MIRROS: a randomized, placebo-controlled, Phase III trial of cytarabine ± idasanutlin in relapsed or refractory acute myeloid leukemia

p53 rapidly restructures 3D chromatin organization to trigger a transcriptional response

Activation of the p53 tumor suppressor triggers a transcriptional program to control cellular response to stress. However, the molecular mechanisms by which p53 controls gene transcription are not completely understood. Here, we uncover the critical role of spatio-temporal genome architecture in this process. We demonstrate that p53 drives direct and indirect changes in genome compartments, topologically associating domains, and DNA loops prior to one hour of its activation, which escort the p53 transcriptional program. Focusing on p53-bound enhancers, we report 340 genes directly regulated by p53 over a median distance of 116 kb, with 74% of these genes not previously identified. Finally, we showcase that p53 controls transcription of distal genes through newly formed and pre-existing enhancer-promoter loops in a cohesin dependent manner. Collectively, our findings demonstrate a previously unappreciated architectural role of p53 as regulator at distinct topological layers and provide a reliable set of new p53 direct target genes that may help designs of cancer therapies.

Advancements in MDM2 inhibition: Clinical and pre-clinical investigations of combination therapeutic regimens

Cancer cells often depend on multiple pathways for their growth and survival, resulting in therapeutic resistance and the limited effectiveness of treatments. Combination therapy has emerged as a favorable approach to enhance treatment efficacy and minimize acquired resistance and harmful side effects. The murine double minute 2 (MDM2) protein regulates cellular proliferation and promotes cancer-related activities by negatively regulating the tumor suppressor protein p53. MDM2 aberrations have been reported in a variety of human cancers, making it an appealing target for cancer therapy. As a result, several small-molecule MDM2 inhibitors have been developed and are currently being investigated in clinical studies. Nevertheless, it has been shown that the inhibition of MDM2 alone is inadequate to achieve long-term suppression of tumor growth, thus prompting the need for further investigation into combination therapeutic strategies. In this review, possible clinical and preclinical MDM2 combination inhibitor regimens are thoroughly analyzed and discussed. It provides a rationale for combining MDM2 inhibitors with other therapeutic approaches in the management of cancer, taking into consideration ongoing clinical trials that evaluate the combination of MDM2 inhibitors. The review explores the current status of MDM2 inhibitors in combination with chemotherapy or targeted therapy, as well as promising approach of combining MDM2 inhibitors with immunotherapy. In addition, it investigates the function of PROTACs as MDM2 degraders in cancer treatment. A comprehensive examination of these combination regimens highlights the potential for advancing MDM2-inhibitor therapy and improving clinical outcomes for cancer patients and establishes the foundation for future research and development in this promising area of study.

Differential Susceptibility of Ex Vivo Primary Glioblastoma Tumors to Oncolytic Effect of Modified Zika Virus

Glioblastoma (GBM), the most common primary malignant brain tumor, is a highly lethal form of cancer with a very limited set of treatment options. High heterogeneity in the tumor cell population and the invasive nature of these cells decrease the likely efficacy of traditional cancer treatments, thus requiring research into novel treatment options. The use of oncolytic viruses as potential therapeutics has been researched for some time. Zika virus (ZIKV) has demonstrated oncotropism and oncolytic effects on GBM stem cells (GSCs). To address the need for safe and effective GBM treatments, we designed an attenuated ZIKV strain (ZOL-1) that does not cause paralytic or neurological diseases in mouse models compared with unmodified ZIKV. Importantly, we found that patient-derived GBM tumors exhibited susceptibility (responders) and non-susceptibility (non-responders) to ZOL-1-mediated tumor cell killing, as evidenced by differential apoptotic cell death and cell viability upon ZOL-1 treatment. The oncolytic effect observed in responder cells was seen both in vitro in neurosphere models and in vivo upon xenograft. Finally, we observed that the use of ZOL-1 as combination therapy with multiple PI3K-AKT inhibitors in non-responder GBM resulted in enhanced chemotherapeutic efficacy. Altogether, this study establishes ZOL-1 as a safe and effective treatment against GBM and provides a foundation to conduct further studies evaluating its potential as an effective adjuvant with other chemotherapies and kinase inhibitors.

Shared Gene Targets of the ATF4 and p53 Transcriptional Networks

The master tumor suppressor p53 regulates multiple cell fate decisions, such as cell cycle arrest and apoptosis, via transcriptional control of a broad gene network. Dysfunction in the p53 network is common in cancer, often through mutations that inactivate p53 or other members of the pathway. Induction of tumor-specific cell death by restoration of p53 activity without off-target effects has gained significant interest in the field. In this study, we explore the gene regulatory mechanisms underlying a putative anticancer strategy involving stimulation of the p53-independent integrated stress response (ISR). Our data demonstrate the p53 and ISR pathways converge to independently regulate common metabolic and proapoptotic genes. We investigated the architecture of multiple gene regulatory elements bound by p53 and the ISR effector ATF4 controlling this shared regulation. We identified additional key transcription factors that control basal and stress-induced regulation of these shared p53 and ATF4 target genes. Thus, our results provide significant new molecular and genetic insight into gene regulatory networks and transcription factors that are the target of numerous antitumor therapies.

The Development of p53-Targeted Therapies for Human Cancers

p53 plays a critical role in tumor suppression and is the most frequently mutated gene in human cancers. Most p53 mutants (mutp53) are missense mutations and are thus expressed in human cancers. In human cancers that retain wtp53, the wtp53 activities are downregulated through multiple mechanisms. For example, the overexpression of the negative regulators of p53, MDM2/MDMX, can also efficiently destabilize and inactivate wtp53. Therefore, both wtp53 and mutp53 have become promising and intensively explored therapeutic targets for cancer treatment. Current efforts include the development of small molecule compounds to disrupt the interaction between wtp53 and MDM2/MDMX in human cancers expressing wtp53 and to restore wtp53-like activity to p53 mutants in human cancers expressing mutp53. In addition, a synthetic lethality approach has been applied to identify signaling pathways affected by p53 dysfunction, which, when targeted, can lead to cell death. While an intensive search for p53-targeted cancer therapy has produced potential candidates with encouraging preclinical efficacy data, it remains challenging to develop such drugs with good efficacy and safety profiles. A more in-depth understanding of the mechanisms of action of these p53-targeting drugs will help to overcome these challenges.

MDM2 Inhibition in the Treatment of Glioblastoma: From Concept to Clinical Investigation

Inhibition of the interaction between MDM2 and p53 has emerged as a promising strategy for combating cancer, including the treatment of glioblastoma (GBM). Numerous MDM2 inhibitors have been developed and are currently undergoing rigorous testing for their potential in GBM therapy. Encouraging results from studies conducted in cell culture and animal models suggest that MDM2 inhibitors could effectively treat a specific subset of GBM patients with wild-type TP53 or functional p53. Combination therapy with clinically established treatment modalities such as radiation and chemotherapy offers the potential to achieve a more profound therapeutic response. Furthermore, an increasing array of other molecularly targeted therapies are being explored in combination with MDM2 inhibitors to increase the effects of individual treatments. While some MDM2 inhibitors have progressed to early phase clinical trials in GBM, their efficacy, alone and in combination, is yet to be confirmed. In this article, we present an overview of MDM2 inhibitors currently under preclinical and clinical investigation, with a specific focus on the drugs being assessed in ongoing clinical trials for GBM patients.

Shared gene targets of the ATF4 and p53 transcriptional networks

The master tumor suppressor p53 regulates multiple cell fate decisions, like cell cycle arrest and apoptosis, via transcriptional control of a broad gene network. Dysfunction in the p53 network is common in cancer, often through mutations that inactivate p53 or other members of the pathway. Induction of tumor-specific cell death by restoration of p53 activity without off-target effects has gained significant interest in the field. In this study, we explore the gene regulatory mechanisms underlying a putative anti-cancer strategy involving stimulation of the p53-independent Integrated Stress Response (ISR). Our data demonstrate the p53 and ISR pathways converge to independently regulate common metabolic and pro-apoptotic genes. We investigated the architecture of multiple gene regulatory elements bound by p53 and the ISR effector ATF4 controlling this shared regulation. We identified additional key transcription factors that control basal and stress-induced regulation of these shared p53 and ATF4 target genes. Thus, our results provide significant new molecular and genetic insight into gene regulatory networks and transcription factors that are the target of numerous antitumor therapies.

p52-ZER6: a determinant of tumor cell sensitivity to MDM2-p53 binding inhibitors

Targeting MDM2-p53 interaction has emerged as a promising antitumor therapeutic strategy. Several MDM2-p53 inhibitors have advanced into clinical trials, but results are not favorable. The lack of appropriate biomarkers for selecting patients has been assumed as the critical reason for this failure. We previously identified ZER6 isoform p52-ZER6 as an oncogene upregulated in tumor tissues. In this study we investigated whether p52-ZER6 acted as a blocker of MDM2-p53 binding inhibitors, and whether p52-ZER6 could be used as a biomarker of MDM2-p53 binding inhibitors. In p53 wild-type colorectal carcinoma HCT116, hepatocarcinoma HepG2 and breast cancer MCF-7 cells, overexpression of p52-ZER6 enhanced MDM2-p53 binding and promoted p53 ubiquitination/proteasomal degradation. Furthermore, overexpression of p52-ZER6 in the tumor cells dose-dependently reduced their sensitivity to both nutlin and non-nutlin class MDM2-p53 binding inhibitors. We showed that p52-ZER6 restored tumor cell viability, which was suppressed by nutlin-3, through restoring their proliferation potential while suppressing their apoptotic rate, suggesting that MDM2-p53 binding inhibitors might not be effective for patients with high p52-ZER6 levels. We found that nutlin-3 treatment or p52-ZER6 knockdown alone promoted the accumulation of p53 protein in the tumor cells, and their combinatorial treatment significantly increased the accumulation of p53 protein. In HCT116 cell xenograft nude mouse model, administration of shp52-ZER6 combined with an MDM2-p53 binding inhibitor nutlin-3 exerted synergistic antitumor response. In conclusion, this study reveals that p52-ZER6 might be a potential biomarker for determining patients appropriate for MDM2-p53 binding inhibition-based antitumor therapy, and demonstrates the potential of combinatorial therapy using MDM2-p53 binding inhibitors and p52-ZER6 inhibition.

Drugging p53 in cancer: one protein, many targets

Mutations in the TP53 tumour suppressor gene are very frequent in cancer, and attempts to restore the functionality of p53 in tumours as a therapeutic strategy began decades ago. However, very few of these drug development programmes have reached late-stage clinical trials, and no p53-based therapeutics have been approved in the USA or Europe so far. This is probably because, as a nuclear transcription factor, p53 does not possess typical drug target features and has therefore long been considered undruggable. Nevertheless, several promising approaches towards p53-based therapy have emerged in recent years, including improved versions of earlier strategies and novel approaches to make undruggable targets druggable. Small molecules that can either protect p53 from its negative regulators or restore the functionality of mutant p53 proteins are gaining interest, and drugs tailored to specific types of p53 mutants are emerging. In parallel, there is renewed interest in gene therapy strategies and p53-based immunotherapy approaches. However, major concerns still remain to be addressed. This Review re-evaluates the efforts made towards targeting p53-dysfunctional cancers, and discusses the challenges encountered during clinical development.

Phase I dose-escalation study of milademetan in patients with relapsed or refractory acute myeloid leukemia

Long-term survival in patients with acute myeloid leukemia (AML) remains low, and current treatment modalities are inadequate. Milademetan (DS-3032, RAIN-32), a small-molecule specific murine double minute 2 inhibitor, has shown a p53 status-dependent antitumor effect in vitro studies. This is the first phase I study report of milademetan monotherapy in relapsed/refractory (R/R) AML patients evaluating the safety, tolerability, pharmacokinetics, and preliminary tumor response for further clinical development. Fourteen patients received 90 (starting dose, n = 4), 120 (n = 6), or 160 mg (n = 4) of oral milademetan once daily in a 14/28 treatment cycle. The median total treatment duration was 1.5 cycles. Dose-limiting toxicity did not occur, and the maximum tolerated dose was not reached. Thus, the recommended dose was defined as 160 mg. The most common adverse events (AEs) were decreased appetite (64.3%), febrile neutropenia (50%), nausea (42.9%), and anemia (35.7%). No deaths or AEs leading to treatment discontinuation occurred. Five serious treatment-emergent AEs occurred in 4 patients. Plasma concentration increased linearly with milademetan dose. However, trends in the safety and efficacy of oral milademetan in patients with R/R AML warrant further clinical investigation. This study can inform future milademetan studies in hematologic malignancies.

Experimental drugs in clinical trials for acute myeloid leukemia: innovations, trends, and opportunities

INTRODUCTION

Acute myeloid leukemia (AML) is a heterogeneous disease characterized by many cytogenetic and molecular alterations. Due to better knowledge of the molecular basis of AML, many targeted therapies have been introduced and registered, e.g. FMS-like tyrosine kinase 3 inhibitors, isocitrate dehydrogenase 1/2 mutation inhibitors, and Bcl-2 inhibitor. Despite that, the cure for AML remains an unmet clinical need in most patients.

AREAS COVERED

The review aims to present new, not yet registered drugs for AML. We searched the English literature for articles concerning AML, targeted drugs, menin inhibitors, DOT1L, BET, IDH inhibitors, FLT3, hedgehog inhibitors, Polo-like kinase inhibitors, RNA splicing, and immune therapies via PubMed. Publications from January 2000 to August 2022 were scrutinized. Additional relevant publications were obtained by reviewing the references from the chosen articles and Google search. Conference proceedings from the previous 5 years of The American Society of Hematology, the European Hematology Association, and the American Society of Clinical Oncology were searched manually. Additional relevant publications were obtained by reviewing the references.

EXPERT OPINION

For several years, the therapeutic approach in AML has become more individualized. Novel groups of drugs give hope for greater curability. High response rates have agents that restore the activity of the p53 protein. In addition, agents that work independently of a particular mutation seem promising for AML without any known mutation.

Extended Applications of Small-Molecule Covalent Inhibitors toward Novel Therapeutic Targets

Recently, small-molecule covalent inhibitors have been accepted as a practical tool for targeting previously "undruggable" proteins. The high target selectivity of modern covalent inhibitors is now alleviating toxicity concerns regarding the covalent modifications of proteins. However, despite the tremendous clinical success of current covalent inhibitors, there are still unmet medical needs that covalent inhibitors have not yet addressed. This review categorized representative covalent inhibitors based on their mechanism of covalent inhibition: conventional covalent inhibitors, targeted covalent inhibitors (TCIs), and expanded TCIs. By reviewing both Food and Drug Administration (FDA)-approved drugs and drug candidates from recent literature, we provide insight into the future direction of covalent inhibitor development.

MDM2 inhibitors-mediated disruption of mitochondrial metabolism: A novel therapeutic strategy for retinoblastoma

MDM2 is the principal inhibitor of p53, and MDM2 inhibitors can disrupt the physical interaction between MDM2 and p53. The half-life of p53 is very short in normal cells and tissues, and an uncontrolled increase in p53 levels has potential harmful effects. It has been shown that p53 is frequently mutated in most cancers; however, p53 mutations are rare in retinoblastoma. Therefore, therapeutic strategies aimed at increasing the expression levels of wild-type p53 are attractive. In this minireview, we discuss the potential use of nutlin-3, the prototype small molecule inhibitor that disrupts the MDM2-p53 interaction, for the treatment of retinoblastoma. Although p53 has pleiotropic biological effects, the functions of p53 depend on its sub-cellular localization. In the nucleus, p53 induces the transcription of a vast array of genes, while in mitochondria, p53 regulates mitochondrial metabolism. This review also discusses the relative contribution of p53-mediated gene transcription and mitochondrial perturbation for retinoblastoma treatment.

Targeting Apoptosis in AML: Where Do We Stand?

Simple Summary

In patients with acute myeloid leukemia (AML), genetic mutations can cause cells to evade regulated cell death (RCD), resulting in excessive cell proliferation. The best-known form of RCD is apoptosis, which prevents the emergence of cancer cells; disturbances in this process are an important factor in the development and progression of AML. Clearly, it is essential to understand the mechanisms of apoptosis to establish a personalized, patient-specific approach in AML therapy. Therefore, this paper comprehensively reviews the current range of AML treatment approaches related to apoptosis and highlights other promising concepts such as neddylation.

Abstract

More than 97% of patients with acute myeloid leukemia (AML) demonstrate genetic mutations leading to excessive proliferation combined with the evasion of regulated cell death (RCD). The most prominent and well-defined form of RCD is apoptosis, which serves as a defense mechanism against the emergence of cancer cells. Apoptosis is regulated in part by the BCL-2 family of pro- and anti-apoptotic proteins, whose balance can significantly determine cell survival. Apoptosis evasion plays a key role in tumorigenesis and drug resistance, and thus in the development and progression of AML. Research on the structural and biochemical aspects of apoptosis proteins and their regulators offers promise for new classes of targeted therapies and strategies for therapeutic intervention. This review provides a comprehensive overview of current AML treatment options related to the mechanism of apoptosis, particularly its mitochondrial pathway, and other promising concepts such as neddylation. It pays particular attention to clinically-relevant aspects of current and future AML treatment approaches, highlighting the molecular basis of individual therapies.

MDM2-Based Proteolysis-Targeting Chimeras (PROTACs): An Innovative Drug Strategy for Cancer Treatment

Proteolysis-targeting chimeras (PROTACs) are molecules that selectively degrade a protein of interest (POI). The incorporation of ligands that recruit mouse double minute 2 (MDM2) into PROTACs, forming the so-called MDM2-based PROTACs, has shown promise in cancer treatment due to its dual mechanism of action: a PROTAC that recruits MDM2 prevents its binding to p53, resulting not only in the degradation of POI but also in the increase of intracellular levels of the p53 suppressor, with the activation of a whole set of biological processes, such as cell cycle arrest or apoptosis. In addition, these PROTACs, in certain cases, allow for the degradation of the target, with nanomolar potency, in a rapid and sustained manner over time, with less susceptibility to the development of resistance and tolerance, without causing changes in protein expression, and with selectivity to the target, including the respective isoforms or mutations, and to the cell type, overcoming some limitations associated with the use of inhibitors for the same therapeutic target. Therefore, the aim of this review is to analyze and discuss the characteristics of MDM2-based PROTACs developed for the degradation of oncogenic proteins and to understand what potential they have as future anticancer drugs.

p53 as a biomarker and potential target in gastrointestinal stromal tumors

KIT and PDGFRA play a major role in the oncogenic process in gastrointestinal stroma tumors (GIST) and small molecules have been employed with great success to target the KIT and PDGFRA pathways in this cancer. However, approximately 10% of patients with GIST are resistant to current targeted drug therapy. There is a need to explore other potential targets. Although p53 alterations frequently occur in most cancers, studies regarding p53 in GIST have been limited. The CDKN2A/MDM2/p53 axis regulates cell cycle progression and DNA damage responses, which in turn control tumor growth. This axis is the major event required for transformation from low- to high-risk GIST. Generally, p53 mutation is infrequent in GIST, but p53 overexpression has been reported to be associated with high-risk GIST and unfavorable prognosis, implying that p53 should play a critical role in GIST. Also, Wee1 regulates the cell cycle and the antitumor activity of Wee1 inhibition was reported to be p53 mutant dependent. In addition, Wee1 was reported to have potential activity in GIST through the regulation of KIT protein and this mechanism may be dependent on p53 status. In this article, we review previous reports regarding the role of p53 in GIST and propose targeting the p53 pathway as a novel additional treatment strategy for GIST.

Targeting signaling pathways in prostate cancer: mechanisms and clinical trials

Prostate cancer (PCa) affects millions of men globally. Due to advances in understanding genomic landscapes and biological functions, the treatment of PCa continues to improve. Recently, various new classes of agents, which include next-generation androgen receptor (AR) signaling inhibitors (abiraterone, enzalutamide, apalutamide, and darolutamide), bone-targeting agents (radium-223 chloride, zoledronic acid), and poly(ADP-ribose) polymerase (PARP) inhibitors (olaparib, rucaparib, and talazoparib) have been developed to treat PCa. Agents targeting other signaling pathways, including cyclin-dependent kinase (CDK)4/6, Ak strain transforming (AKT), wingless-type protein (WNT), and epigenetic marks, have successively entered clinical trials. Furthermore, prostate-specific membrane antigen (PSMA) targeting agents such as ¹⁷⁷Lu-PSMA-617 are promising theranostics that could improve both diagnostic accuracy and therapeutic efficacy. Advanced clinical studies with immune checkpoint inhibitors (ICIs) have shown limited benefits in PCa, whereas subgroups of PCa with mismatch repair (MMR) or CDK12 inactivation may benefit from ICIs treatment. In this review, we summarized the targeted agents of PCa in clinical trials and their underlying mechanisms, and further discussed their limitations and future directions.

The Role of the TP53 Pathway in Predicting Response to Neoadjuvant Therapy in Esophageal Adenocarcinoma

PURPOSE

In patients with locally advanced esophageal adenocarcinoma, response to neoadjuvant therapy strongly predicts survival, but robust molecular predictors of response have been lacking. We therefore sought to discover meaningful predictors of response in these patients.

EXPERIMENTAL DESIGN

We retrospectively identified all patients with adenocarcinoma of the lower esophagus or gastroesophageal junction who (i) were treated with multimodality therapy with curative intent at our institution from 2014 through 2020 and (ii) underwent prospective sequencing by Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets. Clinicopathologic and genomic data were analyzed to identify potential genomic features, somatic alterations, and oncogenic pathways associated with treatment response.

RESULTS

In total, 237 patients were included. MDM2 amplification was independently associated with poor response to neoadjuvant therapy [OR, 0.10 (95% confidence interval, 0.01-0.55); P = 0.032], when accounting for significant clinicopathologic variables, including clinical stage, tumor grade, and chemotherapy regimen. Moreover, TP53 pathway alterations, grouped according to inferred severity of TP53 dysfunction, were significantly associated with response to neoadjuvant therapy (P = 0.004, q = 0.07). Patients with MDM2 amplifications or truncating biallelic TP53 mutations had similar outcomes in terms of poor responses to neoadjuvant therapy and, consequently, shorter progression-free survival, compared with patients with TP53 pathway wild-type tumors. Thus, worsening TP53 dysfunction was directly correlated with worse outcomes.

CONCLUSIONS

MDM2 amplification and TP53 status are associated with response to therapy in patients with esophageal adenocarcinoma. Given the dearth of actionable targets in esophageal adenocarcinoma, MDM2 inhibition, in combination with cytotoxic chemotherapy, may represent an important therapeutic strategy to overcome treatment resistance and improve outcomes in these patients.

Genome-wide CRISPR/Cas9 screening for therapeutic targets in NSCLC carrying wild-type TP53 and receptor tyrosine kinase genes

Background

Targeted drugs have greatly improved the therapeutic outcome of non‐small cell lung cancer (NSCLC) patients compared with conventional chemotherapy, whereas about one‐third of patients are so far not suitable for targeted therapy due to lack of known driver oncogenes such as a mutated receptor tyrosine kinase (RTK) genes. In this study, we aimed to identify therapeutic targets for this subgroup of NSCLC patients.

Methods

We performed genome‐wide CRISPR/Cas9 screens in two NSCLC cell lines carrying wild‐type TP53 and receptor tyrosine kinase (wtTP53‐RTK) genes using a GeCKO v2.0 lentiviral library (containing 123411 sgRNAs and targeting 19050 genes). MAGeCKFlute was used to analyse and identify candidate genes. Genetic perturbation and pharmacological inhibition were used to validate the result in vitro and in vivo.

Results

The Genome‐wide CRISPR/Cas9 screening identified MDM2 as a potential therapeutic target for wtTP53‐RTK NSCLC. Genetic and pharmacological inhibition of MDM2 reduced cell proliferation and impaired tumour growth in the xenograft model, thus confirming the finding of the CRISPR/Cas9 screening. Moreover, treatment by a selective MDM2 inhibitor RG7388 triggered both cell cycle arrest and apoptosis in several NSCLC cell lines. Additionally, RG7388 and pemetrexed synergistically blocked the cell proliferation and growth of wtTP53‐RTK tumours but had limited effects for other genotypes.

Conclusions

We identified MDM2 as an essential gene and a potential therapeutic target in wtTP53‐RTK NSCLC via a genome‐wide CRISPR/Cas9 screening. For this subgroup, treatment by RG7388 alone or by its combination with pemetrexed resulted in significant tumour inhibition.

Exploiting Extracellular Vesicles Strategies to Modulate Cell Death and Inflammation in COVID-19

The coronavirus disease (COVID-19) is responsible for more than 5 million deaths worldwide, with respiratory failure being the most common clinical presentation. COVID-19 complications still present a considerable burden on healthcare systems, and signs of the post-COVID syndrome are concerns for potential long-term damages. An increasing body of evidence highlights extracellular vesicles’ (EVs) relevance in modulating inflammation and cell death in the diseases related to these processes. Several types of EVs-based investigational new drugs against COVID-19 have been approved by the US Food and Drug Administration to initiate a Phase I/II trial under an Investigational New Drug protocol. EVs can be employed as natural drug delivery nanoparticle-based systems due to their inherent potential in transferring material between cells, their natural origin, and their capability to encapsulate various biological molecules, offering an exciting alternative for administering drugs acting on the cell cycle control. In this context, small-molecule inhibitors of Mouse Double Minute 2 (MDM2) such as Nutlin-3 and Idasanutlin by promoting p53 survival and its antiviral activity might be helpful to modulate the IFN signalling pathway and reduce the overall pro-inflammatory burden.

Single-cell analysis reveals selection of TP53-mutated clones after MDM2 inhibition

The mechanisms of transformation of chronic myeloproliferative neoplasms (MPN) to leukemia are largely unknown, but TP53 mutations acquisition is considered a key event in this process. p53 is a main tumor suppressor, but mutations in this protein per se do not confer a proliferative advantage to the cells, and a selection process is needed for the expansion of mutant clones. MDM2 inhibitors may rescue normal p53 from degradation and have been evaluated in a variety of cancers with promising results. However, the impact of these drugs on TP53-mutated cells is underexplored. We report herein evidence of a direct effect of MDM2 inhibition on the selection of MPN patients' cells harboring TP53 mutations. To decipher whether these mutations can arise in a specific molecular context, we used a DNA single-cell approach to determine the clonal architecture of TP53-mutated cells. We observed that TP53 mutations are late events in MPN, mainly occurring in the driver clone, whereas clonal evolution frequently consists of sequential branching instead of linear consecutive acquisition of mutations in the same clone. At the single-cell level, the presence of additional mutations does not influence the selection of TP53 mutant cells by MDM2 inhibitor treatment. Also, we describe an in vitro test allowing to predict the emergence of TP53 mutated clones. Altogether, this is the first demonstration that a drug treatment can directly favor the emergence of TP53-mutated subclones in MPN.

New Perspectives in Treating Acute Myeloid Leukemia: Driving towards a Patient-Tailored Strategy

For decades, intensive chemotherapy (IC) has been considered the best therapeutic option for treating acute myeloid leukemia (AML), with no curative option available for patients who are not eligible for IC or who have had failed IC. Over the last few years, several new drugs have enriched the therapeutic arsenal of AML treatment for both fit and unfit patients, raising new opportunities but also new challenges. These include the already approved venetoclax, the IDH1/2 inhibitors enasidenib and ivosidenib, gemtuzumab ozogamicin, the liposomal daunorubicin/cytarabine formulation CPX-351, and oral azacitidine. Venetoclax, an anti BCL2-inhibitor, in combination with hypomethylating agents (HMAs), has markedly improved the management of unfit and elderly patients from the perspective of improved quality of life and better survival. Venetoclax is currently under investigation in combination with other old and new drugs in early phase trials. Recently developed drugs with different mechanisms of action and new technologies that have already been investigated in other settings (BiTE and CAR-T cells) are currently being explored in AML, and ongoing trials should determine promising agents, more synergic combinations, and better treatment strategies. Access to new drugs and inclusion in clinical trials should be strongly encouraged to provide scientific evidence and to define the future standard of treatment in AML.

Altered pathways and targeted therapy in double hit lymphoma

High-grade B-cell lymphoma with translocations involving MYC and BCL2 or BCL6, usually referred to as double hit lymphoma (DHL), is an aggressive hematological malignance with distinct genetic features and poor clinical prognosis. Current standard chemoimmunotherapy fails to confer satisfying outcomes and few targeted therapeutics are available for the treatment against DHL. Recently, the delineating of the genetic landscape in tumors has provided insight into both biology and targeted therapies. Therefore, it is essential to understand the altered signaling pathways of DHL to develop treatment strategies with better clinical benefits. Herein, we summarized the genetic alterations in the two DHL subtypes (DHL-BCL2 and DHL-BCL6). We further elucidate their implications on cellular processes, including anti-apoptosis, epigenetic regulations, B-cell receptor signaling, and immune escape. Ongoing and potential therapeutic strategies and targeted drugs steered by these alterations were reviewed accordingly. Based on these findings, we also discuss the therapeutic vulnerabilities that coincide with these genetic changes. We believe that the understanding of the DHL studies will provide insight into this disease and capacitate the finding of more effective treatment strategies.

Cross-Talk between p53 and Wnt Signaling in Cancer

Targeting cancer hallmarks is a cardinal strategy to improve antineoplastic treatment. However, cross-talk between signaling pathways and key oncogenic processes frequently convey resistance to targeted therapies. The p53 and Wnt pathway play vital roles for the biology of many tumors, as they are critically involved in cancer onset and progression. Over recent decades, a high level of interaction between the two pathways has been revealed. Here, we provide a comprehensive overview of molecular interactions between the p53 and Wnt pathway discovered in cancer, including complex feedback loops and reciprocal transactivation. The mutational landscape of genes associated with p53 and Wnt signaling is described, including mutual exclusive and co-occurring genetic alterations. Finally, we summarize the functional consequences of this cross-talk for cancer phenotypes, such as invasiveness, metastasis or drug resistance, and discuss potential strategies to pharmacologically target the p53-Wnt interaction.

Early-Stage Lung Adenocarcinoma MDM2 Genomic Amplification Predicts Clinical Outcome and Response to Targeted Therapy

Simple Summary

Invasive subtypes of lung adenocarcinoma (LUAD) show MDM2 amplification that is associated with poor survival. Mouse double minute 2 (MDM2) is frequently amplified in lung adenocarcinoma (LUAD) and is a negative regulator of p53, which binds to p53 and regulates its activity and stability. Genomic amplification and overexpression of MDM2, together with genetic alterations in p53, leads to genomic and genetic heterogeneity in LUAD that represents a therapeutic target. In vitro assays in a panel of LUAD cell lines showed that tumor cell response to MDM2-targeted therapy is associated with MDM2 amplification.

Abstract

Lung cancer is the most common cause of cancer-related deaths in both men and women, accounting for one-quarter of total cancer-related mortality globally. Lung adenocarcinoma is the major subtype of non-small cell lung cancer (NSCLC) and accounts for around 40% of lung cancer cases. Lung adenocarcinoma is a highly heterogeneous disease and patients often display variable histopathological morphology, genetic alterations, and genomic aberrations. Recent advances in transcriptomic and genetic profiling of lung adenocarcinoma by investigators, including our group, has provided better stratification of this heterogeneous disease, which can facilitate devising better treatment strategies suitable for targeted patient cohorts. In a recent study we have shown gene expression profiling identified novel clustering of early stage LUAD patients and correlated with tumor invasiveness and patient survival. In this study, we focused on copy number alterations in LUAD patients. SNP array data identified amplification at chromosome 12q15 on MDM2 locus and protein overexpression in a subclass of LUAD patients with an invasive subtype of the disease. High copy number amplification and protein expression in this subclass correlated with poor overall survival. We hypothesized that MDM2 copy number and overexpression predict response to MDM2-targeted therapy. In vitro functional data on a panel of LUAD cells showed that MDM2-targeted therapy effectively suppresses cell proliferation, migration, and invasion in cells with MDM2 amplification/overexpression but not in cells without MDM2 amplification, independent of p53 status. To determine the key signaling mechanisms, we used RNA sequencing (RNA seq) to examine the response to therapy in MDM2-amplified/overexpressing p53 mutant and wild-type LUAD cells. RNA seq data shows that in MDM2-amplified/overexpression with p53 wild-type condition, the E2F → PEG10 → MMPs pathway is operative, while in p53 mutant genetic background, MDM2-targeted therapy abrogates tumor progression in LUAD cells by suppressing epithelial to mesenchymal transition (EMT) signaling. Our study provides a potentially clinically relevant strategy of selecting LUAD patients for MDM2-targeted therapy that may provide for increased response rates and, thus, better survival.

Epstein Barr virus-positive B-cell lymphoma is highly vulnerable to MDM2 inhibitors in vivo

MDM2 inhibitors have potent in vivo activity against and could be a novel therapy for EBV-positive B-cell lymphoma.

EBV positivity or loss of BCL6 expression can be a potential predictive biomarker for response to MDM2 inhibitors in patients with lymphoma

Epstein-Barr virus–positive (EBV-positive) B-cell lymphomas are common in immunocompromised patients and remain an unmet medical need. Here we report that MDM2 inhibitors (MDM2is) navtemadlin and idasanutlin have potent in vivo activity in EBV-positive B-cell lymphoma established in immunocompromised mice. Tumor regression was observed in all 5 EBV-positive xenograft–associated B-cell lymphomas treated with navtemadlin or idasanutlin. Molecular characterization showed that treatment with MDM2is resulted in activation of p53 pathways and downregulation of cell cycle effectors in human lymphoma cell lines that were either EBV-positive or had undetectable expression of BCL6, a transcriptional inhibitor of the TP53 gene. Moreover, treatment with navtemadlin resulted in tumor regression and prevented systemic dissemination of EBV-positive lymphoma derived from 2 juvenile patients with posttransplant lymphoproliferative diseases, including 1 whose tumor was resistant to virus-specific T-cell therapy. These results provide proof-of-concept for targeted therapy of EBV-positive lymphoma with MDM2is and the feasibility of using EBV infection or loss of BCL6 expression to identify responders to MDM2is.

Management of Acute Myeloid Leukemia: Current Treatment Options and Future Perspectives

Treatment of acute myeloid leukemia (AML) has improved in recent years and several new therapeutic options have been approved. Most of them include mutation-specific approaches (e.g., gilteritinib for AML patients with activating FLT3 mutations), or are restricted to such defined AML subgroups, such as AML-MRC (AML with myeloid-related changes) or therapy-related AML (CPX-351). With this review, we aim to present a comprehensive overview of current AML therapy according to the evolved spectrum of recently approved treatment strategies. We address several aspects of combined epigenetic therapy with the BCL-2 inhibitor venetoclax and provide insight into mechanisms of resistance towards venetoclax-based regimens, and how primary or secondary resistance might be circumvented. Furthermore, a detailed overview on the current status of AML immunotherapy, describing promising concepts, is provided. This review focuses on clinically important aspects of current and future concepts of AML treatment, but will also present the molecular background of distinct targeted therapies, to understand the development and challenges of clinical trials ongoing in AML patients.

TP53 in Acute Myeloid Leukemia: Molecular Aspects and Patterns of Mutation

Mutation of the tumor suppressor gene, TP53, is associated with abysmal survival outcomes in acute myeloid leukemia (AML). Although it is the most commonly mutated gene in cancer, its occurrence is observed in only 5–10% of de novo AML, and in 30% of therapy related AML (t-AML). TP53 mutation serves as a prognostic marker of poor response to standard-of-care chemotherapy, particularly in t-AML and AML with complex cytogenetics. In light of a poor response to traditional chemotherapy and only a modest improvement in outcome with hypomethylation-based interventions, allogenic stem cell transplant is routinely recommended in these cases, albeit with a response that is often short lived. Despite being frequently mutated across the cancer spectrum, progress and enthusiasm for the development of p53 targeted therapeutic interventions is lacking and to date there is no approved drug that mitigates the effects of TP53 mutation. There is a mounting body of evidence indicating that p53 mutants differ in functionality and form from typical AML cases and subsequently display inconsistent responses to therapy at the cellular level. Understanding this pathobiological activity is imperative to the development of effective therapeutic strategies. This review aims to provide a comprehensive understanding of the effects of TP53 on the hematopoietic system, to describe its varying degree of functionality in tumor suppression, and to illustrate the need for the adoption of personalized therapeutic strategies to target distinct classes of the p53 mutation in AML management.

Targeted Therapies for the Evolving Molecular Landscape of Acute Myeloid Leukemia

Despite considerable growth in our understanding of the heterogeneous biology and pathogenesis of acute myeloid leukemia (AML) in recent decades, for nearly forty years, little progress was gained in the realm of novel therapeutics. Since 2017, however, nine agents have been FDA-approved for patients with AML in both the upfront and relapsed/refractory (R/R) settings. Most of these compounds function as inhibitors of key cell cycle enzymatic pathways or mediators of leukemic proliferation and survival. They have been approved both as single agents and in combination with conventional or reduced-intensity conventional chemotherapeutics. In this article, we review the molecular landscape of de novo vs. R/R AML and highlight the potential translational impact of defined molecular disease subsets. We also highlight several recent agents that have entered the therapeutic armamentarium and where they fit in the AML treatment landscape, with a focus on FLT3 inhibitors, IDH1 and IDH2 inhibitors, and venetoclax. Finally, we close with a survey of two promising novel agents under investigation that are poised to enter the mainstream clinical arena in the near future.

Clinico-genomic profiling and clonal dynamic modeling of TP53-aberrant myelodysplastic syndrome and acute myeloid leukemia

TP53-aberrant myelodysplastic syndrome and acute myeloid leukemia have dismal outcomes. Here, we define the clinico-genomic landscape of TP53 disruptions in 40 patients and employ clonal dynamic modeling to map the mutational hierarchy against clinical outcomes. Most TP53 mutations (45.2%) localized to the L3 loop or LSH motif of the DNA-binding domain. TP53 disruptions had high co-occurrence with mutations in epigenetic regulators, spliceosome machinery, and cohesin complex and low co-occurrence with mutations in proliferative signaling genes. Ancestral and descendant TP53 mutations constituted measurable residual disease and fueled relapse. High mutant TP53 gene dosage predicted low durability of remission. The median overall survival (OS) was 280 days. Hypomethylating agent-based therapy served as an effective bridge to transplant, leading to improved median OS compared to patients who did not receive a transplant (14.7 vs. 5.1 months). OS was independent of the genomic location of TP53 disruption, which has implications for rational therapeutic design.

[Metabolic pathways controlled by E3 ligases: an opportunity for therapeutic targeting]

Since its discovery, the Ubiquitin Proteasome System (UPS) has been recognized for its major role in controlling most of the cell's metabolic pathways. In addition to its essential role in the degradation of proteins, it is also involved in the addressing, signaling or repair of DNA, which makes it a key player in cellular homeostasis. Although other control systems exist in the cell, the UPS is often referred to as the conductor. In view of its importance, any dysregulation of the UPS leads to more or less severe disorders for the cell and therefore the body, which accounts for UPS implication in many pathologies (cancer, Alzheimer's disease, Huntington's disease, etc.). UPS is made up of more than 1000 different proteins, the combinations of which allow the fine targeting of virtually all proteins in the body. UPS uses an enzymatic cascade (E1, 2 members; E2 > 35; E3 > 800) which allows the transfer of ubiquitin, a small protein of 8.5 kDa onto the protein to be targeted either for its degradation or to modify its activity. This ubiquitinylation signal is reversible and many deubiquitinylases (DUB, ∼ 80 isoforms) also have an important role. E3 enzymes are the most numerous and their function is to recognize the target protein, which makes them important players in the specific action of UPS. The very nature of E3 and the complexity of their interactions with different partners offer a very broad field of investigation and therefore significant potential for the development of therapeutic approaches. Without being exhaustive, this review illustrates the different strategies that have already been implemented to fight against different pathologies (excluding bacterial or viral infections).

Tumor suppressor p53: Biology, signaling pathways, and therapeutic targeting

TP53 is the most commonly mutated gene in human cancer with over 100,000 literature citations in PubMed. This is a heavily studied pathway in cancer biology and oncology with a history that dates back to 1979 when p53 was discovered. The p53 pathway is a complex cellular stress response network with multiple diverse inputs and downstream outputs relevant to its role as a tumor suppressor pathway. While inroads have been made in understanding the biology and signaling in the p53 pathway, the p53 family, transcriptional readouts, and effects of an array of mutants, the pathway remains challenging in the realm of clinical translation. While the role of mutant p53 as a prognostic factor is recognized, the therapeutic modulation of its wild-type or mutant activities remain a work-in-progress. This review covers current knowledge about the biology, signaling mechanisms in the p53 pathway and summarizes advances in therapeutic development.

MDM2/X Inhibitors as Radiosensitizers for Glioblastoma Targeted Therapy

Inhibition of the MDM2/X-p53 interaction is recognized as a potential anti-cancer strategy, including the treatment of glioblastoma (GB). In response to cellular stressors, such as DNA damage, the tumor suppression protein p53 is activated and responds by mediating cellular damage through DNA repair, cell cycle arrest and apoptosis. Hence, p53 activation plays a central role in cell survival and the effectiveness of cancer therapies. Alterations and reduced activity of p53 occur in 25-30% of primary GB tumors, but this number increases drastically to 60-70% in secondary GB. As a result, reactivating p53 is suggested as a treatment strategy, either by using targeted molecules to convert the mutant p53 back to its wild type form or by using MDM2 and MDMX (also known as MDM4) inhibitors. MDM2 down regulates p53 activity via ubiquitin-dependent degradation and is amplified or overexpressed in 14% of GB cases. Thus, suppression of MDM2 offers an opportunity for urgently needed new therapeutic interventions for GB. Numerous small molecule MDM2 inhibitors are currently undergoing clinical evaluation, either as monotherapy or in combination with chemotherapy and/or other targeted agents. In addition, considering the major role of both p53 and MDM2 in the downstream signaling response to radiation-induced DNA damage, the combination of MDM2 inhibitors with radiation may offer a valuable therapeutic radiosensitizing approach for GB therapy. This review covers the role of MDM2/X in cancer and more specifically in GB, followed by the rationale for the potential radiosensitizing effect of MDM2 inhibition. Finally, the current status of MDM2/X inhibition and p53 activation for the treatment of GB is given.

Targeting the Ubiquitin-Proteasome System for Cancer Therapeutics by Small-Molecule Inhibitors

The ubiquitin-proteasome system (UPS) is a critical regulator of cellular protein levels and activity. It is, therefore, not surprising that its dysregulation is implicated in numerous human diseases, including many types of cancer. Moreover, since cancer cells exhibit increased rates of protein turnover, their heightened dependence on the UPS makes it an attractive target for inhibition via targeted therapeutics. Indeed, the clinical application of proteasome inhibitors in treatment of multiple myeloma has been very successful, stimulating the development of small-molecule inhibitors targeting other UPS components. On the other hand, while the discovery of potent and selective chemical compounds can be both challenging and time consuming, the area of targeted protein degradation through utilization of the UPS machinery has seen promising developments in recent years. The repertoire of proteolysis-targeting chimeras (PROTACs), which employ E3 ligases for the degradation of cancer-related proteins via the proteasome, continues to grow. In this review, we will provide a thorough overview of small-molecule UPS inhibitors and highlight advancements in the development of targeted protein degradation strategies for cancer therapeutics.

Emerging agents and regimens for AML

Until recently, acute myeloid leukemia (AML) patients used to have limited treatment options, depending solely on cytarabine + anthracycline (7 + 3) intensive chemotherapy and hypomethylating agents. Allogeneic stem cell transplantation (Allo-SCT) played an important role to improve the survival of eligible AML patients in the past several decades. The exploration of the genomic and molecular landscape of AML, identification of mutations associated with the pathogenesis of AML, and the understanding of the mechanisms of resistance to treatment from excellent translational research helped to expand the treatment options of AML quickly in the past few years, resulting in noteworthy breakthroughs and FDA approvals of new therapeutic treatments in AML patients. Targeted therapies and combinations of different classes of therapeutic agents to overcome treatment resistance further expanded the treatment options and improved survival. Immunotherapy, including antibody-based treatment, inhibition of immune negative regulators, and possible CAR T cells might further expand the therapeutic armamentarium for AML. This review is intended to summarize the recent developments in the treatment of AML.

Novel Targeted Therapeutics in Acute Myeloid Leukemia: an Embarrassment of Riches

PURPOSE OF REVIEW

Acute myeloid leukemia (AML) is an aggressive malignancy of the bone marrow that has a poor prognosis with traditional cytotoxic chemotherapy, especially in elderly patients. In recent years, small molecule inhibitors targeting AML-associated IDH1, IDH2, and FLT3 mutations have been FDA approved. However, the majority of AML cases do not have a targetable mutation. A variety of novel agents targeting both previously untargetable mutations and general pathways in AML are currently being investigated. Herein, we review selected new targeted therapies currently in early-phase clinical investigation in AML.

RECENT FINDINGS

The DOT1L inhibitor pinometostat in KMT2A-rearranged AML, the menin inhibitors KO-539 and SYNDX-5613 in KMT2Ar and NPM1-mutated AML, and the mutant TP53 inhibitor APR-246 are examples of novel agents targeting specific mutations in AML. In addition, BET inhibitors, polo-like kinase inhibitors, and MDM2 inhibitors are promising new drug classes for AML which do not depend on the presence of a particular mutation. AML remains in incurable disease for many patients but advances in genomics, epigenetics, and drug discovery have led to the development of many potential novel therapeutic agents, many of which are being investigated in ongoing clinical trials. Additional studies will be necessary to determine how best to incorporate these novel agents into routine clinical treatment of AML.

Pharmacological Activation of p53 during Human Monocyte to Macrophage Differentiation Attenuates Their Pro-Inflammatory Activation by TLR4, TLR7 and TLR8 Agonists

Simple Summary

Pharmacological activation of tumor suppressor p53 is a promising therapeutic strategy for a range of hematologic and solid cancers. Whether p53 activation augments or suppresses anti-tumor innate immunity is less understood. Here we show that treatment of differentiating human macrophages with a p53 activator idasanutlin suppresses their inflammatory responses to activators of toll-like receptors (TLR) -4 and -7/8. This is accompanied by reduced expression of TLR7, TLR8, as well as TLR4 co-receptor CD14. These data help evaluating the possibilities of combining p53-targeting and immunostimulatory anti-cancer therapies.

Abstract

The transcription factor p53 has well-recognized roles in regulating cell cycle, DNA damage repair, cell death, and metabolism. It is an important tumor suppressor and pharmacological activation of p53 by interrupting its interaction with the ubiquitin E3 ligase mouse double minute 2 homolog (MDM2) is actively explored for anti-tumor therapies. In immune cells, p53 modulates inflammatory responses, but the impact of p53 on macrophages remains incompletely understood. In this study, we used the MDM2 antagonist idasanutlin (RG7388) to investigate the responses of primary human macrophages to pharmacological p53 activation. Idasanutlin induced a robust p53-dependent transcriptional signature in macrophages, including several pro-apoptotic genes. However, idasanutlin did not generally sensitize macrophages to apoptosis, except for an enhanced response to a Fas-stimulating antibody. In fully differentiated macrophages, idasanutlin did not affect pro-inflammatory gene expression induced by toll-like receptor 4 (TLR4), TLR3, and TLR7/8 agonists, but inhibited interleukin-4-induced macrophage polarization. However, when present during monocyte to macrophage differentiation, idasanutlin attenuated inflammatory responses towards activation of TLR4 and TLR7/8 by low doses of lipopolysaccharide or resiquimod (R848). This was accompanied by a reduced expression of CD14, TLR7, and TLR8 in macrophages differentiated in the presence of idasanutlin. Our data suggest anti-inflammatory effects of pharmacological p53 activation in differentiating human macrophages.

Murine double minute 2 inhibition alone or with cytarabine in acute myeloid leukemia: Results from an idasanutlin phase 1/1b study⋆

The prognosis remains poor for patients with relapsed or refractory (r/r) acute myeloid leukemia; thus, novel therapies are needed. We evaluated idasanutlin-a new, potent murine double minute 2 antagonist-alone or with cytarabine in patients with r/r acute myeloid leukemia, de novo untreated acute myeloid leukemia unsuitable for standard treatment or with adverse features, or secondary acute myeloid leukemia in a multicenter, open-label, phase 1/1b trial. Primary objectives were to determine the maximum tolerated dose (MTD) and recommended dose for expansion (RDE) and characterize the safety profile of idasanutlin monotherapy and combination therapy. Clinical activity and pharmacokinetics were secondary objectives. Two idasanutlin formulations were investigated: a microprecipitate bulk powder (MBP) and optimized spray-dried powder (SDP). Following dose escalation, patients (N = 122) received idasanutlin at the RDE in the extension cohorts. No formal MTD was identified. Idasanutlin was tolerable alone and in combination with cytarabine. The RDE was determined as 600 mg twice a day for the MBP formulation and 300 mg twice a day for the SDP formulation. Adverse events were mostly grade 1/2 (76.2 %). The most common any-grade adverse events were gastrointestinal (including diarrhea [90.2 %]). The early death rate across all patients was 14.8 %. Plasma idasanutlin exposure was dose related. In TP53 wild-type patients, composite complete remission rates were 18.9 % with monotherapy and 35.6 % with combination therapy. Based on these results, idasanutlin development continued with further investigation in the treatment of acute myeloid leukemia. ClinicalTrials.gov: NCT01773408.

Risk and Response-Adapted Treatment in Multiple Myeloma

Simple Summary

Therapeutic strategies in multiple myeloma have been adapted only to age and comorbidities for a long time. Given the currently available therapeutic and technologic arsenal, the time may have come to refine this adaptation. First, high-risk patients should benefit from the most intensive and efficient combinations from diagnosis. Here, we review these different strategies and how to define and identify high-risk myeloma patients in current clinical practice. In addition, the advent of technologies detecting minimal residual disease gives us this opportunity to define the quality of response to treatment with an unpreceded sensitivity and adapt treatment accordingly. Finally, even if molecular targeting is still nascent in myeloma, some molecular features are interesting to detect at relapse to determine optimal salvage treatments.

Abstract

Myeloma therapeutic strategies have been adapted to patients’ age and comorbidities for a long time. However, although cytogenetics and clinical presentations (plasmablastic cytology; extramedullary disease) are major prognostic factors, until recently, all patients received the same treatment whatever their initial risk. No strong evidence allows us to use a personalized treatment according to one cytogenetic abnormality in newly diagnosed myeloma. Retrospective studies showed a benefit of a double autologous transplant in high-risk cytogenetics according to the International Myeloma Working Group definition (t(4;14), t(14;16) or del(17p)). Moreover, this definition has to be updated since other independent abnormalities, namely gain 1q, del(1p32), and trisomies 5 or 21, as well as TP53 mutations, are also prognostic. Another very strong predictive tool is the response to treatment assessed by the evaluation of minimal residual disease (MRD). We are convinced that the time has come to use it to adapt the strategy to a dynamic risk. Many trials are ongoing to answer many questions: when and how should we adapt the therapy, its intensity and duration. Nevertheless, we also have to take into account the clinical outcome for one patient, especially adverse events affecting his or her quality of life and his or her preferences for continuous/fixed duration treatment.

A precision medicine approach to management of acute myeloid leukemia in older adults

PURPOSE OF REVIEW

Therapy selection in older adults with acute myeloid leukemia (AML) can be challenging because of a higher incidence of high-risk cytogenetic and molecular features conferring chemoresistance and poor functional status leading to increased treatment-related toxicities. The purpose of this review is to highlight the recent advances in precision medicine in AML that have shown promise to improve outcomes of older adults.

RECENT FINDINGS

The utilization of next generation sequencing to identify and target actionable mutations can influence therapy selection in one-third of patients and can result in higher response rates as well as survival compared with those who do not receive targeted therapy. Oral targeted agents are available for AML with IDH 1, IDH2, or FLT3 mutations. Low-intensity venetoclax-based regimens have shown high rates of responses in AML, particularly among those with NPM1 and IDH2 mutations; responses are often durable and associated with minimal residual disease (MRD) negativity. Multiple studies have demonstrated the prognostic significance of flow cytometric MRD, with potential implications for subsequent therapy.

SUMMARY

Novel approaches for AML risk-stratification, MRD assessment, and a precision medicine approach offer significant promise to improve survival and quality of life of older adults.

Targeting p53 in chronic lymphocytic leukemia

INTRODUCTION

Genomic studies have allowed to identify molecular predictors for chronic lymphocytic leukemia (CLL) treatment tailoring. TP53 disruption is the strongest predictor of chemo-refractoriness and its assessment is the first decisional node in the disease treatment algorithm.

AREAS COVERED

The review covers the p53 biological pathway, its genetic alterations and clinical implications in CLL, and its druggable targets. The potential therapeutic options for TP53 disrupted patients are described, including: i) agents circumventing TP53 disruption; ii) targeted therapies restoring the physiological function of mutant p53; and iii) medicines potentiating p53 function.

EXPERT OPINION

The key approach to improve CLL outcome is treatment tailoring in individual patients. BCR and BCL2 inhibitors have significantly improved CLL survival, however TP53 disrupted patients still have a less favorable outcome than wild type cases, possibly because these novel drugs do not directly target p53 and do not restore the function of the disrupted p53 pathway. Emerging innovative molecules in cancer are able to restore the p53 mutant protein and/or potentiate the activity of the p53 wild type protein. If these compounds were confirmed as efficacious also for CLL, they would represent another step forward in the care of high risk CLL patients with TP53 abnormalities.

Precision medicine in acute myeloid leukemia: where are we now and what does the future hold?

INTRODUCTION

Precision medicine has revolutionized the diagnostic and therapeutic management of acute myeloid leukemia (AML), from standardized schemes based on chemotherapy to tailored approaches according to molecular and genetic profile and targeted therapy.

AREAS COVERED

The main topics of precision medicine in AML were reviewed in MEDLINE, EMBASE, and Cochrane Central Register databases, and future directions in this therapeutic area were addressed. This review included targeted therapies, drug-sensitivity tests and predictive biomarkers, and genetic studies employing pharmacogenetic and deep sequencing strategies.

EXPERT OPINION

Precision medicine has opened the door to personalized therapy for specific AML patient populations with promising results. Several targeted therapies have been approved or are being tested for specific mutations (i.e. FLT3, IDH, BCL-2, TP53), obtaining improvements in clinical outcomes and less toxicity as compared with intensive treatment, allowing potential combination therapy. Ongoing trials and real data will establish the role of these molecules in monotherapy or combined in different AML settings (front-line, relapsed/refractory, or post-transplant). Experience in drug-sensitivity predictors and pharmacogenetic biomarkers is encouraging and could be useful tools in the next years, but we need a better understanding of AML biology and pathogenesis as well as confirmatory studies to demonstrate the utility in clinical practice.

MDM2 inhibition: an important step forward in cancer therapy

Targeting the interaction between tumor suppressor p53 and the E3 ligase MDM2 represents an attractive treatment approach for cancers with wild-type or functional TP53. Indeed, several small molecules have been developed and evaluated in various malignancies. We provide an overview of MDM2 inhibitors under preclinical and clinical investigation, with a focus on molecules with ongoing clinical trials, as indicated by ClinicalTrials.gov . Because preclinical and clinical exploration of combination strategies is underway, data supporting these combinations are also described. We identified the following molecules for inclusion in this review: RG7112 (RO5045337), idasanutlin (RG7388), AMG-232 (KRT-232), APG-115, BI-907828, CGM097, siremadlin (HDM201), and milademetan (DS-3032b). Information about each MDM2 inhibitor was collected from major congress records and PubMed using the following search terms: each molecule name, "MDM2"and "HDM2." Only congress records were limited by date (January 1, 2012-March 6, 2020). Special attention was given to available data in hematologic malignancies; however, available safety data in any indication are reported. Overall, targeting MDM2 is a promising treatment strategy, as evidenced by the increasing number of MDM2 inhibitors entering the clinic. Additional clinical investigation is needed to further elucidate the role of MDM2 inhibitors in the treatment of human cancers.

Targeting Mouse Double Minute 2: Current Concepts in DNA Damage Repair and Therapeutic Approaches in Cancer

Defects in DNA damage repair may cause genome instability and cancer development. The tumor suppressor gene p53 regulates cell cycle arrest to allow time for DNA repair. The oncoprotein mouse double minute 2 (MDM2) promotes cell survival, proliferation, invasion, and therapeutic resistance in many types of cancer. The major role of MDM2 is to inhibit p53 activity and promote its degradation. In this review, we describe the influence of MDM2 on genomic instability, the role of MDM2 on releasing p53 and binding DNA repair proteins to inhibit repair, and the regulation network of MDM2 including its transcriptional modifications, protein stability, and localization following DNA damage in genome integrity maintenance and in MDM2-p53 axis control. We also discuss p53-dependent and p53 independent oncogenic function of MDM2 and the outcomes of clinical trials that have been used with clinical inhibitors targeting p53-MDM2 to treat certain cancers.