Clinical Study to Evaluate the Efficacy and Safety of VR506 Using a New Inhaler for the Treatment of Asthma

Inclusion: * Written informed consent * Adolescents aged 12-17 years \& adults aged 18-65 years (both inclusive) * Documented clinical history of severe asthma requiring prednisone/prednisolone therapy, high-intensity treatment ICS, OCS, LABA * Stable OCS dose for ≥7 days before Screening Visit \& during Screening Period. * At least 80% compliant w/regular asthma medication per investigator at end of Screening Period * Documented asthma reversibility within 5 yrs prior to/during Screening Period, or diagnosis of asthma that is incontrovertible per investigator * Ability to use nDPI correctly, per investigator's review of completed inhaler operation checklist * Ability to use eDiary correctly, assessed by investigator at end of Screening Period * Ability to comply w/study procedures, including blood sampling * Ability to perform technically satisfactory pulmonary function tests * Available to complete all study visits before 12 noon * BMI of 16-26 kg/m2 in adolescents and 18-32 kg/m2 in adults * Oral PIF ≥40 L/min, using an appropriate device set to match resistance of inhaler * Good health, except for presence of asthma, per medical history/physical examination * Negative drug/alcohol/urine cotinine screen. Subjects must test negative for amphetamines, barbiturates, benzodiazepines, cannabinoids, cocaine, cotinine, ethanol \& opiates (unless given as prescription medicine) * Non-smokers or ex-smokers with a smoking history of less than 10 pack-yrs (e.g. \<20 cigarettes per day for 10 years or \<40 cigarettes per day for 5 years) \& stopped smoking for at least 1 year prior to Screening Visit. Smoking will not be permitted throughout study * Female subjects of child-bearing potential must be using medically acceptable forms of contraception \[abstinence, hormonal (oral/implant/transdermal/injection), in use for ≥3 consecutive months before first dose of study medication, double barrier (condom w/spermicide, or diaphragm w/spermicide), IUD, or vasectomised partner (≥6 months since vasectomy)\]. Exclusion: * Regular use (≥3 times/wk) of topical steroids to treat dermatitis/rhinitis/allergic conjunctivitis, within 28 days of Screening Visit * Subjects who have/who have had, an upper/lower respiratory tract infection within 28 days of Screening Visit * Subjects w/"brittle asthma * Subjects w/asthma that required admission to an ICU and/or ventilation within previous 12 months * Subjects whose comorbidities, per investigator's opinion, are major contributors to their respiratory symptoms (e.g. COPD, bronchiectasis, dysfunctional breathlessness, vocal cord dysfunction, gastro-oesophageal reflux) * Previously/currently diagnosed as having Churg-Strauss syndrome * Previously/currently diagnosed as having pulmonary eosinophilia * History of lung cancer * Subjects w/current diagnosis of HIV infection * Active chronic hepatitis B or C infection * Subjects who have clinically significant abnormality/finding from examination, tests, or history that may compromise subject safety, specifically any history of cardiac, renal or hepatic impairment * Subjects with an abnormal ECG * Persistent arterial hypotension, with average SBP readings of ≤95 mmHg * Persistent elevation of blood pressure, with average SBP readings of ≥160 mmHg or average DBP readings of ≥100 mmHg * Pregnant or lactating females * Participation in another clinical study in 28 days prior to Screening Visit * Evidence of clinically significant renal, hepatic, cardiac, pulmonary (apart from asthma) or metabolic dysfunction, e.g. diabetes mellitus, thyrotoxicosis, uncorrectable hypokalaemia, or predisposition to low levels of serum potassium * Current/history of drug/alcohol abuse/dependence per WHO criteria * Inability to communicate well w/investigator * Donation of ≥450 mL of blood/blood products within previous 3 months prior to screening * History of allergy/intolerance/contraindications to corticosteroids/lactose, or severe allergy to milk proteins * Consumption of alcohol- or caffeine-containing foods/beverages from midnight before or during Screening Visit * History of medically diagnosed chronic respiratory diseases other than asthma (e.g. chronic obstructive pulmonary disease, ABPA in the absence of asthma)