Asthma endotypes in flux: integrating type 1 and type 2 inflammation for biological therapy advancement.

Objective: To synthesize current understanding of type 1 (T1) and type 2 (T2) asthma endotypes and evaluate how their integration can advance precision biological therapy selection for improved patient outcomes.

Data sources: Comprehensive literature review of peer-reviewed articles from PubMed, Embase, and Cochrane databases focusing on asthma immunopathology, endotype characterization, biomarker development, and biological therapies. Additional sources included clinical trial registries, regulatory agency documents, and recent conference proceedings.

Study selection: Studies were selected based on relevance to T1/T2 inflammatory pathways, biomarker validation, biological therapy efficacy, and endotype-guided treatment strategies. Priority was given to randomized controlled trials, systematic reviews, and large observational studies with clear endotype characterization.

Results: T2 inflammation, characterized by interleukin-4 (IL-4), IL-5, and IL-13 pathways with eosinophilic involvement, has well-established biomarkers (blood eosinophils, fractional exhaled nitric oxide (FeNO), periostin) and successful targeted biologics (anti-IL-5, anti-IL-4 receptor alpha (anti-IL-4Rα), anti-immunoglobulin E (anti-IgE)). T1 inflammation, involving interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), and IL-17 with neutrophilic predominance, lacks validated biomarkers and effective therapeutics. Emerging evidence demonstrates significant T1/T2 overlap in severe asthma, challenging traditional dichotomous classification. Multi-pathway targeting strategies and upstream cytokine inhibition show promise for mixed endotypes.

Conclusion: Integration of T1 and T2 endotype characterization through validated biomarkers and multi-omics approaches is essential for advancing precision medicine in asthma. Future therapeutic strategies must address endotype plasticity and mixed inflammatory patterns to optimize biological therapy selection and improve treatment outcomes in heterogeneous asthma populations.