MDM2 Inhibitors for Cancer Therapy: The Past, Present, and Future.

Since its discovery over 35 years ago, MDM2 has emerged as an attractive target for the development of cancer therapy. MDM2's activities extend from carcinogenesis to immunity to the response to various cancer therapies. Since the report of the first MDM2 inhibitor more than 30 years ago, various approaches to inhibit MDM2 have been attempted, with hundreds of small-molecule inhibitors evaluated in preclinical studies and numerous molecules tested in clinical trials. Although many MDM2 inhibitors and degraders have been evaluated in clinical trials, there is currently no Food and Drug Administration (FDA)-approved MDM2 inhibitor on the market. Nevertheless, there are several current clinical trials of promising agents that may overcome the past failures, including agents granted FDA orphan drug or fast-track status. We herein summarize the research efforts to discover and develop MDM2 inhibitors, focusing on those that induce MDM2 degradation and exert anticancer activity, regardless of the p53 status of the cancer. We also describe how preclinical and clinical investigations have moved toward combining MDM2 inhibitors with other agents, including immune checkpoint inhibitors. Finally, we discuss the current challenges and future directions to accelerate the clinical application of MDM2 inhibitors. In conclusion, targeting MDM2 remains a promising treatment approach, and targeting MDM2 for protein degradation represents a novel strategy to downregulate MDM2 without the side effects of the existing agents blocking p53-MDM2 binding. Additional preclinical and clinical investigations are needed to finally realize the full potential of MDM2 inhibition in treating cancer and other chronic diseases where MDM2 has been implicated. SIGNIFICANCE STATEMENT: Overexpression/amplification of the MDM2 oncogene has been detected in various human cancers and is associated with disease progression, treatment resistance, and poor patient outcomes. This article reviews the previous, current, and emerging MDM2-targeted therapies and summarizes the preclinical and clinical studies combining MDM2 inhibitors with chemotherapy and immunotherapy regimens. The findings of these contemporary studies may lead to safer and more effective treatments for patients with cancers overexpressing MDM2.

An anti-GD2 aptamer-based bifunctional spherical nucleic acid nanoplatform for synergistic therapy targeting MDM2 for retinoblastoma.

Retinoblastoma (RB) is a type of pediatric solid tumor in the fundus. The lack of precision therapies combined with the difficulty of delivering small interfering RNA (siRNA) into the eyes means that there is currently no nucleic acid-based therapy for RB in clinical practice. Here, we reported on anti-GD2 and glutathione-responsive spherical nucleic acids (SNAs), loaded with siRNA and the inhibitor NVP-CGM097, which jointly blocked the oncogenic factor n in RB cells (Y79 and WERI-RB-1). The SNAs were formed through the self-assembly of bifunctional cholesterol amphiphiles containing aptamers that specifically targeted GD2-positive RB cells, allowing for the formation of an SNA with a dense DNA shell. The aptamer/siRNA component functioned both as a carrier and a payload, enhancing the specific recognition and delivery of both components and constituting an active agent for MDM2 regulation. Following SNA endocytosis by RB cells, siRNA and NVP-CGM097 were released from the SNA particles by glutathione, which synergistically blocked the MDM2-p53 pathway, increasing p53 protein content and inducing cell apoptosis. This study showed a potent antitumor effect following intravitreal injection of SNAs in Y79 tumor-bearing mice through clinical manifestation and tumor pathological analysis. In hematological analysis and hepatotoxicity assays, SNAs were safer for mice than melphalan, the favored drug for treating RB in clinical practice. Our results illustrated the potential of intravitreally injected SNAs as a precision medicine for treating RB.

Targeting MDM2 in malignancies is a promising strategy for overcoming resistance to anticancer immunotherapy.

MDM2 has been established as a biomarker indicating poor prognosis for individuals undergoing immune checkpoint inhibitor (ICI) treatment for different malignancies by various pancancer studies. Specifically, patients who have MDM2 amplification are vulnerable to the development of hyperprogressive disease (HPD) following anticancer immunotherapy, resulting in marked deleterious effects on survival rates. The mechanism of MDM2 involves its role as an oncogene during the development of malignancy, and MDM2 can promote both metastasis and tumor cell proliferation, which indirectly leads to disease progression. Moreover, MDM2 is vitally involved in modifying the tumor immune microenvironment (TIME) as well as in influencing immune cells, eventually facilitating immune evasion and tolerance. Encouragingly, various MDM2 inhibitors have exhibited efficacy in relieving the TIME suppression caused by MDM2. These results demonstrate the prospects for breakthroughs in combination therapy using MDM2 inhibitors and anticancer immunotherapy.

SF3B1 Mutations Are Associated with Resistance to Non-Genotoxic MDM2 Inhibition in Chronic Lymphocytic Leukemia.

Chronic lymphocytic leukemia (CLL) is a genetically and clinically heterogeneous malignancy affecting older individuals. There are a number of current treatment options for CLL, including monoclonal antibodies, targeted drugs, chemotherapy, and different combinations of these. However, for those patients who are intrinsically treatment resistant, or relapse following initial responses, novel targeted therapies are still needed. Targeting the mouse double-minute-2 human homolog (MDM2), a primary negative regulator of p53, is an appealing therapeutic strategy for non-genotoxic reactivation of p53, since the TP53 gene is in its wild-type state at diagnosis in approximately 90% of patients. Mutated SF3B1 and TP53 are both associated with more aggressive disease, resistance to therapies and poorer overall survival for CLL. In this study, we performed a screen for SF3B1 and TP53 mutations and tested RG7388 (idasanutlin), a second-generation MDM2 inhibitor, in a cohort of CLL primary patient samples. SF3B1 mutations were detected in 24 of 195 cases (12.3%) and found associated with poor overall survival (hazard ratio [HR] 2.12, p = 0.032) and high CD38 expression (median CD38 (%) 32 vs. 5; p = 0.0087). The novel striking finding of this study was an independent link between SF3B1 mutational status and poor response to RG7388. Overall, SF3B1 mutations in CLL patient samples were associated with resistance to treatment with RG7388 ex vivo, and patients with the wild type for both SF3B1 and TP53 are more likely to benefit from treatment with MDM2 inhibitors.

In Vitro/In Vivo Translation of Synergistic Combination of MDM2 and MEK Inhibitors in Melanoma Using PBPK/PD Modelling: Part II.

The development of in vitro/in vivo translational methods for synergistically acting drug combinations is needed to identify the most effective therapeutic strategies. We performed PBPK/PD modelling for siremadlin, trametinib, and their combination at various dose levels and dosing schedules in an A375 xenografted mouse model (melanoma cells). In this study, we built models based on in vitro ADME and in vivo PK/PD data determined from the literature or estimated by the Simcyp Animal simulator (V21). The developed PBPK/PD models allowed us to account for the interactions between siremadlin and trametinib at PK and PD levels. The interaction at the PK level was described by an interplay between absorption and tumour disposition levels, whereas the PD interaction was based on the in vitro results. This approach allowed us to reasonably estimate the most synergistic and efficacious dosing schedules and dose levels for combinations of siremadlin and trametinib in mice. PBPK/PD modelling is a powerful tool that allows researchers to properly estimate the in vivo efficacy of the anticancer drug combination based on the results of in vitro studies. Such an approach based on in vitro and in vivo extrapolation may help researchers determine the most efficacious dosing strategies and will allow for the extrapolation of animal PBPK/PD models into clinical settings.

Milademetan is a highly potent MDM2 inhibitor in Merkel cell carcinoma.

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine carcinoma of the skin with 2 etiologies. Merkel cell polyomavirus (MCPyV) integration is present in about 80% of all MCC. Virus-positive MCC (MCCP) tumors have few somatic mutations and usually express WT p53 (TP53). By contrast, virus-negative MCC (MCCN) tumors present with a high tumor mutational burden and predominantly UV mutational signature. MCCN tumors typically contain mutated TP53. MCCP tumors express 2 viral proteins: MCPyV small T antigen and a truncated form of large T antigen. MCPyV ST specifically activates expression of MDM2, an E3 ubiquitin ligase of p53, to inhibit p53-mediated tumor suppression. In this study, we assessed the efficacy of milademetan, a potent, selective, and orally available MDM2 inhibitor in several MCC models. Milademetan reduced cell viability of WT p53 MCC cell lines and triggered a rapid and sustained p53 response. Milademetan showed a dose-dependent inhibition of tumor growth in MKL-1 xenograft and patient-derived xenograft models. Here, along with preclinical data for the efficacy of milademetan in WT p53 MCC tumors, we report several in vitro and in vivo models useful for future MCC studies.

Murine Double Minute 2 Antagonist Nutlin-3 Enhanced Chemosensitivity in Esophageal Squamous Cell Carcinoma.

BACKGROUND/AIM: Murine double minute 2 (MDM2) is well known to inhibit p53 function and its over-expression is associated with poor prognosis in several human malignancies. Nutlin-3, a small-molecule inhibitor of MDM2, exerts antitumor effects on various solid tumors harboring wild-type p53. We aimed to clarify its effects on esophageal cancer. MATERIALS AND METHODS: We first examined the potential antitumor effects of nutlin-3 according to MDM2 status using esophageal carcinoma cell lines (KYSE 170/180). We then immunolocalized MDM2 immunoreactivity in 62 surgical cases of esophageal squamous cell carcinoma undergoing neoadjuvant chemotherapy followed by esophagectomy and correlated the findings with clinicopathological variables. RESULTS: MDM2 mRNA expression in KYSE 170 was significantly higher than that in KYSE 180 cells. No significant changes were detected in both cell lines when nutlin-3 was added. However, cell proliferation was significantly decreased in KYSE 170 cells treated with nutlin-3 and cisplatin compared to cisplatin alone but not in KYSE 180. MDM2 immunoreactivity was also significantly associated with poor sensitivity to neoadjuvant chemotherapy in the cases examined. CONCLUSION: The combination of nutlin-3 with chemotherapeutic agents may become a novel therapeutic strategy in esophageal cancer over-expressing MDM2.

2-Methoxy-5((3,4,5-trimethosyphenyl) seleninyl) phenol causes G2/M cell cycle arrest and apoptosis in NSCLC cells through mitochondrial apoptotic pathway and MDM2 inhibition.

Nonsmall cell lung cancer (NSCLC) is one of the most common malignancies and needs novel and effective chemotherapy. In this study, our purpose is to explore the anticancer effects of 2-methoxy-5((3,4,5-trimethosyphenyl) seleninyl) phenol (SQ) on human NSCLC (A549 and H460) cells. We found that SQ suppressed the proliferation of NSCLC cells in time- and dose-dependent manners, and blocked the cells at G2/M phase, which was relevant to microtubule depolymerization. Additionally, SQ induced A549 and H460 cell apoptosis by activating the mitochondrial apoptotic pathway. Further, we demonstrated that SQ enhanced the generation of reactive oxygen species (ROS), and pretreatment with N-acetyl- L-cysteine (NAC) attenuated SQ-induced cell apoptosis. Meanwhile, SQ mediated-ROS generation caused DNA damage in A549 and H460 cells. Our data also revealed that SQ-induced apoptosis was correlated with the inhibition of mouse double minute 2 (MDM2) in A549 and H460 cells. In summary, our research indicates that the novel compound SQ has great potential for therapeutic treatment of NSCLC in future.

Phe19 modification of HDM2-p53 PPI inhibitors to alleviate CYP3A4 metabolism/mechanism-based inhibition liability.

The discovery of potent, bioavailable small molecule inhibitors of p53-HDM2 PPI led us to investigate subsequent modifications to address a CYP3A4 time-dependent inhibition liability. On the basis of the crystal structure of HDM2 in complex with 2, further functionalization of the solvent exposed area of the molecule that binds to Phe19 pocket were investigated as a strategy to modulate the molecule liphophilicity. Introduction of 2-oxo-nicotinic amide at Phe19 proved a viable strategy in obtaining inhibitors exempt from CYP3A4 time-dependent inhibition liability.

Combined MEK/MDM2 inhibition demonstrates antitumor efficacy in TP53 wild-type thyroid and colorectal cancers with MAPK alterations.

Most tumors with activating MAPK (mitogen-activated protein kinase) pathway alterations respond poorly to MEK inhibitors alone. Here, we evaluated combination therapy with MEK inhibitor selumetinib and MDM2 inhibitor KRT-232 in TP53 wild-type and MAPK altered colon and thyroid cancer models. In vitro, we showed synergy between selumetinib and KRT-232 on cell proliferation and colony formation assays. Immunoblotting confirmed p53 upregulation and MEK pathway inhibition. The combination was tested in vivo in seven patient-derived xenograft (PDX) models (five colorectal carcinoma and two papillary thyroid carcinoma models) with different KRAS, BRAF, and NRAS mutations. Combination therapy significantly prolonged event-free survival compared with monotherapy in six of seven models tested. Reverse-phase protein arrays and immunohistochemistry, respectively, demonstrated upregulation of the p53 pathway and in two models cleaved caspase 3 with combination therapy. In summary, combined inhibition of MEK and MDM2 upregulated p53 expression, inhibited MAPK signaling and demonstrated greater antitumor efficacy than single drug therapy in both in vitro and in vivo settings. These findings support further clinical testing of the MEK/MDM2 inhibitor combination in tumors of epithelial origin with MAPK pathway alterations.

Hinokiflavone, as a MDM2 inhibitor, activates p53 signaling pathway to induce apoptosis in human colon cancer HCT116 cells.

Hinokiflavone (HF), a natural biflavonoid that possesses various biological activities, has reported that HF could be a pre-mRNA splicing modulator, whereas its underlying mechanisms remain elusive. In the present study, we identified HF as a potential MDM2 inhibitor. What's more, we found that HF suppressed mdm2 mRNA synthesis at the transcriptional level. Then, this MDM2 inhibition led in turn to increase p53 protein expression and activate p53 pathway, which could decrease the survival of HCT116 colon cells by G2/M phase arrest and apoptosis induction. Then, bioinformatics suggested that ESR1 was a predicted and potential target of HF. Finally, we used molecular docking and molecular dynamics simulation to demonstrate the binding patterns of HF and ESR1. To sum up, our study unearthed that HF was a feasible agent for MDM2 inhibitor through down-regulating mdm2 RNA level and activating p53 signaling pathway.

Targeting p53 for the treatment of cancer.

Dysfunction of the TP53 (p53) gene occurs in most if not all human malignancies. Two principal mechanisms are responsible for this dysfunction; mutation and downregulation of wild-type p53 mediated by MDM2/MDM4. Because of its almost universal inactivation in malignancy, p53 is a highly attractive target for the development of new anticancer drugs. Although multiple strategies have been investigated for targeting dysfunctional p53 for cancer treatment, only 2 of these have so far yielded compounds for testing in clinical trials. These strategies include the identification of compounds for reactivating the mutant form of p53 back to its wild-type form and compounds for inhibiting the interaction between wild-type p53 and MDM2/MDM4. Currently, multiple p53-MDM2/MDM4 antagonists are undergoing clinical trials, the most advanced being idasanutlin which is currently undergoing testing in a phase III clinical trial in patients with relapsed or refractory acute myeloid leukemia. Two mutant p53-reactivating compounds have progressed to clinical trials, i.e., APR-246 and COTI-2. Although promising data has emerged from the testing of both MDM2/MDM4 inhibitors and mutant p53 reactivating compounds in preclinical models, it is still unclear if these agents have clinical efficacy. However, should any of the compounds currently being evaluated in clinical trials be shown to have efficacy, it is likely to usher in a new era in cancer treatment, especially as p53 dysfunction is so prevalent in human cancers.

The Discovery of Potential MDM2 Inhibitors: A Combination of Pharmacophore Modeling, Virtual Screening, Molecular Docking Studies, and in†vitro/in†vivo Biological Evaluation.

Small-molecule inhibitors of MDM2 that block the MDM2-p53 protein-protein interaction have been considered as potential therapeutic agents for the treatment of cancer. Here, we identify five highly potent inhibitors of MDM2 (termed as WY 1-5) that display significant inhibitory effects on MDM2-p53 interaction by using a combined strategy of pharmacophore modeling, virtual screening, and molecular docking studies. Among them, WY-5 is the most active MDM2 inhibitor with an IC50 value of 14.1±2.8 nM. Moreover, WY-5 significantly up-regulate the protein level of p53 in SK-Hep-1 cells harboring wild-type p53. In vitro anticancer study reveals that WY-5 markedly inhibits the survival of SK-Hep-1 cells. In vivo anticancer study suggests that WY-5 significantly inhibits the growth of SK-Hep-1 cells-derived xenograft in nude mice, with no observable toxicity. Our results demonstrate that WY-5 may be a promising candidate for the treatment of cancer harboring wild-type p53.

Resistance mechanisms to inhibitors of p53-MDM2 interactions in cancer therapy: can we overcome them?

Since the discovery of the first MDM2 inhibitors, we have gained deeper insights into the cellular roles of MDM2 and p53. In this review, we focus on MDM2 inhibitors that bind to the p53-binding domain of MDM2 and aim to disrupt the binding of MDM2 to p53. We describe the basic mechanism of action of these MDM2 inhibitors, such as nutlin-3a, summarise the determinants of sensitivity to MDM2 inhibition from p53-dependent and p53-independent points of view and discuss the problems with innate and acquired resistance to MDM2 inhibition. Despite progress in MDM2 inhibitor design and ongoing clinical trials, their broad use in cancer treatment is not fulfilling expectations in heterogenous human cancers. We assess the MDM2 inhibitor types in clinical trials and provide an overview of possible sources of resistance to MDM2 inhibition, underlining the need for patient stratification based on these aspects to gain better clinical responses, including the use of combination therapies for personalised medicine.

Molecular hybridization design and synthesis of novel spirooxindole-based MDM2 inhibitors endowed with BCL2 signaling attenuation; a step towards the next generation p53 activators.

Despite the achieved progress in developing efficient MDM2-p53 protein-protein interaction inhibitors (MDM2 inhibitors), the acquired resistance of tumor cells to such p53 activators posed an argument about the druggability of the pathway. Combination studies disclosed that concomitant inhibition of MDM2 and BCL2 functions can sensitize the tumor cells and synergistically induce apoptosis. Herein, we employed a rapid combinatorial approach to generate a novel series of hybrid spirooxindole-based MDM2 inhibitors (5a-s) endowed with BCL2 signaling attenuation. The adducts were designed to mimic the thematic features of the chemically stable potent spiro[3H-indole-3,2'-pyrrolidin]-2(1H)-ones MDM2 inhibitors while installing a pyrrole ring on the core via a carbonyl spacer inspired by the natural product marinopyrrole A that efficiently inhibits BCL2 family functions by various mechanisms. NCI 60 cell-line panel screening revealed their promising broad-spectrum antiproliferative activities. The NCI-selected derivatives were screened for cytotoxic activities against normal fibroblasts, MDA-MB 231, HepG-2, and Caco-2 cells via MTT assay, subjected to mechanistic apoptosis studies for assessment of p53, BCL2, p21, and caspase 3/7 status, then evaluated for potential MDM2 inhibition utilizing MST assay. The most balanced potent and safe derivatives; 5i and 5q were more active than 5-fluorouracil, exhibited low µmrange MDM2 binding (KD=1.32and 1.72 µm, respectively), induced apoptosis-dependent anticancer activities up to 50%, activated p53 by 47-63%, downregulated the BCL2 gene to 59.8%, and reduced its protein level (13.75%) in the treated cancer cells. Further downstream p53 signaling studies revealed > 2 folds p21 upregulation and > 3 folds caspase 3/7 activation. Docking simulations displayed that the active MDM2 inhibitors resided well into the p53 binding sites of MDM2, and shared key interactions with the co-crystalized inhibitor posed by the indolinone scaffold (5i, 5p, and 5q), the halogen substituents (5r), or the installed spiro ring (5s). Finally, in silico ADMET profiling predicted acceptable drug-like properties with full accordance to Lipinski's, Veber's, and Muegge's bioavailability parameters for 5i and a single violation for 5q.

TP53 wild-type/PPM1D mutant diffuse intrinsic pontine gliomas are sensitive to a MDM2 antagonist.

Diffuse intrinsic pontine gliomas (DIPGs) are high-grade tumors of the brainstem that often occur in children, with a median overall survival of less than one year. Given the fact that DIPGs are resistant to chemotherapy and are not amenable to surgical resection, it is imperative to develop new therapeutic strategies for this deadly disease. The p53 pathway is dysregulated by TP53 (~ 60%) or PPM1D gain-of-function mutations (~ 30%) in DIPG cases. PPM1D gain-of-function mutations suppress p53 activity and result in DIPG tumorigenesis. While MDM2 is a major negative regulator of p53, the efficacy of MDM2 inhibitor has not been tested in DIPG preclinical models. In this study, we performed a comprehensive validation of MDM2 inhibitor RG7388 in patient-derived DIPG cell lines established from both TP53 wild-type/PPM1D-mutant and TP53 mutant/PPM1D wild-type tumors, as well in TP53 knockout isogenic DIPG cell line models. RG7388 selectively inhibited the proliferation of the TP53 wild-type/PPM1D mutant DIPG cell lines in a dose- and time-dependent manner. The anti-proliferative effects were p53-dependent. RNA-Seq data showed that differential gene expression induced by RG7388 treatment was enriched in the p53 pathways. RG7388 reactivated the p53 pathway and induced apoptosis as well as G1 arrest. In vivo, RG7388 was able to reach the brainstem and exerted therapeutic efficacy in an orthotopic DIPG xenograft model. Hence, this study demonstrates the pre-clinical efficacy potential of RG7388 in the TP53 wild-type/PPM1D mutant DIPG subgroup and may provide critical insight on the design of future clinical trials applying this drug in DIPG patients.

Discovery of MK-4688: an Efficient Inhibitor of the HDM2-p53 Protein-Protein Interaction.

Identification of low-dose, low-molecular-weight, drug-like inhibitors of protein-protein interactions (PPIs) is a challenging area of research. Despite the challenges, the therapeutic potential of PPI inhibition has driven significant efforts toward this goal. Adding to recent success in this area, we describe herein our efforts to optimize a novel purine carboxylic acid-derived inhibitor of the HDM2-p53 PPI into a series of low-projected dose inhibitors with overall favorable pharmacokinetic and physical properties. Ultimately, a strategy focused on leveraging known binding hot spots coupled with biostructural information to guide the design of conformationally constrained analogs and a focus on efficiency metrics led to the discovery of MK-4688 (compound 56), a highly potent, selective, and low-molecular-weight inhibitor suitable for clinical investigation.

Fluorine-18 Labeling of the MDM2 Inhibitor RG7388 for PET Imaging: Chemistry and Preliminary Evaluation.

RG7388 (Idasanutlin) is a potent inhibitor of oncoprotein murine double minute 2 (MDM2). Herein we investigated the feasibility of developing 18F-labeled RG7388 as a radiotracer for imaging MDM2 expression in tumors with positron emission tomography (PET). Two fluorinated analogues of RG7388, 6 and 7, were synthesized by attaching a fluoronicotinyl moiety to RG7388 via a polyethylene glycol (PEG3) or a propyl linker. The inhibitory potency (IC50) of 6 and 7 against MDM2 was determined by a fluorescence polarization (FP)-based assay. Next, compound 6 was labeled with 18F using a trimethylammonium triflate precursor to obtain [18F]FN-PEG3-RG7388 ([18F]6), and its properties were evaluated in MDM2 expressing wild-type p53 tumor cell lines (SJSA-1 and HepG2) in vitro and in tumor xenografts in vivo. The FP assays revealed an IC50 against MDM2 of 119 nM and 160 nM for 6 and 7, respectively. 18F-labeling of 6 was achieved in 50.3 ± 7.5% radiochemical yield. [18F]6 exhibited a high uptake (∼70% of input dose) and specificity in SJSA-1 and HepG2 cell lines. Saturation binding assays revealed a binding affinity (Kd) of 128 nM for [18F]6 on SJSA-1 cells. In mice, [18F]6 showed fast clearance from blood with a maximum tumor uptake of 3.80 ± 0.85% injected dose per gram (ID/g) in HepG2 xenografts at 30 min postinjection (p.i.) and 1.32 ± 0.32% ID/g in SJSA-1 xenografts at 1 h p.i. Specificity of [18F]6 uptake in tumors was demonstrated by pretreatment of mice with SJSA-xenografts with a blocking dose of RG7388 (35 mg/kg body weight, i.p.). In vivo stability studies in mice using HPLC showed ∼60% and ∼30% intact [18F]6 remaining in plasma at 30 min and 1 h p.i., respectively, with the remaining activity attributed to polar peaks. Our results suggest that RG7388 is a promising molecular scaffold for 18F-labeled probe development for MDM2. Additional labeling strategies and functionalizing locations on RG7388 are under development to improve binding affinity and in vivo stability of the 18F-labeled compound to make it more amenable for PET imaging of MDM2 in vivo.

A Supramolecular Nanomedicine Based on Bendamustine and MDM2-Targeted D-peptide Inhibitor for Breast Cancer Therapy.

Bendamustine (BEN) is a FDA-approved bifunctional DNA-alkylating chemotherapy drug, but it suffers from short half-life, instability, and poor biocompatibility in the clinical application. Due to unique biostability of d-amino acid-containing peptides (D-peptides), constructing D-peptide-small molecule drug conjugates is emerging as a promising strategy for cancer therapy. Here, a high-affinity MDM2-targeted D-peptide (peptide 5) is discovered by applying structure-based drug design (SBDD). Taking the advantages of d-amino acids, a novel self-assembling D-peptide-small molecule drug conjugate (BEN-FF-peptide 5) is developed by simultaneously conjugating small molecule drug BEN and peptide 5 to the self-assembling peptide. In vitro results demonstrate that BEN-FF-peptide 5 exhibits superior cellular uptake ability, good biostability in human serum and strong inhibitory effect on the growth of human breast cancer (MCF-7) cells. In vivo study reveals that BEN-FF-peptide 5 significantly inhibits the growth of MCF-7 cells-derived xenograft in nude mice with no obvious side effects. This work provides a useful strategy to construct D-peptide-small molecule drug conjugates for high-efficacy and low-toxicity cancer therapy.

Recent advances on the intervention sites targeting USP7-MDM2-p53 in cancer therapy.

The ubiquitin-specific protease 7 (USP7)-murine double minute 2 (MDM2)-p53 network plays an important role in the regulation of p53, a tumor suppressor which plays critical roles in regulating cell growth, proliferation, cell cycle progression, apoptosis and immune response. The overexpression of USP7 and MDM2 in human cancers contributes to cancer initiation and progression, and their inhibition reactivates p53 signalings and causes cell cycle arrest and apoptosis. Herein, the current state of pharmacological characterization, potential applications in cancer treatment and mechanism of action of small molecules used to target and inhibit MDM2 and USP7 proteins are highlighted, along with the outcomes in clinical and preclinical settings. Moreover, challenges and advantages of these strategies, as well as perspectives in USP7-MDM2-p53 field are analyzed in detail. The investigation and application of MDM2 and USP7 inhibitors will deepen our understanding of the function of USP7-MDM2-p53 network, and feed in the development of effective and safe cancer therapies where USP7-MDM2-p53 network is implicated.