Potent and selective phosphodiesterase (PDE) 4 inhibitor (IC50 = 72 nM). Exhibits >40-fold selectivity over PDE3, PDE10, and PDE11. Displays no significant activity on a panel of 442 kinases, 158 GPCRs and 21 phosphatases. Suppresses hedgehog signaling through PDE antagonism, downstream of smoothened signaling. Reduces transcription of Gli1 and Ptc1. Purity 98%. MW (observed): 416.58