Background Drug hypersensitivity reactions (DHRs) to platinum-based drugs are heterogenous and restrict their access, and drug desensitization (DD) has provided a ground-breaking procedure for their re-introduction, although the response is heterogeneous. We aimed to identify the phenotypes, endotypes and biomarkers of reactions to carboplatin and oxaliplatin and their response to DD. Methods Seventy-nine patients presenting with DHRs to oxaliplatin (N=46), and carboplatin (N=33) were evaluated at the Allergy Departments of two tertiary care hospitals in Spain. Patient symptoms, skin testing, biomarkers, and outcomes of 267 DDs were retrospectively analyzed. Results Oxaliplatin-reactive patients presented with type I (74%), cytokine release reaction (CRR) (11%), and mixed (Mx) (15%) phenotypes. In contrast, carboplatin reactive patients presented with predominantly type I (85%) and Mx (15%) but no CRRs. Out of 267 DDs, breakthrough reactions (BTRs) to oxaliplatin occurred twice as frequently as carboplatin (32% versus 15%; p<0.05). Phenotype switching from type I to another phenotype was observed in 46% of oxaliplatin DDs compared to 21% of carboplatin DDs. Tryptase was elevated in type I and Mx reactions, and IL-6 in CRR and Mx, indicating different mechanisms and endotypes. Conclusion Carboplatin and oxaliplatin induced three different types of reactions with defined phenotypes and endotypes amendable to DD. Although most of the initial reactions for both were type I, oxaliplatin presented with unique CRR reactions. During DD, carboplatin reactive patients presented mostly type I BTR, while oxaliplatin reactive patients frequently switched from type I to CRR, providing a critical difference and the need for personalized DD protocols.

Background Beta-lactams generate different allergenic determinants that induce selective or cross-reactive drug hypersensitivity reactions (DHRs). We aimed to identify the drugs involved, the selectivity of the response, the mechanism, and the value of the different diagnostic tests for establishing a diagnosis in children evaluated for DHRs to beta-lactams. Methods Prospective study evaluating children aged under 16 years reporting DHRs to beta-lactams. Reactions were classified as immediate and nonimmediate reactions. The work-up included sIgE, skin testing and drug provocation tests (DPTs) for immediate reactions and patch testing and DPTs for nonimmediate ones. Results Of the 510 included children, 133 were evaluated for immediate reactions and confirmed in 8.3%. Skin test/in vitro IgE contributed to diagnosing half of the cases. Selective reactions occurred with amoxicillin (63%), followed by common penicillin determinants (27%) and cephalosporins (0.9%). Among nonimmediate reactions (11,4% of the 377 children evaluated), most required DPTs, 52.7% of which were positive at 6–7 days of drug challenge. Selective reactions were identified with amoxicillin (80%), penicillin G (7.5%), cephalosporins (7.5%), and clavulanic acid (5%). Urticaria and maculopapular exanthema were the most frequent entities. Conclusions There were few confirmed cases of either type of reaction. Skin testing proved less valuable in nonimmediate reactions, over half of which would also have been lost in a short DPT protocol. Selective responders to amoxicillin were more likely to have nonimmediate reactions, while clavulanic acid-selectivity was exclusive to the nonimmediate typology. Over half the cases with DPTs required 6-7 days of treatment for DHR confirmation.