No abstract

Regorafenib (Stivarga) is an oral small molecule kinase inhibitor used to treat metastatic colorectal cancer, hepatocellular carcinomas, and gastrointestinal stromal tumors. Diarrhea is one of the most frequently observed adverse reactions associated with regorafenib. This toxicity may arise from the reactivation of the inactive regorafenib-glucuronide to regorafenib by gut microbial βglucuronidase (GUS) enzymes in the gastrointestinal tract. We sought to unravel the molecular basis of regorafenib-glucuronide processing by human intestinal GUS enzymes and to examine the potential inhibition of these enzymes. Using a panel of 31 unique gut microbial GUS enzymes derived from the 279 mapped from the human gut microbiome, we found that only four were capable of regorafenib-glucuronide processing. Using crystal structures as a guide, we pinpointed the molecular features unique to these enzymes that confer regorafenib-glucuronide processing activity. Furthermore, a pilot screen identified the FDA-approved raloxifene as an inhibitor of regorafenib reactivation by the GUS proteins discovered. Novel synthetic raloxifene analogs *

Increased activity of the lysine methyltransferase NSD2 driven by translocation and activating mutations is associated with multiple myeloma and acute lymphoblastic leukemia, but no NSD2-targeting chemical probe has been reported to date. Here, we present the first antagonists that block the protein–protein interaction between the N-terminal PWWP domain of NSD2 and H3K36me2. Using virtual screening and experimental validation, we identified the small-molecule antagonist 3f, which binds to the NSD2-PWWP1 domain with a K d of 3.4 μM and abrogates histone H3K36me2 binding to the PWWP1 domain in cells. This study establishes an alternative approach to targeting NSD2 and provides a small-molecule antagonist that can be further optimized into a chemical probe to better understand the cellular function of this protein.

The programmed cell death protein 1 (PD-1) signaling axis is among the most important therapeutic targets in modern oncology. Aurigene Discovery Technologies Ltd. (Aurigene) has patented a series of peptidomimetic small molecules derived from the PD-1 protein sequence for use in targeting the interaction between PD-1 and its ligand, PD-L1. We evaluated three of Aurigene's most potent compounds in SPR binding assays. Our results showed that these compounds each of which is known to be potently effective in a splenocyte recovery assaydo not directly inhibit the PD-1/PD-L1 interaction nor do they appear to bind to either of the constituent proteins, indicating that another mechanism is at play. As a result of these studies and upon consideration of structural features within the PD-1/PD-L1 complex, we hypothesize that the Aurigene molecules may interact with a currently unknown protein capable of regulating the PD-1 axis.