A Multi-center, Randomized, Placebo, Multi-Dose study to evaluate the efficacy of AMG 317 compared with placebo as measured by change in Asthma Control Questionnaire (ACQ) symptom scores from baseline to week 12.

Inclusion Criteria:

• Males or females 18 to 65 years of age at the time of screening
• Baseline percent of predicted FEV1 ≥ 50% to ≤ 80% at screening
• At least 12% reversibility over baseline FEV1 with beta agonist inhalation, which can be demonstrated in the office or documented by medical record within the past 12 months
• Inhaled corticosteroid (ICS) ≥ 200 and ≤ 1000 µg/day fluticasone or equivalent. Stable ICS dose for ≥ 30 days before screening and dose expected to remain stable during treatment with investigational agent. Must have used ICS for at least the last 3 consecutive months before screening
• If receiving allergen immunotherapy, a stable dose for > 3 months before screening and anticipated to remain stable for the duration of the study
• Positive to skin prick or RAST
• Ongoing asthma symptoms with ACQ score at screening and baseline ≥ 1.5 points
• Nonsmoker or ex-smoker with < 10 pack-years (eg, 1 pack per day for 10 years) who stopped ≥ 1 year ago

Exclusion Criteria:

• Acute asthma exacerbation requiring emergency room (ER) treatment or hospitalization within 3 months
• History of endotracheal intubation for asthma-related exacerbation within 3 years of screening
• Respiratory illness within 4 weeks of screening
• History of chronic obstructive pulmonary disease (COPD) or other chronic pulmonary condition other than asthma
• Received long-acting beta agonist, theophylline, inhaled anticholinergics, oral beta 2 agonists, or cromolyn therapeutics within 1 week of first run-in visit.
• Leukotriene antagonists within 2 weeks before first run-in visit
• Oral or parenteral corticosteroids within 6 weeks before first run-in visit
• Live/attenuated vaccinations within 4 weeks of screening or during the study
• Any uncontrolled, clinically significant systemic disease (eg, chronic renal failure, uncontrolled hypertension, liver disease)