| Description: |
In vitro:
VLX1570 is an analogue of b-AP15 that shows higher potency and improved solubility. VLX1570 preferentially inhibits proteasomal DUB activity while not inhibiting the activities of a panel of non-proteasomal DUBs. VLX1570 binds to and inhibits the activity of ubiquitin-specific protease-14 (USP14) in vitro, with comparatively weaker inhibitory activity towards UCHL5 (ubiquitin-C-terminal hydrolase-5). Treatment of multiple myeloma cells with VLX1570 induces the accumulation of proteasome-bound high molecular weight polyubiquitin conjugates and an apoptotic response. VLX1570 induces the expression of the chaperone HSP70B′, the oxidative stress marker Hmox-1, and the ER stress marker XBP-1s. VLX1570 is retained in cells after removal of drug and that USP14 was engaged by drug 17 hours after wash-out, as evidenced by thermal stabilization and persistent enzyme inhibition.
In vivo: VLX1570 is an inhibitor of proteasome DUB activity currently in clinical trials for relapsed multiple myeloma. Treatment with VLX1570 is found to lead to extended survival in xenograft models of multiple myeloma. The in vivo IC50 for inhibition of proteasome DUB activity and induction of apoptosis is <1 μM, with multiple myeloma cells showing greater levels of sensitivity compared to other tumor types. The lower IC50 for activity in vivo is presumably due to rapid drug uptake and enrichment in cells. |
