## Endpoint to Predict
- Endpoint scope: assay
- Measurement type: IC50
- Label type: continuous
- Binary semantics: pchembl
- Assay description: HDAC Enzyme Activity Inhibition Assay (In Vitro): The effectiveness, or potency, of a present HDACI with respect to inhibiting the activity of an HDAC is measured by an IC50 value. The quantitative IC50 value indicates the concentration of a particular compound that is needed to inhibit the activity of an enzyme by 50% in vitro. Stated alternatively, the IC50 value is the half maximal (50%) inhibitory concentration of a compound tested using a specific enzyme, e.g., HDAC, of interest. The smaller the IC50 value, the more potent the inhibiting action of the compound because a lower concentration of the compound is needed to inhibit enzyme activity by 50%.In preferred embodiments, a present HDACI inhibits HDAC enzymatic activity by about at least 50%, preferably at least about 75%, at least 90%, at least 95%, or at least 99%.Compounds of the present invention were tested for IC50 values against both HDAC6 and HDAC1. In some embodiments, a present compound also was tested against HDAC1, 2, 3, 4, 5, 8, 10, and 11. The tested compounds showed a range of IC50 values vs. HDAC6 of about 1 nm to greater than 30 μm, and a range of IC50 values vs. HDAC1 of about 91 nm to greater than 30 μm. Therefore, in some embodiments, a present HDACI is a selective HDAC6 inhibitor which, because of a low affinity for other HDAC isozymes, e.g., HDAC1, give rise to fewer side effects than compounds that are non-selective HDAC inhibitors.In some embodiments, the present HDACIs interact with and reduce the activity of all histone deacetylases in a cell. In some preferred embodiments, the present HDACIs interact with and reduce the activity of fewer than all histone deacetylases in the cell. In certain preferred embodiments, the present HDACIs interact with and reduce the activity of one histone deacetylase (e.g., HDAC-6), but do not substantially interact with or reduce the activities of other histone deacetylases (e.g., HDAC-1, HDAC-2, HDAC-3, HDAC-4, HDAC-5, HDAC-7, HDAC-8, HDAC-9, HDAC-10, and HDAC-11).
- Assay organism: Homo sapiens
- Target name: Histone deacetylase 9
- Target type: SINGLE PROTEIN
- Target organism: Homo sapiens

## Reference Molecule A
- Canonical SMILES: CN1CCc2c(c3ccccc3n2Cc2ccc(C(=O)NO)cc2)C1
- Properties:
- ChEMBL ID: CHEMBL2018302
- Preferred name: TUBASTATIN A
- Molecule type: Small molecule
- Molecular weight: 335.41
- Heavy atoms: 25
- Hydrogen bond donors: 2
- Hydrogen bond acceptors: 3
- TPSA: 57.5
- LogP: 2.8
- Rotatable bonds: 3
- Ring count: 4
- Aromatic rings: 3
- Formal charge: 0
- Fraction Csp3: 0.25
- QED: 0.57

## Known Reference Result on This Endpoint
- Molecule A clean result: median pChEMBL = 6.02
- This result is provided as context for predicting Molecule B on the same endpoint.

## Reference Molecule A Other ChEMBL Evidence
- type IC50; relation =; value 950; units nM; pChEMBL 6.02; comment 836785

## Query Molecule B
- Canonical SMILES: O=C(NO)c1ccc(CN2CCCc3cc(Cl)ccc32)cc1
- Properties:
- ChEMBL ID: CHEMBL4536605
- Molecule type: Unknown
- Molecular weight: 316.79
- Heavy atoms: 22
- Hydrogen bond donors: 2
- Hydrogen bond acceptors: 3
- TPSA: 52.57
- LogP: 3.41
- Rotatable bonds: 3
- Ring count: 3
- Aromatic rings: 2
- Formal charge: 0
- Fraction Csp3: 0.24
- QED: 0.67

## Molecule Similarity
- Weighted Tanimoto: 0.35

Answer: 5.46