In vitro and in vivo evaluation of topical formulations of spantide II.

The purpose of this study was to develop and evaluate topical formulations of Spantide II, a neurokinin-1 receptor (NK-1R) antagonist, for the treatment of inflammatory skin disorders. Spantide II lotion and gel was formulated with and without n-methyl-2-pyrrolidone (NMP) as a penetration enhancer. The release of Spantide II from gels was evaluated using microporous polyethylene and polypropylene membranes in a Franz Diffusion cell setup. In vitro percutaneous absorption of Spantide II from lotion and gel formulations was evaluated using the above setup by replacing the membranes with hairless rat skin. The in vivo anti-inflammatory activity of Spantide II formulations was evaluated in an allergic contact dermatitis (ACD) mouse model. Among different gels studied, PF127 gel showed highest (70-fold) release of Spantide II compared with hydroxypropyl methylcellulose (HPMC) and hydroxypropyl cellulose (HPC) gels. Lotion and gel formulations with or without NMP showed no detectable levels of Spantide II in the receiver compartment of the Franz diffusion cell until 24 hours. However, Spantide II showed significant retention in epidermis and dermis from lotion and gel formulations at 24 hours. The dermal levels increased approximately 3.5- and 2-fold when the lotion and gel formulations contained NMP as compared with the formulation with no NMP (P < .05). The in vivo studies indicated that Spantide II formulations with NMP were effective in significantly reducing ACD response, similar to dexamethasone (0.5 mM). In conclusion, Spantide II was stable as a topical formulation and delivered to target skin tissue (epidermis and dermis) for the treatment of ACD. In addition this study supports the role of cutaneous neurosensory system in modulating inflammatory responses in the skin.