## Endpoint to Predict
- Endpoint scope: assay
- Measurement type: IC50
- Label type: continuous
- Binary semantics: pchembl
- Assay description: FLIPR Ca2+ Flux Assay: In a typical experiment the OX1 and OX2 receptor antagonistic activity of the compounds of the present invention was determined in accordance with the following experimental method. For intracellular calcium measurements, Chinese hamster ovary (CHO) cells expressing the rat or human orexin-1 receptor or the human orexin-2 receptor, are grown in Iscove's modified DMEM containing 2 mM L-glutamine, 0.5 g/ml G418, 1% hypoxanthine-thymidine supplement, 100 U/ml penicillin, 100 μg/ml streptomycin and 10% heat-inactivated fetal calf serum (FCS). The cells are seeded at 20,000 cells/well into Becton-Dickinson black 384-well clear bottom sterile plates coated with poly-D-lysine. All reagents were from GIBCO-Invitrogen Corp. The seeded plates are incubated overnight at 37° C. and 5% CO2. Ala-6,12 human orexin-A as the agonist is prepared as a 1 mM stock solution in 1% bovine serum albumin (BSA) and diluted in assay buffer (HBSS containing 20 mM HEPES, 0.1% BSA and 2.5 mM probenecid, pH7.4) for use in the assay at a final concentration of 70 pM. Test compounds are prepared as 10 mM stock solution in DMSO, then diluted in 384-well plates, first in DMSO, then assay buffer. On the day of the assay, cells are washed 3 times with 100 μl assay buffer and then incubated for 60 min (37° C., 5% CO2) in 60 μl assay buffer containing 1 μM Fluo-4AM ester, 0.02% pluronic acid, and 1% BSA. The dye loading solution is then aspirated and cells are washed 3 times with 100 μl assay buffer. 30 μl of that same buffer is left in each well. Within the Fluorescent Imaging Plate Reader (FLIPR, Molecular Devices), test compounds are added to the plate in a volume of 25 μl, incubated for 5 min and finally 25 μl of agonist is added. Fluorescence is measured for each well at 1 second intervals for 5 minutes and the height of each fluorescence peak is compared to the height of the fluorescence peak induced by 70 pM Ala-6,12 orexin-A with buffer in place of antagonist. For each antagonist, IC50 value (the concentration of compound needed to inhibit 50% of the agonist response) is determined. Alternatively, compound potency can be assessed by a radioligand binding assay (described in Bergman et. al. Bioorg. Med. Chem. Lett. 2008, 18, 1425-1430) in which the inhibition constant (Ki) is determined in membranes prepared from CHO cells expressing either the OX1 or OX2 receptor. The intrinsic orexin receptor antagonist activity of a compound which may be used in the present invention may be determined by these assays.
- Assay organism: Homo sapiens
- Target name: Orexin receptor type 2
- Target type: SINGLE PROTEIN
- Target organism: Homo sapiens

## Reference Molecule A
- Canonical SMILES: CCN(CCc1nc(C(C)(C)O)c(C)o1)C(=O)c1ccccc1-n1nccn1
- Properties:
- ChEMBL ID: CHEMBL5912983
- Molecular weight: 383.45
- Heavy atoms: 28
- Hydrogen bond donors: 1
- Hydrogen bond acceptors: 6
- TPSA: 97.28
- LogP: 2.5
- Rotatable bonds: 7
- Ring count: 3
- Aromatic rings: 3
- Formal charge: 0
- Fraction Csp3: 0.4
- QED: 0.67

## Known Reference Result on This Endpoint
- Molecule A clean result: median pChEMBL = 7.2
- This result is provided as context for predicting Molecule B on the same endpoint.

## Reference Molecule A Other ChEMBL Evidence
- type IC50; relation =; value 27; units nM; pChEMBL 7.57; comment 827451
- type IC50; relation =; value 152; units nM; pChEMBL 6.82; comment 827479

## Query Molecule B
- Canonical SMILES: CCN(CCc1nc(C(C)(C)O)c(C)o1)C(=O)c1sccc1-n1nccn1
- Properties:
- ChEMBL ID: CHEMBL5974508
- Molecular weight: 389.48
- Heavy atoms: 27
- Hydrogen bond donors: 1
- Hydrogen bond acceptors: 7
- TPSA: 97.28
- LogP: 2.56
- Rotatable bonds: 7
- Ring count: 3
- Aromatic rings: 3
- Formal charge: 0
- Fraction Csp3: 0.44
- QED: 0.67

## Molecule Similarity
- Weighted Tanimoto: 0.73

Answer: 6.36