Methods: A post-hoc analysis of INNOVATE trial data (Humbert et al. Allergy 2005) was performed to determine the impact of treatment on exacerbation rates and health-related quality-of-life (AQLQ) of SAA patients stratified by peripheral blood eosinophils per mcl (EOS) and serum IgE (IU/ml). Negative binomial regressions were utilized within biomarker strata to estimate response to omalizumab vs placebo, controlling for potential confounders.
Results: An exacerbation reduction was observed among omalizumab-treated patients vs placebo in EOS-high strata: EOS≥300 (n=245) 38.98%, p=0.0399; EOS≥150 (n=316) 39.01%, p=0.0178. Exacerbation reduction increased further upon enriching these strata according to increased IgE (>75 IU/ml): EOS≥300/IgE>75 (n=184) 53.88%, p=0.0018; EOS≥150/IgE>75 (n=235) 53.75%, p=0.0005. Mean placebo-subtracted benefits on AQLQ exceeded the minimal clinically-important difference (≥0.5) and demonstrated statistically significant improvements in both EOS-high strata: EOS≥300 (n=24) 0.55, p=0.0001; EOS≥150 (n=310) 0.53, p<0.0001. The benefit on AQLQ was most apparent in the EOS≥150/IgE>75 stratum (n=231): 0.59, p<0.0001.
Conclusions: This analysis is among the first to examine a combination of biomarkers to assess response to omalizumab in SAA patients. They suggest that subgroups with a combination of increased IgE and EOS may experience a greater clinical benefit. However, caution must be used in interpreting these results given their post-hoc nature.