Inhibitors of phosphodiesterase type 4 (PDE4) act by increasing intracellular concentrations of cyclic AMP, which has a broad range of anti-inflammatory effects. However, the therapeutic potential of PDE4 inhibitors has been limited by dose limiting adverse events such as nausea and emesis.HPP737 is a PDE4 inhibitor that addresses inflammatory diseases and offers an improved tolerability profile based on reduced CNS penetrance.

HPP737, a novel, potent and selective PDE4 inhibitor, has shown potent inhibition of IL23 and TNF production and therapeutic in vivo activity in several animal models of inflammation. HPP737 has completed Phase 1, demonstrating that it was safe and well tolerated at all doses tested, and demonstrating superior safety and comparable target engagement at much lower doses than marketed PDE4 inhibitors.. Preclinical and clinical data suggests HPP737 may not have the side effects common to other PDE4 inhibitors in development.