D2.473 - Omalizumab as adjuvant therapy in drug desensitization to chemotherapy- a single Center experience

Chemotherapy can be associated with immediate hypersensitivity reactions (IHSRs) and drug desensitization (DD) represents a therapeutic strategy to overcome them. Though most DDs are successfully completed, some can be complicated by breakthrough reactions (BTRs), preventing further drug administrations. The use of omalizumab, an anti-IgE monocloncal antibody, has been described in food, hymenoptera venom and drug allergy. We present our experience with omalizumab as adjuvant therapy in DD to chemotherapy.

Omalizumab was used in patients undergoing 16-step DDs who had positive skin testing and experienced BTRs that were severe or could not be overcome by prompt treatment and a slower infusion rate. The protocol consisted in an induction phase in which omalizumab was administered 15 and 2 days before the first optimized DD and subsequently every two weeks in the maintenance phase. Furthermore, we used a fixed dose of 600 mg for each administration, the maximum amount allowed in asthma, to maximize its biological effect.

From March 2019 to February 2026, 21 patients received omalizumab. The most common culprit drug was carboplatinum (12, 57%), followed by paclitaxel (5, 24%) and other platins (4, 19%). The index reactions occurred mainly during treatment resumption after a gap (16, 76%) and only 3 during the first infusion. In all patients BTRs occurred during the first DD, mainly during the fourth bag (13, 62%), though they also happened during the third (4, 19%) and second bag (4, 19%). Severe BTRs occurred only in two patients (9%). After using omalizumab, 17 patients (81%) completed their treatment cycle: 10 reached the target dose during the first optimized DD and 7 during the second. Four patients (19%) continued to experience BTRs despite omalizumab and switched to second-line therapies: three had reacted to paclitaxel upon the first infusion and one to carboplatinum during the eighth.  

Omalizumab as adjuvant therapy to DD allowed most patients to safely complete their treatment regimen. While further studies are needed to define the most appropriate dosing and administration schedule, it represents a promising option for patients who experience BTRs during DD to chemotherapy, when an IgE-mediated mechanism is suspected.