discretion of the Investigator. * Other diseases/abnormalities: Subjects with historical or current evidence of clinically significant cardiovascular, neurological, psychiatric, renal, hepatic, immunological, gastrointestinal, urogenital, nervous system, musculoskeletal, skin, sensory, endocrine (including uncontrolled diabetes or thyroid disease) or hematological abnormalities that are uncontrolled. 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 would affect the efficacy or safety analysis if the disease/condition exacerbated during the study. * Unstable liver disease as defined by the presence of ascites, encephalopathy, coagulopathy, hypoalbuminemia, esophageal or gastric varices or persistent jaundice, cirrhosis, known biliary abnormalities (with the exception of Gilbert's syndrome or asymptomatic gallstones). Note: Chronic stable hepatitis B and C are acceptable if the subject otherwise meets entry criteria. * Clinically significant Electrocardiogram abnormality: Evidence of a clinically significant abnormality in the 12-lead ECG performed during screening. The Investigator will determine the clinical significance of each abnormal ECG finding in relation to the subject's medical history and exclude subjects who would be at undue risk by participating in the trial. An abnormal and clinically significant finding is defined as a 12-lead tracing that is interpreted as, but not limited to, any of the following: Atrial fibrillation (AF) with rapid ventricular rate \>120 Beats Per Minute (BPM); sustained or non-sustained ventricular tachycardia (VT); Second degree heart block Mobitz type II and third degree heart block (unless pacemaker or defibrillator had been inserted); QT interval corrected for heart rate by Fridericia's formula (QTcF) \>=500 milliseconds (msec) in subjects with QRS \<120 msec and QTcF \>=530 msec in subjects with QRS \>=120 msec. * Unstable or life threatening cardiac disease: Subjects with any of the following at Screening (Visit 1) would be excluded: Myocardial infarction or unstable angina in the last 6 months; Unstable or life threatening cardiac arrhythmia requiring intervention in the last 3 months; New York Heart Association (NYHA) Class IV Heart failure. * Antimuscarinic effects: Subjects with a medical condition such as narrow-angle glaucoma, urinary retention, prostatic hypertrophy or bladder neck obstruction should only be included if in the opinion of the Investigator the benefit outweighs the risk and that the condition would not contraindicate study participation. * Cancer: Subjects with carcinoma that has not been in complete remission for at least 5 years. Subjects who have had carcinoma in situ of the cervix, squamous cell carcinoma and basal cell carcinoma of the skin would not be excluded based on the 5 year waiting period if the subject has been considered cured by treatment. * Questionable validity of consent: Subjects with a history of psychiatric disease, intellectual deficiency, poor motivation or other conditions that will limit the validity of informed consent to participate in the study. * Medication prior to spirometry: Subjects who are medically unable to withhold their albuterol/salbutamol for the 6-hour period required prior to spirometry testing at each study visit. * Tobacco Use: Subjects who are: Current smokers (defined as subjects who have used inhaled tobacco products within the 12 months prior to Visit 1 \[i.e., cigarettes, e-cigarettes/vaping, cigars or pipe tobacco\]) or former smokers with a smoking history of \>=10 pack years (e.g., \>=20 cigarettes/day for 10 years). * Drug/alcohol abuse: Subjects with a known or suspected history of alcohol or drug abuse within the last 2 years. * Allergy or Hypersensitivity: A history of allergy or hypersensitivity to any corticosteroid, anticholinergic/muscarinic receptor antagonist, beta2-agonist, lactose/milk protein or magnesium stearate. * Non-compliance: Subjects at risk of non-compliance, or unable to comply with the study procedures. Any infirmity, disability, or geographic location that would limit compliance for scheduled visits. * Affiliation with Investigator site: Study Investigators, sub-Investigators, study coordinators, employees of a participating Investigator or study site, or immediate family members of the aforementioned that is involved with this study. * Inability to read: In the opinion of the Investigator, any subject who is unable to read and/or would not be able to complete study related materials. Inclusion Criteria for Enrolment * Inadequately controlled asthma: Subjects with inadequately controlled asthma (ACQ-6 score \>=1.5) at Visit 2. * Percent-predicted FEV1: A best pre-bronchodilator morning (AM) FEV1 \>=30% and \<90% of the predicted normal value at Visit 2. Predicted values will be based upon the ERS Global Lung Function Initiative * Liver function tests at Visit 1: alanine aminotransferase (ALT) \<2 x upper limit of normal (ULN); alkaline phosphatase \<=1.5xULN; bilirubin \<=1.5xULN (isolated bilirubin \>1.5xULN is acceptable if bilirubin is fractionated and direct bilirubin \<35%) * Compliance with completion of the Daily eDiary reporting defined as completion of all questions/assessments on \>=4 of the last 7 days during the run-in period. Exclusion Criteria for Enrolment * Respiratory Infection: Occurrence of a culture-documented or suspected bacterial or viral infection of the upper or lower respiratory tract, sinus or middle ear during the run-in period that led to a change in asthma management or, in the opinion of the Investigator, is expected to affect the subject's asthma status or the subject's ability to participate in the study. * Severe asthma exacerbation: Evidence of a severe exacerbation during screening or the run-in period, defined as deterioration of asthma requiring the use of systemic corticosteroids (tablets, suspension, or injection) for at least 3 days or an in-patient hospitalization or emergency department visit due to asthma that required systemic corticosteroids. * Asthma medication: Changes in asthma medication (excluding run-in medication and albuterol/salbutamol inhalation aerosol provided at Visit 1). * Laboratory test abnormalities: Evidence of clinically significant abnormal laboratory tests during screening or run-in which are still abnormal upon repeat analysis and are not believed to be due to disease(s) present. Each Investigator will use his/her own discretion in determining the clinical significance of the abnormality. Inclusion Criteria for Randomization * Compliance with completion of the Daily eDiary reporting defined as completion of all questions/assessments on \>=4 of the last 7 days during the stabilization period. Exclusion Criteria for Randomization * Respiratory Infection: Occurrence of a culture-documented or suspected bacterial or viral infection of the upper or lower respiratory tract, sinus or middle ear during the stabilization period that led to a change in asthma management or, in the opinion of the Investigator, is expected to affect the subject's asthma status or the subject's ability to participate in the study. * Severe asthma exacerbation: Evidence of a severe exacerbation during enrolment or the stabilization period, defined as deterioration of asthma requiring the use of systemic corticosteroids (tablets, suspension, or injection) for at least 3 days or an inpatient hospitalization or emergency department visit due to asthma that required systemic corticosteroids. * Asthma medication: Changes in asthma medication (excluding stabilization period medication provided at Visit 2 and albuterol/salbutamol inhalation aerosol provided at Visit 1).