Discovery And Early Clinical Development Of Isobutyl 1-[8-Methoxy-5-(1-Oxo-3h-Isobenzofuran-5-Yl)-[1,2,4]Triazolo[1,5-A]Pyrid In-2-Yl]Cyclopropanecarboxylate (Leo 39652), A Novel "Dual-Soft" Pde4 Inhibitor For Topical Treatment Of Atopic Dermatitis

We describe the design of a novel PDE4 scaffold and the exploration of the dual-soft concept to reduce systemic side effects via rapid elimination: introducing ester functionalities that can be inactivated in blood as well as by the liver (dual-soft) while being stable in human skin. Compound 40 was selected as a clinical candidate as it was potent and rapidly degraded by blood and liver to inactive metabolites and because in preclinical studies it showed high exposure at the target organ: the skin. Preclinical and clinical data are presented confirming the value of the dual-soft concept in reducing systemic exposure.