Mechanisms of Drug Desensitization: Not Only Mast Cells

Methimazole Desensitization in a Patient Experiencing a Thionamide-induced Hypersensitivity Reaction

Patients with newly diagnosed Graves disease often elect for treatment with the drug methimazole (MMI) over alternative therapies. However, MMI can commonly result in skin allergy that in severe cases can lead to discontinuation of therapy. We present a case of Graves thyrotoxicosis with a delayed hypersensitivity reaction while on MMI. The patient was successfully treated with a novel, individualized, 27-day desensitization protocol that resulted in tolerance of MMI with subsequent improvement in thyroid indices. Previous literature has offered various rapid desensitization protocols to MMI for immediate type hypersensitivity reactions. However, in nonimmediate, delayed hypersensitivity reactions, a slower desensitization protocol can be considered. As demonstrated in this case, desensitization to MMI is a reasonable alternative in patients who wish to avoid definitive therapy who develop an initial adverse reaction to MMI, as this can occur in up to 13% of treated cases.

Research progress on desensitization of hypersensitivity reaction to iodinated contrast media

Desensitization therapy for iodinated contrast media (ICM) aims to induce drug tolerance in patients with a history of severe allergic reactions to ICM in a short time. Currently, there is no widely accepted consensus on inducing desensitization to avoid severe allergic responses to ICM. The clinically successful cases have shown that prophylactic use of antihistamines and glucocorticoids can increase the desensitization effect; repeatedly desensitizing and gradually increasing the dose can be conducive to establishing better tolerance to ICM. Most desensitization effects, including stress resistance, can endure 24-48 h. The mechanisms of desensitization therapy remain unclear, the initial dose, administration interval and dose gradient are largely based on clinical experiences and the reaction of patients. This article reviews the current research progress on ICM-related allergies, desensitization methods and related mechanisms, as well as the benefits and hazards of desensitization, to provide a reference for desensitization treatment of hypersensitivity to ICM .

Analysis of Breakthrough Reactions in 1,143 Desensitization Procedures in a Single Tertiary Hospital Using a One-Bag Desensitization Protocol

Background

Drug desensitization is helpful for patients who have experienced significant hypersensitivity reactions (HSRs) to antineoplastic agents. One-bag desensitization protocols, attracting attention in recent years, need to be validated on their safety and efficacy in a large number.

Methods

One-bag desensitization procedures conducted from 2018 to 2020 were analyzed; their outcomes and the risk factors for breakthrough reactions (BTRs) were assessed in desensitization procedures to major drug types (platins, taxanes, and monoclonal antibodies).

Results

A total of 1,143 procedures of one-bag desensitization were performed in 228 patients with 99% completion rate. BTRs occurred in 26% of the total desensitization procedures—34% in platins, 12% in taxanes, and 18% in mAbs. BTR occurrence rate decreased along the desensitization process with 80% of BTRs occurring within the 6th desensitization attempts. Severe BTR occurred more frequently with severe initial HSRs (1% in mild to moderate initial HSRs vs. 16% in severe). Severe initial HSR was also a significant risk factor for moderate to severe BTR in platins (odds ratio 1.56, 95% confidence interval [CI] 1.06–2.29, p = 0.025). The use of steroid was also associated with lower occurrence of moderate to severe BTR (odds ratio 0.50, 95% CI 0.35–0.72, p < 0.001).

Conclusion

Most patients with HSRs to antineoplastic agents can safely receive chemotherapy through a one-bag desensitization protocol. Further studies on each drug with larger sample size can help verify the risk factors of BTRs and evaluate the efficacy of steroid premedication in improving the safety of desensitization in high-risk patients.

Temporal Modulation of Drug Desensitization Procedures

Drug hypersensitivity reactions are an unavoidable clinical consequence of the presence of new therapeutic agents. These adverse reactions concern patients afflicted with infectious diseases (e.g., hypersensitivity to antibiotics), and with non-infectious chronic diseases, such as in cancers, diabetes or cystic fibrosis treatments, and may occur at the first drug administration or after repeated exposures. Here we revise recent key studies on the mechanisms underlying the desensitization protocols, and propose an additional temporal regulation layer that is based on the circadian control of the signaling pathway involved and on the modulation of the memory effects established by the desensitization procedures.

Desensitization for the prevention of drug hypersensitivity reactions

Drug desensitization is the temporary induction of tolerance to a sensitized drug by administering slow increments of the drug, starting from a very small amount to a full therapeutic dose. It can be used as a therapeutic strategy for patients with drug hypersensitivity when no comparable alternatives are available. Desensitization has been recommended for immunoglobulin E (IgE)-mediated immediate hypersensitivity; however, its indications have recently been expanded to include non-IgE-mediated, non-immunological, or delayed T cell-mediated reactions. Currently, the mechanism of desensitization is not fully understood. However, the attenuation of various intracellular signals in target cells is an area of active research, such as high-affinity IgE receptor (FcεRI) internalization, anti-drug IgG4 blocking antibody, altered signaling pathways in mast cells and basophils, and reduced Ca2+ influx. Agents commonly requiring desensitization include antineoplastic agents, antibiotics, antituberculous agents, and aspirin/nonsteroidal antiinflammatory drugs. Various desensitization protocols (rapid or slow, multi-bag or one-bag, with different target doses) have been proposed for each drug. An appropriate protocol should be selected with the appropriate concentration, dosage, dosing interval, and route of administration. In addition, the protocol should be adjusted with consideration of the severity of the initial reaction, the characteristics of the drug itself, as well as the frequency, pattern, and degree of breakthrough reactions.

Converter Phenotype: A New Profile That Is Not Exclusive to Taxanes

Introduction: Phenotype I hypersensitivity reactions are the most commonly reported drug reactions; however, precision medicine has made it possible to characterize new phenotypes. A recent communication proposed the existence of a “converter phenotype,” which would affect patients who present non-immediate hypersensitivity reactions and in subsequent exposures develop immediate hypersensitivity reactions. This study aimed to describe the clinical characteristics of converter phenotype reactions and their evolution during desensitization to chemotherapeutic drugs and monoclonal antibodies.

Methods: We retrospectively reviewed our database of patients undergoing desensitization to chemotherapy or biological agents and selected those with a converter phenotype. Demographic and clinical characteristics of the patients, the results of skin tests, tryptase and IL-6 levels, and desensitization outcomes were assessed.

Results: Of 116 patients evaluated, 12 (10.3%) were identified as having a converter phenotype. The median interval between drug exposure and reaction was 90.6 h (range 8-288 h). After the conversion, phenotype I was the most frequent (58.3%), followed by cytokine release reactions (33.3%). Fifty-one desensitizations were undertaken and all treatments completed, with 10 (19.6%) breakthrough reactions. No new changes in the phenotype were detected.

Conclusions: The symptoms of non-immediate drug hypersensitivity reactions may indicate the need for an early allergological evaluation to assess the risk of future immediate drug reactions. Clinical characteristics, skin test results, and biomarkers can help predict responses to rapid drug desensitization, guiding clinicians on how to optimize therapy delivery while maintaining patient safety.

Use of Skin Testing Screening and Desensitization Before the First Exposure of Rituximab

Objective

This study aimed to evaluate the incidence and severity of immediate hypersensitivity reactions (HSRs) in the first exposure to rituximab with the adoption of skin testing screening and desensitization and investigate the value of skin testing as a predictive tool for immediate HSR to rituximab.

Methods

This was a prospective intervention study. Patients with hematological malignancies who required rituximab were recruited. Skin testing screening with rituximab was conducted before the first infusion. Patients with positive skin testing results underwent desensitization, while those with negative results received rituximab at a standard infusion rate. All immediate HSRs were recorded, and the predictive value of positive skin testing results for immediate HSRs to rituximab was analyzed.

Results

In the 19 patients who adopted the novel protocol, six patients (31.6%) had immediate HSRs during the first infusion, with three mild reactions (15.8%), two moderate reactions (10.5%), and only one severe reaction (5.3%). The positive predictive value of intradermal test (IDT) with 1 mg/mL rituximab solution for immediate HSR was 100%, and the negative predictive value was 84.6%.

Conclusion

The protocol of skin testing screening and desensitization might have some potential to control the incidence and severity of immediate HSRs to rituximab during the first exposure. IDT result before the first infusion could become a useful predictor for immediate HSR to rituximab.

How to Prevent and Mitigate Hypersensitivity Reactions to Biologicals Induced by Anti-Drug Antibodies?

Biologicals are widely used therapeutic agents for rheumatologic diseases, cancers, and other chronic inflammatory diseases. They are characterized by complex structures and content of variable amounts of foreign regions, which may lead to anti-drug antibodies (ADA) development. ADA onset may limit the clinical usage of biologicals because they may decrease their safety. In fact they are mainly associated with immediate hypersensitivity reactions (HSRs). Development of ADAs is reduced by concomitant immunosuppressive treatment, while it is increased by longer intervals between drug administrations; thus, regular infusion regimens should be preferred to reduce HSRs. Once ADAs have formed, some procedures can be implemented to reduce the risk of HSRs. ADAs may belong to different isotype; the detection of IgE ADA is advisable to be assessed when high and early ADAs are detected, in order to reduce the risk of severe HRs. In patients who need to reintroduce the biological culprit, as alternative therapies are not available, drug desensitization (DD) may be applied. Desensitization should be conceptually dedicated to patients with an IgE-mediated HSR; however, it can be performed also in patients who had developed non-IgE-mediated HSRs. Although the underlying mechanisms behind successful DD has not been fully clarified, the DD procedure is associated with the inhibition of mast cell degranulation and cytokine production. Additionally, some data are emerging about the inhibition of drug-specific immune responses during DD.

Mechanisms of human drug-induced anaphylaxis

Drug-induced anaphylaxis is a hyperacute reaction affecting multiple organs that can be of fatal consequence. Its incidence is increasing, consistent with a global increased sensitization to various allergens and drugs in the population. Few risk factors and mechanisms have been identified from human studies due to the rarity of anaphylactic events and their unpredictability. This systemic reaction is caused by the rapid release of a large range of functionally diverse mediators, including histamine and platelet-activating factor as the main drivers identified. Mechanisms defined from models of experimental anaphylaxis identify drug-specific antibodies of the IgE and IgG class that link the drug to antibody receptors on multiple cell types, causing their activation and mediator release. In the case of drugs with peculiar chemical structures, antibodies may not be necessary because drug-binding receptors, such as Mas-related G protein-coupled receptor member X2, have been identified. This review describes the complex reaction leading to drug-induced anaphylaxis that can involve various antibody classes, various cell types-including mast cells, neutrophils, platelets, basophils, macrophages, and monocytes-and their mediators and receptors that, importantly, can be activated alone or in association to participate in the severity of the reaction.