## Endpoint to Predict
- Endpoint scope: assay
- Measurement type: IC50
- Label type: continuous
- Binary semantics: pchembl
- Assay description: Enzymatic Inhibition Assay: Substrate (NH2-KGGEEEEYFELVKK-CO2), internal standard peptide (NH2-SWGAIETDKEYYTVKD-CO2) and product peptide (for standard curve only) (NH2-KGGEEEEY-Pi-FELVKK-CO2), were purchased from AnaSpec (Fremont, Calif., USA). JAK1-JH1JH2 (574-1154 with a His-GST Tag and a C-terminal tev (ENLYFQ-G) cleavage site), JAK3-JH1JH2 (512-1124 with a GST Tag and a C-terminal tev (ENLYFQ-G) cleavage site), and Tyk2-JH1JH2 (8H_tev_580-1182-C936A-C1142A with a C-terminal tev (ENLYFQ-G) cleavage site) were purified internally. JAK2-JH1JH2 (532-1132 with a GST tag and C-terminal tev (ENLYFQ-G) cleavage site), was purchased from Invitrogen. LC/MS grade water and acetonitrile (ACN), were purchased from HoneyWell, Burdick & Jackson (Muskegon, Mich., USA). Dimethylsulfoxide 99.8% (DMSO) and trifluoroacetic acid 99.5% (TFA) were purchased from EMD Chemical (Gibbstown, N.J., USA). Adenosine triphosphate (ATP), 4-morpholinepropanesulfonic acid (MOPS), magnesium chloride (MgCl2), ethylenediaminetetraacetic acid (EDTA), dithiothreitol (DTT), formic acid>95% (FA) and Tween-20 were purchased from Sigma (St Louis, Mo., USA). 384-well polypropylene plates, Cat#781280 were purchased from Greiner (Monroe, N.C.), RapidFire cartridge A C4 Column (Agilent Technologies, Santa Clara, Calif.).The HTMS experiments were performed in positive ionization mode on a RapidFire 300 instrument (Agilent Technologies, Santa Clara, Calif.), coupled with an ABSiex QTrap 4000 system with an Electrospray Ionization source (RF-MS) (Concord, ON, Canada). The RapidFire system was run with 3 Agilent 1200 series isocratic pumps Agilent Technologies (Santa Clara, Calif.) and one peristaltic pump model ISM832C from Ismatec (Wertheim, Germany). The entire system was operated using the RapidFire software interfaced with Analyst software for the mass spectrometer.Assay Protocol11-point dosing series were made for each compound by serially diluting 1:3 or 1:4 in DMSO, with point 12 being a DMSO control. From the serial dilution plates, sample was transferred to a 384 wells assay plate (#781280, Greiner, Monroe, N.C.) using Labcyte Echo (Sunnyvale, Calif.), or Biosero ATS (San Diego, Calif.). The compounds were tested in duplicate. Column 12 was used for positive controls, and column 24 contained negative controls with no enzyme added. A compound from our internal collection, with inhibitory activity for JAK isoforms, was used as a reference compound. The final concentration of DMSO was ≤0.25% in a 20 μL reaction. Assay conditions for each of the proteins are summarized in Table 3. The enzyme reaction was initiated by the addition of 10 μL of enzyme and ATP mixture to 10 μL of substrate solution prepared in reaction buffer (50 mM MOPS pH 7.5, 10 mM MgCl2, 1 mM EDTA, 2 mM DTT, 0% Tween-20). The Tyk2 enzyme was pre-incubated with 2 mM ATP for 30 min prior to the reaction initiation. Immediately after the addition of the enzyme to the reaction mixture, the plate was centrifuged at 1000 rpm for 1 minute and incubated at 25° C. for 45 minutes for JAK3 and 90 minutes for JAK1, JAK2 and Tyk2. The reaction was quenched by the addition of 20 μL of 0.5% TFA containing 0.15 μM of internal standard peptide using Multidrop Combi reagent dispenser (Thermo Scientific, Waltham, Mass.). Several wells in column 24 were typically used for the product standard curve. After the quench, the assay plate was centrifuged at 3000 rpm for 3 minutes and sealed with pierceable aluminum foil (Cat#06644-001, Agilent) using a PlateLoc (Agilent Technologies, Santa Clara, Calif.). The plates then were transferred on to the RapidFire for the MS analysis. Compound inhibition was assessed by a decrease of the phosphorylated product levels in sample wells compared to the non-inhibited enzyme reaction.
- Assay organism: Homo sapiens
- Target name: Tyrosine-protein kinase JAK2
- Target type: SINGLE PROTEIN
- Target organism: Homo sapiens

## Reference Molecule A
- Canonical SMILES: N#CCCNC(=O)Cc1nc2cnc3[nH]ccc3c2n1[C@H]1CC[C@H](CC#N)CC1
- Properties:
- ChEMBL ID: CHEMBL4563534
- Molecule type: Unknown
- Molecular weight: 389.46
- Heavy atoms: 29
- Hydrogen bond donors: 2
- Hydrogen bond acceptors: 5
- TPSA: 123.18
- LogP: 3.13
- Rotatable bonds: 6
- Ring count: 4
- Aromatic rings: 3
- Formal charge: 0
- Fraction Csp3: 0.48
- QED: 0.63

## Known Reference Result on This Endpoint
- Molecule A clean result: median pChEMBL = 8.18
- This result is provided as context for predicting Molecule B on the same endpoint.

## Reference Molecule A Other ChEMBL Evidence
- type IC50; relation =; value 6.6; units nM; pChEMBL 8.18; comment 774670

## Query Molecule B
- Canonical SMILES: N#CC[C@H]1CC[C@H](n2c(CC(=O)Nc3cc[nH]n3)nc3cnc4[nH]ccc4c32)CC1
- Properties:
- ChEMBL ID: CHEMBL5874150
- Molecular weight: 402.46
- Heavy atoms: 30
- Hydrogen bond donors: 3
- Hydrogen bond acceptors: 5
- TPSA: 128.07
- LogP: 3.46
- Rotatable bonds: 5
- Ring count: 5
- Aromatic rings: 4
- Formal charge: 0
- Fraction Csp3: 0.38
- QED: 0.47

## Molecule Similarity
- Weighted Tanimoto: 0.73

Answer: 8.8