Emerging treatments
Interferon alfa
Used in idiopathic hypereosinophilic syndrome, and acts on T cells to influence cytokine production. There are possible direct effects on eosinophils. Limitations may include relapse with discontinuation of the agent. In hepatitis C virus-related cryoglobulinaemia, vasculitis may worsen, and cardiac toxicity may occur. Results from two retrospective observational studies and one phase 2 open label trial suggest that interferon alfa may be effective for the induction and maintenance of remission in patients with refractory EGPA.[58][59][60]
Other interleukin (IL)-5 antagonists
Interleukin (IL)-5 is important for eosinophilic maturation, chemotaxis, and adhesion to vascular endothelium. Pilot open label studies have demonstrated that both benralizumab and reslizumab reduce daily oral corticosteroid use in patients with EPGA.[61][62] Larger controlled trials are required.
Omalizumab
Murine anti-human immunoglobulin (Ig) E monoclonal antibody. Inhibits binding of IgE to IgE receptors, and binds free IgE in serum. Reduces early and late phase response to allergens, with variable effects on eosinophilic infiltration. Limitations include contraindication in helminthic infections, and should not be used if this is a strong differential diagnosis. One systematic review reported that omalizumab may be effective in selected patients with EGPA, but caution is required when tapering corticosteroids due to a possible risk of patients with asthma developing EGPA, although the quality of included evidence was limited.[63]
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