Mount Sinai researchers have developed a therapy that shows promise against a deadly pediatric leukemia. The small-molecule therapy was highly effective in fighting a type of acute myeloid leukemia in both in vitro and in vivo experiments, according to research published in Science Translational Medicine in September.

The therapy, named MS67, causes the degradation of the WDR5 protein, which drives the proliferation of acute myeloid leukemia with a specific genetic makeup called mixed lineage leukemia rearrangement. This type of leukemia is more common in children, has very poor response to standard treatments and a dismal prognosis, and until now has confounded researchers.

WDR5 also plays an important role in driving the proliferation of other cancers such as pancreatic cancer, so researchers believe that it is likely that WDR5 small-molecule degraders such as MS67 could also be effective in treating those cancers.

"This study is the first to demonstrate that pharmacological degradation of WDR5, which selectively eliminates the protien, is an effective and superior therapeutic strategy than pharmacological inhibition, or blocking, of WDR5 for the treatment of WDR5-dependent cancers including acute myeloid leukemia with mixed lineage leukemia rearrangement," said Jian Jin, PhD, the Mount Sinai Professor in Therapeutics Discovery and Director of the Mount Sinai Center for Therapeutics Discovery at the Icahn School of Medicine at Mount Sinai. "In addition, MS67 is the first WDR5 small-molecule degrader that exhibits robust anti-tumor activities in vivo."

The research team led by Dr. Jin; Greg Wang, PhD, of the University of North Carolina at Chapel Hill; and Aneel Aggarwal, PhD, Professor of Pharmacological Sciences, and Oncological Sciences, at The Tisch Cancer Institute at Mount Sinai, discovered MS67, a novel, highly potent and selective small-molecule degrader of WDR5, which effectively suppressed the growth of this type of acute myeloid leukemia cells derived from patients both in vitro and in vivo, using patient cancer cells in mouse models. Using a battery of biochemical, biophysical, structural, cellular, genomic, and in vivo studies, the research team demonstrated that MS67 is a much superior therapeutic agent than other therapies that inhibit instead of degrade WDR5.

Interactions between WD40 repeat domain protein 5 (WDR5) and its various partners such as mixed lineage leukemia (MLL) and c-MYC are essential for sustaining oncogenesis in human cancers. However, inhibitors that block protein-protein interactions (PPIs) between WDR5 and its binding partners exhibit modest cancer cell killing effects and lack in vivo efficacy. Here, we present pharmacological degradation of WDR5 as a promising therapeutic strategy for treating WDR5-dependent tumors and report two high-resolution crystal structures of WDR5-degrader-E3 ligase ternary complexes. We identified an effective WDR5 degrader via structure-based design and demonstrated its in vitro and in vivo antitumor activities. On the basis of the crystal structure of an initial WDR5 degrader in complex with WDR5 and the E3 ligase von Hippel–Lindau (VHL), we designed a WDR5 degrader, MS67, and demonstrated the high cooperatively of MS67 binding to WDR5 and VHL by another ternary complex structure and biophysical characterization. MS67 potently and selectively depleted WDR5 and was more effective than WDR5 PPI inhibitors in suppressing transcription of WDR5-regulated genes, decreasing the chromatin-bound fraction of MLL complex components and c-MYC, and inhibiting the proliferation of cancer cells. In addition, MS67 suppressed malignant growth of MLL-rearranged acute myeloid leukemia patient cells in vitro and in vivo and was well tolerated in vivo. Collectively, our results demonstrate that structure-based design can be an effective strategy to identify highly active degraders and suggest that pharmacological degradation of WDR5 might be a promising treatment for WDR5-dependent cancers.

For more details go through: Archives in Cancer Research.

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