Spantide II is an undecapeptide (MW 1668.76) designed as a potent neurokinin-1 receptor (NK-1R) antagonist, featuring seven substitutions from the native substance P sequence to eliminate neurotoxicity while preserving high binding affinity. By blocking substance P-mediated signaling, it inhibits the cascade of proinflammatory activities underlying conditions like contact dermatitis and psoriasis. In preclinical models, Spantide II demonstrates a shelf life of 230 days in aqueous ethanol at 25°C, with maximum stability at pH 3.0 (half-life of 95 days at 60°C), and achieves significant retention in the epidermis and dermis—where dermal levels increase up to 3.5-fold with penetration enhancers like N-methyl-2-pyrrolidone. This compound is widely utilized in dermatological research to investigate neurogenic inflammation and evaluate topical anti-inflammatory efficacy in allergic contact dermatitis models.