Alpha-Lipoic acid-based PPARgamma agonists for treating inflammatory skin diseases.

Novel thiazolidinedione derivatives of the potent antioxidant, alpha-lipoic (thioctic, 1,2-dithiolane) acid, were prepared. The prototype N-(2-[4-[2,4-dioxo(1,3-thiazolidin-5-yl)methyl]phenoxy]ethyl)-5-(1,2-dithiolan-3-yl)- N-methylpentanamide (designated BP-1003), and dithioester derivatives thereof were shown to be potent activators of peroxisome proliferator-activated receptor gamma (PPARgamma) (EC(50) range 15-101 nM) and modest activators of PPARalpha (EC(50) 5 microM). Both the relatively hydrophobic dithiolane prototype, BP-1003, and its water-soluble dithioglycinate derivative, BP-1017, were shown to inhibit the proliferation of human keratinocytes and suppress the production of interleukin-2 by human peripheral lymphocytes to a greater extent than the antidiabetic thiazolidinedione, rosiglitazone. Both oral and topical administration of BP-1017 showed significant antiinflammatory effects in the oxazolone-sensitized mouse model of allergic contact dermatitis (ACD). These findings suggest that water-soluble lipoic acid-based thiazolidinediones may be efficacious as oral and topical agents for treating inflammatory skin conditions such as contact dermatitis, atopic dermatitis, and psoriasis.