Polymerbasierte Implantate für die kontrollierte Freisetzung von Allergoid für die Allergen-Immuntherapie

In allergen immunotherapy (AIT) allergy remission is achieved through regular application of allergy-triggering substances (allergens), either in their native or chemically modified form (allergoids). One of the main factors affecting AIT efficiency is the low adherence.

The development of a subcutaneous implant loaded with an allergoid represents a new and innovative route of administration for controlled release of the allergoid, resulting in sustained drug levels over several months with minimized applications.

The presented work reports the development of implants based on the biodegradable polymer poly(lactic-co-glycolic acid) (PLGA) for a controlled long-term release of birch allergoid. Various implant formulations based on the PLGA polymers RG 504 H and RG 756 S were manufactured by hot melt extrusion using a twin-screw extruder. Characterisation of the implants by scanning electron microscopy and quantitative determination of the allergoid within the extrudate confirmed the successful implementation of the process. The structural integrity of the allergoid in the various implant formulations was investigated by combined evaluation of different physicochemical methods, including FTIR, SEC, DLS and IEF, while the preservation of the immunological properties was analysed by determination of IgG- or IgE-binding activity.

The allergoid showed high stability towards the high process temperatures of up to 95°C which was further improved by the inclusion of a protein-stabilising agent (trehalose). In-vitro release experiments demonstrated a long-term release of the allergoid from PLGA-based implants for up to 40 weeks. Polymer- and formulation-dependent influences on the erosion behaviour of the polymer and the release of the allergoid were observed.The presented results could serve as a base to develop a platform technology for the future treatment of IgE-mediated allergies.

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