The purpose of this study is to evaluate the efficacy, safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of JNJ-38518168 compared with placebo in participants with persistent asthma that is inadequately controlled despite current treatment.

This study will be randomized (treatment group assigned by chance, like flipping a coin), double-blind (study investigators and participants will not know what treatment is being administered), and placebo-controlled (a placebo is identical to the study agent, but contains no active ingredients). A total of 160 participants will receive either placebo or JNJ-38518168 once daily. The study duration will be approximately 32 weeks and will include a screening phase of approximately 4 weeks, a 24-week placebo-controlled treatment phase, and a 4-week follow-up phase. Participant safety will be monitored throughout the entire study period..

Inclusion Criteria:

• Have a diagnosis of asthma for at least 26 weeks, confirmed by the investigator at Screening Visit 1
• Have been receiving inhaled corticosteroid (ICS) (≤1000 µg/day fluticasone or its equivalent) for at least 12 weeks prior to Screening Visit 1
• At Screening Visit 1, be receiving the same dose of ICS ≤1000 µg/day fluticasone (or equivalent) alone or in conjunction with long-acting β2-agonist (LABA) and/or montelukast for at least 4 weeks prior to screening with no changes in dose or dosing regimen of any of these therapies during that 4 week period prior to screening
• Have an Asthma Control Questionnaire (ACQ) score ≥1.5 at Screening Visit 1
• Have a prebronchodilator forced expiratory volume in 1 second (FEV1) equal to 40% to 80%, inclusive, of predicted value at Screening Visit 1
• Have a ≥12% relative change and ≥200 mL change in FEV1 postbronchodilator at either Screening Visit 1 or 2

Exclusion Criteria:

• Has ever had a life-threatening asthma attack including respiratory arrest, intubation, or intensive care unit (ICU) admission due to asthma
• Has a history of any other chronic respiratory condition including, but not limited to, chronic obstructive pulmonary disease (COPD), bronchiolitis, bronchiectasis, allergic bronchopulmonary aspergillosis (mycosis), occupational asthma, sleep apnea, pulmonary hypertension, or any other obstructive pulmonary disease
• Has any use of the following asthma therapies: systemic corticosteroids within 6 weeks of Screening Visit 1; oral beta-agonists within 4 weeks of Screening Visit 1; cromolyns within 4 weeks of Screening Visit 1; leukotriene inhibitors other than montelukast within 4 weeks of Screening Visit 1; theophylline within 4 weeks of Screening Visit 1; inhaled anti-cholinergic agents within 4 weeks of Screening Visit 1; or omalizumab within 130 days of Screening Visit 1
• Has initiated or discontinued allergen immunotherapy within 12 weeks of Screening Visit 1
• Has smoked within 3 years of Screening Visit 1 or has a history of smoking ≥ 10 pack years
• Body-Mass Index (BMI) greater than or equal to 40 kg/m2