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Following the discovery of small molecule acyl piperazine ROMK inhibitors and their initial preclinical validation as a novel diuretic agent, our group set out to discover new ROMK inhibitors with reduced risk for QT effects, suitable for further pharmacological experiments in additional species. Several strategies for decreasing hERG affinity while maintaining ROMK inhibition were investigated and are described herein. The most promising candidate, derived from the newly discovered 4- N -heteroaryl acetyl series, improved functional hERG/ROMK ratio by >10× over the previous lead. In vivo evaluation demonstrated comparable diuretic effects in rat with no detectable QT effects at the doses evaluated in an in vivo dog model. [ABSTRACT FROM AUTHOR]

Following the discovery of small molecule acyl piperazine ROMK inhibitors, the acyl octahydropyrazino[2,1-c][1,4]oxazine series was identified. This series displays improved ROMK/hERG selectivity, and as a consequence, the resulting ROMK inhibitors do not evoke QTc prolongation in an in vivo cardiovascular dog model. Further efforts in this series led to the discovery of analogs with improved pharmacokinetic profiles. This new series also retained comparable ROMK potency compared to earlier leads. [ABSTRACT FROM AUTHOR]

Abstract: Selective phosphodiesterase 2 (PDE2) inhibitors are shown to have efficacy in a rat model of osteoarthritis (OA) pain. We identified potent, selective PDE2 inhibitors by optimizing residual PDE2 activity in a series of phosphodiesterase 4 (PDE4) inhibitors, while minimizing PDE4 inhibitory activity. These newly designed PDE2 inhibitors bind to the PDE2 enzyme in a cGMP-like binding mode orthogonal to the cAMP-like binding mode found in PDE4. Extensive structure activity relationship studies ultimately led to identification of pyrazolodiazepinone, 22, which was >1000-fold selective for PDE2 over recombinant, full length PDEs 1B, 3A, 3B, 4A, 4B, 4C, 7A, 7B, 8A, 8B, 9, 10 and 11. Compound 22 also retained excellent PDE2 selectivity (241-fold to 419-fold) over the remaining recombinant, full length PDEs, 1A, 4D, 5, and 6. Compound 22 exhibited good pharmacokinetic properties and excellent oral bioavailability (F =78%, rat). In an in vivo rat model of OA pain, compound 22 had significant analgesic activity 1 and 3h after a single, 10mg/kg, subcutaneous dose. [Copyright &y& Elsevier]

Abstract: We identified potent, selective PDE2 inhibitors by optimizing residual PDE2 activity in a series of PDE4 inhibitors, while simultaneously minimizing PDE4 activity. These newly designed PDE2 inhibitors bind to the PDE2 enzyme in a cGMP-like mode in contrast to the cAMP-like binding mode found in PDE4. Structure activity relationship studies coupled with an inhibitor bound crystal structure in the active site of the catalytic domain of PDE2 identified structural features required to minimize PDE4 inhibition while simultaneously maximizing PDE2 inhibition. [Copyright &y& Elsevier]