CHARACTERIZATION OF A NOVEL, POTENT SMALL MOLECULE MDM2 ANTAGONIST WHICH ACTIVATES WILD-TYPE P53 AND INDUCES APOPTOSIS IN AML
Author(s): ,
Nicola Ferrari
Affiliations:
Astex Pharmaceuticals,Cambridge,United Kingdom
,
Luke Bevan
Affiliations:
Astex Pharmaceuticals,Cambridge,United Kingdom
,
Juan Castro
Affiliations:
Astex Pharmaceuticals,Cambridge,United Kingdom
,
Gianni Chessari
Affiliations:
Astex Pharmaceuticals,Cambridge,United Kingdom
,
Lynsey Fazal
Affiliations:
Astex Pharmaceuticals,Cambridge,United Kingdom
,
Steven Howard
Affiliations:
Astex Pharmaceuticals,Cambridge,United Kingdom
,
Justyna Kucia-Tran
Affiliations:
Astex Pharmaceuticals,Cambridge,United Kingdom
,
Martin Sims
Affiliations:
Astex Pharmaceuticals,Cambridge,United Kingdom
,
George Ward
Affiliations:
Astex Pharmaceuticals,Cambridge,United Kingdom
,
Steve Wedge
Affiliations:
Northern Institute for Cancer Research, Newcastle University,Newcastle upon Tyne,United Kingdom
,
Elaine Willmore
Affiliations:
Northern Institute for Cancer Research, Newcastle University,Newcastle upon Tyne,United Kingdom
Maria Ahn
Affiliations:
Astex Pharmaceuticals,Cambridge,United Kingdom
EHA Library. Ferrari N. Jun 15, 2019; 267289; PS988
Dr. Nicola Ferrari
Dr. Nicola Ferrari
Contributions
Abstract

Abstract: PS988

Type: Poster Presentation

Presentation during EHA24: On Saturday, June 15, 2019 from 17:30 - 19:00

Location: Poster area

Background

In the presence of various stress signals, p53 acts as a tumor suppressor by regulating the expression of a multitude of genes to elicit cellular responses such as cell cycle arrest and apoptosis. The activity of p53 is tightly regulated by MDM2, an E3 ubiquitin ligase that acts as a primary inhibitor of p53 function by, for example, targeting p53 for proteasomal degradation. Early studies have demonstrated that blocking the MDM2-p53 interaction in tumors carrying wild-type p53 prevents p53 degradation and reactivates it. Small molecule MDM2 antagonists that inhibit the MDM2-p53 interaction, therefore, present a promising strategy for cancer therapy and a number of these compounds are in clinical development. 

Aims

Herein, we describe the characterization of a novel, potent small molecule MDM2 antagonist in AML in vitro and in vivo pre-clinical models and in patient-derived AML blast cells.

Methods

A panel of p53 wild-type AML cell lines was tested for reduction in cell proliferation using Alamar Blue assay following treatment with the compound. Induction of apoptosis was measured by flow cytometry using a fluorescent caspase-3 substrate or Annexin V. Target engagement was analyzed by Western Blotting and TaqMan qRT-PCR. The MV-4-11 mouse systemic model was used to test in vivo sensitivity to the compound. Primary AML blasts were isolated from patients using combinations of antibodies against CD34, CD33, CD45, and CD117.

Results

We have applied structure-based design to develop a novel, potent, orally bioavailable MDM2 antagonist. The compound exhibits EC50 <1 nM against the full-length MDM2 protein in a cell-free ELISA and increases p53 levels in a wide range of p53 wild-type cells (e.g. EC50=10 nM for p53 induction in SJSA-1 osteosarcoma cells).

When tested in a panel of p53 wild-type AML cell lines, the compound exerted a strong anti-proliferative effect with GI50 values of <30 nM being observed in 9 out of 11 cell lines. In contrast, the compound had little effect on p53 mutant KG-1 cells (GI50 >10 mM). In addition, many of the p53 wild-type AML cell lines showed a strong induction of apoptosis in response to treatment with the compound. Activation of p53 was evident by an increase in the expression of p53 and that of its well-known transcriptional targets such as p21 and MDM2. Consistent with these findings, a detailed study of gene expression changes in MV-4-11 confirmed clear transcriptional activation of several p53 target genes (CDKN1A, MDM2, BBC3, FAS, GADD45, BAX) 2-6 hours after addition of the compound.

In accordance with its potent activity in vitro, the compound displayed significant in vivo efficacy in the MV-4-11 mouse systemic model of AML. Here, QDx14 oral dosing at well tolerated doses demonstrated a clear reduction in tumor burden. Furthermore, p53 activation by the compound triggered apoptosis when tested in primary AML blast cells isolated from patients.

Conclusion

Taken together, our findings demonstrate that the compound exhibits potent activity against AML cells that retain wild-type p53, thus meriting further clinical investigations.

Session topic: 3. Acute myeloid leukemia - Biology & Translational Research

Keyword(s): AML, Drug sensitivity, P53

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