## Endpoint to Predict
- Endpoint scope: assay
- Measurement type: IC50
- Label type: continuous
- Binary semantics: pchembl
- Assay description: Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) Assay: The activities were measured using a time-resolved fluorescence resonance energy transfer (TR-FRET) assay. TR-FRET monitored the formation of 3,4,5-inositol triphosphate molecule that competed with fluorescently labeled PIP3 for binding to the GRP-1 pleckstrin homology domain protein. An increase in phosphatidylinositide 3-phosphate product resulted in a decrease in TR-FRET signal as the labeled fluorophore was displaced from the GRP-1 protein binding site. Class I PI3K isoforms were expressed and purified as heterodimeric recombinant proteins. All assay reagents and buffers for the TR-FRET assay were purchased from Millipore. PI3K isoforms were assayed under initial rate conditions in the presence of 25 mM Hepes (pH 7.4), and 2xKm ATP (75-500 uM), 2 uM PIP2, 5% glycerol, 5 mM MgCl2, 50 mM NaCl, 0.05% (v/v) Chaps, 1 mM dithiothreitol, and 1% (v/v) DMSO at the following concentrations for each isoform: PI3Kα, PI3Kβ, and PI3Kδ between 25 and 50 uM, and PI3Kγ at 2 nM. The compounds of Table 1 and Compound X ((S)-2,4-diamino-6-((1-(5-chloro-4-oxo-3-(pyridin-3-yl)-3,4-dihydroquinazolin-2-yl)ethyl)amino)pyrimidine-5-carbonitrile) and Compound Y ((S)-2,4-diamino-6-((1-(5-chloro-4-oxo-3-(pyridin-3-yl)-3,4-dihydroquinazolin-2-yl)ethyl)amino)pyrimidine-5-carbonitrile) were added to the assay solution and incubated for 30 minutes at 25° C. The reactions were terminated with a final concentration of 10 mM EDTA, 10 nM labeled-PIP3, and 35 nM Europium labeled GRP-1 detector protein before reading TR-FRET on an Envision plate reader (Ex: 340 nm; Em: 615/665 nm; 100 us delay and 500 us read window). The results were normalized based on positive (1 uM wortmanin) and negative (DMSO) controls, and the IC50 values for PI3K α, β, δ and γ were calculated from the fit of the dose-response curves to a four-parameter equation.
- Assay organism: Homo sapiens
- Target name: Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit delta isoform
- Target type: SINGLE PROTEIN
- Target organism: Homo sapiens

## Reference Molecule A
- Canonical SMILES: C[C@H](Nc1nc(N)nc(N)c1Cl)c1nc2c(Cl)cc(F)cc2c(=O)n1-c1cnc(N)cn1
- Properties:
- ChEMBL ID: CHEMBL3968564
- Molecule type: Small molecule
- Molecular weight: 477.29
- Heavy atoms: 32
- Hydrogen bond donors: 4
- Hydrogen bond acceptors: 10
- TPSA: 176.54
- LogP: 2.33
- Rotatable bonds: 4
- Ring count: 4
- Aromatic rings: 4
- Formal charge: 0
- Fraction Csp3: 0.11
- QED: 0.34

## Known Reference Result on This Endpoint
- Molecule A clean result: median pChEMBL = 6.11
- This result is provided as context for predicting Molecule B on the same endpoint.

## Reference Molecule A Other ChEMBL Evidence
- type IC50; relation =; value 780; units nM; pChEMBL 6.11; comment 445496

## Query Molecule B
- Canonical SMILES: N#Cc1c(N)nc(N)nc1N[C@H](c1nc2cccc(Cl)c2c(=O)n1-c1cnc(N)cn1)C1CC1
- Properties:
- ChEMBL ID: CHEMBL3912814
- Molecule type: Small molecule
- Molecular weight: 475.9
- Heavy atoms: 34
- Hydrogen bond donors: 4
- Hydrogen bond acceptors: 11
- TPSA: 200.33
- LogP: 1.8
- Rotatable bonds: 5
- Ring count: 5
- Aromatic rings: 4
- Formal charge: 0
- Fraction Csp3: 0.19
- QED: 0.33

## Molecule Similarity
- Weighted Tanimoto: 0.43

Answer: 8.57