Third expansion
Please go to Researchers involved for a list of researchers who contributed to this work
2024-12-19
In the third series of compounds to explore the SAR of RA-3301, emphasis was placed on trying to ascertain if the Mannish phenol motif of the compound is a PAIN element and if activity is connected to this phenol. Ten compounds were synthesized in-house, structures outlined below along with results.
The compounds antiviral activity, along with toxicity has been determined for active compounds. In general the activity seems to be much lower than for other compounds, comparing the new batch of RA-188637 with the previously reported data showed a 3-fold reduction in activity. Because of this the compounds will be tested again. The results of the antiviral and toxicity tests are summarized here:
- A lot of the activity of RA-3301 seems to come from a hydroxy bond via the phenol; methylating RA-3301 to compound RA-189176 showed complete loss of activity.
- Notably, removing the phenol from RA-188637 (compound RA-189175) did not show any loss of activity.
- Replacing the phenol with a fluoro (compound RA-189174) showed loss of activity on DENV4 but retained activity on DENV2, however this was not translated to the RA-3301 core which showed complete loss of activity (RA-189172).
- Moving the hydroxy-group from the ortho to the meta position seems to move the potential interaction out of alignment.
- Opening the isoindoline ring (as in compound RA-189177) showed the same activity as RA-188637, but a fluoro-replacement of the hydroxy (RA-189179) or removing the hydroxy (RA-189178) was not favored indicating the importance of this interaction for activity.
- In the first expansion, RA-20641 was included to check the activity of the headgroup, however the chloro-motif of the compound can act as a covalent warhead and thus, to confirm if the headgroup alone provides activity compound RA-189180 was included in the third expansion. This compound failed to provide activity above 50% inhibition at 10 μM, but it should be noted that this fragment might no be able to elicit an antiviral response and will be tested in a protein assay.
2024-12-20
Compound RA-188637 has also been evaluated in the gelbased RdRp inhibition assay but failed to inhibit the RNA production.
- Compounds will be re-evaluated to confirm results.
- Active compounds have been sent to additional assays (SPR, aggregation, and picogreen) to continue evaluation.