Allosteric inhibition of SHP2 variants containing cancer-associated activating mutations

SHP2 (PTPN11) is a non-receptor protein tyrosine phosphatase and scaffold protein that functions in multiple signal transduction pathways. Genetic and pharmacologic evidence supports a role for SHP2 in driving the proliferation of cancer cells dependent upon a range of activated RTKs, certain RAS and BRAF mutations, and NF1 loss-of-function mutations. In addition, dominant activating mutations in PTPN11 fuel pathogenic RAS/MAPK signaling and underlie certain human RASopathies (40% of Noonan syndrome and 80% of LEOPARD syndrome) and cancers (35% of JMML and up to 5% of many other cancers). These mutants destabilize an autoinhibited conformation of SHP2, which can also be activated by binding to diphosphotyrosine motifs in vivo or to synthetic diphosphopeptides in vitro. Multiple selective, allosteric inhibitors that stabilize this autoinhibited state and potently inhibit wild-type (WT) SHP2 have recently been reported, but the impact of these inhibitors on mutant forms of the protein is less well established. Here we investigate the activity of a diverse set of over fifty allosteric SHP2 inhibitors on multiple cancer-associated activating mutants of SHP2, both in the presence and absence of an activating diphosphopeptide. The rank order of potencies of the inhibitors remains identical for all mutants, although a decrease in potency relative to WT is seen in some mutants, which is magnified further in the presence of activating peptide. These results conform to a simple equilibrium model, where inhibitors show a reduction in potency against activated mutants that is proportional to the energetic magnitude of the activating mutation. Surprisingly, some common activating mutations of SHP2 (e.g., D61G) have a relatively modest energetic effect, and exhibit similar sensitivity to allosteric inhibitors as WT SHP2. We follow up these biochemical results with cellular inhibition studies in HEK293 cells stably transfected with the respective SHP2 mutants. Collectively, these results suggest that potent allosteric SHP2 inhibitors will be effective at inhibiting the growth of cancers driven by a subset of activating mutations in SHP2. Citation Format: David Wildes, Naing Aay, Andreas Buckl, Daphne Hsieh, Ashutosh S. Jogalekar, Gert Kiss, Elena S. Koltun, Abby Marquez, Kevin T. Mellem, Jason Romero, Mae Saldajeno-Concar, Christopher J. Schulze, Chris M. Semko, Walter Won, Robert J. Nichols, Carlos Stahlhut, Christos Tzitzilonis, Adrian L. Gill, Jacqueline A. Smith. Allosteric inhibition of SHP2 variants containing cancer-associated activating mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4877.