Two major endotypes for asthma have been described:
- TH2-high, manifested by increased eosinophils in the sputum and airways of patients
- TH2-low, with increased neutrophils or a pauci-granulocytic profile
This review article evaluated human clinical trials using biologics for T-helper type 2 cell (TH2)-low and TH2-high asthma.
Multiple immune response modifiers have been evaluated in TH2-high asthma geared at blocking interleukin (IL)-5, IL-13, immunoglobulin E, prostaglandin D2, and other pathways. As of year 2016, 3 immune response modifiers approved by the Food and Drug Administration are available for treating severe TH2-high asthma:
- anti-immunoglobulin E, omalizumab, available for more than 10 years
- anti–IL-5 monoclonal antibodies, mepolizumab (SC) and reslizumab (IV)
Many of the TH2-high therapies have shown better efficacy when certain biomarkers are elevated, especially blood eosinophils. The TH2-low endotype does not have any readily available point-of-care biomarkers, and development of therapies has lagged behind that for TH2-high asthma.
Characterization of asthma endotypes: implications for therapy. Jeffrey R. Stokes et al. Annals of Allergy, Asthma and Immunology, August 2016, Volume 117, Issue 2, Pages 121–125 (free full text).
The World Allergy Organization (WAO) Small Airways Working Group publishes a monthly "What's New?" summary and I have served as its editor since 2011. The summary features the top 3 asthma/small airways articles each month. The article above is a part of the project. The archive is here: http://www.worldallergy.org/small_airways_group/reviews/archive.php
Image source: Image source: FDA and Wikipedia, public domain.