Discovery of indole tetrafluorophenoxymethylketone-based potent novel small molecule inhibitors of caspase-3

Abstract

BackgroundCaspase-3 inhibition has been demonstrated to be therapeutically effective in moderating excessive programmed cell death. Interest in caspase-3 as a therapeutic target has led many to pursue the development of inhibitors. To date, only a few series of non-peptide inhibitors have been described, and these have limitations on their drug-like properties.MethodsHere, we report the screening of 70 novel small molecules against the caspase-3 enzyme which belongs to four different series (indole fluoromethylketone, indole difluoro and tetrafluorophenoxymethylketone, and oxalamide). Selected molecules were subjected for counter-screening, cell-based, ADME/PK assays in order to understand the potency and drug-like properties.ResultsThe screening yielded series of hits with IC50 values ranging from 0.11 to 10 μM with reasonable SAR, irreversible mode of inhibition, and reasonable selectivity against other proteases including caspase-1, cathepsin B and D, and thrombin. On the basis of in vitro profile, the selected molecules were evaluated for their drug-like properties. Among the compounds evaluated, compound 3D exhibited good solubility, low permeability, interaction with efflux pump, and low potential for CYP450 drug-drug interaction. After intravenous administration, compound 3D showed low clearance (588 ml/hr/kg), medium volume of distribution, and good oral bioavailability (90%).ConclusionsThese results support further advancement of compound 3D in different apoptotic models to develop as a new anti-apoptotic agent in relevant disease conditions.

Investigation of Orally Administered Small Molecule Inhibitors of Caspase-3 in Murine Models of Apoptosis

“…It also suppresses the caspase-3 activity in lung tissue extract (figure 1B) similar to IDN6556 24 hours post injection. Compound 3D displayed survival advantage despite one log less potency when compare to IDN6556 in biochemical and cellular assay 9 . This may be due to better exposure in central circulation and low tissue partitioning property.…”

“…Caspase play an important role in different pathophysiological conditions and specific inhibition is expected to be therapeutically valuable [13][14][15][16][17] . Towards identifying inhibitors of caspases with desirable selectivity, ADME and efficacy profile; we screened a focused library of compounds and identified inhibitors from four chemical series that are distinct from other known small molecule caspase-3 inhibitors 9 . Table 1 shows profile of selected set of compounds from 3 series which exhibited better oral exposure were tested in rapid mice model of endotoxic shock along with the reported caspase inhibitor IDN6556 [7][8] .…”

“…Biological screening of compounds as well as their chemical synthesis was based on a focused diversity approach belonging to four different series (indole fluromethylketone, indole difluro & tetrafluro phenoxymethylketone and oxalamide); which has been discussed in detail earlier [9][10][11] and summarized in Table 1 (potency as well as DMPK profile of the selected compounds from the above series).…”

“…Protein concentrations of the resulting supernatant suspension were determined Bradford's method with bovine serum albumin as the standard. The substrate cleavage activity was measured under similar conditions as mentioned earlier 9 .…”

“…This indicates caspase-3 an interesting therapeutic target and the search for caspase-3 inhibitors has been a constant attempt by many pharmaceutical companies. In this paper, we evaluated the effect of five NCEs (Chemistry and Preliminary biological results were discussed earlier [9][10][11] ) encompass better oral pharmacokinetic along with reasonable potency in the LPS induced endotoxic shock model and one NCE (Compound 3D) was further profiled in LPS/ D-Gal induced liver injury model.…”