Structure-based design of human immuno- and constitutive proteasomes inhibitors

Abstract

Starting from the X-ray structure of our previous tripeptidic linear mimics of TMC-95A in complex with yeast 20S proteasome, we introduced new structural features to induce a differential inhibition between human constitutive and immunoproteasome 20S particles. Libraries of 24 tripeptidic and 6 dipeptidic derivatives were synthesized. The optimized preparation of 3-hydroxyoxindolyl alanine residues from tryptophan and their incorporation in peptides were described. Several potent inhibitors of human constitutive proteasome and immunoproteasome acting at the nanomolar level (IC = 7.1 nM against the chymotrypsin-like activity for the best inhibitor) were obtained. A cytotoxic effect at the submicromolar level was observed against 6 human cancer cell lines.

Conversion of Isatins to Tryptanthrins, Heterocycles Endowed with a Myriad of Bioactivities

“…Proteasome Inhibition: Purified human 20S constitutive proteasome was purchased from Boston Biochem. Proteasome activities were determined as described previously . Briefly, the enzyme‐catalyzed hydrolysis of the appropriate fluorogenic substrate (Suc‐LLVY‐AMC, concentration 20 µ m for the ChT‐L activity; Z‐LLE‐βNA concentration 50 µ m for the PA activity; Boc‐LRR‐AMC, concentration 50 µ m for the T‐L activity) was followed in microplates for 45 min, at 37 °C and pH 8, by monitoring the fluorescence emission of the released fluorophore ( λ exc = 360 nm and λ em = 460 nm for 7‐amino‐4‐methyl‐coumarin AMC and λ exc = 340 nm and λ em = 404 nm for β‐naphthylamine βNA).…”

Natural product scaffolds as inspiration for the design and synthesis of 20S human proteasome inhibitors

“…The Vidal group-in collaboration with many other research groups-has used this linear TMC-95A approach to synthesize effective inhibitors. [94][95][96][97][98][99] In particular, the linear 3-hydroxyoxindole-containing derivatives exhibited subunit selectivity towards the C-L site). 96 Optimization of the scaffold led to the discovery of potent inhibitor 29, which inhibited the ChT-L of the constitutive and immunoproteasomes (IC 50 : 7.1 AE 0.2 and 10.2 AE 0.1 nM, respectively).…”

“…96 Optimization of the scaffold led to the discovery of potent inhibitor 29, which inhibited the ChT-L of the constitutive and immunoproteasomes (IC 50 : 7.1 AE 0.2 and 10.2 AE 0.1 nM, respectively). 99 Dimerized linear TMC-95A mimics using the active derivative 29 scaffold have also been synthesized to evaluate their ability to inhibit multiple active sites at once. Using either PEG spacers 100 or oligomers of aminohexanoic and adipic acid as spacers, 101 researchers were able to achieve nanomolar inhibition of the ChT-L sites of the 20S proteasome.…”

Psoralen Derivatives as Inhibitors of Mycobacterium tuberculosis Proteasome

“…The first identified inhibitors of the Mtb proteasome were indeed primarily developed to target the human proteasome, including bortezomib (Table 1) and epoxomicin, later upgraded to carfilzomib [27,32]. Bortezomib, carfilzomib and orally administered ixazomib are FDA-approved covalent peptidic inhibitors, used as therapeutics for multiple myeloma and mantle cell lymphoma that target both the constitutive proteasome and the IP [32], thus often resulting in severe toxicities [33]. As selective inhibition of IP is expected to attenuate the adverse effects, considerable efforts have been devoted to developing IP-specific inhibitors, resulting in some fairly advanced IP-selective compounds, such as ONX-0914 (formerly PR-957, Table 1) and KZR-616, which are epoxyketone-based tripeptides [34].…”

“…While the Mtb proteasome is an attractive target for the treatment of tuberculosis [20,30,31], the existence of human proteasomes poses a challenge for the development of selective inhibitors. The first identified inhibitors of the Mtb proteasome were indeed primarily developed to target the human proteasome, including bortezomib (Table 1) and epoxomicin, later upgraded to carfilzomib [27,32]. Bortezomib, carfilzomib and orally administered ixazomib are FDA-approved covalent peptidic inhibitors, used as therapeutics for multiple myeloma and mantle cell lymphoma that target both the constitutive proteasome and the IP [32], thus often resulting in severe toxicities [33].…”