Nucala Injection contains mepolizumab 100 mg, a humanized monoclonal antibody targeting interleukin-5 (IL-5), indicated for the treatment of severe eosinophilic asthma and other eosinophil-driven diseases. By selectively binding to IL-5, mepolizumab inhibits the activation and survival of eosinophils, reducing airway inflammation and improving clinical outcomes. Nucala is administered via subcutaneous injection, typically once every four weeks, under the supervision of a healthcare professional. Clinical studies have demonstrated its efficacy in decreasing the frequency of asthma exacerbations, improving lung function, and reducing the need for oral corticosteroids in patients with severe eosinophilic asthma inadequately controlled by standard therapies. Additionally, Nucala is approved for use in eosinophilic granulomatosis with polyangiitis (EGPA) and hypereosinophilic syndrome (HES). Common adverse reactions include headache, injection site reactions, back pain, and fatigue. Hypersensitivity reactions, including anaphylaxis, though rare, may occur and require immediate medical attention. Prior to initiation, patients should be evaluated for parasitic infections, as eosinophils play a role in host defense. Nucala should be used with caution in patients with active infections. Regular monitoring of clinical response and eosinophil counts is recommended to assess treatment efficacy and safety.