AZD1981 is an investigational compound that has been studied primarily for its potential in treating respiratory diseases, particularly asthma and chronic obstructive pulmonary disease (COPD). It functions as a selective antagonist of the prostaglandin D2 receptor (DP2/CRTH2), which plays a role in allergic inflammation and immune cell activation. By blocking this receptor, AZD1981 helps reduce the migration and activation of inflammatory cells such as eosinophils and Th2 lymphocytes, which are involved in the airway inflammation seen in asthma. In clinical trials, AZD1981 was evaluated for its ability to improve lung function and reduce asthma symptoms, especially in patients with a type 2 inflammatory phenotype. Although development was discontinued due to insufficient efficacy in later-stage trials, it contributed to the understanding of CRTH2 antagonism as a therapeutic strategy. Research on AZD1981 helped pave the way for other compounds targeting the same pathway, supporting ongoing efforts to develop more effective anti-inflammatory treatments for respiratory conditions.