Syrbactin proteasome inhibitor TIR-199 overcomes bortezomib chemoresistance and inhibits multiple myeloma tumor growth in vivo

Abstract

Multiple myeloma (MM) and mantle cell lymphoma (MCL) are blood cancers that respond to proteasome inhibitors. Three FDA-approved drugs that block the proteasome are currently on the market, bortezomib, carfilzomib, and ixazomib. While these proteasome inhibitors have demonstrated clinical efficacy against refractory and relapsed MM and MCL, they are also associated with considerable adverse effects including peripheral neuropathy and cardiotoxicity, and tumor cells often acquire drug resistance. TIR-199 belongs to the syrbactin class, which constitutes a novel family of irreversible proteasome inhibitors. In this study, we compare TIR-199 head-to-head with three FDA-approved proteasome inhibitors. We demonstrate that TIR-199 selectively inhibits to varying degrees the sub-catalytic proteasomal activities (C-L/β1, T-L/β2, and CT-L/β5) in three actively dividing MM cell lines, with Ki 50 (CT-L/β5) values of 14.61 ± 2.68 nM (ARD), 54.59 ± 10.4 nM (U266), and 26.8 ± 5.2 nM (MM.1R). In most instances, this range was comparable with the activity of ixazomib. However, TIR-199 was more effective than bortezomib, carfilzomib, and ixazomib in killing bortezomib-resistant MM and MCL cell lines, as *

Proteasome Inhibitors against Cancer: Determining Biology and Finding Novel Compounds

“…Eneamides have received increased attention by drug developers in recent years in the form of syrbactins, a class of natural compounds that can inhibit the UPS and overcomes bortezomib resistance. (203,204) The remaining 6 compounds were all enones, of which 1 was classified as a PAIN. In the library of 4896 compounds, enones were proportionally overrepresented as proteasome inhibitors with only one compound flagged as a PAIN.…”

Syrbactin-class dual constitutive- and immuno-proteasome inhibitor TIR-199 impedes myeloma-mediated bone degenerationin vivo

“…However, bortezomib binding involves a critical hydrogen bond with Ala49 on PSMB5 (38) which is not observed in case of TIR-199 (Fig 2C and supplementary Fig S2A) and this explains the mechanism by which TIR-199 is able to bypass bortezomib resistance in the AA/TV PSMB5 mutation (Fig 4C). Indeed, a previous study has reported bortezomib-resistant myeloma and mantle-cell lymphoma cells were sensitive to TIR-199(31). Furthermore, TIR-199 clearly prefers the PSMB8 subunit over PSMB9 ( Fig 2B ) and this is probably due to the reduced number of hydrogen bonds predicted for TIR-199-PSMB9 interaction ( Supplementary Fig S2B ).…”

“…The virulence factor derivatives called syrbactins are a family of bacterial, macrocyclic, non-ribosomal peptide natural products which reacts covalently with the catalytic Thr1 residue of proteasome peptidase subunits (27–29). Upon further structure-activity-relationship studies, syrbactin analog TIR-199 was developed and found to inhibit proteasome activity(30) and induce cell death in myeloma, mantel-cell lymphoma and neuroblastoma celllines (31). Preliminary studies show that TIR-199 is active in vivo and arrests tumor cell growth in mice (30,31).…”

“…Upon further structure-activity-relationship studies, syrbactin analog TIR-199 was developed and found to inhibit proteasome activity(30) and induce cell death in myeloma, mantel-cell lymphoma and neuroblastoma celllines (31). Preliminary studies show that TIR-199 is active in vivo and arrests tumor cell growth in mice (30,31). The current work builds on the initial studies with TIR-199 and shows that TIR-199 is indeed a dual constitutive and immuno-proteasome inhibitor with high inhibitory activity against PSMB5 and PSMB8 subunits and can bypass bortezomib resistant mutant of PSMB5.…”

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

“…69 TIR-199 also inhibits the proteasome in multiple myeloma cell line MM1.RL and neuroblastoma cell line MYCN2 and has demonstrated exciting cytotoxic activity against bortezomib-resistant cell lines (MM1.S BzR and U266 BzR), indicating it can overcome bortezomib resistance in vivo. 70 Clerc et al further investigated the effects of substitution at the N-terminus through the synthesis of a syringolin A-glidobactin A hybrid 17. 71 The inhibitory activity and subsite selectivity of the analogue was tested using competitive activitybased protein profiling (ABPP) in HEK cell lysates and living cells, compared to known syrbactin inhibitors.…”