Severe Asthma 2026: The CHEST Framework for Choosing — and Switching — Biologics
August 27, 2026
A clinical brief for referring providers — part 4 of a 4-part asthma pharmacotherapy series.
Test your knowledge
In the low-eosinophil, low-FeNO ("T2-low") patient, which biologic is the one with demonstrated efficacy? a) Mepolizumab b) Dupilumab c) Tezepelumab
(Answer at the bottom — it's the agent that doesn't need a type-2 biomarker to work.)
The patient at the top of the ladder
To close the series: the patient who stays uncontrolled at the top of the ladder. Severe asthma — asthma requiring high-dose inhaled corticosteroid (ICS) plus a second controller, with or without systemic corticosteroids, to keep it from becoming uncontrolled, or which stays uncontrolled despite that therapy — is 5–10% of patients but more than half of asthma costs (Oberle et al., Chest 2026).
Before any biologic, confirm five things
Because 12–50% of "severe asthma" is misdiagnosed (Oberle et al., Chest 2026):
1. Correct diagnosis of asthma.
2. Adherence and inhaler technique are adequate.
3. Comorbidities addressed — GERD, rhinosinusitis, vocal cord dysfunction, obesity, OSA.
4. Modifiable risk factors managed — allergen exposure, smoking.
5. Step 4–5 therapy optimized — ICS-LABA with or without LAMA (long-acting muscarinic antagonist).
The CHEST 2026 framework
The first evidence-based approach to selecting and switching biologics:
Start with oral corticosteroid (OCS) dependency. OCS-dependent patients: anti-IL5/5Rα (mepolizumab, benralizumab) or dupilumab, both OCS-sparing. If the absolute eosinophil count (AEC) is >1,500 cells/μL, favor anti-IL5/5Rα. Tezepelumab did not show a significant OCS-sparing effect in SOURCE.
Refine with biomarkers. Fractional exhaled nitric oxide (FeNO) differentiates dupilumab and tezepelumab — FeNO ≥25 ppb predicts response, and >50 ppb a larger one. For anti-IL5/5Rα, FeNO does not predict outcomes. In the T2-low patient (low AEC and low FeNO), tezepelumab is the only agent with demonstrated efficacy (Oberle et al., Chest 2026; Israel et al., Lancet 2025).
Layer in comorbidities. Chronic rhinosinusitis with nasal polyps: omalizumab, mepolizumab, or dupilumab. Atopic dermatitis: dupilumab. EGPA: mepolizumab or benralizumab. Food allergy: omalizumab.
Check response at 4–6 months — exacerbations, control (ACT/ACQ), lung function, OCS reduction, comorbidity effect, patient satisfaction. Continue the other controllers; do not stop ICS when starting a biologic.
Switch if needed. Up to 10% don't respond to the first agent; use pre-biologic AEC and FeNO to guide the next choice.
The reassuring bottom line
All six agents cut severe exacerbations 30–70% versus placebo — and there are no head-to-head trials, which is exactly why the framework above (dependency, then biomarkers, then comorbidities) is how you choose (Mosnaim, NEJM 2023).
That closes the four-part series. We're always glad to see the patient who stays uncontrolled despite optimized Step 4–5 therapy — referrals welcome.
The answer
c) Tezepelumab. It targets TSLP upstream of the type-2 cascade, so it works without a type-2 biomarker — the one agent with demonstrated efficacy in the low-AEC, low-FeNO T2-low subgroup (Oberle et al., Chest 2026; Israel et al., Lancet 2025).