Salirasib

Farnesyl Thiosalicylic Acid is a synthetic farnesylcysteine mimic which blocks anchorage of Ras oncoproteins to the cell membrane and to Ras-escort chaperones. The Ras proteins are GTPases responsible for signaling events regulating cell growth and differentiation, and are implicated in producing oncogenic states upon mutational activation. Prenylation of the C-terminus of Ras proteins provides an anchor which inserts into the membrane and is identified and then uptaken by Ras-escort proteins. The mimetic structure of Farnesyl Thiosalicylic Acid blocks anchorage of Ras to the membrane and competes for uptake by the escort proteins, suspending the Ras protein in the cytosol where it is susceptible to protein degradation. Subsequent reduction in active Ras levels has been correlated to the suppression of chronically-Ras-active cancer proliferation. Farnesyl Thiosalicylic acid is also described to detach anchored Ras back into the cytosol and into degradation, observed to quickly decrease total cellular Ras up to 80% in one report. Prenylated protein methyltransferase (PPMTase), responsible for methylating Ras proteins, is also inhibited by Farnesyl Thiosalicylic Acid, similarly due to recognition of the farnesylcysteine mimetic structure by PPMTase.