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Background:Mouse Double Minute 2 protein (MDM2) is a cellular regulator of p53 tumor suppressor (p53). Inhibition of the interaction between MDM2 and p53 proteins is a promising anticancer therapy.Objective:This updated patent review is an attempt to compile the research and achievements of the various researchers working on small molecule MDM2 inhibitors from 2010 to date. We provide an outlook into the future for therapy based on MDM2 inhibition by presenting an overview of the most relevant patents which have recently appeared in the literature.Methods:Literature and recent patents focusing on the anticancer potential of MDM2-p53 interaction inhibitors and its applications have been analyzed. We put the main emphasis on the most perspective compounds which are or were examined in clinical trials.Results:Literature data indicated that MDM2 inhibitors are therapeutically effective in specific types of cancer or non-cancer diseases. A great number of patents and research work around new MDM2- p53 interaction inhibitors, possible combinations, new indications, clinical regimens in previous years prove that this targeted therapy is in the scope of interest for many business and academic research groups.Conclusion:Novel MDM2 inhibitors thanks to higher potency and better ADME properties have shown effectiveness in preclinical and clinical development however the final improvement of therapeutic potential for MDM2 inhibitors might depend on the useful combination therapy and exploring new cancer and non-cancer indications.

Background Metallothionein 1M (MT1M) functions to regulate cell proliferation and cancer metastasis. This study assessed the effects of MT1M overexpression and mouse double minute 2 homolog (MDM2) knockdown on the regulation of non-small cell lung cancer A549 cell viability, migration, and protein expression in vitro and explored the underlying molecular events. Methods A549 cells were stably infected with lentivirus carrying MT1M cDNA or transiently transfected MDM2 siRNA and/or treated with the p53 inhibitor for the assessment of changes in cell viability, wound healing, Transwell migration, and qRT-PCR and Western blot assays. Luciferase reporter assay was performed to investigate p53 binding to the MT1M promoter. Results The data showed that MT1M overexpression inhibited A549 cell viability and migration capacity in vitro, whereas the p53 inhibitor reversed the inhibition of A549 cell viability and migration caused by MT1M overexpression as well as the expression of MMP2, MMP9, and MMP14. Furthermore, knockdown of MDM2, an upstream inhibitor of p53 activity, was able to reduce A549 cell viability, migration, and protein expression. Thus, MDM2 knockdown had synergistic effects with MT1M overexpression on the suppression of A549 cell viability, migration, and protein expression. Conclusions In conclusion, MDM2 can bind to and phosphorylate p53 protein to inactivate the protein, thereby reducing MT1M expression and leading to tumor cell proliferation and migration.

Background Some ribosomal proteins (RPs) might regulate the MDM2–p53 loop by binding to RPL5 or RPL11. This study aimed to explore whether ribosomal protein S27a (RPS27a) interacted with the ribosomal protein L11 (RPL11) to regulate p53 in lung adenocarcinoma (LUAD) cells. Methods RPL11-interacting proteins were identified using a proteomics approach. Co-immunoprecipitation (co-IP), docking analysis, GST-fusion and in vitro ubiquitination assay were used to analyze the interaction of RPS27a and RPL11. Cell cycle, apoptosis, cell invasion, cell viability and colony-formation assay were analyzed by knocking down RPS27a. The RPS27a mRNA expression in LUAD was analyzed based on the TCGA dataset and the RPS27a expression was detected by immunohistochemistry in LUAD samples. At last, the RPS27a and p53 expression were analyzed by immunohistochemistry in xenograft tumors by blocking RPS27a. Results The ablation of RPS27a inhibits murine double minute 2 (MDM2)-mediated p53 ubiquitination, induced G1/S cell cycle arrest and apoptosis, and inhibited the proliferation of LUAD cells. Also, it induced p53-dependent cell cycle arrest and RPL11-dependent p53 activation. The protein–protein docking results revealed that RPS27a and RPL11 formed a stable complex structure. The GST-fusion protein–protein association assay demonstrated that RPS27a bound to RPL11. The overexpressed RPS27a in LUAD was found to be correlated with a poorer prognosis based on the TCGA dataset. RPS27a expression was high in patients with LUAD. Blocking RPS27a increased p53, thus, suppressing cell proliferation and A549 xenograft growth in nude mice. Conclusions This study was novel in reporting that RPs bound to RPL11 to regulate the MDM2-p53 feedback loop, revealing that RPS27a plays an important function in LUAD growth. Hence, RPS27a might provide a diagnostic marker or therapeutic target for patients with LUAD.

BackgroundHigh NPRL2 (Nitrogen permease regulator-like 2) expression is a prognostic marker for poor clinical outcomes in prostate cancer (PCa). However, the regulatory mechanisms of NPRL2 in PCa remain unknown.MethodsThe expression level of NPRL2 in prostate cancer tissues were verified through The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. The effect of NPRL2 gene in promoting the proliferation of prostate cancer was determined by CCK8 and clone formation assays. The apoptosis rate and cell cycle analysis were tested by flow cytometry. Luciferase reporter gene and ChIP were used to verify the binding relationship between transcription factor c-Jun and the NPRL2 5’ region. The effect of NPRL2 and the MK2206 on the AKT/MDM2/p53 signaling pathway was verified by western blotting.ResultsNPRL2 expression level was significantly increased in prostate cancer tissues than normal tissues base on TCGA and GEO database. We investigated that transcription factor c-Jun can bind to the NPRL2 promoter and regulated NPRL2 transcription directly. Then, we revealed that NPRL2 significantly promotes proliferation and reduces apoptosis in PCa cells. Further mechanistic investigations revealed that NPRL2 mediated proliferation promotion effect is associated with the AKT/MDM2/p53 pathway's participation. Besides, CDK2 might serve as an intermediate effector for NPRL2 to regulate the AKT pathway. ConclusionTaken together, our study identified that c-Jun contributes to transcriptional control of NPRL2 and NPRL2 can promote prostate cancer proliferation by activating AKT/MDM2/p53 signaling.

Background This study aimed to investigate the aberrant expression of hsa_circ_0002874 in non-small cell lung cancer (NSCLC) and elucidate associated molecular mechanisms that influence apoptosis and induce paclitaxel (PTX) resistance. Methods Inhibitors were used to downregulate circRNA or miRNA expression. pCDNA plasmid transfection and mimics were used to upregulate circRNA or miRNA expression. Dual-luciferase reporter assays were conducted to evaluate interactions between miR1273f and MDM2. Xenograft tumor models were used to assess the effect of hsa_circ_0002874 and miR1273f on tumor growth. NSCLC tissues and matched non-cancerous tissues were also collected for correlation analysis. Results hsa_circ_0002874 acts as a sponge for miR1273f which targets MDM2/P53. The stability of the hsa_circ_0002874/miR1273f/MDM2/P53 pathway was verified by upregulating and downregulating the expression of hsa_circ_0002874 and miR1273f. hsa_circ_0002874 downregulation or miR1273f upregulation reversed the resistance of the A549/Taxol cells in xenograft models. The expression of hsa_circ_0002874 was high, and the level of MDM2 was low in NSCLC tissues. P53 was only weakly expressed in NSCLC tissues with high expression of MDM2. Conclusions hsa_circ_0002874 is strongly expressed in NSCLC tissues and maybe a potential marker for PTX resistance. hsa_circ_0002874 downregulation could regulate miR1273f/MDM2/P53 signaling pathway to reverse the PTX resistance of NSCLC and induce apoptosis in vitro and vivo.

Pituitary adenomas constitute one of the most common intracranial tumors. MicroRNAs play an important role in development and progression of pituitary adenomas. In this study, we showed that miR-219a-2-3p was significantly down-regulated in pituitary adenomas cells. Overexpression of miR-219a-2-3p suppressed the proliferation and promoted apoptosis of pituitary adenomas cells. After bioinformatics analysis, we found that MDM2 was one of the downstream targets of miR-219a-2-3p. Further researches showed that miR-219a-2-3p could reduce the protein level of MDM2 by binding to the 3ʹ-UTR of MDM2 and promoted p53 expression. Then, we overexpressed both miR-219a-2-3p and MDM2 in the same group and found that it could counteract the effect of overexpressing miR-219a-2-3p alone on proliferation and apoptosis of pituitary adenoma cells. Taken together, these results suggested that miR-219a-2-3p regulated the proliferation and apoptosis by targeting MDM2/p53 in pituitary adenomas. Therefore, miR-219a-2-3p may serve as a novel marker and therapeutic target for pituitary adenomas.

In tumor cells, p53 is always inactivated due to the mutation or deletion of TP53 gene or inhibited by the overexpressed MDM2. Small-molecule induced restoring of p53 function by blocking MDM2-p53 protein-protein interactions has been highly pursued as an attractive therapeutic strategy for cancer therapy. To date, a large number of small-molecule inhibitors have been identified based on the compact and well-defined MDM2-p53 interactions, of which SAR405838, MK-8242, DS-3032b, NVP-CGM097, RG7112, HDM201, RG7388, ALRN-6924 and AMG 232 are undergoing clinical assessment at different phases for cancer therapy. This review is focused on the discovery and development of piperidinone-based MDM2-p53 inhibitors for cancer therapy, including the identification of hit compounds, hit-to-lead optimizations, binding models of ligands in the active site of MDM2, metabolic studies, and preclinical data of advanced piperidinone-based MDM2-p53 inhibitors. Additionally, acquired resistance of MDM2 inhibitors and potential toxicity toward normal tissues are briefly discussed.

MDM2 is a key oncogenic protein that serves as a negative regulator of the tumor suppressor p53. While a number of inhibitors of the MDM2-p53 interaction have progressed to clinical testing as treatments for a variety of hematologic and solid tumor cancers, the results thus far have been mixed, with perhaps the strongest responses observed in relapsed/refractory acute myeloid leukemia (AML). In an effort to improve the efficacy for this class of compounds, researchers have turned to targeted degradation of MDM2. IMiD-based MDM2 PROTAC 8, which potently reduces MDM2 protein levels through targeted degradation, exhibits enhanced efficacy in the RS4;11 xenograft model relative to a nondegrading MDM2-p53 inhibitor MI-1061.

We present the first application of hydrophobic tagging to a non-covalent inhibitor of protein–protein interactions. Nutlin-3a-HT, created by fusing the hydrophobic tag HyT13 to the MDM2–p53 interaction inhibitor Nutlin-3a, prevented cellular accumulation of MDM2 upon p53 reactivation, and had a stronger effect on cell viability and the induction of apoptosis than Nutlin-3a.

3016 Background: BI 907828, a highly potent and orally administered MDM2-p53 antagonist, showed antitumor efficacy in vivo, especially in TP53 wild-type MDM2-amplified de-differentiated liposarcoma (DDLPS) patient-derived xenografts and syngeneic models. Methods: NCT03449381 is a phase I study of BI 907828 in pts with solid tumors. The objectives of the dose-escalation part were to determine the maximum tolerated dose (MTD) based on the frequency of pts with dose-limiting toxicities (DLTs) during cycle 1, determine the recommended dose for expansion, and evaluate the safety and tolerability of two dosing schedules: BI 907828 given on day 1 of 21-day cycles (Arm A) or days 1 and 8 of 28-day cycles (Arm B). Dose escalation was guided by a Bayesian logistic regression model. The secondary objectives include pharmacokinetics (PK), pharmacodynamics and antitumor activity. Results: At January 15, 2021, 54 pts with advanced solid tumors (median of 2 lines of prior systemic therapies; range 0–11) were treated with BI 907828 (Arm A, 29 pts, dose range 10–80 mg; Arm B, 25 pts, dose range 5–60 mg). In Arm A, 5 pts experienced DLTs in cycle 1, including one Grade (Gr) 3 Nausea and one Gr 3 Thrombocytopenia at 45 mg, one Gr 3 Enterocolitis at 60 mg, and one Gr 4 Neutropenia and one Gr 4 Thrombocytopenia at 80 mg. In Arm B, 3 DLTs were reported: one Gr 4 Thrombocytopenia at 45 mg, one Gr 4 Neutropenia associated with Gr 4 Thrombocytopenia, and one Gr 3 Neutropenia at 60 mg. The most common Gr 3/4 treatment-related adverse events (AEs) were Thrombocytopenia (28.6%), Neutropenia (10.7%) and Nausea (10.7%) in Arm A, and Thrombocytopenia (16.6%) and Neutropenia (12.5%) in Arm B. Preliminary PK data indicate that BI 907828 reaches Tmax at 4–6 h. Mean plasma exposures (Cmax and AUC0-inf) increased with dose. The geometric mean (gMean) Clearance/F was 5–19 mL/min and the gMean apparent volume of distribution was 23–57 L. The gMean half-lives estimated after the 1st dose were 26–55 h. Inter-patient variability in exposure was moderate. An increase in the target engagement biomarker GDF-15 in plasma was observed. The mean fold-change from baseline ranged from 8 to 49. Antitumor activity was seen in both schedules. In Arm A, a confirmed PR was seen in 2 pts with MDM2-amplified LPS (one PR lasted > 2 years) and SD in 17 pts. In Arm B, 2 pts had PR (one confirmed in MDM2-amplified LPS and one not yet confirmed in MDM2-amplified pancreatic adenocarcinoma) and 14 had SD. Of note, 5 of 10 pts with DDLPS were progression-free for ≥9 months. Conclusions: BI 907828 showed a manageable safety profile, favorable PK properties and early signs of efficacy, especially in MDM2-amplified tumors. With both dosing regimens, DLTs were Neutropenia and Thrombocytopenia. Non-hematologic AEs, mainly gastrointestinal, were mostly low-grade and not dose-limiting. The MTD of 60 mg in Arm A (day 1 of 21-day cycles) and 45 mg in Arm B (days 1 and 8 of 28-day cycles) are awaiting confirmation. Clinical trial information: NCT03449381.

11542 Background: APG-115 is a potent, small-molecule MDM2 inhibitor and immune modulator with promising antitumor activities in various tumors, especially those wild-type TP53 with MDM2 amplification ( TP53wt+MDM2 amp). To better delineate safety, optimal dosage, and potential target population, we report updated results. Methods: Patients with advanced liposarcoma and other solid tumors received APG-115 (100-200 mg) orally every other day for 21 days of a 28-day cycle. The primary endpoints were safety and tolerability. Efficacy (assessed by RECIST v1.1), pharmacokinetics (PK) and pharmacodynamics (PD) have also been analyzed. Results: Enrollment of this Phase I study (CTR20170975) was completed. As of January 7, 2020, 21 patients (14 liposarcomas, 2 synovial sarcomas, 2 adenoid cystic carcinomas, 1 chondrosarcoma, 1 osteosarcoma, 1 rhabdomyosarcoma) were treated in 3 dose levels of APG-115: 100 mg (n = 11), 150 mg (n = 8) and 200 mg (n = 2). The median number of cycles of APG-115 was 2 (0; 6). Two DLTs were observed at 200 mg, thrombocytopenia and febrile neutropenia. The most common treatment-emergent adverse events (TEAEs) (≥20%) included leukopenia, thrombocytopenia, neutropenia, anemia, increased blood creatinine, hypercholesterolemia, hypertriglyceridemia, hypoalbuminemia, vomiting, and nausea. The incidence of TEAEs was much lower at 100 mg. Serious AEs occurred in 5 patients (23.8%) which were assessed as possibly drug related by investigators. In 20 efficacy-evaluable patients, there was 1 patient with a partial response, 12 patients with stable disease, and 7 patients with progressive disease, yielding a disease control rate (CR, PR, SD) of 61.9%. Among the 13 patients (9 liposarcomas) who benefited, 11 had TP53wt and 7 had TP53wt+MDM2 amp, including one liposarcoma patient (150 mg) who had a PR, she was kept-up over 10 months, even though the treatment was discontinued for over 5 months, indicating the host immune modulatory effects of APG-115. Another patient with liposarcoma (100 mg, TP53wt+MDM2 amp) had 28.5% tumor shrinkage at cycle 4 and remained on treatment. PK results showed an approximately dose-proportional increase in exposure on Day 1. PK-PD analyses showed the serum macrophage inhibitory cytokine-1 (MIC-1) increased with increased APG-115 exposure. Conclusions: The phase I data have demonstrated that APG-115 monotherapy was well tolerated, with minimal toxicity at 100mg (RP2D), and conferred encouraging anti-tumor activities in patients with liposarcomas. Clinical trial information: CTR20170975 .

3124 Background: APG-115 is a novel and orally active small-molecule MDM2 inhibitor. APG-115 alone or in combination with chemotherapeutic, targeted or IO agents have shown potent antitumor activities in multiple human xenograft tumor models and human cancer patient derived xenograft (PDX) models. Methods: The patients with advanced solid tumors were enrolled in this study in China (CTR20170975). The study objectives were to assess safety, pharmacokinetics (PK), pharmacodynamics (PD) and antitumor activity of APG-115. The patients received APG-115 (ranging 100–200 mg) orally QOD for first 21 days of a 28-day-cycle, until disease progression. Antitumor response assessment was performed every 8 weeks per RECIST v1.1. Archived tumor tissues were collected for analyses of MDM2 and TP53 before treatment. Results: As cut-off on Jan 4 2019, total 13 patients (9 soft tissue sarcomas (STSs), 2 adenoid cystic carcinomas (ACCs) and 2 osteosarcomas) were treated in 3 cohorts of APG-115 (100mg, 150mg, 200mg). The median number of prior systemic anticancer therapies was 2 (range 0-4). Two DLTs were observed in one patient at 200mg including thrombocytopenia and febrile neutropenia. The most common TEAEs (≥50% of pts) included: anemia, thrombocytopenia, vomiting, hypercholesterolaemia, and leukopenia. SAEs occurred in 7 patients (54%), four of which were treatment related. The most common Grade 3 or 4 TRAEs were anemia (38.5%), thrombocytopenia (38.5%), leukopenia (30.8%), and neutropenia (23.1%). One partial response was observed in a liposarcoma patient with MDM2-amplification and TP53-wild type at the 150mg cohort, 5 patients (3 STSs, 2 ACCs) had SD as the best overall response. PK analyses indicated an approximately dose proportional increase in Cmax and AUC0-t following a single or multiple oral administration across dose levels. Preliminary PD data showed that serum MIC-1 increase was exposure dependent within the dose range tested. Conclusions: Preliminary data suggested that APG-115 had promising anti-tumor activity in treatment of patients with MDM2-amplification and TP53-WT liposarcoma. Safety profile and PD effect were consistent with other MDM2 inhibitors. Dosing regimen optimization are ongoing. Clinical trial information: CTR20170975.

TPS3166 Background: Inactivation of tumor protein 53 (TP53) is a central mechanism of tumors to promote survival and proliferation. The murine double minute 2 ( MDM2) oncogene is the primary cellular negative regulator of TP53. Small molecule inhibitors of the MDM2-p53 interaction are currently being evaluated in clinical trials as new anti-cancer drugs, and clinical data published to date support the rationale to target MDM2-amplified tumors. BI 907828 is a potent MDM2-p53 antagonist that has shown efficacy in mouse models of human cancer. Methods: NCT03449381 is a Phase 1a/1b, open-label, multicenter, dose-escalation trial of BI 907828 in patients aged ≥18 years with advanced/metastatic solid tumors. Primary objectives of the Phase 1a (dose-escalation) part are to determine: the maximum tolerated dose (MTD) of BI 907828 based on dose-limiting toxicities (DLTs) during the first treatment cycle; the recommended dose for expansion (RDE); safety and tolerability. Patients in Arm A will receive one dose of BI 907828 every 21 days, and patients in Arm B one dose on Days 1 and 8, every 28 days. Secondary objectives include pharmacokinetics (PK), pharmacodynamics (PD) [GDF-15 induction in plasma], and preliminary anti-tumor activity. Primary endpoints are the number of patients with DLTs during the first treatment cycle, and the MTD. Phase 1a will include ≈50 evaluable patients with locally advanced or metastatic solid tumors with either a known TP53 wild type (wt) status or unknown TP53 status, regardless of MDM2 amplification status at the time of study entry. The main objectives of Phase 1b (expansion cohorts) are to assess efficacy, safety, and PK profiles at the RDE, and to determine the recommended dose for Phase 2. The primary endpoint is objective response, where best response is determined according to RECIST v1.1, or RANO criteria for patients with glioblastoma. Phase 1b will include up to 150 evaluable patients with TP53 wt tumors, assigned to four different cohorts, including non-squamous NSCLC, soft tissue sarcoma, glioblastoma, urothelial carcinoma, and solid tumors with brain metastases. As of 8th February 2019, 11 patients have been enrolled. Clinical trial information: NCT03449381.

In response to cellular stress, the p53 tumor suppressor is activated to modulate cell cycle progression, DNA repair, and cell death. The activity of p53 is tightly regulated by MDM2, an E3 ubiquitin ligase that targets p53 for proteasomal degradation. Inhibition of the MDM2-p53 interaction in tumors carrying wild-type p53 can therefore reactivate p53 and elicit an anti-cancer effect. Small molecule inhibitors of the MDM2-p53 interaction remains a promising strategy for cancer therapy and a number of these compounds are in clinical development. An isoindolinone series, identified by the Northern Institute for Cancer Research (NICR), has been used as a starting point for the development of potent MDM2-p53 inhibitors. Structure based drug design was applied during lead optimisation to gain potency whilst also focusing on stabilizing the main metabolically labile position and reducing lipophilicity. This approach led to potent compounds with EC50 Citation Format: Lynsey Fazal, Maria Ahn, Luke Bevan, Ildiko Buck, Juan Castro, Gianni Chessari, Ben Cons, Keisha Hearn, Steven Howard, Chris Johnson, Judith Reeks, Emiliano Tamanini, Neil Thompson, Hugh Walton, Pamela Williams, Ruth H. Bawn, Tim J. Blackburn, Celine Cano, Sarah J. Cully, Bernard Golding, Roger Griffin, Karen Haggerty, Ian Hardcastle, Herbie Newell, Martin Noble, Huw Thomas, Elaine Willmore, Yan Zhao, Steve Wedge. Development of a potent class of small molecule inhibitors of the MDM2-p53 protein-protein interaction [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1652.

A primary failsafe program against unrestrained proliferation and oncogenesis is provided by the p53 tumor suppressor protein, inactivation of which is considered as a hallmark of cancer. Intriguingly, mutations of the TP53 gene are rarely encountered in neuroblastoma tumors, suggesting that alternative p53-inactivating lesions account for escape from p53 control in this childhood malignancy. Several recent studies have shed light on the mechanisms by which neuroblastoma cells circumvent the p53-driven antitumor barrier. We review here these mechanisms for evasion of p53-mediated growth control and conclude that deregulation of the p14(ARF)-MDM2-p53 axis seems to be the principal mode of p53 inactivation in neuroblastoma, opening new perspectives for targeted therapeutic intervention.

The p53 protein, a tumor suppressor, is inactivated in many human cancers through mutations or by its interaction with an oncoprotein, MDM2. Blocking the MDM2-p53 protein-protein interaction has the effect of activating wild-type p53 and has been pursued as a novel anticancer strategy. Small-molecule inhibitors of the MDM2-p53 interaction have been discovered through various approaches, and a number of them have progressed into clinical trials for cancer treatment. Here, we describe the methods and techniques used in the discovery of small-molecule inhibitors of the MDM2-p53 interaction.

OBJECTIVE To explore whether MDM2 transfection can alter the MDM2-p53 autoregulatory feedback loop so as to change the sensitivity of ovarian cancer cell lines to cisplatin.

Abnormalities in the TP53 gene and overexpression of MDM2, a transcriptional target and negative regulator of p53, are commonly observed in cancers. The MDM2–p53 feedback loop plays an important role in tumor progression and thus, increased understanding of the pathway has the potential to improve clinical outcomes for cancer patients. Hepatocellular carcinoma (HCC) has emerged as one of the most commonly diagnosed forms of human cancer; yet, the current treatment for HCC is less effective than those used against other cancers. We review the current studies of the MDM2–p53 pathway in cancer with a focus on HCC and specifically discuss the impact of p53 mutations along with other alterations of the MDM2–p53 feedback loop in HCC. We also discuss the potential diagnostic and prognostic applications of p53 and MDM2 in malignant tumors as well as therapeutic avenues that are being developed to target the MDM2–p53 pathway. Cancer Res; 74(24); 7161–7. ©2014 AACR.

Commentary to:A small molecule that disrupts Mdm2-p53 binding activates p53, induces apoptosis, and sensitizes lung cancer cells to chemotherapy Steven H. Sun, Min Zheng, Ke Ding, Shaomeng Wang, Yi Sun

The p53 tumor suppressor protein is a transcriptional factor that plays a key role in regulation of several cellular processes, including the cell cycle, apoptosis, DNA repair, and angiogenesis. The murine double minute 2 (MDM2) protein is the primary cellular inhibitor of p53, functioning through direct interaction with p53. Design of non-peptide, small-molecule inhibitors that block the MDM2-p53 interaction has been sought as an attractive strategy to activate p53 for the treatment of cancer and other human diseases. In recent years, major advances have been made in the design of small-molecule inhibitors of the MDM2-p53 interaction in recent years, and several compounds have moved into advanced preclinical development or clinical trials. In this chapter, we will highlight these advances in the design and development of MDM2 inhibitors, and discuss lessons learned from these efforts.

Prostate cancer: On the right path—Stat3 signalling controls the ARF–Mdm2–p53 tumour-suppressor pathway

Chronic Lymphocytic Leukaemia (CLL) is the most common adult leukaemia in the western world. It is a highly heterogenic disease with variable disease progression. One of the clearest indicators of poor prognosis in CLL is loss of p53 function via deletion of chromosome 17p13 (del17p) and mutation of TP53. Since TP53 mutation rates rise dramatically in treatment-refractory CLL, identifying TP53 mutations at diagnosis may aid treatment decisions. We have compared next generation (NGS) to Sanger sequencing to determine the optimal method and detection level for TP53 mutation in CLL and assess the clinical significance of small TP53-mutated subclones. Since the incidence of TP53 mutation is relatively low (approximately 10%) when first treatment of CLL is required, targeting the p53 pathway may present a treatment option. To investigate this possibility, primary CLL cells were exposed ex vivo to the MDM2-p53 antagonists Nut-3a, RG-7112 and RG-7388 which prevent the interaction between p53 and its inhibitor protein MDM2 to activate p53 leading to growth inhibition and cell death. We analysed genomic DNA from the CLL cells of 140 patients, including 36 with multiple samples from different stages of disease progression (median follow-up 10 years), by NGS using a ROCHE 454 GS-FLX pyrosequencing platform. In addition, 90 samples were previously screened for TP53 mutations by Sanger DNA sequencing. Full clinical diagnostic and outcome data was available. To assess the functional status of the MDM2-p53 pathway, the sensitivity of CLL cells to a range of non-genotoxic MDM2-p53 antagonists was evaluated. Kaplan Meier analysis of NGS data showed that patients with TP53 mutation+del17p had a median overall survival (OS) of 50 months compared to 140 months for wild type TP53 patients (HR = 2.8, CI 1.7-14.6; p = 0.003). 5% of patients harboured a monoallelic TP53 mutation in the absence of del17p, 2.1% had del17p without mutation on the remaining allele, and 9.3% had del17p+TP53 mutation. Interestingly, patients with del17p+TP53 mutation showed poorer survival than patients with TP53 mutation alone (HR 7.2, CI 1.2-14.6; p = 0.02). One patient with TP53 mutation alone has stable disease (10 years, no treatment) since detection of mutation. Four patients had TP53 mutant samples detected by NGS which were not detected by Sanger sequencing. In addition TP53 WT CLL cells showed a cytotoxic response to MDM2-p53 antagonists (RG-7388 LC50 0.4±0.08 μM, n = 11) whereas TP53 mutant CLL cells were 11 fold less sensitive (RG-7388 LC50 4.58±1.36 μM, n = 3) as determined by XTT assay following 48 hour treatment. NGS is a more sensitive method for detection of TP53 mutations compared with Sanger sequencing. Patients with TP53 mutation alone in the absence of del17p display longer OS compared to patients with del17p+TP53 mutation. In addition, MDM2-p53 antagonists provide a potential future treatment option in TP53 WT CLL. Citation Format: Laura Woodhouse, Clark Crawford, Scott Marshall, Nick Bown, Jonathan Wallis, Geoffrey Summerfield, Elaine Willmore, John Lunec. Assessment and targeting of the MDM2-p53 network in CLL. [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 5263. doi:10.1158/1538-7445.AM2015-5263

The p53 tumor suppressor is controlled by MDM2, which binds p53 and negatively regulates its transcriptional activity and stability. Many tumors overproduce MDM2 to impair p53 function. Therefore, restoration of p53 activity by inhibiting the p53-MDM2 binding represents an attractive novel approach to cancer therapy. We previously reported the discovery AM-8553, a potent and selective piperidinone inhibitor of the MDM2-p53 interaction (Rew et al. J. Med. Chem. 2012, 55, 4936). We report here continued research on the N-alkyl substituent of this series, focused in particular on a previously underutilized interaction in a shallow cleft on the MDM2 surface that led to the discovery of variety of sulfonamides and sulfones which gave rise to substantial improvements in biochemical and cellular potency. Further work led to discovery of AMG 232, which is currently being evaluated in human clinical trials for the treatment of cancer. AMG 232 is an extremely potent MDM2 inhibitor (SPR KD = 0.045 nM, SJSA-1 EdU IC50 = 9.1 nM), with remarkable pharmacokinetic properties. The compound interacts specifically with the p53-binding pocket of MDM2 and releases the p53 protein from negative control. Treatment of cancer cells expressing wild-type p53 with AMG 232, stabilizes p53 and activates the p53 pathway, leading to cell cycle arrest and apoptosis. The compound showed excellent efficacy in a number of mouse tumor xenograft models and was well tolerated in preclinical toxicology studies at therapeutically relevant dosages. Citation Format: Zhihong Li. Discovery of AMG 232, an inhibitor of the MDM2-p53 interaction: From lead to a clinical candidate. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1645. doi:10.1158/1538-7445.AM2014-1645

Avoiding the inhibitory effects of p53 on cell growth is important for tumor progression. In this issue of Cancer Cell, Picchiorri et al. describe epigenetic silencing of MDM2-targeting microRNAs in multiple myeloma (MM), which generally appears to have intact p53 function. This provides the rationale for microRNA-targeted therapy for MM.

The murine double minutes 2 (MDM2) oncoprotein inhibits p53-mediated tumor suppression. MDM2 has been shown to be overexpressed in sarcomas and more recently was implicated in the pathogenesis of carcinomas. The purpose of this study was to determine the expression pattern of MDM2 in adenomas and colorectal adenocarcinomas and decide whether there is a correlation between MDM2 and p53 protein status. Paraffin-embedded tissues from 52 colorectal cancer (CRC) specimens and their adjacent normal tissue (N-CRC) were studied. In addition, 56 sporadic adenomas were investigated for the immunohistochemical expression of MDM2 and p53 proteins. Immunoreactivity of p53 indicating p53 gene mutation (p53 +) was significantly higher in CRC (44%) compared to adenomas (23.2%) (P