A Study to Assess Pharmacokinetics, Safety and Tolerability of Multiple Doses of CAT-354 in Subjects With Moderate Asthma

Inclusion Criteria: * Males or infertile females * Subjects with asthma, well controlled on inhaled corticosteroid and taken as required (PRN) short acting beta 2 agonist therapy only * Unchanged dose of inhaled corticosteroid for 3 months prior to Day 0 and no expected need for change in dose during study * Forced expiratory volume in 1 second (FEV1) greater than or equal to 80% predicted at Screening (Baseline) * 18-60 years * General Practitioner diagnosis of asthma of 1 year's minimum duration (with respect to Day 0) * No significant abnormality on clinical examination or medical history (excluding atopic skin signs, symptoms and history) * 12-lead electrocardiogram with no clinical significant abnormality * Clinical chemistry hematology and urinalysis results within the laboratory reference ranges or deemed not clinically significant by the Investigator * A negative screen for drugs of abuse and alcohol * Body weight between 50-120 kg * Subjects aged between 18-40 years inclusive must have body mass index (BMI) 18-32 kilogram per square meter (kg/m\^2) inclusive. Subjects aged between 41-60 years must have BMI between 18-30 kg/m\^2 inclusive. Exclusion Criteria: * Active concomitant disease, with exception of eczema * Expected onset of seasonal allergy before the administration of the last dose of study medication * History of severe exacerbation within 3 years of Day 0 * Recorded use of inhaled short acting beta 2 agonist medication for symptoms within 14 days of Day 0 of: More than 6 doses per day on any 1 day or more than 3 doses per day on 6 or more days * Any medication other than: inhaled short-acting beta 2 agonist, inhaled corticosteroids, topic eczema treatments (with the exception of fluorinated corticosteroid, dermatological preparations which are not permitted), hormone replacement therapy, vitamin preparation/food supplements, occasional use of proton pump inhibitors, ranitidine, cimetidine, antacids or over-the-counter analgesics * Treatment within 6 months of Day 0 with any of the following: methylxanthines, inhaled cromones, leukotriene modifiers, anti- immunoglobulin E (IgE), anticholinergics, ketotifen, oral short acting B2 agonists, long-acting B2 agonists, oral or injected corticosteroids * Treatment of atopic symptoms, other than eczema, within 4 weeks of Day 0 * History of medication that might carry-over effects into the study * Previously received monoclonal antibody, or a similar related protein, that might sensitize to CAT-354 * Participation in another study within three months of the start of the study or 5 half lives of the previously administered investigational medicinal product (IMP), whichever is longer * Lower respiratory tract infection within 4 weeks of Day-14 * Any acute illness in the two weeks before Day 0 * Current smokers, those who have smoked in previous year, and those with smoking history of greater than or equal to 10 pack years * Considered by the investigator to be at risk of transmitting, through blood, the agents responsible for infectious diseases * Blood donation (550 ml) in the previous 2 months * Excessive intake of alcohol (more than 21 units a week for females or 28 units a week for males) * The subject's general practitioner has suggested a reason the subject should not participate in the study * The Investigator considers the subject should not take part for any reason.