## Endpoint to Predict
- Endpoint scope: assay
- Measurement type: Ki
- Label type: continuous
- Binary semantics: pchembl
- Assay description: Inhibitory Activity Assay : Human PDE9 (PDE9A2, GenBank Accession No. NM_001001567), full length with N-terminal GST tag, was purchased from BPS Bioscience. The fluorescence polarization assay for cyclic nucleotide phosphodiesterases was performed using an IMAP FP kit supplied by Molecular Devices, Sunnyvale, Calif. (product # R8139). Assays were performed at room temperature in 384-well microtiter plates with an incubation volume of 20.2 μL. Solutions of test compounds were prepared in DMSO and serially diluted with DMSO to yield 8 μL of each of 10 solutions differing by 3-fold in concentration, at 32 serial dilutions per plate. 100% inhibition is determined using a known PDE9 inhibitor. 0% of inhibition is determined by using DMSO (1% final concentrations). A Labcyte Echo 555 (Labcyte, Sunnyvale, Calif.) is used to dispense 200 nL from each well of the titration plate to the 384 well assay plate. Rhesus membrane preps were diluted to 4 ng/ml, rat membrane preps diluted to 13 ng/ml, and human PDE9A2 diluted to 1 ng/ml. FAM-labeled cGMP substrate (Molecular Devices, Sunnyvale, Calif.) was at a concentration of 100 nM (Km of PDE9 for cGMP is 70-170 nM) in the assay buffer (10 mM Tris HCl, pH 7.2, 10 mM MgCl2, 0.05% NaN3 0.01% Tween-20, and 1 mM DTT). PDE9 enzyme mix and compounds were mixed and incubated at room temperature for 30 min. Following which, FAMcGMP substrate was added, shaken and incubated for an additional 60 min at room temperature. The final concentrations of rhesus and rat membrane preparations were 2 ng/ml and 6.5 ng/ml, respectively, while the human PDE9 was used at a final concentration of 0.5 ng/ml. The final concentration of FAM-cGMP was 50 nM. After the incubation period, the enzymatic reaction was stopped by addition of binding solution (IMAP-FP, Molecular Devices, comprised of 80% Solution A, 20% Solution B and a 1:600 dilution of binding reagent) to each well. The plates were shaken then incubated at room temperature for 1 h prior to determining the fluorescence polarization (mP) using a Perkin Elmer EnVision plate reader (Waltham, Mass.).
- Assay organism: Homo sapiens
- Target name: High affinity cGMP-specific 3',5'-cyclic phosphodiesterase 9A
- Target type: SINGLE PROTEIN
- Target organism: Homo sapiens

## Reference Molecule A
- Canonical SMILES: N#Cc1c(OC2CCCCC2)c2ccccc2[nH]c1=O
- Properties:
- ChEMBL ID: CHEMBL5976005
- Molecular weight: 268.32
- Heavy atoms: 20
- Hydrogen bond donors: 1
- Hydrogen bond acceptors: 3
- TPSA: 65.88
- LogP: 3.11
- Rotatable bonds: 2
- Ring count: 3
- Aromatic rings: 2
- Formal charge: 0
- Fraction Csp3: 0.38
- QED: 0.91

## Known Reference Result on This Endpoint
- Molecule A clean result: median pChEMBL = 7.3
- This result is provided as context for predicting Molecule B on the same endpoint.

## Reference Molecule A Other ChEMBL Evidence
- type Ki; relation =; value 50.3; units nM; pChEMBL 7.3; comment 818318

## Query Molecule B
- Canonical SMILES: CCC(C)(CO)COc1c(C#N)c(=O)[nH]c2ccccc12
- Properties:
- ChEMBL ID: CHEMBL5872313
- Molecular weight: 286.33
- Heavy atoms: 21
- Hydrogen bond donors: 2
- Hydrogen bond acceptors: 4
- TPSA: 86.11
- LogP: 2.19
- Rotatable bonds: 5
- Ring count: 2
- Aromatic rings: 2
- Formal charge: 0
- Fraction Csp3: 0.38
- QED: 0.88

## Molecule Similarity
- Weighted Tanimoto: 0.51

Answer: 6.74