## Endpoint to Predict
- Endpoint scope: assay
- Measurement type: IC50
- Label type: continuous
- Binary semantics: pchembl
- Assay description: Pharmacological Activity Assay: Methods for the determination of MPO inhibitory activity are disclosed in WO 02/090575. The pharmacological activity of compounds disclosed herein was tested in the following screen (Test A) in which the compounds were tested in the presence of ascorbate, which reacts with MPO-derived hypochlorous acid (HOCl) to form dehydro-ascorbate. The loss of ascorbate is followed by measuring absorbance at 260 nm.Assay buffer: 100 μM diethyl triamine pentaacetic acid (DTPA) in buffer consisting of 10 mM Na2HPO4/NaH2PO4, 3 mM KCl in 140 mM NaCl, pH 7.4.Enzyme solution: MPO purified from the human cell line HL60, 1.38 nM (final concentration 0.7 nM) and L-ascorbate, 100 μM (final concentration 50 μM) in Assay bufferSubstrate solution: H2O2, 98 μM (final concentration 49 μM)Forty μL of the enzyme solution was added to 0.6 μL compound serially diluted in DMSO. Absorbance was measured at 260 nm to obtain a compound blank value. After an additional 10 min, 40 μL of the substrate solution was added and the absorbance at 260 nm was recorded between 4 and 40 min to obtain kinetic readings of enzyme activity. IC50 values of the compounds tested were obtained using recordings of absorbance at 260 nm 20 minutes after substrate addition and calculated using standard procedures.To detect thyroid peroxidase (TPO) inhibitory activity, the production of hypoiodous acid (HOI) was quantified. HOI was detected by reacting it with methionine, which is converted to dehydro-methionine, which in turn is detected by reacting it with excess iodide at acidic pH. The reaction converts I− to I3 − that has absorbance at 353 nm. In brief, 0.6 μL compound serially diluted in DMSO was added to 25 μL 50 nM baculovirus-expressed recombinant human TPO (obtained from RSR Ltd, Cardiff, UK) in assay buffer (100 mM Na2HPO4/NaH2PO4, pH 7.4), after which absorbance at 353 nm was read to obtain a blank value. The enzyme reaction was initiated by the addition of 25 μL of a mix consisting of 2 mM methionine, 20 μM NaI and 100 μM H2O2 in assay buffer, and stopped by the addition of 10 μL catalase, 0.25 mg/mL. After an additional 5 min, 25 μL 600 mM sulphuric acid followed by 25 μL 100 mM KI were added, and absorbance at 353 nm was read 5 min after this addition. IC50 values of the compounds tested were obtained using standard procedures.
- Assay organism: Homo sapiens
- Target name: Myeloperoxidase
- Target type: SINGLE PROTEIN
- Target organism: Homo sapiens

## Reference Molecule A
- Canonical SMILES: O=c1[nH]c(=S)n(Cc2ccccc2CNC2CCCC2)c2cc[nH]c12
- Properties:
- ChEMBL ID: CHEMBL5850637
- Molecular weight: 354.48
- Heavy atoms: 25
- Hydrogen bond donors: 3
- Hydrogen bond acceptors: 3
- TPSA: 65.61
- LogP: 3.47
- Rotatable bonds: 5
- Ring count: 4
- Aromatic rings: 3
- Formal charge: 0
- Fraction Csp3: 0.37
- QED: 0.61

## Known Reference Result on This Endpoint
- Molecule A clean result: median pChEMBL = 7.85
- This result is provided as context for predicting Molecule B on the same endpoint.

## Reference Molecule A Other ChEMBL Evidence
- type IC50; relation =; value 14; units nM; pChEMBL 7.85; comment 1034174

## Query Molecule B
- Canonical SMILES: O=c1[nH]c(=S)n(Cc2ccccc2CNC2CCC2)c2cc[nH]c12
- Properties:
- ChEMBL ID: CHEMBL5999011
- Molecular weight: 340.45
- Heavy atoms: 24
- Hydrogen bond donors: 3
- Hydrogen bond acceptors: 3
- TPSA: 65.61
- LogP: 3.08
- Rotatable bonds: 5
- Ring count: 4
- Aromatic rings: 3
- Formal charge: 0
- Fraction Csp3: 0.33
- QED: 0.63

## Molecule Similarity
- Weighted Tanimoto: 0.97

Answer: 8