Inclusion Criteria:

• Patient has a history of mild to moderate persistent allergic asthma for at least 6 months with typical symptoms, including cough, wheezing, and shortness of breath, is clinically stable and has no history of recent respiratory tract infection within 3 weeks of the start of the study
• Patient, aside history of asthma, is judged to be in good health based on medical history, physical examination, vital sign measurements, and laboratory safety tests
• Patient is able to perform reproducible pulmonary function test
• Patient has an allergic response to house dust mite allergen, demonstrates a positive early and late phase response to an inhaled allergen challenge (as defined by a bronchoconstrictive response)
• Patient is a nonsmoker for at least 12 months
• Patients must have less than or equal to 10 pack years of smoking to be included. (10 pack years = one pack per day for 10 years.) Patients who have discontinued smoking for at least 10 months may be enrolled at the discretion of the investigator
• Patient is willing to avoid strenuous physical activity (i.e., strenuous or unaccustomed weight lifting, running, bicycling, etc.) for 72 hours prior to each visit when laboratory safety tests are obtained and 48 hours prior to allergen challenge

Exclusion Criteria:

• Patient has a history of any illness that, in the opinion of the study investigator, might confound the results of the study or poses additional risk to the patient by their participation in the study
• Patient has taken oral corticosteroids within 8 weeks or inhaled corticosteroids/nasal corticosteroids within 4 weeks of screening and/or during the study
• Patient has a history of stroke, chronic seizures, or major neurological disorder
• Patient has a history of clinically significant endocrine, gastrointestinal, cardiovascular, hematological, hepatic, immunological, renal, respiratory (other than asthma), or genitourinary abnormalities or diseases, or has a history of neoplastic disease
• Patient is unable to refrain from or anticipates the use of any medication other than the ones permitted in this study, including prescription and non-prescription drugs or herbal remedies prior to administration of the initial dose of study drug, throughout the study (including washout intervals between treatment periods), until the poststudy visit
• Patient consumes excessive amounts of alcohol, defined as greater than 3 glasses of alcoholic beverages per day or >21 drink equivalents per week
• Patient consumes excessive amounts, defined as greater than 6 servings of coffee, tea, cola, or other caffeinated beverages per day