A Study to Assess the Efficacy, Safety, and Tolerability of CAT-354 in Subjects With Asthma

To investigate the effects of CAT-354 on airway hyper-responsiveness (AHR) in uncontrolled asthma.

This is a randomized, stratified, double-blind, placebo-controlled, multicenter, multinational study in subjects with uncontrolled asthma despite optimal treatment. Following confirmation of eligibility, subjects will be randomly assigned on Day 0, to 1 of 4 dose groups 1 mg/kg CAT-354, 5 mg/kg CAT-354, 10 mg/kg CAT or Placebo to match all doses of CAT-354. Doses of the assigned treatment will be administered on three occasions 28 days apart. Subjects will be assessed for efficacy, including airway hyper-responsiveness (AHR), safety, pharmacokinetic, pharmacodynamics and immunogenicity until Day 84 post-first dose.

Eligibility Criteria:
Inclusion Criteria:

* Signed and dated written informed consent is obtained prior to any study related procedure taking place
* Women either infertile (example \[e.g.\], hysterectomized, sterile or post-menopausal with amenorrhea of least 1 year duration) or who are practicing an acceptable form of birth control
* Uncontrolled (refractory) asthma despite treatment with a minimum dose of 800 microgram (mcg) beclomethasonedipropionate or equivalent inhaled corticosteroid per day plus 1 or more additional controller, that is, long-acting beta-agonist, leukotriene antagonist or theophylline. Oral corticosteroids (not parenteral) as additional treatment at any dose are acceptable
* A forced expiratory volume in 1 second (FEV1) acceptable for airway hyper-responsiveness (AHR) challenge tests (greater than 60 percent of predicted normal) on the challenge days
* A provocative concentration of methacholine causing a 20 percent fall in FEV1 (PC20) less than 4 milligram per milliliter (mg/mL)
* Aged 18-80 years
* A 12-lead electrocardiogram (ECG) with no-clinically significant abnormalities
* Clinical chemistry, hematology and urinalysis results within the laboratory reference ranges or deemed not clinically significant by the Investigator
* Body weight of less than 130 kilogram (kg)
* No other clinically significant abnormality on history and clinical examination
* Able to comply with the requirements of the protocol.

Exclusion Criteria:

* Experienced a severe exacerbation within 28 days preceding Day -28/-14 to Day 0
* Onset of uncontrolled seasonal allergy symptoms within 28 days preceding Day -28/-14 to Day 0
* Subjects with a history of allergic rhinitis, seasonal allergy or esophagitis must be optimally controlled and remain on a stable treatment regimen during the study
* Participation in another study within 5 half-lives or 3 months of the start of this study, whichever is the longer
* Lower respiratory tract infection within 6 weeks of Day -28/-14 to Day 0
* Current smokers or ex-smokers with greater than 10 pack-years
* Blood donation (more than 550 mL) in the previous 2 months
* Excessive intake of alcohol (as judged by the Investigator) or evidence of drug or solvent abuse
* Subjects with a physician-diagnosis of any other significant lung disease, including a primary diagnosis of chronic obstructive pulmonary disease or bronchiectasis, or lung cancer, sarcoidosis, tuberculosis, pulmonary fibrosis and cystic fibrosis
* Concurrent medication from Day -28/-14 to Day 0 (Screening visit) and for the duration of the study with any of the prohibited medications
* Significant, uncontrolled disease including serious psychological disorders, chronic renal failure, uncontrolled hypertension
* systolic blood pressure greater than 200 millimeters of mercury (mmHg), or diastolic blood pressure greater than 100 mmHg, heart disease, psoriasis requiring treatment and subjects who have had a heart attack or stroke within the 3 months preceding Day -28/-14 to Day 0, or who have a known aneurysm
* Onset of uncontrolled seasonal allergy symptoms within 28 days preceding Day -28/-14 to Day 0
* Subjects with a history of allergic rhinitis, seasonal allergy or esophagitis must be optimally controlled and remain on a stable treatment regimen during the study
* Any factor which, in the opinion of the Investigator, would jeopardize the evaluation or safety or be associated with poor adherence to the protocol (that is, inability to complete study diary, perform peak expiratory flow (PEF) measurements)
* The subject's primary care physician recommends the subject should not take part in the study
* Known hypersensitivity to CAT-354 or its components, to the challenge agents used in the study or to related drugs.