D1.219 - Efficacy and Safety of 300 IR Liquid Sublingual Immunotherapy in Allergic Asthma: A Systematic Review and Meta-analysis of Randomised Controlled Trials

Several randomised controlled trials (RCTs) have evaluated the efficacy of sublingual immunotherapy (SLIT) in allergic asthma; however, the overall evidence base remains limited, with a relatively small number of studies and patients included in published meta-analyses. Moreover, results across trials have been inconsistent, and previous meta-analyses have reported substantial heterogeneity. Assuming that differences among commercially available SLIT products may contribute to this variability, we conducted a systematic review and meta-analysis specifically focused on a single formulation, 300 IR SLIT-liquid.

Major electronic databases were searched from inception to October 2025 to identify RCTs evaluating 300 IR SLIT-liquid in patients with allergic asthma. Eligible studies reported at least one of the following outcomes: asthma symptom score (SS), asthma medication score (MS), or lung function (FEV₁ % predicted). Meta-analyses were conducted using random-effects models. Treatment effects were expressed as mean difference (MD) or standardised mean differences (SMDs). Meta-regression analyses were performed to explore potential sources of heterogeneity. Risk of bias was assessed using design-specific tools, and the certainty of evidence was evaluated according to the GRADE approach.

Seven RCTs were included, encompassing a total of 330 patients. Pooled analyses showed a significant benefit compared with placebo in asthma SS (SMD −0.78; 95% CI, −1.20 to −0.36; I², 67%), asthma MS (SMD −0.51; 95% CI, −1.03 to 0.01; I², 34%), and FEV₁ (MD 7.90; 95% CI, 3.54 to 12.25; I², 37%) (see Figure). Meta-regression analyses did not consistently identify significant modifiers (patient- or study-level characteristics) for FEV₁ or asthma SS. Adverse events were generally mild, with no relevant safety concerns emerging.

300 IR SLIT-liquid was associated with clinically meaningful improvements in lung function, asthma symptoms, and medication use, with a favourable safety profile. All effects were consistently in favour of 300 IR SLIT-liquid despite a high but acceptable heterogeneity observed for symptom scores. The low heterogeneity for medication score and FEV₁ suggests that focusing on a single SLIT formulation may provide more homogeneous and robust estimates of efficacy. Further well-designed trials may refine effect size estimates and better characterise patient-level determinants of response.