Asthma is a complex, persistent, inflammatory disease characterised by airway hyperresponsiveness in association with airway inflammation. Studies suggest that regular use of high-dose inhaled corticosteroids and long-acting bronchodilators or omalizumab (a humanised monoclonal antibody that binds to immunoglobulin E and is often used as next-step therapy) may not be sufficient to provide asthma control in all patients, highlighting an important unmet need. Interleukin-4, interleukin-13, and the signal transducer and activator of transcription factor-6 are key components in the development of airway inflammation, mucus production, and airway hyperresponsiveness in asthma. Biological compounds targeting these molecules may provide a new therapeutic modality for patients with uncontrolled severe asthma. The purpose of this review is to summarise current studies of compounds targeting the interleukin-4/interleukin-13 pathway and to provide a rationale for the development of such compounds for this use.