Hypersensitivity reactions to therapeutic monoclonal antibodies: Phenotypes and endotypes

BACKGROUND:The increasing use of mAbs has led to a rise in hypersensitivity reactions (HSRs), which prevent their use as first-line therapy. HSRs' symptoms, diagnostic tools, and directed management approaches have not been standardized. OBJECTIVE:We propose a novel evidence-based classification of HSRs to mAbs, based on the clinical phenotypes, underlying endotypes and biomarkers, as well as their management with desensitization. METHODS:Phenotypes, endotypes, and biomarkers of HSRs to 16 mAbs for 104 patients were described and compared with the outcomes of 526 subcutaneous and intravenous desensitizations. RESULTS:Initial reactions presented with 4 patterns: type I-like reactions (63%), cytokine-release reactions (13%), mixed reactions (21%), and delayed type IV reactions (3%). In contrast, of the 23% breakthrough HSRs during desensitization, 52% were cytokine-release reactions, 32% were type 1, 12% were mixed, and 4% were type I with delayed type IV. Skin testing to 10 mAbs in 58 patients was positive in 41% of patients. Serum tryptase was elevated in 1 patient and IL-6 was elevated in 8 patients during desensitization and was associated with a cytokine-release phenotype. CONCLUSIONS:HSRs to mAbs can be defined as type I, cytokine-release, mixed (type I/cytokine-release), and type IV reactions, which are identified by biomarkers such as skin test, tryptase, and IL-6. These phenotypes can be used to improve personalized and precision medicine when diagnosing HSRs to mAbs and providing management recommendations with desensitization. Desensitization provides a safe and effective retreatment option to remain on culprit mAbs as first-line therapy.