Biologic Use in Type 2 versus Non-Type 2 Asthma: Similarities, Differences, and Challenges

Biologic therapy has transformed the management of severe asthma, but its benefit has been distributed unevenly. Six monoclonal antibodies are licensed (omalizumab, mepolizumab, reslizumab, benralizumab, dupilumab and tezepelumab), joined most recently by the ultra-long-acting anti-interleukin (IL)-5 antibody depemokimab. All were developed within, and are prescribed on the basis of, the type 2 (T2) inflammatory pathway. Patients whose disease is driven by IL-4, IL-13, IL-5 and IgE now have several effective options; patients whose disease is not have almost none. This asymmetry is the central problem in severe asthma today, and it is the subject of this review. In this narrative review, informed by a structured literature search, we synthesize evidence from randomized controlled trials of every approved biologic, from real-world data and from the substantial body of negative trials in non-T2 disease. We argue that the T2/non-T2 dichotomy is operationally useful but biologically misleading: its thresholds are arbitrary and unstable under corticosteroid exposure, low T2 biomarkers are not synonymous with absent T2 biology, and non-T2 disease is itself heterogeneous. We examine what the phenotypes share (epithelial alarmin signaling, airway remodeling, corticosteroid-related morbidity and the treatable-traits paradigm) and where they differ. We then address the practical challenges of clinical decision-making: selecting a first biologic when eligibility criteria overlap, managing partial response, switching, de-escalation and clinical remission. Finally, we evaluate agents in development, including anti-TSLP receptor antibodies, IL-33/ST2 blockade, bispecific constructs, OX40L-directed therapy and oral eosinophil-depleting small molecules, and outline the trial designs and biomarkers that will be needed if patients with non-T2 disease are to be served as well as those with T2 disease.