Nutlin-3b ((+)-Nutlin-3) is a p53/MDM2 antagonist or inhibitor (IC50: 13.6 μM), 150-fold less potent (+)-enantiomer of Nutlin-3 as in comparison with opposite (-)-enantiomer Nutlin-3a.

MDM2:13.6 μM

Nutlin-3b is useful as a negative control s for non-MDM2-related cellular activities. Nutlin-3a induces the expression of MDM2 and p21 (but not p53) only in cells with wild-type p53. Nutlin-3b has no effect regardless of the p53 status of the cells. Only the active enantiomer Nutlin-3a shows a potent antiproliferative activity and clear separation of potency between the cells harboring wild-type p53 and those harboring mutant p53. The potency of Nutlin-3b is much lower in the wild-type p53 cells and nearly identical to the potency of Nutlin-3a against the mutant p53 cells. After 48 hours of exposure to the Nutlin-3a, 45% of the cell population became TUNEL positive, but cells treated with the Nutlin-3b are indistinguishable from the untreated controls. [1]

Biacore study: Competition assay is performed on a Biacore S51. A Series S Sensor chip CM5 is utilized for the immobilization of a PentaHis antibody for capture of the His-tagged p53. The level of capture is ~200 response units (1 response unit corresponds to 1 pg of protein per mm 2). The concentration of MDM2 protein is kept constant at 300 nM. Nutlin-3 is dissolved in DMSO at 10 mM and further diluted to make a concentration series of Nutlin-3 in each MDM2 test sample. The assay is run at 25°C in running buffer (10 mM Hepes, 0.15 M NaCl, 2% DMSO). MDM2-p53 binding in the presence of Nutlin-3 is calculated as a percentage of binding in the absence of Nutlin-3 and IC50 is calculated

MTT assay(Only for Reference)