The underlying population of patients selected for each respiratory monoclonal antibody might change as other biologics are approved.

To evaluate effect modification by calendar time of the effectiveness of each respiratory biologics in asthma.

The Effectiveness of Respiratory biologics in Asthma (ERA) is a retrospective cohort of severe asthma patients from the Mass General Brigham clinics between January 2013 and September 2023. Periods were pre-specified as the anti-IgE (2013–2015), anti-IL5 (2016–2018), anti-IL4/13 (2019–2021) or anti-alarmin (2022–2023) era. We evaluated each biologic's effect on asthma-related exacerbations comparing the one-year period before and after therapy initiation using Poisson regression and Cox regression for time-to-first exacerbation.

Of 647 biologic-naïve patients, 165 initiated omalizumab, 235 anti-IL5, 227 dupilumab, and 20 tezepelumab. Omalizumab's effectiveness improved as more biologics were approved: incidence rate ratio (IRR) 1.16 [0.94–1.43] anti-IgE era vs. 0.54 [0.37–0.80] anti-IL4/13-alarmin era. Omalizumab patients in the anti-IL4/13-alarmin era had lower blood eosinophil counts and less chronic rhinosinusitis with nasal polyps (CRSwNP). For anti-IL5s, effectiveness peaked in the anti-IL4/13 era (IRR 0.52 [0.42–0.64]) when patients had higher BMI and less concomitant CRSwNP. Dupilumab was most effective in the anti-IL4/13 era (IRR 0.60 [0.50–0.72]). There were fewer current smokers in dupilumab patients in the anti-IL4/13 era. Results were similar in time-to-event analyses and in sensitivity analyses accounting for the COVID-19 pandemic.

There are temporal variations in the effectiveness of biologics partly explained by the shift in the underlying population, particularly for omalizumab. Though having more choices was associated with better patient selection for omalizumab, this was inconsistent for other biologics.