Omalizumab enables bee venom desensitisation in patients with anaphylactic reactions to venom immunotherapy.

Background: Venom immunotherapy (VIT) is the only treatment for honeybee venom allergy; however, some patients develop severe allergic reactions (SAR) during therapy. Omalizumab, an anti-IgE antibody, may improve VIT tolerance, though data in honeybee VIT remain limited.

Objective: To evaluate the efficacy of adjuvant omalizumab in honeybee VIT, identify predictors of omalizumab requirement, and inform protocol selection.

Methods: A retrospective chart review was conducted of all adults undergoing honeybee VIT at Fiona Stanley Hospital, Perth, Western Australia, from 2015 to 2024. Baseline characteristics, biomarkers, protocols, and outcomes were analysed.

Results: Among 354 VIT patients, 57 (16%) experienced SARs, with 36 (10%) receiving omalizumab. Predictors of omalizumab need included severe sting anaphylaxis, asthma, and elevated basal tryptase. One patient used omalizumab to escalate VIT dosing after already reaching maintenance. Of 35 patients using omalizumab during VIT up-titration, 22 (63%) achieved unsupported maintenance, 7 (20%) ceased due to SARs, and 5 (14%) remain on omalizumab. Excluding 5 patients who declined or lacked access to ongoing omalizumab, the success rate increases to 73%. The most common protocol involved a 12-week VIT up-titration to 100 μg with omalizumab 300 mg loading 2 weeks prior, followed by 150 mg fortnightly until maintenance VIT was reached. SARs most frequently occurred at omalizumab cessation. In 3 cases, these were overcome by resuming omalizumab with a higher VIT maintenance dose target.

Conclusion: Omalizumab could be considered in patients experiencing recurrent SARs to standard VIT. A semi-rush protocol with omalizumab loading 1 to 2 weeks prior was well tolerated.