Ferretti, Stephane Raymond, Holzer, Philipp, Fuchs, Jeannette, Chapeau, Emilie, Wartmann, Markus, Sterker, Dario, Romanet, Vincent, Kerr, Grainne, Durand, Eric, Gaulis, Swann, Kallen, Joerg, Furet, Pascal, Cortes-Cros, Marta, Guerreiro, Nelson, Halilovic, Ensar, Jullion, Astrid, Kuriakose, Emil, Wiesmann, Marion, Jensen, Michael Rugaard, Hofmann, Francesco, Sellers, William, Jeay, Sebastien, Murakami, Masato and Wuerthner, Jens (2018) Dose and schedules determines distinct molecular mechanism underlying the efficacy of the p53-MDM2 inhibitor NVP-HDM201. Cancer research. ISSN 1538-7445; 0008-5472

Abstract

MDM2 counteracts p53 function by mediating ubiquitin-dependent p53 protein degradation. Activation of p53 by small-molecule inhibitors of the p53-MDM2 interaction is being pursued as a therapeutic strategy in p53 wild-type cancers. Here, we report distinct underlying mechanisms by which the novel, highly potent and selective inhibitor of the p53-MDM2 interaction, NVP-HDM201, elicits therapeutic efficacy when applied with different doses and schedules. The level and duration of p53 induction governs the decision to induce cell cycle arrest or apoptosis. However, the majority of MDM2 inhibitors induce primarily a cell-cycle arrest phenotype under continuous in vitro exposure, only promoting modest levels of p53 induction. Taking advantage of the versatile drug-like properties of NVP-HDM201, we analyzed its mode of action when applied as a short-term (pulse) or a longer (continuous) treatment at in vivo relevant doses. Continuous exposures to NVP-HDM201 led to induction of p21 and protracted accumulation of apoptotic cells. Interestingly, the high dose pulse regimen of NVP-HDM201 was associated with a marked induction of PUMA and a rapid onset of apoptosis while both effects were substantially less prominent on the continuous low dose regimen. Consistent with these findings, shRNA screens identified PUMA as a mediator of the p53 response specifically in pulsed high dose regimen revealing a differentiated engagement of the p53 molecular response to NVP-HDM201 in vitro. In contrast to the daily low dose treatment regimen, the single high dose NVP-HDM201 regimen resulted in vivo in a rapid and marked induction of p53-dependent PUMA expression and apoptosis, together with a concomitant down-regulation of Bcl-xL. Interestingly, Bcl-xL knockdown was identified as the top sensitizer to NVP-HDM201 in vitro, and in tumors relapsing on prolonged NVP-HDM201 treatments, Bcl-xL was uniquely found enriched in mice treated with intermittent high doses of NVP-HDM201 in vivo. Overall, our findings define a regimen-dependent molecular mechanism by which disruption of the MDM2-p53 interaction elicits therapeutic efficacy when given with infrequent dosing. The exposure-response relationship of NVP-HDM201 observed in patients indicate that the robust and early onset of apoptosis observed in tumor-bearing animals may be reproduced in patients and further support to compare both daily and intermittent dosing regimens with regard to p53 target gene induction, efficacy and tolerability in the ongoing NVP-HDM201 clinical trial.

Item Type:	Article
Date Deposited:	02 Oct 2018 00:45
Last Modified:	02 Oct 2018 00:45
URI:	https://oak.novartis.com/id/eprint/34237