CXCR4 and asthma: The natural fragment of serum albumin, EPI-X4, has been identified as an endogenous peptide antagonist and inverse agonist of CXCR4, and novel CXCR4 antagonists developed on the basis of this feature can be used in the treatment of atopic dermatitis, asthma, and other CXCR4-related diseases (27).