## Endpoint to Predict
- Endpoint scope: assay
- Measurement type: IC50
- Label type: continuous
- Binary semantics: pchembl
- Assay description: Rat P2X3 Receptor Inhibition RSA Assay: Rat P2X3 receptor gene (GenBank accession number NM_031075) was expressed in C6BU-1 cell. The cells stably expressing rat P2X3 were seeded in a 96-well microtiter plate at a :concentration of 8000 cells/well and cultured in the medium (8.3% fetal bovine serum, 8.3% horse serum, 1% antibiotic and antifungal in DMEM) for one day at 37° C. under 5% carbon dioxide atmosphere. In transiently expressing system, the C6BU-1 cells were seeded in a 96-well microtiter plate at a concentration of 2500 cells/well and cultured in the medium for one day at 37° C. under 5% carbon dioxide atmosphere. The plasmid was transfected into the cells using transfection reagent FuGENE6 (Roche). The transfected cells were cultured in the medium for one day at 37° C. under 5% carbon dioxide atmosphere. The medium was replaced with 4 μM Fluo-3-AM solution (pH 7.5) containing 20 mM HEPES, 137 mM NaCl, 2.7 mM KCl, 0.9 mM MgCl2, 5 mM CaCl2, 5.6 mM D-glucose, 2.5 mM probenecid, 10% BSA, and 0.08% Pluronic F-127, and incubated at 37° C. under 5% carbon dioxide atmosphere for one hour. The plate was washed with washing buffer (20 mM HEPES, 137 mM NaCl, 2.7 mM KCl, 0.9 mM MgCl2, 5 mM CaCl2, 5.6 mM D-glucose, 2.5 mM probenecid, pH 7.5), and each well was added with 40 μL of this buffer. The plate was placed in High-Throughput Screening System FDSS 3000 (Hamamatsu Photonics K.K.). Measurement of fluorescence intensity by FDSS 3000 was started, and 40 μL of DMSO solutions containing 1% RSA (final concentrations) and different concentrations of the test compound as prepared by dilution with dilution buffer (20 mM HEPES, 137 mM NaCl, 2.7 mM KCl, 0.9 mM MgCl2, 5 mM CaCl2, 5 mM D-glucose, 2.5 mM probenecid, 0.1% Pluronic F-127, pH 7.5) were dispensed to each well through the built-in automatic dispenser. Five minutes after, 50 nM ATP solution (50 μL) prepared by dilution with the dilution buffer was dispensed through the built-in automatic dispenser, and the measurement of fluorescence intensity was continued for 3 min. For each well, the specific maximum fluorescence intensity was calculated as the ratio of the maximum fluorescence intensity after addition of the ATP solution to the fluorescence intensity at the starting of the measurement. The 50% inhibitory concentration (IC50) was calculated under the assumption that the specific maximum fluorescence intensity without test compound is 0% inhibition and that the specific maximum fluorescence intensity when the dilution buffer was added in place of ATP solution is 100% inhibition, to evaluate the inhibitory activity of the test compound. FDSS software (Hamamatsu Photonics K.K.) was used for calculation of the specific maximum fluorescence intensity. IC50 was calculated using Microsoft Excel (Microsoft Corporation) and XLfit (idbs Ltd.).
- Assay organism: Rattus norvegicus
- Target name: P2X purinoceptor 3
- Target type: SINGLE PROTEIN
- Target organism: Rattus norvegicus

## Reference Molecule A
- Canonical SMILES: C[C@@H](Cn1c(=O)[nH]/c(=N\c2ccc(OCC3CC3)cc2)n(Cc2ccc(Cl)cc2)c1=O)C(=O)O
- Properties:
- ChEMBL ID: CHEMBL5074942
- Molecule type: Unknown
- Molecular weight: 484.94
- Heavy atoms: 34
- Hydrogen bond donors: 2
- Hydrogen bond acceptors: 5
- TPSA: 118.68
- LogP: 2.78
- Rotatable bonds: 9
- Ring count: 4
- Aromatic rings: 3
- Formal charge: 0
- Fraction Csp3: 0.33
- QED: 0.48

## Known Reference Result on This Endpoint
- Molecule A clean result: median pChEMBL = 7.36
- This result is provided as context for predicting Molecule B on the same endpoint.

## Reference Molecule A Other ChEMBL Evidence
- type IC50; relation =; value 44; units nM; pChEMBL 7.36; comment 506538

## Query Molecule B
- Canonical SMILES: O=c1[nH]/c(=N\c2ccc(Oc3ccon3)cc2)n(Cc2ccc(Cl)cc2)c(=O)n1CC(CO)CO
- Properties:
- ChEMBL ID: CHEMBL5906924
- Molecular weight: 499.91
- Heavy atoms: 35
- Hydrogen bond donors: 3
- Hydrogen bond acceptors: 8
- TPSA: 147.87
- LogP: 1.65
- Rotatable bonds: 9
- Ring count: 4
- Aromatic rings: 4
- Formal charge: 0
- Fraction Csp3: 0.22
- QED: 0.32

## Molecule Similarity
- Weighted Tanimoto: 0.5

Answer: 7.7