Topic automatically created for discussing the designs at:
https://covid.postera.ai/covid/submissions/MAT-POS-a13804f0
The observation in the cell-based assay of an EC50 (0.09 μM; one of the duplicate concentration responses doesn’t look great) for MAT-POS-a13804f0-4 that is significantly less than the IC50 values observed in the fluorescence (0.56 μM) and RapidFire (1.3 μM) assays suggests that it may be beneficial to follow the compound up as if it was a phenotypic screening hit (I’ll also mention @alphalee @frankvondelft @londonir @JohnChodera just in case any of them are interested). This would mean not assuming that that the cell-based SAR will necessarily track the enzyme inhibition SAR. The compound does not appear to be cytotoxic and I see three explanations for the increased potency going from the enzyme inhibition assay to the cell-based assay. First, the compound acts on a target other than MPro. Second, the protein construct used in the enzyme kinetic assay is not a relevant model for the binding of the compound to the intracellular enzyme. Third, the compound is actively transported into cells.
I see the first step in moving MAT-POS-a13804f0-4 forward as separation of the two diastereomers and assaying each for enzyme inhibition and antiviral activity (I would recommend doing this before committing to a lot of synthesis). That said, I see ALP-POS-a9ad2217-2 as a high priority (given the peptidic nature of MAT-POS-a13804f0-4, it would be useful to find out as quickly as possible how well the N-methylation of the phenylglycine amide is tolerated). I have submitted two sets of designs (PET-UNK-1320d94d and PET-UNK-ac320b15 ) which may be helpful in if doing hit-to-lead work on the compound.