OC0000459 reduces inflammation in the tissues in response to allergic stimuli in patients with asthma. This clinical trial, in mildly asthmatic patients, studies the effects of OC000459 and placebo on the asthmatic response to two known stimulants of the asthmatic response in the lungs, namely cat hair, pollen or house dust mite and methacholine.

Inclusion Criteria:

• Known history of asthma (intermittent wheezing, cough, dyspnoea responsive to inhaled short acting beta agonists).
• FEV1 >65% of predicted on at least two occasions at screening.
• At the screening allergen challenge, a decrease in FEV1 of ≥20% in the early asthmatic reaction and of ≥15% in the LAR to allergen on 3 separate occasions between 3-10hrs post allergen, 2 of which must be consecutive.
• No steroid usage in the past 12 weeks.
• Testing positive to skin prick challenge with at least one of the following allergens: house dust mite, pollen or cat hair within the previous 12 months.
• Non smokers for a minimum of 6 months; less than 10 pack year history.

Exclusion Criteria:

• Respiratory tract pathology other than allergic asthma.
• Lower respiratory tract infection within 4 weeks prior to an allergen challenge.
• Receipt of prescribed or OTC medication other than paracetamol or short acting inhaled beta agonists within 14 days of screening or of the first day of each dosing period.