The purpose of the study is to investigate the clinical effects of multiple (28 day) twice-daily doses of OC000459 in comparison to placebo on clinic lung function (FEV1) in mild to moderate asthmatics with an FEV1 of 60-80% of predicted and requiring only short acting inhaled B2-adrenergic agonists for symptomatic control.

Inclusion Criteria At Screening:

• Male or female asthmatics, any racial group. Females of childbearing potential must practise two forms of contraception
• Non smokers
• Mild to moderate asthmatics according to GINA guidelines for at least 12 months.
• History of asthma symptoms increasing in response to external allergens.
• Testing positive on skin prick test to an allergen associated with the subject's asthma

Exclusion Criteria:

• Use of inhaled or local corticosteroids in the period from 28 days prior to screening.
• Receipt of prescribed or over the counter medication within 14 days of the first study day.