an2728 and Inflammation

Atopic dermatitis (AD) is a highly prevalent, chronic inflammatory skin disease that affects children and adults. The pathophysiology of AD is complex and involves skin barrier and immune dysfunction. Many immune cytokine pathways are amplified in AD, including T helper (Th) 2, Th22, Th17 and Th1. Current treatment guidelines recommend topical medications as initial therapy; however, until recently, only two drug classes were available: topical corticosteroids (TCSs) and topical calcineurin inhibitors (TCIs). Several limitations are associated with these agents. TCSs can cause a wide range of adverse effects, including skin atrophy, telangiectasia, rosacea and acne. TCIs can cause burning and stinging, and the prescribing information lists a boxed warning for a theoretical risk of malignancy. Novel medications with new mechanisms of action are necessary to provide better long-term control of AD. Phosphodiesterase 4 (PDE4) regulates cyclic adenosine monophosphate in cells and has been shown to be involved in the pathophysiology of AD, making it an attractive therapeutic target. Several PDE4 inhibitors are in clinical development for use in the treatment of AD, including crisaborole, which recently became the first topical PDE4 inhibitor approved for treatment of mild to moderate AD. This review will further describe the pathophysiology of AD, explain the possible role of PDE4 in AD and review PDE4 inhibitors currently approved or being investigated for use in AD.

Topics: Acetamides; Boron Compounds; Bridged Bicyclo Compounds, Heterocyclic; Cyclic Nucleotide Phosphodiesterases, Type 4; Cytokines; Dermatitis, Atopic; Drug Approval; Humans; Immune System; Inflammation; Phosphodiesterase Inhibitors; Phthalic Acids; Pyridines; Quinazolines; Risk; Skin; Thalidomide

Cytokines are signaling molecules that are believed to be key factors in perpetuating the inflammatory process in psoriasis and atopic dermatitis. AN-2728, being developed by Anacor Pharmaceuticals Inc, is a topically administered, boron-containing, anti-inflammatory compound that inhibits PDE4 activity and thereby suppresses the release of TNFalpha, IL-12, IL-23 and other cytokines. At the time of publication, three phase Ib clinical trials, a IIa trial and a IIb trial of AN-2728 in patients with psoriasis had been completed; the compound was also undergoing phase II development for atopic dermatitis, but no data were available for this indication. AN-2728 was reported to be well tolerated and to demonstrate significant effects on markers of efficacy, with results that were comparable to positive controls. AN-2728 appears to have good therapeutic potential, although further and larger trials are required to assess the long-term safety and characterize the broad utility of this drug.

Topics: Animals; Boron Compounds; Bridged Bicyclo Compounds, Heterocyclic; Clinical Trials as Topic; Cytokines; Dermatitis, Atopic; Humans; Inflammation; Phosphodiesterase 4 Inhibitors; Phosphodiesterase Inhibitors; Psoriasis

Phosphodiesterase 4 (PDE4) is highly expressed in keratinocytes and immune cells and promotes pro-inflammatory responses upon activation. The activity of PDE4 has been attributed to various inflammatory conditions, leading to the development and approval of PDE4 inhibitors as host-directed therapeutics in humans. For example, the topical PDE4 inhibitor, crisaborole, is approved for the treatment of mild-to-moderate atopic dermatitis and has shown efficacy in patients with psoriasis. However, the role of crisaborole in regulating the immunopathogenesis of inflammatory skin diseases and infection is not entirely known. Therefore, we evaluated the effects of crisaborole in multiple mouse models, including psoriasis-like dermatitis, AD-like skin inflammation with and without filaggrin mutations, and Staphylococcus aureus skin infection. We discovered that crisaborole dampens myeloid cells and itch in the skin during psoriasis-like dermatitis. Furthermore, crisaborole was effective in reducing skin inflammation in the context of filaggrin deficiency. Importantly, crisaborole reduced S. aureus skin colonization during AD-like skin inflammation. However, crisaborole was not efficacious in treating S. aureus skin infections, even as adjunctive therapy to antibiotics. Taken together, we found that crisaborole reduced itch during psoriasis-like dermatitis and decreased S. aureus skin colonization upon AD-like skin inflammation, which act as additional mechanisms by which crisaborole dampens the immunopathogenesis in mouse models of inflammatory skin diseases. Further examination is warranted to translate these preclinical findings to human disease.

Topics: Animals; Bridged Bicyclo Compounds, Heterocyclic; Cyclic Nucleotide Phosphodiesterases, Type 4; Dermatitis, Atopic; Disease Models, Animal; Filaggrin Proteins; Humans; Inflammation; Mice; Phosphodiesterase 4 Inhibitors; Pruritus; Psoriasis; Staphylococcal Infections; Staphylococcus aureus