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RAS Covalent Inhibitors

The goal of the Covalent Inhibitors Group is to discover and develop compounds that covalently modify oncogenic RAS protein in cancer cells, leading to its loss or inactivation. We use the disulfide tethering technology first described by Wells and colleagues in 2000 and exemplified by Shokat, et al. in 2013.  This site-directed method of fragment-based drug-discovery allows screening of low-affinity disulfide containing fragments against cysteine residues in a target protein. Fragment binding is not purely driven by cysteine reactivity; it is thermodynamically driven and strongly depends on protein/fragment interaction.  Bound fragments are detected by mass spectrometry and provide a lead into the drug discovery process. 

Our lead projects focus on targeting two potentially “druggable” residues in KRAS. One is the C-terminal cysteine (C185) in the hypervariable region of KRAS4b, which is the site of posttranslational modification that is crucial for KRAS membrane attachment and its oncogenic activity.  A second equally interesting target is histidine-95 that is found in KRAS but not HRAS or NRAS. 

We use a suite of resources, including biophysical, biochemical, and cell-based screens to test compounds for activity in recombinant proteins, and also in cells, especially RAS-dependent mouse embryonic fibroblasts (MEFs) created by Mariano Barbacid (CNIO, Madrid). 

Our Progress

Our group is developing compounds that selectively and covalently modify cysteine-185 and histidine-95 in KRAS, leading to loss of KRAS oncogenic activity.

Our Projects

Anna Maciag, Ph.D.

  • Targeting C185 in KRAS4b
  • Targeting H95 in KRAS

Tools We Use 

  • Cell lines: Mouse embryonic fibroblasts engineered to be dependent on single alleles of RAS; malignant cell lines; engineered cell lines expressing tagged-RAS
  • Medicinal chemistry
  • Computer-aided drug design (CADD), in silico screens
  • NMR, mass spectrometry, proteomics, biophysical/biochemical screens


For more information contact the RAS Covalent Inhibitors team lead:

Dr. Anna Maciag 

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