Nutlin-3 is an activator of p53 that functions by inhibiting the interaction of p53 with MDM2, a negative regulator of p53 activity. Caylin-1 is a nutlin-3 analog which contains chlorine substituents at the 3 and 4 positions on two of the phenyl rings rather than a single 4-chloro as seen in nutlin-3. At high concentrations, caylin-1 inhibits the growth of HCT116 cells with an IC50 value of approximately 7 µM, making it about 7-fold less potent than nutlin-3 in the same assay. Interestingly, at concentrations at or below 1 µM, caylin-1 promotes the growth of HCT116 cells approximately 20% compared to untreated cells. The mechanism of the growth promoting properties of caylin-1 have not yet been elucidated.