Hilary P. Beck

Structure-based design of novel inhibitors of the MDM2-p53 interaction.

Structure-based rational design led to the discovery of novel inhibitors of the MDM2-p53 protein-protein interaction. The affinity of these compounds for MDM2 was improved through conformational control of both the piperidinone ring and the appended N-alkyl substituent. Optimization afforded 29 (AM-8553), a potent and selective MDM2 inhibitor with excellent pharmacokinetic properties and in vivo efficacy.

Discovery of AMG 232, a Potent, Selective, and Orally Bioavailable MDM2–p53 Inhibitor in Clinical Development

We recently reported the discovery of AM-8553 (1), a potent and selective piperidinone inhibitor of the MDM2-p53 interaction. Continued research investigation of the N-alkyl substituent of this series, focused in particular on a previously underutilized interaction in a shallow cleft on the MDM2 surface, led to the discovery of a one-carbon tethered sulfone which gave rise to substantial improvements in biochemical and cellular potency. Further investigation produced AMG 232 (2), which is currently being evaluated in human clinical trials for the treatment of cancer. Compound 2 is an extremely potent MDM2 inhibitor (SPR KD = 0.045 nM, SJSA-1 EdU IC50 = 9.1 nM), with remarkable pharmacokinetic properties and in vivo antitumor activity in the SJSA-1 osteosarcoma xenograft model (ED50 = 9.1 mg/kg).

Rational Design and Binding Mode Duality of MDM2–p53 Inhibitors

Structural analysis of both the MDM2-p53 protein-protein interaction and several small molecules bound to MDM2 led to the design and synthesis of tetrasubstituted morpholinone 10, an MDM2 inhibitor with a biochemical IC50 of 1.0 μM. The cocrystal structure of 10 with MDM2 inspired two independent optimization strategies and resulted in the discovery of morpholinones 16 and 27 possessing distinct binding modes. Both analogues were potent MDM2 inhibitors in biochemical and cellular assays, and morpholinone 27 (IC50 = 0.10 μM) also displayed suitable PK profile for in vivo animal experiments. A pharmacodynamic (PD) experiment in mice implanted with human SJSA-1 tumors showed p21(WAF1) mRNA induction (2.7-fold over vehicle) upon oral dosing of 27 at 300 mg/kg.

Selective and potent morpholinone inhibitors of the MDM2-p53 protein-protein interaction.

We previously reported the discovery of AMG 232, a highly potent and selective piperidinone inhibitor of the MDM2-p53 interaction. Our continued search for potent and diverse analogues led to the discovery of novel morpholinone MDM2 inhibitors. This change to a morpholinone core has a significant impact on both potency and metabolic stability compared to the piperidinone series. Within this morpholinone series, AM-8735 emerged as an inhibitor with remarkable biochemical potency (HTRF IC50 = 0.4 nM) and cellular potency (SJSA-1 EdU IC50 = 25 nM), as well as pharmacokinetic properties. Compound 4 also shows excellent antitumor activity in the SJSA-1 osteosarcoma xenograft model with an ED50 of 41 mg/kg. Lead optimization toward the discovery of this inhibitor as well as key differences between the morpholinone and the piperidinone series will be described herein.

Discovery of potent LPA2 (EDG4) antagonists as potential anticancer agents

The LPA(2) protein is overexpressed in many tumor cells. We report the optimization of a series of LPA(2) antagonists using calcium mobilization assay (aequorin assay) that led to the discovery of the first reported inhibitors selective for LPA(2). Key compounds were evaluated in vitro for inhibition of LPA(2) mediated Erk activation and proliferation of HCT-116 cells. These compounds could be used to evaluate the benefits of LPA(2) inhibition both in vitro and in vivo.

Novel Inhibitors of the MDM2-p53 Interaction Featuring Hydrogen Bond Acceptors as Carboxylic Acid Isosteres.

We previously reported the discovery of potent and selective morpholinone and piperidinone inhibitors of the MDM2-p53 interaction. These inhibitors have in common a carboxylic acid moiety that engages in an electrostatic interaction with MDM2-His96. Our continued search for potent and diverse inhibitors led to the discovery of novel replacements for these acids uncovering new interactions with the MDM2 protein. In particular, using pyridine or thiazole as isosteres of the carboxylic acid moiety resulted in very potent analogues. From these, AM-6761 (4) emerged as a potent inhibitor with remarkable biochemical (HTRF IC50 = 0.1 nM) and cellular potency (SJSA-1 EdU IC50 = 16 nM), as well as favorable pharmacokinetic properties. Compound 4 also shows excellent antitumor activity in the SJSA-1 osteosarcoma xenograft model with an ED50 of 11 mg/kg. Optimization efforts toward the discovery of these inhibitors as well as the new interactions observed with the MDM2 protein are described herein.

Improvement of the synthesis and pharmacokinetic properties of chromenotriazolopyrimidine MDM2-p53 protein-protein inhibitors

Human murine double minute 2 (MDM2) is a negative regulator of p53, which plays an important role in cell cycle and apoptosis. We report several optimizations to the synthesis of the chromenotriazolopyrimidine series of MDM2-p53 protein-protein interaction inhibitors. Additionally, the in vitro and in vivo stability, pharmacokinetic properties and solubility were improved through N-substitution.

Discovery of AM-7209, a Potent and Selective 4-Amidobenzoic Acid Inhibitor of the MDM2-p53 Interaction.

Structure-based rational design and extensive structure-activity relationship studies led to the discovery of AMG 232 (1), a potent piperidinone inhibitor of the MDM2-p53 association, which is currently being evaluated in human clinical trials for the treatment of cancer. Further modifications of 1, including replacing the carboxylic acid with a 4-amidobenzoic acid, afforded AM-7209 (25), featuring improved potency (KD from ITC competition was 38 pM, SJSA-1 EdU IC50 = 1.6 nM), remarkable pharmacokinetic properties, and in vivo antitumor activity in both the SJSA-1 osteosarcoma xenograft model (ED50 = 2.6 mg/kg QD) and the HCT-116 colorectal carcinoma xenograft model (ED50 = 10 mg/kg QD). In addition, 25 possesses distinct mechanisms of elimination compared to 1.

A selective prostaglandin E2 receptor subtype 2 (EP2) antagonist increases the macrophage-mediated clearance of amyloid-beta plaques.

A high-throughput screen resulted in the discovery of benzoxazepine 1, an EP2 antagonist possessing low microsomal stability and potent CYP3A4 inhibition. Modular optimization of lead compound 1 resulted in the discovery of benzoxazepine 52, a molecule with single-digit nM binding affinity for the EP2 receptor and significantly improved microsomal stability. It was devoid of CYP inhibition and was ∼4000-fold selective against the other EP receptors. Compound 52 was shown to have good PK properties in CD-1 mice and high CNS permeability in C57Bl/6s mice and Sprague-Dawley rats. In an ex vivo assay, it demonstrated the ability to increase the macrophage-mediated clearance of amyloid-beta plaques from brain slices in a dose-dependent manner.

Abstract 4290: Potent and selective next generation inhibitors of indoleamine-2,3-dioxygenase (IDO1) for the treatment of cancer

The IDO1 pathway has been proposed to mediate immunosuppressive effects in the tumor microenvironment through its role in the catabolism of tryptophan, resulting in effects on the differentiation and proliferation of T cells. IDO1 inhibition has shown promising clinical benefit as well as exacerbated toxicity in the treatment of melanoma, when combined with the anti-CTLA-4 antibody ipilimumab. We have discovered a novel class of highly selective small molecule inhibitors of IDO1 which surpass the potency of the compounds currently in clinical development. These compounds potently inhibit IDO1 activity in IFN-γ stimulated HeLa cells with single digit nM potency. Importantly, they also retain their potency in the presence of human serum, with IC50 values ranging between 5 and 15 nM in this more physiologically relevant media. Consistent with the role of IDO1+ dendritic cells in the suppression of T cell proliferation, this series of molecules is capable of restoring the proliferative capacity of human T cells (which is inhibited by allogeneic IDO1+ dendritic cells) with EC50 values of 2-3 nM. The molecules exhibit preclinical PK characteristics that are suitable for assessing the contribution of IDO1 to tumor growth in murine models, both alone and in combination with other therapeutic agents. The compounds have high metabolic stability against cultured human hepatocytes and exhibit preclinical PK and ADME characteristics consistent with once-daily dosing in humans. The full preclinical profile of one of these molecules, selected for clinical evaluation, will be the focus of this presentation. In conclusion, we have discovered a novel class of small molecule inhibitors of IDO1, which provides a preclinical basis for the clinical evaluation of a next generation IDO1 inhibitor in combination with other therapeutic agents. Citation Format: Jay P. Powers, Matthew J. Walters, Rajkumar Noubade, Stephen W. Young, Lisa Marshall, Jan Melom, Adam Park, Nick Shah, Pia Bjork, Jordan S. Fridman, Hilary P. Beck, David Chian, Jenny V. McKinnell, Maksim Osipov, Maureen K. Reilly, Hunter P. Shunatona, James R. Walker, Mikhail Zibinsky, Juan C. Jaen. Potent and selective next generation inhibitors of indoleamine-2,3-dioxygenase (IDO1) for the treatment of cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4290. doi:10.1158/1538-7445.AM2015-4290