Chemical Features Important for Activity in a Class of Inhibitors Targeting the Wip1 Flap Subdomain

Abstract

The wild-type p53 induced phosphatase 1, Wip1 (PP2Cδ), is a protein phosphatase 2C (PP2C) family serine/threonine phosphatase that negatively regulates the function of the tumor suppressor p53 and several of its positive regulators such as ATM, Chk1, Chk2, Mdm2, and p38 MAPK. Wip1 dephosphorylates and inactivates its protein targets, which are critical for cellular stress responses. Additionally, Wip1 is frequently amplified and overexpressed in several human cancer types. Because of its negative role in regulating the function of tumor suppressor proteins, Wip1 has been identified as a potential therapeutic target in various types of cancers. Based on a recently reported Wip1 inhibitor (G-1), we performed an extensive structure-activity relationship (SAR) analysis. This led us to interesting findings in SAR trends and to the discovery of new chemical analogues with good specificity and bioavailability.

Clonal Hematopoiesis: Mechanisms Driving Dominance of Stem Cell Clones

“…This class of genes may offer unique opportunities to impede the development of CH. For example, because PPM1D acts dominantly, there have been efforts to develop inhibitors 55 that may offer an opportunity to slow clonal expansion. An improved understanding of the mechanisms and opportunities may drive different choices of chemotherapeutic agents in contexts where CH or secondary malignancies may be deemed a particular risk.…”

Physiologically relevant orthogonal assays for the discovery of small-molecule modulators of WIP1 phosphatase in high-throughput screens

“…Although inhibition of WIP1 by GSK2830371 is highly potent in vitro (IC 50 = 6 n m ) with good efficacy in WT P53 tumor cell lines, the compound exhibits poor pharmacokinetics with a short half-life in vivo (29). Unfortunately, attempts to overcome this problem through modification of the scaffold have resulted in reduced potency, with the chirality of the central l -cyclohexyl alanine moiety being crucial for the inhibitory activity (29, 30). Structure-activity relationship studies based on an analogue of GSK2830371 were performed at three positions of the scaffold.…”

“…Structure-activity relationship studies based on an analogue of GSK2830371 were performed at three positions of the scaffold. All modifications to the central position resulted in a complete loss of WIP1 inhibition, while a few modifications to the other positions, although tolerated, did not significantly improve the activity (30). Therefore, robust assays suitable for HTS are needed for the discovery of selective WIP1 inhibitors with improved pharmacokinetics.…”

“…To estimate K m and k cat values, the initial rates were fit to the Michaelis-Menten equation in GraphPad Prism 7.01. Inhibition of phosphatase activity of WIP1(1–420) (26.0 n m ) were performed as described previously (30). Inhibition of phosphatase activity was determined in the above buffer and 1% DMSO using 90.0 μ m peptide 6 .…”

“…Our group has shown that substrate-based thioether cyclic peptide inhibitors can be developed with low micromolar potency (27, 28); however, these inhibitors suffer from a poor selectivity within the PPM family. GSK2830371, a potent allosteric inhibitor of WIP1, was demonstrated to have good potency and selectivity (29); however, it does not show favorable pharmacokinetics (30). To our knowledge, no small-molecule activator of WIP1 has yet been described.…”