A Study to Evaluate the Efficacy After Allergen Challenge, Safety and Tolerability of Inhaled CHF6001 DPI in Asthmatics

Inclusion Criteria: * written informed consent obtained * Non smoking or ex-smokers from at least 1 year prior to study entry * Males of females between 18 and 60 years inclusive * Body Mass Index between 18 and 32 kg/m2 * Ability to be trained about the proper use of the inhalation device and to perform spirometry * With mild to moderate allergic asthma as defined by the GINA guideline, steroid naive * Atopy to at least one common aeroallergen * Positive allergen-induced Early Asthmatic Response and Late Asthmatic Response at screening * Ability to produce an adequate sputum sample * Post-menopausal women, women of not childbearing potential or males and females of childbearing potential willing (they or their partner) to use a reliable method of contraception. Exclusion Criteria: * Worsening of asthma or respiratory tract infection prior to study entry * History of life-threatening asthma or hospitalization for asthma prior to the study entry * Pregnant or lactating women * History of clinically significant hypotensive episodes or fainting, dizziness or light-headedness * History or symptoms of clinically relevant neurologic disease * Symptomatic hay fever * Unstable concurrent disease that may impact the feasibility of the study * Use of systemic corticosteroids, nebulised bronchodilator or oral beta2-agonist * Use of leukotrienes modifiers, roflumilast or cromoglycate * Use of long acting beta2-agonist or inhaled corticosteroids * Use of short-acting or long-acting non-sedatives antihistamines * Use of any other medication for the treatment of allergic asthma other than salbutamol * Having received an investigational medicinal drug within 30 days prior to study entry * Blood drawn of at least 250 ml in the previous 45 days * Ongoing use of tobacco * Other lung disease * Recent history of alcohol dependency * Inability to comply with the study protocol