## Endpoint to Predict
- Endpoint scope: assay
- Measurement type: IC50
- Label type: continuous
- Binary semantics: pchembl
- Assay description: [35S]-GTPgammaS binding assay for determining antagonist: Materials: GTPγS, [35S] (PerkinElmer, Cat # NEG030H001MC), DMSO (Amresco, Cat #0231), MicroScint™-20 (PerkinElmer, Cat #6013621), CelLytic™ M Cell Lysis Reagent (Sigma, Cat # C2978-250ML), (R)(−)-α-Methylhistamine (Sigma, Cat # H1128), GDP (Sigma, Cat # G7127), GF/C plate (PE, CAT #6005174).Experimental procedure: 1) Membrane preparation for HEK293/Ga15/hH3R; 2) Standard binding assay. Briefly, for membrane parathion, HEK293/Ga15/hH3R cells were grown to confluence, harvested and the cell pellets were suspended in TEL buffer (50 mM Tris-HCl buffer, 1 mM EGTA, 0.1 mM PMSF). Homogenate and centrifuge at 1,000 g for 10 min. Centrifuge the supernatant at 46,000 g for 30 min. Suspend the membrane pellet in 50 mM Tris with 0.32 M sucrose, pH 7. Aliquot at 1 mg protein/mL. Keep frozen and store at −80° C. until use. All compounds were prepared by dissolving in DMSO to make 10 mM stock. The 10 mM stock was used as top concentration (1 μM) to carry out 10-points, 3-fold dilution scheme using DMSO in a 96-well plate to make the compound dose plate. H3R GTPγS binding assay was performed as followings: thaw the membrane at 37° C., chill on ice, add GDP and the membrane to assay buffer (50 mM Tris-HCl, 100 mM NaCl, 5 mM MgCl2, pH 7.4, and 0.2%, BSA). Stay on ice for 20 min. For inverse agonist mode: Add 20 μL testing compound (10 points, 3-fold dilution from 1 μM), 20 μL buffer, 140 μL membrane solution (GDP 10 μM, membrane protein 20 μg/well) to the assay plate, and preincubate at room temperature for 30 min. Add 20 μL [35S]-GTPγS (final 200 μM) and incubate at room temperature for 60 min. For antagonist mode: Add 20 μL agonist (R-alpha-methylhistamine, final concentration 1 μM), 20 μL testing compound (final top concentration 1 μM, 3-fold dilution, 10 points), 20 μL [35S]-GTPγS (final 200 μM), 140 μL membrane solution (total 200 μL, GDP 10 μM, membrane protein 20 μg/well) to the assay plate. Incubate at room temperature for 60 min. Filter the assay plate on GF/C (non-PEI coated) plate to stop the assay. Dry GF/C plate for 1 h. Add 50 μL scintillation fluid and count on the MicroBeta.Data Analysis: The CPM values were calculated into % of inhibition with the following formula:For inverse agonist mode: % of inhibition=(DMSO control CPM−Compound CPM)/(DMSO control CPM−GTP control CPM)×100.IC50s were calculated using Prism5 with log(inhibitor) vs. response equation.
- Assay organism: Homo sapiens
- Target name: Histamine H3 receptor
- Target type: SINGLE PROTEIN
- Target organism: Homo sapiens

## Reference Molecule A
- Canonical SMILES: Cc1nc2ccc(S(F)(F)(F)(F)F)cc2c(=O)n1-c1ccc(OC2CCN(C(=O)C3CCN(C)CC3)CC2)cc1
- Properties:
- ChEMBL ID: CHEMBL6005581
- Molecular weight: 586.63
- Heavy atoms: 40
- Hydrogen bond donors: 0
- Hydrogen bond acceptors: 5
- TPSA: 67.67
- LogP: 6.06
- Rotatable bonds: 5
- Ring count: 5
- Aromatic rings: 3
- Formal charge: 0
- Fraction Csp3: 0.44
- QED: 0.34

## 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 IC50; relation =; value 50.5; units nM; pChEMBL 7.3; comment 932736

## Query Molecule B
- Canonical SMILES: Cc1nc2ccc(S(F)(F)(F)(F)F)cc2c(=O)n1-c1ccc(OCCCN2CCC[C@H](C)C2)cc1
- Properties:
- ChEMBL ID: CHEMBL5822878
- Molecular weight: 517.56
- Heavy atoms: 35
- Hydrogen bond donors: 0
- Hydrogen bond acceptors: 4
- TPSA: 47.36
- LogP: 6.85
- Rotatable bonds: 7
- Ring count: 4
- Aromatic rings: 3
- Formal charge: 0
- Fraction Csp3: 0.42
- QED: 0.25

## Molecule Similarity
- Weighted Tanimoto: 0.57

Answer: 7.44