Allergen Delivery Inhibitors: Characterisation of Potent and Selective Inhibitors of Der p 1 and Their Attenuation of Airway Responses to House Dust Mite Allergens

Abstract

Group 1 allergens of house dust mites (HDM) are globally significant triggers of allergic disease. They are considered as initiator allergens because their protease activity enables the development of allergy to a spectrum of unrelated allergens from various sources. This initiator-perpetuator function identifies Group 1 HDM allergens as attractive drug design targets for the first small-molecule approach directed towards a non-human, root cause trigger of allergic disease. The purpose of this study was to: (i) identify exemplar inhibitors of these allergens using Der p 1 as a design template, and (ii) characterise the pharmacological profiles of these compounds using in vitro and in vivo models relevant to allergy. Potent inhibitors representing four different chemotypes and differentiated by mechanism of action were investigated. These compounds prevented the ab initio development of allergy to the full spectrum of HDM allergens and in established allergy they inhibited the recruitment of inflammatory cells and blunted acute allergic bronchoconstriction following aerosol challenge with the full HDM allergen repertoire. Collectively, the data obtained in these experiments demonstrate that the selective pharmacological targeting of Der p 1 achieves an attractive range of benefits against exposure to all HDM allergens, consistent with the initiator-perpetuator function of this allergen.

Cellular and Molecular Events in the Airway Epithelium Defining the Interaction Between House Dust Mite Group 1 Allergens and Innate Defences

“…One of the commonest trace contaminants of Der p 1 when purified by this technique is serine protease activity arising inter alia from allergens belonging to groups 3, 6, and 9, and rigorous steps are necessary to eradicate it. Partly for that reason, we have preferred a purification strategy for native Der p 1 which bypasses the requirement for enrichment by immunoaffinity chromatography and which incorporates multiple polishing steps for contaminant removal [ 9 , 19 ]. The ability to produce pure allergens to a rigorous and effective protocol is essential when they are being used as drug design targets, or when mechanistic analysis of biochemical or immunological signalling pathways is required.…”

“…The possible presence of contaminants is a factor which is particularly important when using materials with undisclosed methods of preparation. For example, we have reported contaminant activity in a commercially-obtained sample of Der p 2, and although the contamination levels appear low they may nevertheless have the potential to lure the unwary to misleading conclusions [ 9 ]. The problem is not confined to allergens of HDM origin; we have also reported on particularly intransigent serine peptidase contamination of the serodominant cat allergen, Fel d 1 [ 20 ].…”

“…Growing appreciation of how the protease activity of group 1 HDM allergens interacts with innate immune responses, biochemical and biophysical defences provides a compelling case for targeting this activity with selective inhibitors [ 7 ]. The target validation of these proteases has been the subject of recent detailed review, and initial disclosures of developable inhibitors have been made [ 7 , 9 , 10 ]. These new molecular entities form the spine of an unprecedented class of agents known as allergen delivery inhibitors (ADIs) and inspection of their pharmacological profiles suggests a mixture of benefits, some of which were anticipated (e.g., inhibition of eosinophil, neutrophil and dendritic cell recruitment) and some which were not (e.g., inhibition of allergic bronchoconstriction) [ 9 ].…”

“…The target validation of these proteases has been the subject of recent detailed review, and initial disclosures of developable inhibitors have been made [ 7 , 9 , 10 ]. These new molecular entities form the spine of an unprecedented class of agents known as allergen delivery inhibitors (ADIs) and inspection of their pharmacological profiles suggests a mixture of benefits, some of which were anticipated (e.g., inhibition of eosinophil, neutrophil and dendritic cell recruitment) and some which were not (e.g., inhibition of allergic bronchoconstriction) [ 9 ]. The new drugs are differentiated from steroids through mechanism of action and the range of pathways they influence, a combination which significantly attenuates the fundamental innate mechanisms which underlie the progression of disease [ 7 ].…”

“…Establishing the catalytic competence of these proteases was one of the first steps in developing the functionalist view of allergenicity [ 3 ]. In turn, it became the creation of a novel opportunity for an unprecedented approach to the treatment of allergic disease and a new class of small-molecule drugs which have been named allergen delivery inhibitors (ADIs) [ 7 , 9 , 10 , 11 ].…”