## Endpoint to Predict
- Endpoint scope: assay
- Measurement type: IC50
- Label type: continuous
- Binary semantics: pchembl
- Assay description: In Vitro Assay: Potency of candidate molecules for inhibiting syk tyrosine phosphorylation activity is assessed by measuring the ability of a test compound to inhibit syk-mediated tyrosine phosphorylation of a syk-specific substrate.SYK tyrosine phosphorylation activity is measured using the LANCE Technology developed by Perkin Elmer Life and Analytical Sciences (Boston, Mass.). LANCE refers to homogeneous time resolved fluorometry applications using techniques such as time-resolved fluorescence resonance energy transfer assay (TR-FRET) (see generally for procedures in Perkin Elmer Application Note How to Optimize a Tyrosine Kinase Assay Using Time Resolved Fluorescence-Based LANCE Detection, wwww.perkinelmer.com/lifesciences). The assay principle involves detection of a phosphorylated substrate using energy transfer from a phosphospecific europium-labeled antibody to streptavidin-allophycocyanin as an acceptor.To test the ability of candidate molecules to inhibit SYK tyrosine phosphorylation activity, molecules are reconstituted in 30% DMSO and serially diluted 1:3 with the final dilution containing DMSO in the absence of the candidate molecule. The final DMSO concentration in the assay is 3%. Kinase assays are performed as a two part reaction. The first reaction is a kinase reaction and which comprises of a candidate molecule, full length active recombinant SYK enzyme (Millipore, Calif.) and biotin-labeled SYK-specific substrate biotin-DEEDYESP-OH. The second reaction involves termination of the kinase reaction and the simultaneous addition of the detection reagents-europium-labeled anti-phosphotyrosine reagent (Eu-W1024-PY100, Perkin Elmer, Boston, Mass.) and Streptavidin-Allophycocyanin detection reagent (SA-APC, Prozyme, Calif.). The kinase reaction is performed in a black U-bottom 96-well microtitre plate. The final reaction volume is 50 μL and contains a final concentration of 1 nM active SYK enzyme, 550 nM SYK-substrate, and 100 μM ATP diluted in a buffer containing 50 mM Tris pH 7.5, 5 mM MgCl2, and 1 mM DTT. The reaction is allowed to proceed for 1 hour at room temperature. The quench buffer contains 100 mM Tris pH 7.5, 300 mM NaCl2, 20 mM EDTA, 0.02% Brij35, and 0.5% BSA. The detection reagents are added to the reaction mixture at the following dilutions 1:500 for Eu-W1024-PY100 and 1:250 for SA-APC. The kinase reaction is terminated by the addition of 50 μL quench buffer containing the detection reagents. The detection is allowed to proceed for 1 hr at room temperature. Detection of the phosphorlated substrate in the absence and presence of inhibitors is measured in the TR-FRET instrument, Analyst HT (Molecular Probes, Sunnyvale, Calif.) and the condition for measurements are set up using CriterionHost Release 2 (Molecular Probes, Sunnyvale, Calif.). The settings used are a follows: excitation 360 nm, emission 665-7.5 nm, beam splitter 350 nm 50/50, flash 100 pulses, delay 60 us, integration 400 us, z-height 2 mm. Inhibition of SYK-tyrosine kinase activity is calculated as the maximum response observed in the presence of inhibitor, compared to that in the absence of inhibitor. IC50s were derived by non-linear regression analysis.
- Assay organism: Homo sapiens
- Target name: Tyrosine-protein kinase SYK
- Target type: SINGLE PROTEIN
- Target organism: Homo sapiens

## Reference Molecule A
- Canonical SMILES: NC(=O)c1cnc(N[C@@H]2CCCC[C@@H]2N)nc1Nc1cccc(-c2ccnc3ccccc23)c1
- Properties:
- ChEMBL ID: CHEMBL5897918
- Molecular weight: 453.55
- Heavy atoms: 34
- Hydrogen bond donors: 4
- Hydrogen bond acceptors: 7
- TPSA: 131.84
- LogP: 4.22
- Rotatable bonds: 6
- Ring count: 5
- Aromatic rings: 4
- Formal charge: 0
- Fraction Csp3: 0.23
- QED: 0.34

## Known Reference Result on This Endpoint
- Molecule A clean result: median pChEMBL = 6.26
- This result is provided as context for predicting Molecule B on the same endpoint.

## Reference Molecule A Other ChEMBL Evidence
- type IC50; relation =; value 550; units nM; pChEMBL 6.26; comment 554846

## Query Molecule B
- Canonical SMILES: CNC1(CNc2ncc(C(N)=O)c(Nc3cc(C)cc(C)c3)n2)CC1
- Properties:
- ChEMBL ID: CHEMBL5935979
- Molecular weight: 340.43
- Heavy atoms: 25
- Hydrogen bond donors: 4
- Hydrogen bond acceptors: 6
- TPSA: 104.96
- LogP: 2.1
- Rotatable bonds: 7
- Ring count: 3
- Aromatic rings: 2
- Formal charge: 0
- Fraction Csp3: 0.39
- QED: 0.62

## Molecule Similarity
- Weighted Tanimoto: 0.35

Answer: 7.26