PDE1B Inhibitor Compounds for Selective Enzyme Targeting
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Solution Overview
Problem
There is a need for compounds that selectively inhibit phosphodiesterase 1 (PDE1) activity, particularly PDE1B, to address disorders related to dopamine D1 receptor signaling and enhanced progesterone-signaling pathways, such as Parkinson's disease, depression, narcolepsy, and female sexual dysfunction.
Innovation Solution
Development of 1- or 2-substituted (6aR*,9aS*)-3-(phenylamino)-5-6a,7,8,9,9a-hexahydro-5-methyl-cyclopent[4,5]imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4(1H or 2H)-one compounds that inhibit PDE1-mediated hydrolysis of cGMP with high specificity, potentially using these compounds to potentiate dopamine D1 receptor signaling and enhance progesterone signaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compounds are designed to inhibit PDE1B activity with high specificity, then selectivity for PDE1B over other PDE isoforms is improved, but the complexity of achieving isoform-specific inhibition increases
Solution Approach 1:
The patent applies local quality by designing specific substituent patterns at defined positions (R1-R6) on the pyrazolopyrimidine core structure. Each substituent position is optimized to interact with specific residues in the PDE1B binding pocket, creating localized interactions that confer isoform selectivity. For example, specific substituents at R4 or R5 positions are designed to form hydrogen bonds or hydrophobic interactions unique to PDE1B's catalytic domain.
Solution Approach 2:
The patent employs parameter changes by systematically varying substituent types, sizes, and electronic properties at different positions on the core structure. This includes changing from electron-withdrawing to electron-donating groups, varying alkyl chain lengths, and introducing heteroatoms to modulate binding affinity and selectivity. These parameter optimizations allow fine-tuning of the compound's interaction with PDE1B versus other PDE isoforms.
2Reliability
If compound structure is optimized for high PDE1B inhibition potency, then IC50 values decrease, but the complexity of structure-activity relationship optimization increases
Solution Approach 1:
The patent segments the molecule into distinct functional regions: a core pyrazolopyrimidine scaffold that provides baseline PDE inhibition, and multiple substituent positions (R1-R6) that can be independently optimized for potency. This segmentation allows systematic SAR studies where each position can be evaluated for its contribution to binding affinity, facilitating iterative optimization of IC50 values through focused medicinal chemistry efforts.
Solution Approach 2:
The patent incorporates dynamic elements by designing substituents that can adopt different conformations or orientations upon binding to PDE1B. This includes flexible linkers, rotatable bonds, and stereocenters that can optimize spatial arrangement within the binding pocket. The dynamic adaptability of these molecular features allows the compound to achieve high potency by maximizing favorable interactions while minimizing steric clashes.
3Reliability
If compounds are designed to potentiate dopamine D1 receptor signaling, then therapeutic effect for neurodegenerative diseases is improved, but the risk of off-target effects increases
Solution Approach 1:
The patent uses PDE1B inhibition as an intermediary mechanism to indirectly potentiate dopamine D1 receptor signaling. Rather than directly targeting D1 receptors, the compounds inhibit PDE1B, which breaks down cAMP. By increasing cAMP levels through PDE1B inhibition, the signaling pathway downstream of D1 receptors is enhanced. This indirect mechanism provides therapeutic benefit while reducing the risk of direct off-target effects associated with D1 receptor ligands.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The compounds effectively inhibit PDE1B activity with IC50 values of less than 1 μM, potentially treating neurodegenerative diseases, mental disorders, and conditions characterized by reduced dopamine D1 receptor signaling or enhanced progesterone signaling.
Implementation Method 1
The compounds effectively inhibit PDE1B activity with IC50 values of less than 1 μM
Data Source
AI summary
1- or 2-substituted (6aR,9aS)-3-(phenylamino)-5-6a,7,8,9,9a-hexahydro-5-methyl-cyclopent[4,5]imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4(1H or, 2H)-one compounds of Formula (I), processes for their production, their use as pharmaceuticals and pharmaceutical compositions comprising them.