BACKGROUND: RG7112 is a selective inhibitor of p53-MDM2 binding that frees p53 
from negative control, activating the p53 pathway in cancer cells leading to 
cell cycle arrest and apoptosis. RG7112 was selected for evaluation by the 
Pediatric Preclinical Testing Program (PPTP) due to the relatively low incidence 
of p53 mutations in pediatric cancers compared with adult malignancies.
PROCEDURES: RG7112 and its inactive enantiomer RG7112i were evaluated against 
the 23 cell lines of the PPTP in vitro panel using 96 hours exposure (1 nM to 10 
µM). It was tested against the PPTP in vivo panel focusing on p53 wild-type (WT) 
xenografts at a dose of 100 mg/kg daily for 14 days followed by 4 weeks of 
observation. Response outcomes were related to MDM2 and p53 expression datasets 
(http://pptp.nchresearch.org/data.html).
RESULTS: RG7112 demonstrated cytotoxic activity with a lower median IC(50) for 
p53 WT versus p53 mutant cell lines (approximately 0.4 µM vs. >10 µM, 
respectively). RG7112 induced tumor growth inhibition meeting criteria for 
intermediate activity (EFS T/C > 2) in 10 of 26 (38%) solid tumor xenografts. 
Objective responses included medulloblastoma, alveolar rhabdomyosarcoma, Wilms, 
rhabdoid and Ewing sarcoma xenografts. For the ALL panel, there was one partial 
response, five complete responses and one maintained complete response. The ALL 
xenografts expressed the highest levels of p53 among the PPTP panels.
CONCLUSIONS: RG7112 induced tumor regressions in solid tumors from different 
histotype panels, and exhibited consistent high-level activity against ALL 
xenografts. This high level of activity supports prioritization of RG7112 for 
further evaluation.