First-in-human, phase I dose-escalation study of the safety, pharmacokinetics, and pharmacodynamics of RO5126766, a first-in-class dual MEK/RAF inhibitor in patients with solid tumors

RO5126766 attenuates osteoarthritis by inhibiting osteoclastogenesis and protecting chondrocytes through mediating the ERK pathway

Background

Osteoarthritis (OA) is a degenerative joint disease that remains challenging to treat due to lack of complete understanding of its pathogenesis. Previous studies have identified RO5126766 (RO) as a small molecule compound that inhibited RAF/MEK-ERK pathway and garnered much interest for its anti-cancer properties. But its role in the treatment of OA remains unclear.

Methods

This study employed the anterior cruciate ligament transection (ACLT) procedure to create an OA model in mice. The effects of RO on pathological changes in articular cartilage and subchondral bone were assessed using micro-CT and histological staining. Mice received peritoneal injections of RO at 1 mg/kg and 5 mg/kg biweekly for 4 weeks after ACLT, while control mice received saline. In vitro, bone marrow-derived macrophages were cultured to examine the effects of RO on osteoclast activation using immunofluorescence, TRAP staining, and bone resorption assays. The inflammatory degeneration of chondrocytes and gene expression levels were evaluated using staining and RT-qPCR. Western blot and immunohistochemistry were used to analyze MAPK signaling and autophagy-related protein expression, investigating RO's molecular mechanism in OA treatment. Human single-cell data were also analyzed to identify genes and pathways upregulated in OA tissues.

Results

Our findings showed that RO protects subchondral bone by inhibiting osteoclast formation in the ACLT mouse model of OA. In vitro, RO was shown to inhibit osteoclast differentiation and reduce inflammatory degeneration of chondrocytes. Mechanistically, RO counteracted subchondral osteoclast hyperactivation by suppressing the ERK/c-fos/NFATc1 signaling pathway. Additionally, RO inhibited LPS-induced inflammatory degeneration of chondrocytes and enhanced autophagy via the ERK pathway. Single-cell analysis further confirmed significant upregulation of the ERK signaling pathway in human OA tissues.

Conclusions

Overall, our findings suggested that RO inhibited osteoclast differentiation and protected articular cartilage, suggesting its potential as a novel treatment for OA.

Translational potential of this article

In this study, we have, for the first time, substantiated the therapeutic potential of RO in the treatment of OA. By demonstrating its ability to inhibit osteoclast differentiation and protect articular cartilage, RO could offer a new avenue for disease-modifying treatments in OA. Thus, this paper provides valuable insights into understanding the molecular mechanisms and treatment of OA.

Trametinib Suppresses the Stimulated T Cells Through G1 Arrest and Apoptosis

The development of efficient immunosuppressants may bring significant benefits to patients after organ/stem transplantation and those with allergies or autoimmune diseases. MEK inhibitors were originally developed as anticancer reagents, but recent reports have suggested that they may have the potential to be immunosuppressants. Trametinib is a first-in-class MEK inhibitor. Here, we examined the effects of trametinib on the immune system and revealed its mechanism. Trametinib suppressed both CD4 and CD8 T-cell proliferation and activated T cells, which expressed CD25 and TIM3, in a dose-dependent manner in vitro. Trametinib also suppressed T cell-related cytokine secretion in a dose-dependent manner. Notably, trametinib suppressed T cell proliferation through the induction of G1 arrest and apoptosis in stimulated T cells. In addition, trametinib induced regulatory T cells (Tregs). We confirmed that low concentrations of trametinib (1 and 10 nM) were not toxic toward splenic naïve T cells and normal mouse liver cells. In this study, we demonstrated whether trametinib suppressed CD4 and CD8 T cell proliferation by inducing G1 arrest and apoptosis along with suppression of cytokine secretion.

Intermittent MEK Inhibition with GITR Costimulation Rescues T-cell Function for Increased Efficacy with CTLA-4 Blockade in Solid Tumor Models

MEK inhibitors (MEKi) have shown limited success as a treatment for MAPK/ERK pathway-dependent cancers due to various resistance mechanisms tumor cells can employ. CH5126766 (CKI27) is an inhibitor that binds to MEK and prevents release of RAF, reducing the relief of negative feedback commonly observed with other MEKis. We observed that CKI27 increased MHC expression in tumor cells and improved T cell-mediated killing. Yet, CKI27 also decreased T-cell proliferation, activation, and cytolytic activity by inhibiting the MAPK/ERK pathway that is activated downstream of T-cell receptor signaling. Therefore, we aimed to balance the positive and negative immunomodulatory effects of MEKis for optimal combination with immunotherapy. Intermittent administration of CKI27 allowed T cells to partially recover and costimulation via GITR and OX-40 agonist antibodies completely alleviated inhibition of function. In Kras mutant lung and colon tumor mouse models, intermittent CKI27 and anti-GITR significantly decreased tumor growth and prolonged survival when further combined with CTLA-4 immune checkpoint blockade. Moreover, this triple combination increased CD8+ and CD4+ T-cell proliferation, activation, and effector/memory subsets in the tumor-draining lymph nodes and tumors and led to intratumoral regulatory T-cell destabilization. These data, collectively, will allow for more informed decisions when optimizing combination regimens by overcoming resistance, reducing toxicity, and generating long-term immune responses.

Prospects of focal adhesion kinase inhibitors as a cancer therapy in preclinical and early phase study

INTRODUCTION

FAK, a nonreceptor cytoplasmic tyrosine kinase, plays a crucial role in tumor metastasis, drug resistance, tumor stem cell maintenance, and regulation of the tumor microenvironment. FAK has emerged as a promising target for tumor therapy based on both preclinical and clinical data.

AREAS COVERED

This paper aims to summarize the molecular mechanisms underlying FAK's involvement in tumorigenesis and progression. Encouraging results have emerged from ongoing clinical trials of FAK inhibitors. Additionally, we present an overview of clinical trials for FAK inhibitors, examining their potential as promising treatments. The pertinent studies gathered from databases including PubMed, ClinicalTrials.gov.

EXPERT OPINION

Since the first finding in 1990s, targeting FAK has became the focus of interests in many pharmaceutical companies. Through 30 years' discovery, the industry and academy gradually realized the features of FAK target which may not be a driver gene but a solid defense system for the cancer initiation and development. Currently, the ongoing clinical regimens involving FAK inhibition are all the combination strategies in which FAK inhibitors can further strengthen the cancer cell killing effects of other testing agents. The emerging positive signal in clinical trials foresee targeting FAK as class will be an effective mean to fight against cancers.

Mediator kinase inhibition impedes transcriptional plasticity and prevents resistance to ERK/MAPK-targeted therapy in KRAS-mutant cancers

Acquired resistance remains a major challenge for therapies targeting oncogene activated pathways. KRAS is the most frequently mutated oncogene in human cancers, yet strategies targeting its downstream signaling kinases have failed to produce durable treatment responses. Here, we developed multiple models of acquired resistance to dual-mechanism ERK/MAPK inhibitors across KRAS-mutant pancreatic, colorectal, and lung cancers, and then probed the long-term events enabling survival against this class of drugs. These studies revealed that resistance emerges secondary to large-scale transcriptional adaptations that are diverse and cell line-specific. Transcriptional reprogramming extends beyond the well-established early response, and instead represents a dynamic, evolved process that is refined to attain a stably resistant phenotype. Mechanistic and translational studies reveal that resistance to dual-mechanism ERK/MAPK inhibition is broadly susceptible to manipulation of the epigenetic machinery, and that Mediator kinase, in particular, can be co-targeted at a bottleneck point to prevent diverse, cell line-specific resistance programs.

BRAF - a tumour-agnostic drug target with lineage-specific dependencies

In June 2022, the FDA granted Accelerated Approval to the BRAF inhibitor dabrafenib in combination with the MEK inhibitor trametinib for the treatment of adult and paediatric patients (≥6 years of age) with unresectable or metastatic BRAFV600E-mutant solid tumours, except for BRAFV600E-mutant colorectal cancers. The histology-agnostic approval of dabrafenib plus trametinib marks the culmination of two decades of research into the landscape of BRAF mutations in human cancers, the biochemical mechanisms underlying BRAF-mediated tumorigenesis, and the clinical development of selective RAF and MEK inhibitors. Although the majority of patients with BRAFV600E-mutant tumours derive clinical benefit from BRAF inhibitor-based combinations, resistance to treatment develops in most. In this Review, we describe the biochemical basis for oncogenic BRAF-induced activation of MAPK signalling and pan-cancer and lineage-specific mechanisms of intrinsic, adaptive and acquired resistance to BRAF inhibitors. We also discuss novel RAF inhibitors and drug combinations designed to delay the emergence of treatment resistance and/or expand the population of patients with BRAF-mutant cancers who benefit from molecularly targeted therapies.

Recent advances of anti-angiogenic inhibitors targeting VEGF/VEGFR axis

Vascular endothelial growth factors (VEGF), Vascular endothelial growth factor receptors (VEGFR) and their downstream signaling pathways are promising targets in anti-angiogenic therapy. They constitute a crucial system to regulate physiological and pathological angiogenesis. In the last 20 years, many anti-angiogenic drugs have been developed based on VEGF/VEGFR system to treat diverse cancers and retinopathies, and new drugs with improved properties continue to emerge at a fast rate. They consist of different molecular structures and characteristics, which enable them to inhibit the interaction of VEGF/VEGFR, to inhibit the activity of VEGFR tyrosine kinase (TK), or to inhibit VEGFR downstream signaling. In this paper, we reviewed the development of marketed anti-angiogenic drugs involved in the VEGF/VEGFR axis, as well as some important drug candidates in clinical trials. We discuss their mode of action, their clinical benefits, and the current challenges that will need to be addressed by the next-generation of anti-angiogenic drugs. We focus on the molecular structures and characteristics of each drug, including those approved only in China.

Navigating the ERK1/2 MAPK Cascade

The RAS-ERK pathway is a fundamental signaling cascade crucial for many biological processes including proliferation, cell cycle control, growth, and survival; common across all cell types. Notably, ERK1/2 are implicated in specific processes in a context-dependent manner as in stem cells and pancreatic β-cells. Alterations in the different components of this cascade result in dysregulation of the effector kinases ERK1/2 which communicate with hundreds of substrates. Aberrant activation of the pathway contributes to a range of disorders, including cancer. This review provides an overview of the structure, activation, regulation, and mutational frequency of the different tiers of the cascade; with a particular focus on ERK1/2. We highlight the importance of scaffold proteins that contribute to kinase localization and coordinate interaction dynamics of the kinases with substrates, activators, and inhibitors. Additionally, we explore innovative therapeutic approaches emphasizing promising avenues in this field.

MEK inhibitors in cancer treatment: structural insights, regulation, recent advances and future perspectives

MEK1/2 are critical components of the RAS-RAF-MEK-ERK or MAPK signalling pathway that regulates a variety of cellular functions including proliferation, survival, and differentiation. In 1997, a lung cancer cell line was first found to have a MEK mutation (encoding MEK2P298L). MEK is involved in various human cancers such as non-small cell lung cancer (NSCLC), spurious melanoma, and pancreatic, colorectal, basal, breast, and liver cancer. To date, 4 MEK inhibitors i.e., trametinib, cobimetinib, selumetinib, and binimetinib have been approved by the FDA and several are under clinical trials. In this review, we have highlighted structural insights into the MEK1/2 proteins, such as the αC-helix, catalytic loop, P-loop, F-helix, hydrophobic pocket, and DFG motif. We have also discussed current issues with all FDA-approved MEK inhibitors or drugs under clinical trials and combination therapies to improve the efficacy of clinical drugs. Finally, this study addressed recent developments on synthetic MEK inhibitors (from their discovery in 1997 to 2022), their unique properties, and their relevance to MEK mutant inhibition.

The potential of RAS/RAF/MEK/ERK (MAPK) signaling pathway inhibitors in ovarian cancer: A systematic review and meta-analysis

BACKGROUND

The RAS/RAF/MEK/ERK (MAPK) pathway plays a role in ovarian carcinogenesis. Low-grade serous ovarian carcinoma (LGSOC) frequently harbors activating MAPK mutations. MAPK inhibitors have been used in small subsets of ovarian carcinoma (OC) patients to control tumor growth. Therefore, we performed a meta-analysis to evaluate the effectiveness of MAPK inhibitors in OC patients. We aimed to determine the clinical benefit rate (CBR), the subgroup of MAPK inhibitors with the best CBR and overall response rate (ORR), and the most common adverse events.

METHODS

We conducted a search in PubMed, Embase via Ovid, the Cochrane library and clinicaltrials.gov on studies evaluating the efficacy of single MAPK pathway inhibition with MAPK pathway inhibitors in OC patients. Our primary outcome included the CBR, defined by the proportion of patients with stable disease (SD), complete (CR) and partial response (PR). Secondary outcomes included the ORR (including PR and CR) and grade 3 and 4 adverse events. Meta-analysis was performed using a random-effects model.

RESULTS

We included nine studies with a total of 319 OC patients, for which we determined a pooled CBR of 63% (95%-CI 39-84%, I² = 92%). Combined treatment with Raf- and MEK inhibitors in in BRAF^v600 mutated LGSOC (n = 6) had the greatest efficacy with a CBR of 100% and ORR of 83%. MEK inhibitors had the best efficacy as a single agent. Subgroup analysis by tumor histology demonstrated a significantly higher CBR and ORR in patients with LGSOC, with a pooled CBR and ORR of 87% (95%-CI 81-92%, I² = 0%) and 27% (95%-CI 10-48%, I² = 77%) respectively. Adverse events of grade 3 or higher were reported frequently: 123 in 167 patients.

CONCLUSIONS

MEK inhibitors are the most promising single agents in (LGS)OC. However, dual MAPK pathway inhibition should be considered in patients with a BRAF^v600 mutation, or non-mutated OC with depleted treatment options due indications of higher efficacy and tolerable toxicity profiles.

Onco-immunomodulatory properties of pharmacological interference with RAS-RAF-MEK-ERK pathway hyperactivation

Hyperactivation of the RAS-RAF-MEK-ERK cascade - a mitogen-activated protein kinase pathway – has a well-known association with oncogenesis of leading tumor entities, including non-small cell lung cancer, colorectal carcinoma, pancreatic ductal adenocarcinoma, and malignant melanoma. Increasing evidence shows that genetic alterations leading to RAS-RAF-MEK-ERK pathway hyperactivation mediate contact- and soluble-dependent crosstalk between tumor, tumor microenvironment (TME) and the immune system resulting in immune escape mechanisms and establishment of a tumor-sustaining environment. Consequently, pharmacological interruption of this pathway not only leads to tumor-cell intrinsic disruptive effects but also modification of the TME and anti-tumor immunomodulation. At the same time, the importance of ERK signaling in immune cell physiology and potentiation of anti-tumor immune responses through ERK signaling inhibition within immune cell subsets has received growing appreciation. Specifically, a strong case was made for targeted MEK inhibition due to promising associated immune cell intrinsic modulatory effects. However, the successful transition of therapeutic agents interrupting RAS-RAF-MEK-ERK hyperactivation is still being hampered by significant limitations regarding durable efficacy, therapy resistance and toxicity. We here collate and summarize the multifaceted role of RAS-RAF-MEK-ERK signaling in physiology and oncoimmunology and outline the rationale and concepts for exploitation of immunomodulatory properties of RAS-RAF-MEK-ERK inhibition while accentuating the role of MEK inhibition in combinatorial and intermittent anticancer therapy. Furthermore, we point out the extensive scientific efforts dedicated to overcoming the challenges encountered during the clinical transition of various therapeutic agents in the search for the most effective and safe patient- and tumor-tailored treatment approach.

A Genome-Wide Screen Identifies PDPK1 as a Target to Enhance the Efficacy of MEK1/2 Inhibitors in NRAS Mutant Melanoma

Melanomas frequently harbor activating NRAS mutations. However, limited advance has been made in developing targeted therapy options for patients with NRAS mutant melanoma. MEK inhibitors (MEKi) show modest efficacy in the clinic and their actions need to be optimized. In this study, we performed a genome-wide CRISPR-Cas9-based screen and demonstrated that loss of phosphoinositide-dependent kinase-1 (PDPK1) enhances the efficacy of MEKi. The synergistic effects of PDPK1 loss and MEKi was validated in NRAS mutant melanoma cell lines using pharmacologic and molecular approaches. Combined PDPK1 inhibitors (PDPK1i) with MEKi suppressed NRAS mutant xenograft growth and induced gasdermin E-associated pyroptosis. In an immune-competent allograft model, PDPK1i+MEKi increased the ratio of intratumoral CD8+ T cells, delayed tumor growth, and prolonged survival; the combination treatment was less effective against tumors in immune-deficient mice. These data suggest PDPK1i+MEKi as an efficient immunostimulatory strategy against NRAS mutant melanoma.

SIGNIFICANCE

Targeting PDPK1 stimulates antitumor immunity and sensitizes NRAS mutant melanoma to MEK inhibition, providing rationale for the clinical development of a combinatorial approach for treating patients with melanoma.

The overview of Mitogen-activated extracellular signal-regulated kinase (MEK)-based dual inhibitor in the treatment of cancers

Mitogen-activated extracellular signal-regulated kinase 1 and 2 (MEK1/2) are the critical components of the mitogen-activated protein kinase/extracellular signal-regulated kinase 1 and 2 (MAPK/ERK1/2) signaling pathway which is one of the well-characterized kinase cascades regulating cell proliferation, differentiation, growth, metabolism, survival and mobility both in normal and cancer cells. The aberrant activation of MAPK/ERK1/2 pathway is a hallmark of numerous human cancers, therefore targeting the components of this pathway to inhibit its dysregulation is a promising strategy for cancer treatment. Enormous efforts have been done in the development of MEK1/2 inhibitors and encouraging advancements have been made, including four inhibitors approved for clinical use. However, due to the multifactorial property of cancer and rapidly arising drug resistance, the clinical efficacy of these MEK1/2 inhibitors as monotherapy are far from ideal. Several alternative strategies have been developed to improve the limited clinical efficacy, including the dual inhibitor which is a single drug molecule able to simultaneously inhibit two targets. In this review, we first introduced the activation and function of the MAPK/ERK1/2 components and discussed the advantages of MEK1/2-based dual inhibitors compared with the single inhibitors and combination therapy in the treatment of cancers. Then, we overviewed the MEK1/2-based dual inhibitors for the treatment of cancers and highlighted the theoretical basis of concurrent inhibition of MEK1/2 and other targets for development of these dual inhibitors. Besides, the status and results of these dual inhibitors in both preclinical and clinical studies were also the focus of this review.

Targeting Mutant Kirsten Rat Sarcoma Viral Oncogene Homolog in Non-Small Cell Lung Cancer: Current Difficulties, Integrative Treatments and Future Perspectives

In the past few decades, several gene mutations, including the anaplastic lymphoma kinase, epidermal growth factor receptor, ROS proto-oncogene 1 and rat sarcoma viral oncogene homolog (RAS), have been discovered in non-small cell lung cancer (NSCLC). Kirsten rat sarcoma viral oncogene homolog (KRAS) is the isoform most frequently altered in RAS-mutated NSCLC cases. Due to the structural and biochemical characteristics of the KRAS protein, effective approaches to treating KRAS-mutant NSCLC still remain elusive. Extensive recent research on KRAS-mutant inhibitors has made a breakthrough in identifying the covalent KRASG12C inhibitor as an effective agent for the treatment of NSCLC. This review mainly concentrated on introducing new covalent KRASG12C inhibitors like sotorasib (AMG 510) and adagrasib (MRTX 849); summarizing inhibitors targeting the KRAS-related upstream and downstream effectors in RAF/MEK/ERK pathway and PI3K/AKT/mTOR pathway; exploring the efficacy of immunotherapy and certain emerging immune-related therapeutics such as adoptive cell therapy and cancer vaccines. These inhibitors are being investigated in clinical trials and have exhibited promising effects. On the other hand, naturally extracted compounds, which have exhibited safe and effective properties in treating KRAS-mutant NSCLC through suppressing the MAPK and PI3K/AKT/mTOR signaling pathways, as well as through decreasing PD-L1 expression in preclinical studies, could be expected to enter into clinical studies. Finally, in order to confront the matter of drug resistance, the ongoing clinical trials in combination treatment strategies were summarized herein.

Kinase Inhibitors as Potential Therapeutic Agents in the Treatment of COVID-19

Corona virus is quickly spreading around the world. The goal of viral management is to disrupt the virus's life cycle, minimize lung damage, and alleviate severe symptoms. Numerous strategies have been used, including repurposing existing antivirals or drugs used in previous viral outbreaks. One such strategy is to repurpose FDA-approved kinase inhibitors that are potential chemotherapeutic agents and have demonstrated antiviral activity against a variety of viruses, including MERS, SARS-CoV-1, and others, by inhibiting the viral life cycle and the inflammatory response associated with COVID-19. The purpose of this article is to identify licensed kinase inhibitors that have the ability to reduce the virus's life cycle, from entrance through viral propagation from cell to cell. Several of these inhibitors, including imatinib, ruxolitinib, silmitasertib, and tofacitinib (alone and in conjunction with hydroxychloroquine), are now undergoing clinical studies to determine their efficacy as a possible treatment drug. The FDA approved baricitinib (a Janus kinase inhibitor) in combination with remdesivir for the treatment of COVID-19 patients receiving hospital care in November 2020. While in vitro trials with gilteritinib, fedratinib, and osimertinib are encouraging, further research is necessary before these inhibitors may be used to treat COVID-19 patients.

Targeting KRAS G12C mutation in lung adenocarcinoma

Lung cancer continues to be a major cause of cancer related death globally. Therapies targeting driver mutations have significantly extended the survival of patients whose lung cancer cells harbor these mutations. Patients with KRAS mutations, however, lacked specific targeted therapy until the recent FDA approval of sotorasib, a specific inhibitor of KRAS G12C mutant protein. We will discuss the efficacy and toxicities of the novel KRAS G12C inhibitors as well as other indirect strategies for targeting oncogenic KRAS mutations. We will review the limited literature on acquired resistance to these inhibitors and the novel combinatorial treatment strategies that are being tested currently in clinical trials.

Kinases as Potential Therapeutic Targets for Anti-coronaviral Therapy

The global coronavirus disease-19 (COVID-19) has affected more than 140 million and killed more than 3 million people worldwide as of April 20, 2021. The novel human severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been identified as an etiological agent for COVID-19. Several kinases have been proposed as possible mediators of multiple viral infections, including life-threatening coronaviruses like SARS-CoV-1, Middle East syndrome coronavirus (MERS-CoV), and SARS-CoV-2. Viral infections hijack abundant cell signaling pathways, resulting in drastic phosphorylation rewiring in the host and viral proteins. Some kinases play a significant role throughout the viral infection cycle (entry, replication, assembly, and egress), and several of them are involved in the virus-induced hyperinflammatory response that leads to cytokine storm, acute respiratory distress syndrome (ARDS), organ injury, and death. Here, we highlight kinases that are associated with coronavirus infections and their inhibitors with antiviral and potentially anti-inflammatory, cytokine-suppressive, or antifibrotic activity.

MEK1/2 inhibition rescues neurodegeneration by TFEB-mediated activation of autophagic lysosomal function in a model of Alzheimer's Disease

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder, which is characterized by cognitive deficit due to synaptic loss and neuronal death. Extracellular amyloid β plaques are one of the pathological hallmarks of AD. The autophagic lysosomal pathway is the essential mechanism to maintain cellular homeostasis by driving clearance of protein aggregates and is dysfunctional in AD. Here, we showed that inhibiting MEK/ERK signaling using a clinically available MEK1/2 inhibitor, trametinib (GSK1120212, SNR1611), induces the protection of neurons through autophagic lysosomal activation mediated by transcription factor EB (TFEB) in a model of AD. Orally administered trametinib recovered impaired neural structures, cognitive functions, and hippocampal long-term potentiation (LTP) in 5XFAD mice. Trametinib also reduced Aβ deposition via induction of autophagic lysosomal activation. RNA-sequencing analysis revealed upregulation of autophagic lysosomal genes by trametinib administration. In addition, trametinib inhibited TFEB phosphorylation at Ser142 and promoted its nuclear translocation, which in turn induced autophagic lysosomal related genes, indicating that trametinib activates the autophagic lysosomal process through TFEB activation. From these observations, we concluded that MEK inhibition provides neuronal protection from the Aβ burden by increasing autophagic lysosomal activity. Thus, MEK inhibition may be an effective therapeutic strategy for AD.

Recent Developments in Targeting RAS Downstream Effectors for RAS-Driven Cancer Therapy

Aberrant activity of oncogenic rat sarcoma virus (RAS) protein promotes tumor growth and progression. RAS-driven cancers comprise more than 30% of all human cancers and are refractory to frontline treatment strategies. Since direct targeting of RAS has proven challenging, efforts have been centered on the exploration of inhibitors for RAS downstream effector kinases. Two major RAS downstream signaling pathways, including the Raf/MEK/Erk cascade and the phosphatidylinositol-3-kinase (PI3K) pathway, have become compelling targets for RAS-driven cancer therapy. However, the main drawback in the blockade of a single RAS effector is the multiple levels of crosstalk and compensatory mechanisms between these two pathways that contribute to drug resistance against monotherapies. A growing body of evidence reveals that the sequential or synergistic inhibition of multiple RAS effectors is a more convenient route for the efficacy of cancer therapy. Herein, we revisit the recent developments and discuss the most promising modalities targeting canonical RAS downstream effectors for the treatment of RAS-driven cancers.

Emerging Therapies in the Treatment of Advanced Melanoma

Great strides in immunotherapy and targeted therapy have revolutionized the management of previously devastating, advanced melanomas. Although these subfields continue to progress, novel approaches in intratumoral oncolytic therapy, adoptive cell therapy, and vaccine therapies are being developed as adjuncts or alternatives. Cytokines, meanwhile, are seeing a resurgence as a viable option as well. The array of effective agents will, in the next few years, provide options for therapy not only in the adjuvant or unresectable settings but also in the neoadjuvant settings. Perhaps, too, in earlier stage melanomas.

Searching for treatments for non-G12C-KRAS mutant cancers

KRAS mutations drive a wide variety of cancers. Drugs targeting the protein product of KRAS^G12C mutations are currently being evaluated show preliminary efficacy in clinical trials. A clinical trial of VS-6766, a dual RAF-MEK inhibitor, has reported early single agent activity in non-G12C mutated KRAS driven cancers.

Blockade of mutant RAS oncogenic signaling with a special emphasis on KRAS

RAS proteins (HRAS, KRAS, NRAS) participate in many physiological signal transduction processes related to cell growth, division, and survival. The RAS proteins are small (188/189 amino acid residues) and they function as GTPases. These proteins toggle between inactive and functional forms; the conversion of inactive RAS-GDP to active RAS-GTP as mediated by guanine nucleotide exchange factors (GEFs) turns the switch on and the intrinsic RAS-GTPase activity stimulated by the GTPase activating proteins (GAPs) turns the switch off. RAS is upstream to the RAS-RAF-MEK-ERK and the PI3-kinase-AKT signaling modules. Importantly, the overall incidence of RAS mutations in all cancers is about 19% and RAS mutants have been a pharmacological target for more than three decades. About 84% of all RAS mutations involve KRAS. Except for the GTP/GDP binding site, the RAS proteins lack other deep surface pockets thereby hindering efforts to identify high-affinity antagonists; thus, they have been considered to be undruggable. KRAS mutations frequently occur in lung, colorectal, and pancreatic cancers, the three most deadly cancers in the United States. Studies within the last decade demonstrated that the covalent modification of KRAS C12, which accounts for about 10% of all RAS mutations, led to the discovery of an adjacent pocket (called the switch II pocket) that accommodated a portion of the drug. This led to the development of sotorasib as a second-line treatment of KRAS^G12C-mutant non-small cell lung cancer. Considerable effort also has been expended to develop MAP kinase and PI3-kinase pathway inhibitors as indirect RAS antagonists.

New perspectives on targeting RAF, MEK and ERK in melanoma

PURPOSE OF REVIEW

Although immune checkpoint inhibitors and small molecule inhibitors targeting the MAPK pathway have revolutionized the management of metastatic melanoma, long-term disease control occurs only for a minority of patients because of multiple resistance mechanisms. One way to tackle resistance is to develop the next-generation of RAF, MEK and ERK inhibitors using our understanding of the molecular mechanisms that fine-tune the MAPK pathway.

RECENT FINDINGS

Studies on the regulation of the MAPK pathway have revealed a dominant role for homo-dimerization and hetero-dimerization of RAF, MEK and ERK. Allosteric inhibitors that break these dimers are, therefore, undergoing various stages of preclinical and clinical evaluation. Novel MEK inhibitors are less susceptible to differences in MEK's activation state and do not drive the compensatory activation of MEK that could limit efficacy. Innovations in targeting ERK originate from dual inhibitors that block MEK-catalyzed ERK phosphorylation, thereby limiting the extent of ERK reactivation following feedback relief.

SUMMARY

The primary goal in RAF, MEK and ERK inhibitors' development is to produce molecules with less inhibitor paradox and off-target effects, giving robust and sustained MAPK pathway inhibition.

Emerging strategies to target RAS signaling in human cancer therapy

RAS mutations (HRAS, NRAS, and KRAS) are among the most common oncogenes, and around 19% of patients with cancer harbor RAS mutations. Cells harboring RAS mutations tend to undergo malignant transformation and exhibit malignant phenotypes. The mutational status of RAS correlates with the clinicopathological features of patients, such as mucinous type and poor differentiation, as well as response to anti-EGFR therapies in certain types of human cancers. Although RAS protein had been considered as a potential target for tumors with RAS mutations, it was once referred to as a undruggable target due to the consecutive failure in the discovery of RAS protein inhibitors. However, recent studies on the structure, signaling, and function of RAS have shed light on the development of RAS-targeting drugs, especially with the approval of Lumakras (sotorasib, AMG510) in treatment of KRASG12C-mutant NSCLC patients. Therefore, here we fully review RAS mutations in human cancer and especially focus on emerging strategies that have been recently developed for RAS-targeting therapy.

Current therapy of KRAS-mutant lung cancer

KRAS mutations are the most frequent gain-of-function alterations in patients with lung adenocarcinoma (LADC) in the Western world. Although they have been identified decades ago, prior efforts to target KRAS signaling with single-agent therapeutic approaches such as farnesyl transferase inhibitors, prenylation inhibition, impairment of KRAS downstream signaling, and synthetic lethality screens have been unsuccessful. Moreover, the role of KRAS oncogene in LADC is still not fully understood, and its prognostic and predictive impact with regards to the standard of care therapy remains controversial. Of note, KRAS-related studies that included general non-small cell lung cancer (NSCLC) population instead of LADC patients should be very carefully evaluated. Recently, however, comprehensive genomic profiling and wide-spectrum analysis of other co-occurring genetic alterations have identified unique therapeutic vulnerabilities. Novel targeted agents such as the covalent KRAS G12C inhibitors or the recently proposed combinatory approaches are some examples which may allow a tailored treatment for LADC patients harboring KRAS mutations. This review summarizes the current knowledge about the therapeutic approaches of KRAS-mutated LADC and provides an update on the most recent advances in KRAS-targeted anti-cancer strategies, with a focus on potential clinical implications.

Drug-Induced Pseudo-Central Serous Chorioretinopathy in Carcinoma Patients

PURPOSE

Patients with carcinomas often share symptoms of vision deterioration as part of paraneoplastic retinopathy (PNR), based on a cross-reaction between antigens expressed by the underlying tumor and retinal proteins. However, some of the underlying symptoms may be explained by a drug-induced toxicity. The application of new therapeutic strategies with mitogen-activated protein kinase (MEK) and fibroblast growth factor receptor (FGFR) inhibitors in advanced cancers are still under evaluation for safety and tolerability, but also for dose-limiting toxicities. In the presented data, we identified a drug-induced pseudo-central serous chorioretinopathy (pCSC) to be the reason for central vision deterioration.

METHODS

A retrospective, observational, case-controlled study included seven patients receiving MEK and six patients receiving FGFR inhibitor treatment for bronchopulmonal cancer. We compared the clinical and diagnostic pictures of pCSC patients with that of 50 CSC patients (100 eyes) and 7 patients (14 eyes) with PNR. The activity of pCSC was assessed by clinical examination, supported by multimodal imaging. The relationships between clinical symptomatology and systemic disease activity were evaluated.

RESULTS

Three out of thirteen patients (23.1%) showed signs of pCSC (one FGFR and two MEK inhibitor patients). All three pCSC patients showed central bilateral detachment of the neurosensory retina on OCT imaging, but also paracentral multifocal lesions in the second subject. Compared to our CSC and PNR patients, the lesions in pCSC patients showed no lipofuscin irregularities on FAF. With reduction of the MEK treatment, the lesions on one MEK subject disappeared and BCVA restored to 0.8. In one MEK- and the FGFR subject, the lesions reduced in size without therapy discontinuation.

CONCLUSION

Based on our data, MEK and FGFR inhibitor-associated pCSC is a mild, self-limited retinopathy that seems to disappear simultaneously or shortly after discontinuation of medication, with subsequent restoration of the central visual function.

Binimetinib, pemetrexed and cisplatin, followed by maintenance of binimetinib and pemetrexed in patients with advanced non-small cell lung cancer (NSCLC) and KRAS mutations. The phase 1B SAKK 19/16 trial

BACKGROUND

KRAS mutations are found in 20-25 % of non-squamous non-small cell lung cancer (NSCLC) and therapies targeting the RAS/MEK/ERK pathway are in development. We performed a multicenter open-label phase 1B trial to determine the recommended phase 2 dose and early antitumor activity of the MEK-inhibitor binimetinib combined with cisplatin and pemetrexed.

METHODS

Eligible patients (pts) had stage III-IV NSCLC unsuitable for curative treatment, KRAS exon 2 or 3 (codon 12, 13 or 61) mutations, no prior systemic therapy. Pts were enrolled into part 1: 3 + 3 design with dose escalation in 2 dose levels (DL) of binimetinib and part 2: expansion cohort at the maximum tolerated dose (MTD). Pts received 4 cycles of cisplatin 75 mg/m², pemetrexed 500 mg/m²and binimetinib 30 (DL1)/45 mg (DL2) orally twice a day (bid) d1-14 q3w followed by pemetrexed and binimetinib until progressive disease (PD) or unacceptable toxicity.

RESULTS

From May 2017 to Dec 2019, 18 pts (13 dose escalation, 5 expansion cohort) were enrolled. Median age was 60 (48-73, range). KRAS mutations were 87.5 % at codon 12. No DLT occurred in the dose escalation cohort. Median number of cycles was 2 (1-17, range). Treatment discontinuation was mainly due to PD (33 %) or pts/physicians' decision (27 %). Together with the expansion cohort, 16 pts were evaluable for safety. Most frequent treatment-related grade 3 AEs were lung infection (25 %), fatigue (19 %), anemia (19 %). Overall response rate among 9 evaluable pts receiving binimetinib at MTD (45 mg bid) was 33 % (7-70 %, 95 % CI). Median progression-free survival was 5.7 months (1.1-14.0, 95 % CI) and overall survival 6.5 months (1.8-NR, 95 % CI).

CONCLUSIONS

Pts treated with combination of cisplatin, pemetrexed and binimetinib presented no unexpected toxicity. No early signal of increased antitumor activity of binimetinib added to chemotherapy was observed in our pts population.

Role of glioblastoma stem cells in cancer therapeutic resistance: a perspective on antineoplastic agents from natural sources and chemical derivatives

Glioblastoma (GBM) is the highest-grade form of glioma, as well as one of the most aggressive types of cancer, exhibiting rapid cellular growth and highly invasive behavior. Despite significant advances in diagnosis and therapy in recent decades, the outcomes for high-grade gliomas (WHO grades III-IV) remain unfavorable, with a median overall survival time of 15–18 months. The concept of cancer stem cells (CSCs) has emerged and provided new insight into GBM resistance and management. CSCs can self-renew and initiate tumor growth and are also responsible for tumor cell heterogeneity and the induction of systemic immunosuppression. The idea that GBM resistance could be dependent on innate differences in the sensitivity of clonogenic glial stem cells (GSCs) to chemotherapeutic drugs/radiation prompted the scientific community to rethink the understanding of GBM growth and therapies directed at eliminating these cells or modulating their stemness. This review aims to describe major intrinsic and extrinsic mechanisms that mediate chemoradioresistant GSCs and therapies based on antineoplastic agents from natural sources, derivatives, and synthetics used alone or in synergistic combination with conventional treatment. We will also address ongoing clinical trials focused on these promising targets. Although the development of effective therapy for GBM remains a major challenge in molecular oncology, GSC knowledge can offer new directions for a promising future.

Research progress of MEK1/2 inhibitors and degraders in the treatment of cancer

Mitogen-activated protein kinase kinases 1 and 2 (MEK1/2) are the crucial part of the RAS-RAF-MEK-ERK pathway (or ERK pathway), which is involved in the regulation of various cellular processes including proliferation, survival, and differentiation et al. Targeting MEK has become an important strategy for cancer therapy, and 4 MEK inhibitors (MEKis) have been approved by FDA to date. However, the application of MEKis is limited due to acquired resistance under long-term treatment. Fortunately, an emerging technology, named proteolysis targeting chimera (PROTAC), could break through this limitation by inducing MEK1/2 degradation. Compared to MEKis, MEK1/2 PROTAC is rarely studied and only three MEK1/2 PROTAC molecules, have been reported until now. This paper will outline the ERK pathway and the mechanism and research progress of MEK1/2 inhibitors, but focus on the development of MEK degraders and their optimization strategies. PAC-1 strategy which can induce MEK degradation indirectly, other PROTACs on ERK pathway, the advantages and challenges of PROTAC technology will be subsequently discussed.

MEK inhibitors for the treatment of non-small cell lung cancer

BRAF and KRAS are two key oncogenes in the RAS/RAF/MEK/MAPK signaling pathway. Concomitant mutations in both KRAS and BRAF genes have been identified in non-small cell lung cancer (NSCLC). They lead to the proliferation, differentiation, and apoptosis of tumor cells by activating the RAS/RAF/MEK/ERK signaling pathway. To date, agents that target RAS/RAF/MEK/ERK signaling pathway have been investigated in NSCLC patients harboring BRAF mutations. BRAF and MEK inhibitors have gained approval for the treatment of patients with NSCLC. According to the reported findings, the combination of MEK inhibitors with chemotherapy, immune checkpoint inhibitors, epidermal growth factor receptor-tyrosine kinase inhibitors or BRAF inhibitors is highly significant for improving clinical efficacy and causing delay in the occurrence of drug resistance. This review summarized the existing experimental results and presented ongoing clinical studies as well. However, further researches need to be conducted to indicate how we can combine other drugs with MEK inhibitors to significantly increase therapeutic effects on patients with lung cancer.

Computational evaluation of potent 2-(1H-imidazol-2-yl) pyridine derivatives as potential V600E-BRAF inhibitors

Background

V600E-BRAF is a major protein target involved in various types of human cancers. However, the acquired resistance of the V600E-BRAF kinase to the vemurafenib and the side effects of other identified drugs initiate the search for efficient inhibitors. In the current paper, virtual docking screening combined with drug likeness and ADMET properties predictions were jointly applied to evaluate potent 2-(1H-imidazol-2-yl) pyridines as V600E-BRAF kinase inhibitors.

Results

Most of the studied compounds showed better docking scores and favorable interactions with theiV600E-BRAF target. Among the screened compounds, the two most potent (14 and 30) with good rerank scores (−124.079 and − 122.290) emerged as the most effective, and potent V600E-BRAF kinase inhibitors which performed better than vemurafenib (−116.174), an approved V600E-BRAF kinase inhibitor. Thus, the docking studies exhibited that these compounds have shown competing inhibition of V600E-BRAF kinase with vemurafenib at the active site and revealed better pharmacological properties based on Lipinski’s and Veber’s drug-likeness rules for oral bioavailability and ADMET properties.

Conclusion

The docking result, drug-likeness rules, and ADMET parameters identified compounds (14 and 30) as the best hits against V600E-BRAF kinase with better pharmacological properties. This suggests that these compounds may be developed as potent V600E-BRAF inhibitors.

Intermittent schedules of the oral RAF-MEK inhibitor CH5126766/VS-6766 in patients with RAS/RAF-mutant solid tumours and multiple myeloma: a single-centre, open-label, phase 1 dose-escalation and basket dose-expansion study

BACKGROUND

CH5126766 (also known as VS-6766, and previously named RO5126766), a novel MEK-pan-RAF inhibitor, has shown antitumour activity across various solid tumours; however, its initial development was limited by toxicity. We aimed to investigate the safety and toxicity profile of intermittent dosing schedules of CH5126766, and the antitumour activity of this drug in patients with solid tumours and multiple myeloma harbouring RAS-RAF-MEK pathway mutations.

METHODS

We did a single-centre, open-label, phase 1 dose-escalation and basket dose-expansion study at the Royal Marsden National Health Service Foundation Trust (London, UK). Patients were eligible for the study if they were aged 18 years or older, had cancers that were refractory to conventional treatment or for which no conventional therapy existed, and if they had a WHO performance status score of 0 or 1. For the dose-escalation phase, eligible patients had histologically or cytologically confirmed advanced or metastatic solid tumours. For the basket dose-expansion phase, eligible patients had advanced or metastatic solid tumours or multiple myeloma harbouring RAS-RAF-MEK pathway mutations. During the dose-escalation phase, we evaluated three intermittent oral schedules (28-day cycles) in patients with solid tumours: (1) 4·0 mg or 3·2 mg CH5126766 three times per week; (2) 4·0 mg CH5126766 twice per week; and (3) toxicity-guided dose interruption schedule, in which treatment at the recommended phase 2 dose (4·0 mg CH5126766 twice per week) was de-escalated to 3 weeks on followed by 1 week off if patients had prespecified toxic effects (grade 2 or worse diarrhoea, rash, or creatinine phosphokinase elevation). In the basket dose-expansion phase, we evaluated antitumour activity at the recommended phase 2 dose, determined from the dose-escalation phase, in biomarker-selected patients. The primary endpoints were the recommended phase 2 dose at which no more than one out of six patients had a treatment-related dose-limiting toxicity, and the safety and toxicity profile of each dosing schedule. The key secondary endpoint was investigator-assessed response rate in the dose-expansion phase. Patients who received at least one dose of the study drug were evaluable for safety and patients who received one cycle of the study drug and underwent baseline disease assessment were evaluable for response. This trial is registered with ClinicalTrials.gov, NCT02407509.

FINDINGS

Between June 5, 2013, and Jan 10, 2019, 58 eligible patients were enrolled to the study: 29 patients with solid tumours were included in the dose-escalation cohort and 29 patients with solid tumours or multiple myeloma were included in the basket dose-expansion cohort (12 non-small-cell lung cancer, five gynaecological malignancy, four colorectal cancer, one melanoma, and seven multiple myeloma). Median follow-up at the time of data cutoff was 2·3 months (IQR 1·6-3·5). Dose-limiting toxicities included grade 3 bilateral retinal pigment epithelial detachment in one patient who received 4·0 mg CH5126766 three times per week, and grade 3 rash (in two patients) and grade 3 creatinine phosphokinase elevation (in one patient) in those who received 3·2 mg CH5126766 three times per week. 4·0 mg CH5126766 twice per week (on Monday and Thursday or Tuesday and Friday) was established as the recommended phase 2 dose. The most common grade 3-4 treatment-related adverse events were rash (11 [19%] patients), creatinine phosphokinase elevation (six [11%]), hypoalbuminaemia (six [11%]), and fatigue (four [7%]). Five (9%) patients had serious treatment-related adverse events. There were no treatment-related deaths. Eight (14%) of 57 patients died during the trial due to disease progression. Seven (27% [95% CI 11·6-47·8]) of 26 response-evaluable patients in the basket expansion achieved objective responses.

INTERPRETATION

To our knowledge, this is the first study to show that highly intermittent schedules of a RAF-MEK inhibitor has antitumour activity across various cancers with RAF-RAS-MEK pathway mutations, and that this inhibitor is tolerable. CH5126766 used as a monotherapy and in combination regimens warrants further evaluation.

FUNDING

Chugai Pharmaceutical.

OCULAR ADVERSE EVENTS ASSOCIATED WITH MEK INHIBITORS

PURPOSE

Mitogen-activates protein kinase (MAPK) inhibitors, particularly MEK inhibitors, have shifted the treatment paradigm for metastatic BRAF-mutant cutaneous melanoma; however, oncologists, ophthalmologists, and patients have noticed different toxicities of variable importance. This review aims to provide an update of the ocular adverse events (OAEs), especially retinal toxicity, associated with the use of MEK inhibitors.

METHODS

We conducted a scientific literature search using the PubMed database up to July 2018 with the terms "MEK inhibitors" with a "review" filter and "MEK inhibitors" with a "clinical trials" filter. Phase I-III experimental studies and reviews were selected. Current principles and techniques for diagnosing and managing MEK inhibitor retinopathy and other OAEs are discussed.

RESULTS

In patients treated with MEK inhibitors, including asymptomatic patients, OAEs occur with an incidence of up to 90%. Mild to severe ophthalmic toxicities are described, including visual disturbances, a 2-line decrease in Snellen visual acuity, dry eye symptoms, ocular adnexal abnormalities, visual field defects, panuveitis, and retinal toxicities, such as different degrees of MEK-associated retinopathy, vascular injury, and retinal vein occlusion.

CONCLUSION

MEK inhibitors can lead to different degrees of retinal, uveal, and adnexal OAE, causing visual disturbances or discomfort. One of the most relevant OAE of MEK therapy is MEK inhibitor-associated retinopathy (MEKAR), which is usually mild, self-limited, and may subside after continuous use of the drug for weeks or months, or discontinuation, thereby restoring the normal visual function of the retina, with some exceptions. Ocular adverse events are often associated with other systemic adverse effects that can modify the dosage of treatment, so the communication with the oncologist is fundamental.

KRAS oncogene may be another target conquered in non-small cell lung cancer (NSCLC)

Kirsten rat sarcoma viral oncogene homolog (KRAS) is one of the most common mutant oncogenes in non‐small cell lung cancer (NSCLC). The survival of patients with KRAS mutations may be much lower than patients without KRAS mutations. However, due to the complex structure and diverse biological properties, it is difficult to achieve specific inhibitors for the direct elimination of KRAS activity, making KRAS a challenging therapeutic target. At present, with the tireless efforts of medical research, including KRAS G12C inhibitors, immunotherapy and other combination strategies, this dilemma is expected to an end. In addition, inhibition of the downstream signaling pathways of KRAS may be a promising combination strategy. Given the rapid development of treatments, understanding the details will be important to determine the individualized treatment options, including combination therapy and potential resistance mechanisms.

The survival of patients with KRAS mutations may be much lower than patients without KRAS mutations. At present, with the tireless efforts of medical research, including KRAS G12C inhibitors, immunotherapy and other combination strategy, this dilemma of KRAS mutated NSCLC is expected to an end.

Growth Factor Receptor Signaling Inhibition Prevents SARS-CoV-2 Replication

SARS-CoV-2 infections are rapidly spreading around the globe. The rapid development of therapies is of major importance. However, our lack of understanding of the molecular processes and host cell signaling events underlying SARS-CoV-2 infection hinders therapy development. We use a SARS-CoV-2 infection system in permissible human cells to study signaling changes by phosphoproteomics. We identify viral protein phosphorylation and define phosphorylation-driven host cell signaling changes upon infection. Growth factor receptor (GFR) signaling and downstream pathways are activated. Drug-protein network analyses revealed GFR signaling as key pathways targetable by approved drugs. The inhibition of GFR downstream signaling by five compounds prevents SARS-CoV-2 replication in cells, assessed by cytopathic effect, viral dsRNA production, and viral RNA release into the supernatant. This study describes host cell signaling events upon SARS-CoV-2 infection and reveals GFR signaling as a central pathway essential for SARS-CoV-2 replication. It provides novel strategies for COVID-19 treatment.

In silico evaluation of some 4-(quinolin-2-yl)pyrimidin-2-amine derivatives as potent V600E-BRAF inhibitors with pharmacokinetics ADMET and drug-likeness predictions

Background

The resistance of V600E-BRAF to the vemurafenib and the side effects of the identified inhibitors trigger the research for a novel and more potent anti-melanoma agents. In this study, virtual docking screening along with pharmacokinetics ADMET and drug-likeness predictions were combined to evaluate some 4-(quinolin-2-yl)pyrimidin-2-amine derivatives as potent V600E-BRAF inhibitors.

Results

Some of the selected compounds exhibited better binding scores and favorable interaction with the V600E-BRAF enzyme. Out of the screened compounds, two most potent (5 and 9) having good Rerank scores (− 128.011 and − 126.258) emerged as effective and potent V600E-BRAF inhibitors that outperformed the FDA-approved V600E-BRAF inhibitor (vemurafenib, − 118.607). Thus, the molecular docking studies revealed that the studied compounds showed competing for inhibition of V600E-BRAF with vemurafenib at the binding site and possessed better pharmacological parameters based on the drug-likeness rules filters for the oral bioavailability, and ADMET risk parameters.

Conclusion

The docking analysis, drug-likeness rules filters, and ADMET study identified compounds (5 and 9) as the best hits against V600E-BRAF kinase with enhanced pharmacological properties. This recommends that these compounds may be developed as potent anti-melanoma agents.

MEK Inhibitor Augments Antitumor Activity of B7-H3-Redirected Bispecific Antibody

Targeting cancer antigens by T cell-engaging bispecific antibody (BiAb) or chimeric antigen receptor T cell therapy has achieved successes in hematological cancers, but attempts to use it to fight solid cancers have been disappointing, in part due to antigen escape. MEK inhibitor had limited activity as a single agent, but enhanced antitumor activity when combined with other therapies, such as targeted drugs or immunotherapy agents. This study aimed to analyze the expression of B7-H3 in non-small-cell lung cancer (NSCLC) and bladder cancer (BC) and to evaluate the combinatorial antitumor effect of B7-H3 × CD3 BiAb with MEK inhibitor trametinib. We found B7-H3 was highly expressed in NSCLC and BC compared with normal samples and its increased expression was associated with poor prognosis. Treatment with trametinib alone could induce apoptosis in tumor cell, while has no effect on T cell proliferation, and a noticeable elevation of B7-H3 expression in tumor cells was also observed following treatment. B7-H3 × CD3 BiAb specifically and efficiently redirected their cytotoxicity against B7-H3 overexpressing tumor cells both in vitro and in xenograft mouse models. While trametinib treatment alone affected tumor growth, the combined therapy increased T cell infiltration and significantly suppressed tumor growth. Together, these data suggest that combination therapy with B7-H3 × CD3 BiAb and MEK inhibitor may serve as a new therapeutic strategy in the future clinical practice for the treatment of NSCLC and BC.

The MAPK and AMPK signalings: interplay and implication in targeted cancer therapy

Cancer is characterized as a complex disease caused by coordinated alterations of multiple signaling pathways. The Ras/RAF/MEK/ERK (MAPK) signaling is one of the best-defined pathways in cancer biology, and its hyperactivation is responsible for over 40% human cancer cases. To drive carcinogenesis, this signaling promotes cellular overgrowth by turning on proliferative genes, and simultaneously enables cells to overcome metabolic stress by inhibiting AMPK signaling, a key singular node of cellular metabolism. Recent studies have shown that AMPK signaling can also reversibly regulate hyperactive MAPK signaling in cancer cells by phosphorylating its key components, RAF/KSR family kinases, which affects not only carcinogenesis but also the outcomes of targeted cancer therapies against the MAPK signaling. In this review, we will summarize the current proceedings of how MAPK-AMPK signalings interplay with each other in cancer biology, as well as its implications in clinic cancer treatment with MAPK inhibition and AMPK modulators, and discuss the exploitation of combinatory therapies targeting both MAPK and AMPK as a novel therapeutic intervention.

Targeting PHGDH Upregulation Reduces Glutathione Levels and Resensitizes Resistant NRAS-Mutant Melanoma to MAPK Kinase Inhibition

Melanomas frequently harbor activating NRAS mutations leading to activation of MAPK kinase (MEK) and extracellular signal-regulated kinase 1/2 signaling; however, the clinical efficacy of inhibitors to this pathway is limited by resistance. Tumors rewire metabolic pathways in response to stress signals such as targeted inhibitors and drug resistance, but most therapy-resistant preclinical models are generated in conditions that lack physiological metabolism. We generated human NRAS-mutant melanoma xenografts that were resistant to the MEK inhibitor (MEKi) PD0325901 in vivo. MEKi-resistant cells showed cross-resistance to the structurally distinct MEKi trametinib and elevated extracellular signal-regulated kinase 1/2 phosphorylation and downstream signaling. Additionally, we observed upregulation of the serine synthesis pathway and PHGDH, a key enzyme in this pathway. Suppressing PHGDH in MEKi-resistant cells together with MEKi treatment decreased oxidative stress tolerance and cell proliferation. Together, our data suggest targeting PHGDH as a potential strategy in overcoming MEKi resistance.

Targeting Mutant KRAS for Anticancer Therapy

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Over the past decades, designing therapeutic strategies to target KRAS-mutant cancers, which is one of the most frequent mutant oncogenes among all cancer types, have proven unsuccessful regardless of many concerted attempts. There are key challenges for KRAS-mutant anticancer therapy, as the complex cellular processes involved in KRAS signaling has present. Herein, we highlight the emerging therapeutic approaches for inhibiting KRAS signaling and blocking KRAS functions, in hope to serve as a more effective guideline for future development of therapeutics.

MEK1/2 as a Therapeutic Target in Sickle Cell Disease

Identification of novel therapeutic targets has improved diagnostics and treatment of many diseases. Many innovative treatment strategies have been developed based on the newly identified biomarkers and key molecules. Most of the research focused on ways to manipulate signaling pathways by activating or suppressing them, validate new therapeutic targets for treatment, and epigenetic treatment of diseases. With the identification of aberrations in multiple growth pathways, the focus then shifted to the small molecules involved in these pathways for targeted therapy. In this communication/short review, we highlight the importance of identification of abnormal activation of the mitogen-activated protein kinase (MAPK), ERK1/2, and its upstream mediator MEK1/2, in erythrocytes in patients with sickle cell disease (SCD) critical for the adhesive interactions of these cells with the endothelium, and leukocytes promoting circulatory obstruction leading to tissue ischemia and infraction. We also discuss how targeting this signaling cascade with MEK1/2 inhibitors can reverse acute vasoocclusive crises in SCD.

18F-FDG PET/CT longitudinal studies in patients with advanced metastatic melanoma for response evaluation of combination treatment with vemurafenib and ipilimumab

Sixteen BRAF-mutation positive, metastatic melanoma patients with highly advanced disease received combination therapy of vemurafenib and ipilimumab as an individual treatment decision. Our aim was to assess the role of fluorine-18-fluorodeoxyglucose (F-FDG) PET/computed tomography (PET/CT) in the evaluation of the clinical benefit (CB) of this combination treatment. After clinical improvement under vemurafenib monotherapy, four cycles of ipilimumab were additionally administered. F-FDG PET/CT was performed before the start, after two cycles and after completion of the combined ipilimumab/vemurafenib treatment. PET-based patient response evaluation to treatment was based on the European Organization for Research and Treatment of Cancer and the PET Response Evaluation Criteria for Immunotherapy criteria. Progression-free survival (PFS) from the end of combination treatment was calculated. According to their best clinical response at the end of combination treatment, eight patients showed CB and eight patients had no-CB. Two patients revealed extraordinary good clinical outcome with PFS of more than 5 years. Overall, 13 out of 16 patients were correctly classified by the European Organization for Research and Treatment of Cancer and 15 out of 16 by the PET Response Evaluation Criteria for Immunotherapy criteria. Median PFS was 8.8 months among PET-responders and 3.6 months among nonresponders. During immunotherapy administration seven patients developed radiologic signs of immune-related adverse events (irAEs), with colitis and arthritis being the most frequent ones; these patients had a significantly longer PFS than those without irAEs (P=0.036). F-FDG PET/CT is a valuable tool for the evaluation of patients receiving a combination of targeted treatment and immunotherapy. The appearance of irAEs on PET/CT might correlate with benefit to immunotherapy.

Current and emerging systemic therapies for cutaneous metastatic melanoma

INTRODUCTION

Melanoma therapies have evolved rapidly, and initial successes have translated into survival gains for patients with advanced melanoma. Both targeted and immune-therapy now have evidence in earlier stage disease. There are many new agents and combinations of treatments in development as potential future treatment options. This highlights the need for a reflection on current treatment practice trends that are guiding the development of potential new therapies.

AREAS COVERED

In this review, the authors discuss the evidence for currently approved therapies for cutaneous melanoma, including adjuvant therapy, potential new biomarkers, and emerging treatments with early phase clinical trial data. The authors have searched both the PubMed and clinicaltrials.gov databases for published clinical trials and discuss selected landmark trials of current therapies and of investigational treatment strategies with early evidence for the treatment of melanoma.

EXPERT OPINION

Significant efficacy has been demonstrated with both immune checkpoint inhibitors and targeted therapies in treating advanced melanoma. A multitude of novel therapies are in development and there is need for instructive biomarker assessment to identify patients likely to respond or be refractory to current therapies, to identify mechanisms of resistance and to direct further treatment options to patients based on individual disease biology.

Therapeutic strategies to target RAS-mutant cancers

RAS genes are the most commonly mutated oncogenes in cancer, but effective therapeutic strategies to target RAS-mutant cancers have proved elusive. A key aspect of this challenge is the fact that direct inhibition of RAS proteins has proved difficult, leading researchers to test numerous alternative strategies aimed at exploiting RAS-related vulnerabilities or targeting RAS effectors. In the past few years, we have witnessed renewed efforts to target RAS directly, with several promising strategies being tested in clinical trials at different stages of completion. Important advances have also been made in approaches designed to indirectly target RAS by improving inhibition of RAS effectors, exploiting synthetic lethal interactions or metabolic dependencies, using therapeutic combination strategies or harnessing the immune system. In this Review, we describe historical and ongoing efforts to target RAS-mutant cancers and outline the current therapeutic landscape in the collective quest to overcome the effects of this crucial oncogene.

DPS-2: A Novel Dual MEK/ERK and PI3K/AKT Pathway Inhibitor with Powerful Ex Vivo and In Vivo Anticancer Properties

Development of novel bioactive compounds against KRAS and/or BRAF mutant colorectal cancer (CRC) is currently an urgent need in oncology. In addition, single or multitarget kinase inhibitors against MEK/ERK and PI3K/AKT pathways are of potential therapeutic advantage. A new compound based on the benzothiophene nucleus was synthesized, based on previous important outcomes on other pharmaceutical preparations, to be tested as potential anticancer agent. Treatments by 2-5 μM DPS-2 of several CRC and melanoma cell lines bearing either BRAF or KRAS mutations have shown a remarkable effect on cell viability in 2D and 3D cultures. More detailed analysis has shown that DPS-2 can kill cancer cells by apoptosis, reducing at the same time their autophagy properties. After testing activities of several signaling pathways, the compound was found to have a dual inhibition of two major proliferative/survival pathways, MEK/ERK and PI3K/AKT, in both CRC and melanoma, thus providing a mechanistic evidence for its potent anticancer activity. Antitumor activity of DPS-2 was further validated in vivo, as DPS-2 treatment of mouse xenografts of Colo-205 colorectal cancer cells remarkably reduced their tumor formation properties. Our findings suggest that DPS-2 has significant anti-KRAS/ anti-BRAF mutant CRC activity in preclinical models, potentially providing a novel treatment strategy for these difficult-to-treat tumors, which needs to be further exploited.

[Response evaluation in nuclear medicine : Criteria, results and pitfalls]

CLINICAL/METHODICAL ISSUE

Established criteria to categorize metabolic tumor response to cytotoxic chemotherapies may not be suited to capture the effects of therapy with immune checkpoint inhibitors (ICI) or with kinase inhibitors (KI), such as BRAF or MEK inhibitors.

NUCLEAR MEDICINE STANDARD METHODS

To assess the metabolic response to cytotoxic chemotherapy by positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (FDG), the criteria of the European Organization for Research and Treatment of Cancer (EORTC) and the positron emission tomography response criteria in solid tumors (PERCIST) were conceived. The salient features of both criteria are detailed in a comparative way.

PERFORMANCE AND ACHIEVEMENTS

To date only retrospective data exist for the evaluation of therapies with either ICI or KI. They show that response to ICI cannot be reliably determined using the established criteria. Employing the EORTC criteria the responses to KI can be adequately ascertained so that the metabolic tumor response in FDG-PET is regarded as a surrogate marker for the efficacy of these drugs.

PRACTICAL RECOMMENDATIONS

Tumor response to therapy with ICI cannot at present be assessed with FDG-PET. Responses to BRAF and MEK inhibitors are, however, assessable using the criteria that were originally developed to evaluate responses to cytotoxic chemotherapy.