## Endpoint to Predict
- Endpoint scope: assay
- Measurement type: Ki
- Label type: continuous
- Binary semantics: pchembl
- Assay description: Fluorescence Polarization Assay: The fluorescence polarization assay for cyclic nucleotide phosphodiesterases was performed using an IMAPÂ® FP kit supplied by Molecular Devices, Sunnyvale, Calif. (product #R8139). IMAPÂ® technology has been applied previously to phosphodiesterase assays (Huang, W., et al., J. Biomol Screen, 2002, 7: 215). Assays were performed at room temperature in 384-well microtiter plates with an incubation volume of 20.2 ul. Solutions of test compounds were prepared in DMSO and serially diluted with DMSO to yield 8 uL of each of 10 solutions differing by 3-fold in concentration, at 32 serial dilutions per plate. 100% inhibition is determined using a known PDE10 inhibitor, which can be any compound that is present at 5,000 times its Ki value in the assay described as follows, such as papaverine (see Siuciak, et al. Neuropharmacology (2006) 51:386-396; Becker, et al. Behav Brain Res (2008) 186(2):155-60; Threlfell, et al., J Pharmacol Exp Ther (2009) 328(3):785-795), 2-{4-[pyridin-4-yl-1-(2,2,2-trifluoroethyl)-1H-pyrazol-3-yl]phenoxymethyl}quinoline succinic acid or 2-[4-(1-methyl-4-pyridin-4-yl-1H-pyrazol-3-yl)-phenoxymethyl]quinoline succinic acid (see Schmidt, et al. J Pharmacol Exp Ther (2008) 325:681-690; Threlfell, et al., J Pharmacol Exp Ther (2009) 328(3): 785-795). 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. A solution of enzyme (1/1600 dilution from aliquots; sufficient to produce 20% substrate conversion) and a separate solution of FAM-labeled cAMP PDE from Molecular Devices (product #R7506), at a final concentration of 50 nM are made 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). The enzyme and the substrate are then added to the assay plates in two consecutive additions of 10 uL, and then shaken to mix. The reaction is allowed to proceed at room temperature for 30 minutes. A binding solution is then made from the kit components, comprised of 80% Solution A, 20% Solution B and binding reagent at a volume of 1/600 the total binding solution. The enzymatic reaction is stopped by addition of 60 uL of the binding solution to each well of the assay plates and the plates are sealed and shaken for 10 seconds. The plate was incubated at room temperature for at least one hour prior to determining the fluorescence polarization (FP). The parallel and perpendicular fluorescence of each well of the plate was measured using a Perkin Elmer Enyision plate reader (Waltham, Mass.).
- Assay organism: Homo sapiens
- Target name: cAMP and cAMP-inhibited cGMP 3',5'-cyclic phosphodiesterase 10A
- Target type: SINGLE PROTEIN
- Target organism: Homo sapiens

## Reference Molecule A
- Canonical SMILES: O=c1n(CCc2ccc3ccccc3n2)nc2cccc(Br)n12
- Properties:
- ChEMBL ID: CHEMBL3952599
- Molecule type: Small molecule
- Molecular weight: 369.22
- Heavy atoms: 23
- Hydrogen bond donors: 0
- Hydrogen bond acceptors: 3
- TPSA: 52.19
- LogP: 3.05
- Rotatable bonds: 3
- Ring count: 4
- Aromatic rings: 4
- Formal charge: 0
- Fraction Csp3: 0.12
- QED: 0.52

## Known Reference Result on This Endpoint
- Molecule A clean result: median pChEMBL = 7.23
- This result is provided as context for predicting Molecule B on the same endpoint.

## Reference Molecule A Other ChEMBL Evidence
- type Ki; relation =; value 59; units nM; pChEMBL 7.23; comment 369479

## Query Molecule B
- Canonical SMILES: O=c1n(CCc2ccc3ccccc3n2)nc2cccc(-c3ccncc3)n12
- Properties:
- ChEMBL ID: CHEMBL3986711
- Molecule type: Small molecule
- Molecular weight: 367.41
- Heavy atoms: 28
- Hydrogen bond donors: 0
- Hydrogen bond acceptors: 4
- TPSA: 65.08
- LogP: 3.35
- Rotatable bonds: 4
- Ring count: 5
- Aromatic rings: 5
- Formal charge: 0
- Fraction Csp3: 0.09
- QED: 0.49

## Molecule Similarity
- Weighted Tanimoto: 0.68

Answer: 8.36