Off-label use of omalizumab in pediatric anaphylaxis

Off-label uses of drugs require a careful assessment of benefit-risk ratio. Omalizumab's indications include severe asthma and chronic urticaria in patients older than 6 years. We describe a group of children receiving omalizumab as an off-label use for anaphylaxis and their clinical response. Five children (4 boys/1 girl), median age: 5 years (Interquartile range [IQR]: 3-15). Indications were: 1st case: Enzyme replacement therapy (ERT) induced anaphylaxis, after failed desensitization attempts; 2nd: Recurrent anaphylaxis due to combined milk, egg and nut allergies; 3rd: Traces' induced milk allergy as specific oral tolerance induction (SOTI) premedication; 4th and 5th: Failed SOTI attempts with milk and egg, respectively. Median anaphylaxis episodes before omalizumab: 4 (IQR: 1-6). Total IgE values: 602 kU/L (IQR: 15-2000). Weight: 24 kg (IQR: 11-49). Patients received (median dose) 300 mg/monthly (IQR: 75-600 mg]) for (median) 18 months (IQR: 4-36). Afterwards, a patient developed 2 anaphylaxis (1 during SOTI induction and the other during maintenance phase). ERT has been administered for 18 months so far and the SOTI has been tolerated by the other 3 patients. Omalizumab's doses/frequency have been diminished in 2 out of 5 patients, and increased in another one. Omalizumab's addition allowed continuing SOTI/desensitazation procedures in high risk patients, reducing the number of anaphylaxis episodes. Despite its administration protective measures such as anaphylaxis management plans, cofactors avoidance and rescue medication are to be maintained in such patients. As our sample includes very young children, we must be aware there is no knowledge about our choice’s future consequences.