PQA-18, a potent PAK2 inhibitor (IC50 = 10 nM) and immunosuppressant, derived from Ppc-1 (Item No. 50 = 400 nM), significantly reduces disease severity, serum IgE levels, and skin thickness in atopic dermatitis mouse models upon topical application. It also decreases cutaneous nerve fiber density and enhances graft survival in small intestine transplant rats.