RO4929097 is a small molecule γ-secretase inhibitor (IC₅₀ = 4 nM). It binds to γ-secretase and blocks the activation of Notch receptors, which may inhibit tumor cell proliferation. RO4929097 inhibits Notch processing in tumor cells as measured by the reduction of intracellular Notch expression by Western blot. RO4929097 produces a less transformed and flattened slower-growing phenotype but does not induce apoptosis or block tumor cell proliferation.