## Endpoint to Predict
- Endpoint scope: assay
- Measurement type: IC50
- Label type: continuous
- Binary semantics: pchembl
- Assay description: DELFIA® Assay: In vitro CHK2 kinase activity was measured in a DELFIA® assay that monitors phosphorylation of a CDC25C peptide using a specific phospho antibody. The enzyme reaction was carried out in 96-well polypropylene plates (Greiner). The reaction mix (total volume 25 μL) contained enzyme and peptide mix (15 μL) (containing CHK2, prepared in-house, 1 nM; Biotin-KKKVSRSGLYRSPSMPENLNRPR, 1 μM), ATP (30 μM, 5 μL) and either DMSO (2.5%) or test compound (5 μL) diluted to a give a range of concentrations (0-100 μM in 2.5% DMSO, final concentrations) in assay buffer (40 mM HEPES (pH 7.4), 40 mM KCl, 2 mM MgCl2, 10 mM DTT and 0.02% Tween 20). The reaction mixture was incubated for 30 minutes at room temperature and stopped by the addition of buffer (125 μL) containing 40 mM EDTA, 0.05% Tween 20, 0.1% BSA in TBS (10× concentrate, Sigma). An aliquot (100 μL) of the reaction mix was transferred to a black neutravidin-coated 96-well plate (Perbio) and incubated for 1 hour on a shaker (Titertek, Flow Laboratories) at room temperature. The plates were washed four times with wash buffer (25 mM Tris (pH 8), 150 mM NaCl and 0.1% Tween 20) (WellWash4, Thermo Life Sciences) and incubated for 1 hour as before with antibody mix (100 μL) consisting of anti-phospho CDC25C (diluted 1/4000 equivalent to 0.35 nM-1.25 nM, #9528, Cell Signalling Technology) and europium-labelled anti rabbit IgG, (0.3 μg/mL, AD0105, PerkinElmer Life Sciences) diluted in DELFIA® assay buffer (PerkinElmer Life Sciences). The plates were washed a further four times with wash buffer before the addition of enhancement solution (100 μL/well, PerkinElmer Life Sciences). The plate was read on a Victor2 1420 multi label counter (PerkinElmer Life Sciences) using a time-resolved measurement mode reading fluorescence at 615 nM.
- Assay organism: Homo sapiens
- Target name: Serine/threonine-protein kinase Chk1
- Target type: SINGLE PROTEIN
- Target organism: Homo sapiens

## Reference Molecule A
- Canonical SMILES: COc1cc(Nc2cnc(C#N)c(O[C@H](C)CN(C)C)n2)ncc1-c1cnn(C)c1
- Properties:
- ChEMBL ID: CHEMBL2203843
- Molecule type: Small molecule
- Molecular weight: 408.47
- Heavy atoms: 30
- Hydrogen bond donors: 1
- Hydrogen bond acceptors: 9
- TPSA: 114.01
- LogP: 2.22
- Rotatable bonds: 8
- Ring count: 3
- Aromatic rings: 3
- Formal charge: 0
- Fraction Csp3: 0.35
- QED: 0.6

## Known Reference Result on This Endpoint
- Molecule A clean result: median pChEMBL = 8.22
- This result is provided as context for predicting Molecule B on the same endpoint.

## Reference Molecule A Other ChEMBL Evidence
- type IC50; relation =; value 6; units nM; pChEMBL 8.22; comment 415447

## Query Molecule B
- Canonical SMILES: CNc1cc(Nc2cnc(C#N)c(O[C@H](C)CN(C)C)n2)ncc1-c1cnn(C)c1
- Properties:
- ChEMBL ID: CHEMBL2204592
- Molecule type: Small molecule
- Molecular weight: 407.48
- Heavy atoms: 30
- Hydrogen bond donors: 2
- Hydrogen bond acceptors: 9
- TPSA: 116.81
- LogP: 2.26
- Rotatable bonds: 8
- Ring count: 3
- Aromatic rings: 3
- Formal charge: 0
- Fraction Csp3: 0.35
- QED: 0.58

## Molecule Similarity
- Weighted Tanimoto: 0.79

Answer: 8.1