Identification and pre‐clinical investigation of CKBA as a drug for external use to treat psoriasis

Abstract Background and Purpose Psoriasis vulgaris is a refractory skin inflammatory disorder with 80% of the cases belonging to the mild‐to‐moderate type, which can be controlled by topical treatment. Nevertheless, the drugs for external use have not been upgraded for decades. We modified acetyl‐11‐keto‐beta‐boswellic acid (ABKA), a natural compound shown to treat psoriasis animal models, to improve efficacy and solubility for topical use. Experimental Approach Eleven compounds were synthesized using AKBA as a lead compound, and their effects on Th17 cell differentiation were screened. 3‐O‐cyclohexanecarbonyl‐11‐keto‐β‐boswellic acid (CKBA) potently inhibited Th17 cell differentiation. Its efficacy in a mouse model of psoriasis was assessed along with its pharmacology and safety profile when topically or systemically delivered to several animal species. Key Results CKBA inhibited mouse and human Th17 cell differentiation with an IC 50 of 3.28 and 3.61 μM, respectively, and directly targeted acetyl‐CoA carboxylase 1 (ACC1). Safety evaluation and toxicity tests suggested that systemically delivered high‐dose CKBA for 14 days had no dose‐associated adverse effects on the CNS, haematopoietic, cardiovascular, respiratory and digestive systems of cynomolgus monkeys. CKBA ointment permeated the skin and did not irritate or sensitize intact skin. CKBA ointment mediated dose‐dependent suppression of imiquimod‐induced psoriasis‐like skin inflammation with slow absorption and limited bioavailability (<10% in rats and <1% in minipigs). Conclusions and Implications CKBA is safe when topically or systemically delivered to animals. The beneficial effects of CKBA ointment in a mouse model of psoriasis indicate that this is a promising drug candidate for further development as a treatment for psoriasis.