Human Silent Mating Type Information Regulation 2 Homolog 1 (SIRT1) deacetylates histones and various other proteins, which are involved in multiple signalling pathways in cells.
Human Bromodomain-containing protein 4 (BRD4) a transcription factor that plays an important role in cancer development.
BRD4 is member of a family of at least four proteins sharing the same structural motif.
Methodology
Enamine stock collection of 3.2M compounds was subject to virtual screening.
1000 top-ranked candidate compounds were selected.
100 compounds were used for experimental validation for both targets.
The two-stage virtual screening workflow implemented in the Receptor.AI drug discovery platform was used.
In the first stage, the ligand-based and structure-based drug-target interaction AI models were used for initial screening.
After that, the most relevant ADMET endpoints were evaluated, and the proteome-wide selectivity profiles were computed for the top compounds.
In the stage of secondary screening, molecular docking with AI rescoring, which predicts the activity based on the docking poses, is performed for the molecules shortlisted during the initial screening.
Results
SITR1
94 compounds have been tested in DSF against SIRT1.
Primary hits were subjected to counter-screening for selectivity against BRD4, CA, and Abl SH2.
The acceptable values of quality control indicate the robustness of the screening process.
With the selection criteria '|ΔTm SIRT1| > 3*ΔTm RSD DMSO SIRT1', 4 compounds demonstrated a significant binding effect on SIRT1 Tm.
1 compound showed a selective effect on the target protein, following the selection criteria '|ΔTmDAbl SH2, CA, BRD4| > 3*TmD RSDDMSO Abl SH2, CA, BRD4'.
BRD4
100 best-ranked hit candidates were passed for experimental validation to our partners.
17 of them have shown affinity to BRD4.
These compounds are currently subject to in-depth experimental validation.
7 best compounds were picked for further activity evaluation.
3 compounds have shown notable biological activity:
RAIBD40009 470 nM,
RAIBD40062 730 nM,
RAIBD40067 4.8 uM.
100 compounds have been tested in DSF (Differential Scanning Fluorimetry) against BRD4.
The acceptable values of quality control indicate the robustness of the performed screen.
Following the selection criteria | dTmDBRD4-ligand |** > 3*TmDRSD DMSO BRD4 ***, 17 compounds demonstrate significant binding effect on BRD4.8 of them belong to known classes of BRD4 inhibitors.
There are 9 entirely new BRD4 hits, belonging to 8 diverse chemical classes.
Discovered SIRT1 inhibitors (RAIST10058)
This compound has shown outstanding nanomolar activity (IC50 = 90 nM) measured by a functional assay based on the release of the fluorophore probe from acetylated p53-AFC, which makes it de facto a lead compound.
Discovered BRD4 inhibitors (RAIBD40009)
This compound, belonging to the previously unknown class of BRD4 inhibitors, has shown the best activity in experiments (470 nM).
