Atopic dermatitis (AD) or severe eczema is a very common life-long skin disease, with 3% of adults in the US requiring systemic therapy. Clinical manifestations of AD include multiple inflamed lesions, erosions accompanied by lichenification (thick leathery skin), fibrotic papules, and severely dry skin with increased susceptibility to infection. A major uncontrolled symptom is intense itching and excessive scratching that can cause further excoriation, erosions and infections. The two mainstays of current treatment of AD are immunosuppressant corticosteroids and calcineurin inhibitors. However, these immune-suppressing agents can cause untoward side-effects during chronic treatment. Anti-histamine/creams are not effective in suppressing AD-associated itching which creates the vicious circle of excoriation, skin thickening, and infection. Protease-activated receptor-2 (PAR2) has been identified as an emerging therapeutic target in AD that may significantly impact itch, inflammation and skin-thickening in humans. PAR2 is highly expressed on keratinocytes and inflammatory cells in the AD lesions and is cleaved and activated by inflammatory and environmental proteases such as mast cell tryptase, mite allergen proteases, and a number of endogenous dermal proteases (kallikrein-5, cathepsin S) involved in filaggrin and epidermal homeostasis in the skin. Notably, knock-out of the PAR2 gene results in major suppression of AD lesions in animal models and nearly complete suppression of thymic stromal lymphopoietin (TSLP) which is a major regulator of the Th2-driven inflammatory response. PAR2-deficient mice also exhibit significant suppression of itching in response to dermal irritants. The goal of this proposal is based on our new discovery of the cell-penetrating pepducin, PZ- 235, as a potent inhibitor of PAR2 in AD. Pepducin technology offers a unique opportunity to target the intracellular surface of G-protein coupled receptors (GPCRs) such as PAR2 with exquisite specificity, potency and long half-lives, with prolonged drug exposure to the target tissue, namely skin. The PZ-235 pepducin effectively suppresses skin inflammation, itch, and skin thickening in multiple dermatitis and pruritus models. Rapid completion of the proposed preclinical and IND-enabling studies would generate a novel drug candidate with a triple anti-inflammatory, anti-itch, anti-skin thickening mode of action for the treatment of AD. Phase I will formulate PZ-235 for topical skin penetration and to extensively test the pharmacologic properties of PZ-235 with the milestones of showing significant delivery into the dermal layer and efficacy data to demonstrate suppression of AD lesions/itching in animal models. Phase II goals are to produce pharmaceutical-grade (GMP) active drug substance for topical administration, demonstrate efficacy and GLP safety in appropriate animal models, obtain a pre-IND meeting with the FDA, and produce clinical protocols for Phase I and II studies in humans with our dermatology clinical collaborators.
Atopic Dermatitis (AD) or severe eczema is the most common chronic inflammatory skin disease present in about 18 million people in the US. Current treatment consists of topical or oral immune-suppressing agents for the most severely afflicted patients, which can exhibit severe side effects and are not suitable for long-term use. In this proposal, we identify Protease-Activated Receptor-2 (PAR2) as an emerging new target in AD and provide a blueprint for a drug development plan using cell-penetrating pepducins to effectively suppress the inflammation, itching and skin thickening that afflicts AD patients.
