Does Biologics’ Efficacy in Asthma Always Vary With Blood Eosinophil Counts?

Eosinophil cells
Eosinophil cells
Research presented at ACAAI 2021 evaluated the efficacy of different biologic therapies in controlling asthma exacerbations in patients with varying BECs.

The following article is a part of conference coverage from the American College of Allergy, Asthma & Immunology 2021 Annual Scientific Meeting, being held virtually from November 4 to 8, 2021. The team at Pulmonology Advisor will be reporting on the latest news and research conducted by leading experts in the field. Check back for more from the ACAAI 2021 Annual Scientific Meeting.


The efficacy of biologic therapies in reducing the annual asthma exacerbation rate (AAER) is often associated with baseline blood eosinophil count (BEC). This was among the findings of research presented at the American College of Allergy, Asthma, and Immunology (ACAAI) Annual Scientific Meeting, held in New Orleans, LA, from November 4 to 8, 2021.

Patients with severe, uncontrolled asthma are often prescribed biologic therapies to achieve better control of their disease. However, approvals of several biologics are specific to patients with an eosinophilic phenotype because studies have demonstrated differential results by baseline BEC.

Due to an absence in head-to-head trials, researchers analyzed reductions in the AAER by baseline BEC in randomized controlled trials (RCTs) of biologics by searching MEDLINE and including analyses available on governmental websites. They limited their search to US Food and Drug Administration-approved biologics and doses, and to tezepelumab, which is in late-stage development.

The researchers found that in patients with a baseline BEC at least 300 cells/µL, all biologics reduced the AAER, although the greatest AAER reductions were observed with dupilumab and tezepelumab. In patients with a BEC less than 300 cells/µL, only tezepelumab demonstrated efficacy, whereas with benralizumab and dupilumab, AAER reduction was observed in 1 each of their 2 trials conducted. However, in patients with a BEC of 150 to less than 300 cells/µL, a reduction in AAER was demonstrated with tezepelumab and dupilumab. For patients with a BEC less than 150 cells/µL, an AAER reduction was only demonstrated with tezepelumab.

The researchers concluded, “Tezepelumab showed efficacy in patients with high and low BEC.” They added that for other biologics, efficacy was inconsistent depending upon the BEC range.


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Busse W, FitzGerald M, Korn S, Cook B, Llanos-Ackert J, Ambrose C. Efficacy of biologic therapies in patients with severe, uncontrolled asthma stratified by blood eosinophil count. Ann Allergy Asthma Immunol. 2021;127:S34. Presented at: American College of Allergy, Asthma & Immunology (ACAAI) Annual Scientific Meeting; November 4-8, 2021; New Orleans, LA. Abstract P070.