In vitro activity: Kobe0065-family compounds bind to Ras·GTP and exhibit antiproliferative activity toward cancer cells carrying the activated ras oncogenes. The compounds efficiently inhibit the interaction of Ras·GTP with their multiple effectors including Raf, PI3K, and RalGDS and a regulator/effector Sos and show rather broad binding specificity toward various Ras family small GTPases, which may account for their higher potency at the cellular level compared with that of the in vitro binding inhibition.

Cell Assay: NIH 3T3 cells are transfected with pEF-BOS-HA-H-Ras(G12V) or an empty vector and treated with the 2 and 20 μM compound or the vehicle (DMSO) in the presence of 2% FBS for 1 h. Cell lysate is subjected to detection of c-Raf-1 coimmunoprecipitated with an anti-H-Ras antibody and total c-Raf-1 by Western blotting with an anti-c-Raf-1 antibody. Immunoprecipitated H-Ras(G12V) are detected by an anti-HA antibody.