Clinical Effectiveness Of Omalizumab In Severe Allergic Asthma Above The Recommended Dosing Range: The Australian Xolair Registry

Background: Omalizumab (Xolair) dosing in severe allergic asthma is based on total serum IgE and bodyweight. In Australia, patients exceeding the recommended dosing table range may still receive the ceiling dose of 750mg/4-week cycle. We hypothesized that such patients would still experience clinical benefit, and tested this with data from the Australian Xolair Registry (AXR), which has enrolled 62% of patients receiving PBS-funded omalizumab nationally. Methods: AXR participants approved for subsidised omalizumab were stratified according to whether they were within or above the omalizumab dose table range. Further sub-analyses were conducted according to the reason for being above the dosing table range (IgE only versus IgE and weight). Results: 179 participants were analysed; 55 (31%) above and 124 within the recommended dosing range. Baseline demographics, medication use and ACQ were similar. Patients above the dosing table had higher baseline IgE [812 (IQR 632, 1747) IU/ml versus 209 (IQR 134, 306) IU/ml], and received higher doses of omalizumab [750 (IQR 650, 750) mg versus 450 (IQR, 300, 600) mg] compared to those within range. At 6 months, significant improvements in ACQ (3.61 down to 2.01 for above-range, 3.47 down to 1.93 for within-range, p<0.0001 for both) and AQLQ score (3.22 up to 4.41 for above-range, 3.71 up to 4.88 for within-range, p<0.0001) were observed. Significant improvements in FEV1 were also present among above-range participants. The sub-analysis comparing participants above the dosing range due to IgE alone versus IgE and weight demonstrated similar improvements in ACQ, AQLQ and FEV1. Conclusion: Patients with severe allergic asthma above the dosing range for omalizumab by body weight and/or baseline serum IgE derive clinical benefit from omalizumab, without the need for dose escalation above 750mg/4-week cycle