Phase I/randomized phase II study of afatinib, an irreversible ErbB family blocker, with or without protracted temozolomide in adults with recurrent glioblastoma

Discovery of Novel Small-Molecule-Based Potential PD-L1/EGFR Dual Inhibitors with High Druggability for Glioblastoma Immunotherapy

Based on the close relationship between programmed death protein ligand 1 (PD-L1) and epidermal growth factor receptor (EGFR) in glioblastoma (GBM), we designed and synthesized a series of small molecules as potential dual inhibitors of EGFR and PD-L1. Among them, compound EP26 exhibited the highest inhibitory activity against EGFR (IC50 = 37.5 nM) and PD-1/PD-L1 interaction (IC50 = 1.77 μM). In addition, EP26 displayed superior in vitro antiproliferative activities and in vitro immunomodulatory effects by promoting U87MG cell death in a U87MG/Jurkat cell coculture model. Furthermore, EP26 possessed favorable pharmacokinetic properties (F = 22%) and inhibited tumor growth (TGI = 92.0%) in a GBM mouse model more effectively than Gefitinib (77.2%) and NP19 (82.8%). Moreover, EP26 increased CD4+ cells and CD8+ cells in tumor microenvironment. Collectively, these results suggest that EP26 represents the first small-molecule-based PD-L1/EGFR dual inhibitor deserving further investigation as an immunomodulating agent for cancer treatment.

Mechanistic insights and the clinical prospects of targeted therapies for glioblastoma: a comprehensive review

Glioblastoma (GBM) is a fatal brain tumour that is traditionally diagnosed based on histological features. Recent molecular profiling studies have reshaped the World Health Organization approach in the classification of central nervous system tumours to include more pathogenetic hallmarks. These studies have revealed that multiple oncogenic pathways are dysregulated, which contributes to the aggressiveness and resistance of GBM. Such findings have shed light on the molecular vulnerability of GBM and have shifted the disease management paradigm from chemotherapy to targeted therapies. Targeted drugs have been developed to inhibit oncogenic targets in GBM, including receptors involved in the angiogenic axis, the signal transducer and activator of transcription 3 (STAT3), the PI3K/AKT/mTOR signalling pathway, the ubiquitination-proteasome pathway, as well as IDH1/2 pathway. While certain targeted drugs showed promising results in vivo, the translatability of such preclinical achievements in GBM remains a barrier. We also discuss the recent developments and clinical assessments of targeted drugs, as well as the prospects of cell-based therapies and combinatorial therapy as novel ways to target GBM. Targeted treatments have demonstrated preclinical efficacy over chemotherapy as an alternative or adjuvant to the current standard of care for GBM, but their clinical efficacy remains hindered by challenges such as blood-brain barrier penetrance of the drugs. The development of combinatorial targeted therapies is expected to improve therapeutic efficacy and overcome drug resistance.

Comprehensive mutational scanning of EGFR reveals TKI sensitivities of extracellular domain mutants

The epidermal growth factor receptor, EGFR, is frequently activated in lung cancer and glioblastoma by genomic alterations including missense mutations. The different mutation spectra in these diseases are reflected in divergent responses to EGFR inhibition: significant patient benefit in lung cancer, but limited in glioblastoma. Here, we report a comprehensive mutational analysis of EGFR function. We perform saturation mutagenesis of EGFR and assess function of ~22,500 variants in a human EGFR-dependent lung cancer cell line. This approach reveals enrichment of erlotinib-insensitive variants of known and unknown significance in the dimerization, transmembrane, and kinase domains. Multiple EGFR extracellular domain variants, not associated with approved targeted therapies, are sensitive to afatinib and dacomitinib in vitro. Two glioblastoma patients with somatic EGFR G598V dimerization domain mutations show responses to dacomitinib treatment followed by within-pathway resistance mutation in one case. In summary, this comprehensive screen expands the landscape of functional EGFR variants and suggests broader clinical investigation of EGFR inhibition for cancers harboring extracellular domain mutations.

Modular Hub Genes in DNA Microarray Suggest Potential Signaling Pathway Interconnectivity in Various Glioma Grades

Gliomas have displayed significant challenges in oncology due to their high degree of invasiveness, recurrence, and resistance to treatment strategies. In this work, the key hub genes mainly associated with different grades of glioma, which were represented by pilocytic astrocytoma (PA), oligodendroglioma (OG), anaplastic astrocytoma (AA), and glioblastoma multiforme (GBM), were identified through weighted gene co-expression network analysis (WGCNA) of microarray datasets retrieved from the Gene Expression Omnibus (GEO) database. Through this, four highly correlated modules were observed to be present across the PA (GSE50161), OG (GSE4290), AA (GSE43378), and GBM (GSE36245) datasets. The functional annotation and pathway enrichment analysis done through the Database for Annotation, Visualization, and Integrated Discovery (DAVID) showed that the modules and hub genes identified were mainly involved in signal transduction, transcription regulation, and protein binding, which collectively deregulate several signaling pathways, mainly PI3K/Akt and metabolic pathways. The involvement of several hub genes primarily linked to other signaling pathways, including the cAMP, MAPK/ERK, Wnt/β-catenin, and calcium signaling pathways, indicates potential interconnectivity and influence on the PI3K/Akt pathway and, subsequently, glioma severity. The Drug Repurposing Encyclopedia (DRE) was used to screen for potential drugs based on the up- and downregulated hub genes, wherein the synthetic progestin hormones norgestimate and ethisterone were the top drug candidates. This shows the potential neuroprotective effect of progesterone against glioma due to its influence on EGFR expression and other signaling pathways. Aside from these, several experimental and approved drug candidates were also identified, which include an adrenergic receptor antagonist, a PPAR-γ receptor agonist, a CDK inhibitor, a sodium channel blocker, a bradykinin receptor antagonist, and a dopamine receptor agonist, which further highlights the gene network as a potential therapeutic avenue for glioma.

Crosstalk between glioblastoma and tumor microenvironment drives proneural-mesenchymal transition through ligand-receptor interactions

Glioblastoma (GBM) is the most common intrinsic and aggressive primary brain tumor in adults, with a median survival of approximately 15 months. GBM heterogeneity is considered responsible for the treatment resistance and unfavorable prognosis. Proneural-mesenchymal transition (PMT) represents GBM malignant progression and recurrence, which might be a breakthrough to understand GBM heterogeneity and overcome treatment resistance. PMT is a complicated process influenced by crosstalk between GBM and tumor microenvironment, depending on intricate ligand-receptor interactions. In this review, we summarize the autocrine and paracrine pathways in the GBM microenvironment and related ligand-receptor interactions inducing PMT. We also discuss the current therapies targeting the PMT-related autocrine and paracrine pathways. Together, this review offers a comprehensive understanding of the failure of GBM-targeted therapy and ideas for future tendencies of GBM treatment.

A phase I dose-escalation study of pulsatile afatinib in patients with recurrent or progressive brain cancer

Background

Afatinib (BIBW2992; Gilotrif®) is a selective and irreversible inhibitor of the epidermal growth factor receptor (ErbB; EGFR) family. It inhibits EGFR, HER2, and HER4 phosphorylation, resulting in tumor growth inhibition and regression. This phase I dose-escalation trial of pulsatile afatinib examined the safety, drug penetration into the central nervous system, preliminary antitumor activity, and recommended phase II dose in patients with progressive or recurrent brain cancers.

Methods

Afatinib was taken orally once every 4 days or once every 7 days depending on dose cohort, until disease progression or unacceptable toxicity.

Results

A total of 24 patients received the investigational agent and were evaluable for safety analyses, and 21 patients were evaluable for efficacy. Dosing was administered at 80 mg every 4 days, 120 mg every 4 days, 180 mg every 4 days, or 280 mg every 7 days. A recommended phase II dose of pulsatile afatinib was established at 280 mg every 7 days as there were no dose-limiting toxicities in any of the dosing cohorts and all toxicities were deemed manageable. The most common drug-related toxicities were diarrhea, rash, nausea, vomiting, fatigue, stomatitis, pruritus, and limb edema. Out of the 21 patients evaluable for efficacy, 2 patients (9.5%) exhibited partial response based on Response Assessment in Neuro-Oncology criteria and disease stabilization was seen in 3 patients (14.3%).

Conclusions

Afatinib taken orally was safe and well-tolerated up to 280 mg every 7 days in brain cancer patients.

Rhizochalinin Exhibits Anticancer Activity and Synergizes with EGFR Inhibitors in Glioblastoma In Vitro Models

Rhizochalinin (Rhiz) is a recently discovered cytotoxic sphingolipid synthesized from the marine natural compound rhizochalin. Previously, Rhiz demonstrated high in vitro and in vivo efficacy in various cancer models. Here, we report Rhiz to be highly active in human glioblastoma cell lines as well as in patient-derived glioma-stem like neurosphere models. Rhiz counteracted glioblastoma cell proliferation by inducing apoptosis, G2/M-phase cell cycle arrest, and inhibition of autophagy. Proteomic profiling followed by bioinformatic analysis suggested suppression of the Akt pathway as one of the major biological effects of Rhiz. Suppression of Akt as well as IGF-1R and MEK1/2 kinase was confirmed in Rhiz-treated GBM cells. In addition, Rhiz pretreatment resulted in a more pronounced inhibitory effect of γ-irradiation on the growth of patient-derived glioma-spheres, an effect to which the Akt inhibition may also contribute decisively. In contrast, EGFR upregulation, observed in all GBM neurospheres under Rhiz treatment, was postulated to be a possible sign of incipient resistance. In line with this, combinational therapy with EGFR-targeted tyrosine kinase inhibitors synergistically increased the efficacy of Rhiz resulting in dramatic inhibition of GBM cell viability as well as a significant reduction of neurosphere size in the case of combination with lapatinib. Preliminary in vitro data generated using a parallel artificial membrane permeability (PAMPA) assay suggested that Rhiz cannot cross the blood brain barrier and therefore alternative drug delivery methods should be used in the further in vivo studies. In conclusion, Rhiz is a promising new candidate for the treatment of human glioblastoma, which should be further developed in combination with EGFR inhibitors.

Telomerase inhibition is an effective therapeutic strategy in TERT promoter-mutant glioblastoma models with low tumor volume

BACKGROUND

Glioblastoma is one of the most lethal forms of cancer, with 5-year survival rates of only 6%. Glioblastoma-targeted therapeutics have been challenging to develop due to significant inter- and intra-tumoral heterogeneity. Telomerase reverse transcriptase gene (TERT) promoter mutations are the most common known clonal oncogenic mutations in glioblastoma. Telomerase is therefore considered to be a promising therapeutic target against this tumor. However, an important limitation of this strategy is that cell death does not occur immediately after telomerase ablation, but rather after several cell divisions required to reach critically short telomeres. We, therefore, hypothesize that telomerase inhibition would only be effective in glioblastomas with low tumor burden.

METHODS

We used CRISPR interference to knock down TERT expression in TERT promoter-mutant glioblastoma cell lines and patient-derived models. We then measured viability using serial proliferation assays. We also assessed for features of telomere crisis by measuring telomere length and chromatin bridge formation. Finally, we used a doxycycline-inducible CRISPR interference system to knock down TERT expression in vivo early and late in tumor development.

RESULTS

Upon TERT inactivation, glioblastoma cells lose their proliferative ability over time and exhibit telomere shortening and chromatin bridge formation. In vivo, survival is only prolonged when TERT knockdown is induced shortly after tumor implantation, but not when the tumor burden is high.

CONCLUSIONS

Our results support the idea that telomerase inhibition would be most effective at treating glioblastomas with low tumor burden, for example in the adjuvant setting after surgical debulking and chemoradiation.

The Glioblastoma Landscape: Hallmarks of Disease, Therapeutic Resistance, and Treatment Opportunities

Malignant brain tumors are aggressive and difficult to treat. Glioblastoma is the most common and lethal form of primary brain tumor, often found in patients with no genetic predisposition. The median life expectancy for individuals diagnosed with this condition is 6 months to 2 years and there is no known cure. New paradigms in cancer biology implicate a small subset of tumor cells in initiating and sustaining these incurable brain tumors. Here, we discuss the heterogenous nature of glioblastoma and theories behind its capacity for therapy resistance and recurrence. Within the cancer landscape, cancer stem cells are thought to be both tumor initiators and major contributors to tumor heterogeneity and therapy evasion and such cells have been identified in glioblastoma. At the cellular level, disruptions in the delicate balance between differentiation and self-renewal spur transformation and support tumor growth. While rapidly dividing cells are more sensitive to elimination by traditional treatments, glioblastoma stem cells evade these measures through slow division and reversible exit from the cell cycle. At the molecular level, glioblastoma tumor cells exploit several signaling pathways to evade conventional therapies through improved DNA repair mechanisms and a flexible state of senescence. We examine these common evasion techniques while discussing potential molecular approaches to better target these deadly tumors. Equally important, the presented information encourages the idea of augmenting conventional treatments with novel glioblastoma stem cell-directed therapies, as eliminating these harmful progenitors holds great potential to modulate tumor recurrence.

Efficacy and safety of pharmacotherapy for recurrent high-grade glioma: a systematic review and network meta-analysis

Objective: To compare the efficacy and safety of treatments for patients with recurrent high-grade gliomas. Methods: Electronic databases including Pubmed, Embase, Cochrane Library and ClinicalTrials.gov were searched for randomized controlled trials (RCT) related to high-grade gliomas. The inclusion of qualified literature and extraction of data were conducted by two independent reviewers. The primary clinical outcome measures of network meta-analysis were overall survival (OS) while progression-free survival (PFS), objective response rate (ORR) and adverse event of grade 3 or higher were secondary measures. Results: 22 eligible trials were included in the systematic review, involving 3423 patients and 30 treatment regimens. Network meta-analysis included 11 treatments of 10 trials for OS and PFS, 10 treatments of 8 trials for ORR, and 8 treatments of 7 trials for adverse event grade 3 or higher. Regorafenib showed significant benefits in terms of OS in paired comparison with several treatments such as bevacizumab (hazard ratio (HR), 0.39; 95% confidence interval (CI), 0.21-0.73), bevacizumab plus carboplatin (HR, 0.33; 95%CI, 0.16-0.68), bevacizumab plus dasatinib (HR, 0.44; 95%CI, 0.21-0.93), bevacizumab plus irinotecan (HR, 0.4; 95%CI, 0.21-0.74), bevacizumab plus lomustine (90 mg/m²) (HR, 0.53; 95%CI, 0.33-0.84), bevacizumab plus lomustine (110 mg/m²) (HR, 0.21; 95%CI, 0.06-0.7), bevacizumab plus vorinostat (HR, 0.42; 95%CI, 0.18-0.99), lomustine (HR, 0.5; 95%CI, 0.33-0.76), and nivolumab (HR, 0.38; 95%CI, 0.19-0.73). For PFS, only the hazard ratio between bevacizumab plus vorinostat and bevacizumab plus lomustine (90 mg/m²) was significant (HR,0.51; 95%CI, 0.27-0.95). Lomustine and nivolumab conferred worse ORR. Safety analysis showed fotemustine as the best and bevacizumab plus temozolomide as the worst. Conclusion: The results suggested that regorafenib and bevacizumab plus lomustine (90 mg/m²) provide improvements in terms of survival but may have poor ORR in patients with recurrent high-grade glioma.

Glioblastoma treatment slowly moves toward change: novel druggable targets and translational horizons in 2022

INTRODUCTION

Glioblastoma (GBM) is the most common primary brain tumor in adults. GBM treatment options have been the same for the past 30 years and have only modestly extended survival, despite aggressive multimodal treatments. The progressively better knowledge of GBM biology and a comprehensive analysis of its genomic profile have elucidated GBM heterogeneity, contributing to a more effective molecular classification and to the development of innovative targeted therapeutic approaches.

AREAS COVERED

This article reports all the noteworthy innovations for immunotherapy and targeted therapy, providing insights into the current advances in trial designs, including combination therapies with immuno-oncology agents and target combinations.

EXPERT OPINION

GBM molecular heterogeneity and brain anatomical characteristics critically restrain drug effectiveness. Nevertheless, stimulating insights for future research and drug development come from innovative treatment strategies for GBM, such as multi-specific 'off-the-shelf' CAR-T therapy, oncolytic viral therapy and autologous dendritic cell vaccination. Disappointing results from targeted therapies-clinical trials are mainly due to complex interferences between signaling pathways and biological processes leading to drug resistance: hence, it is imperative in the future to develop combinatorial approaches and multimodal therapies.

MRI radiomics and potential applications to glioblastoma

MRI plays an important role in the evaluation of glioblastoma, both at initial diagnosis and follow up after treatment. Quantitative analysis via radiomics can augment the interpretation of MRI in terms of providing insights regarding the differential diagnosis, genotype, treatment response, and prognosis. The various MRI radiomic features of glioblastoma are reviewed in this article.

Molecular targeted therapy: A new avenue in glioblastoma treatment

Glioblastoma, also referred to as glioblastoma multiforme (GBM), is grade IV astrocytoma characterized by being fast-growing and the most aggressive brain tumor. In adults, it is the most prevalent type of malignant brain tumor. Despite the advancements in both diagnosis tools and therapeutic treatments, GBM is still associated with poor survival rate without any statistically significant improvement in the past three decades. Patient's genome signature is one of the key factors causing the development of this tumor, in addition to previous radiation exposure and other environmental factors. Researchers have identified genomic and subsequent molecular alterations affecting core pathways that trigger the malignant phenotype of this tumor. Targeting intrinsically altered molecules and pathways is seen as a novel avenue in GBM treatment. The present review shed light on signaling pathways and intrinsically altered molecules implicated in GBM development. It discussed the main challenges impeding successful GBM treatment, such as the blood brain barrier and tumor microenvironment (TME), the plasticity and heterogeneity of both GBM and TME and the glioblastoma stem cells. The present review also presented current advancements in GBM molecular targeted therapy in clinical trials. Profound and comprehensive understanding of molecular participants opens doors for innovative, more targeted and personalized GBM therapeutic modalities.

Anoctamins and Calcium Signalling: An Obstacle to EGFR Targeted Therapy in Glioblastoma?

Glioblastoma is the most common form of high-grade glioma in adults and has a poor survival rate with very limited treatment options. There have been no significant advancements in glioblastoma treatment in over 30 years. Epidermal growth factor receptor is upregulated in most glioblastoma tumours and, therefore, has been a drug target in recent targeted therapy clinical trials. However, while many inhibitors and antibodies for epidermal growth factor receptor have demonstrated promising anti-tumour effects in preclinical models, they have failed to improve outcomes for glioblastoma patients in clinical trials. This is likely due to the highly plastic nature of glioblastoma tumours, which results in therapeutic resistance. Ion channels are instrumental in the development of many cancers and may regulate cellular plasticity in glioblastoma. This review will explore the potential involvement of a class of calcium-activated chloride channels called anoctamins in brain cancer. We will also discuss the integrated role of calcium channels and anoctamins in regulating calcium-mediated signalling pathways, such as epidermal growth factor signalling, to promote brain cancer cell growth and migration.

Leveraging extrachromosomal DNA to fine-tune trials of targeted therapy for glioblastoma: opportunities and challenges

Glioblastoma evolution is facilitated by intratumour heterogeneity, which poses a major hurdle to effective treatment. Evidence indicates a key role for oncogene amplification on extrachromosomal DNA (ecDNA) in accelerating tumour evolution and thus resistance to treatment, particularly in glioblastomas. Oncogenes contained within ecDNA can reach high copy numbers and expression levels, and their unequal segregation can result in more rapid copy number changes in response to therapy than is possible through natural selection of intrachromosomal genomic loci. Notably, targeted therapies inhibiting oncogenic pathways have failed to improve glioblastoma outcomes. In this Perspective, we outline reasons for this disappointing lack of clinical translation and present the emerging evidence implicating ecDNA as an important driver of tumour evolution. Furthermore, we suggest that through detection of ecDNA, patient selection for clinical trials of novel agents can be optimized to include those most likely to benefit based on current understanding of resistance mechanisms. We discuss the challenges to successful translation of this approach, including accurate detection of ecDNA in tumour tissue with novel technologies, development of faithful preclinical models for predicting the efficacy of novel agents in the presence of ecDNA oncogenes, and understanding the mechanisms of ecDNA formation during cancer evolution and how they could be attenuated therapeutically. Finally, we evaluate the feasibility of routine ecDNA characterization in the clinic and how this process could be integrated with other methods of molecular stratification to maximize the potential for clinical translation of precision medicines.

Identification of a lncRNA based signature for pancreatic cancer survival to predict immune landscape and potential therapeutic drugs

Pancreatic cancer is one major digestive malignancy with a poor prognosis. Given the clinical importance of lncRNAs, developing a novel molecular panel with lncRNAs for pancreatic cancer has great potential. As a result, an 8-lncRNA-based robust prognostic signature was constructed using a random survival forest model after examing the expression profile and prognostic significance of lncRNAs in the PAAD cohort from TCGA. The efficacy and effectiveness of the lncRNA-based signature were thoroughly assessed. Patients with high- and low-risk defined by the signature underwent significantly distinct OS expectancy. Most crucially the training group’s AUCs of ROC approached 0.90 and the testing group similarly had the AUCs above 0.86. The lncRNA-based signature was shown to behave as a prognostic indicator of pancreatic cancer, either alone or simultaneously with other factors, after combined analysis with other clinical-pathological factors in Cox regression and nomogram. Additionally, using GSEA and CIBERSORT scoring methods, the immune landscape and variations in biological processes between high- and low-risk subgroups were investigated. Last but not least, drug databases were searched for prospective therapeutic molecules targeting high-risk patients. The most promising compound were Afatinib, LY-303511, and RO-90-7501 as a result. In conclusion, we developed a novel lncRNA based prognostic signature with high efficacy to stratify high-risk pancreatic cancer patients and screened prospective responsive drugs for targeting strategy.

Engaging innate immunity for targeting the epidermal growth factor receptor: Therapeutic options leveraging innate immunity versus adaptive immunity versus inhibition of signaling

The epidermal growth factor receptor (EGFR) is a key player in the normal tissue physiology and the pathology of cancer. Therapeutic approaches have now been developed to target oncogenic genetic aberrations of EGFR, found in a subset of tumors, and to take advantage of overexpression of EGFR in tumors. The development of small-molecule inhibitors and anti-EGFR antibodies targeting EGFR activation have resulted in effective but limited treatment options for patients with mutated or wild-type EGFR-expressing cancers, while therapeutic approaches that deploy effectors of the adaptive or innate immune system are still undergoing development. This review discusses EGFR-targeting therapies acting through distinct molecular mechanisms to destroy EGFR-expressing cancer cells. The focus is on the successes and limitations of therapies targeting the activation of EGFR versus those that exploit the cytotoxic T cells and innate immune cells to target EGFR-expressing cancer cells. Moreover, we discuss alternative approaches that may have the potential to overcome limitations of current therapies; in particular the innate cell engagers are discussed. Furthermore, this review highlights the potential to combine innate cell engagers with immunotherapies, to maximize their effectiveness, or with unspecific cell therapies, to convert them into tumor-specific agents.

Polymeric Nanoparticles in Brain Cancer Therapy: A Review of Current Approaches

Translation of novel therapies for brain cancer into clinical practice is of the utmost importance as primary brain tumors are responsible for more than 200,000 deaths worldwide each year. While many research efforts have been aimed at improving survival rates over the years, prognosis for patients with glioblastoma and other primary brain tumors remains poor. Safely delivering chemotherapeutic drugs and other anti-cancer compounds across the blood-brain barrier and directly to tumor cells is perhaps the greatest challenge in treating brain cancer. Polymeric nanoparticles (NPs) are powerful, highly tunable carrier systems that may be able to overcome those obstacles. Several studies have shown appropriately-constructed polymeric NPs cross the blood-brain barrier, increase drug bioavailability, reduce systemic toxicity, and selectively target central nervous system cancer cells. While no studies relating to their use in treating brain cancer are in clinical trials, there is mounting preclinical evidence that polymeric NPs could be beneficial for brain tumor therapy. This review includes a variety of polymeric NPs and how their associated composition, surface modifications, and method of delivery impact their capacity to improve brain tumor therapy.

Small Molecules and Immunotherapy Agents for Enhancing Radiotherapy in Glioblastoma

Glioblastoma (GBM) is an aggressive primary brain tumor that is associated with a poor prognosis and quality of life. The standard of care has changed minimally over the past two decades and currently consists of surgery followed by radiotherapy (RT), concomitant and adjuvant temozolomide, and tumor treating fields (TTF). Factors such as tumor hypoxia and the presence of glioma stem cells contribute to the radioresistant nature of GBM. In this review, we discuss the current treatment modalities, mechanisms of radioresistance, and studies that have evaluated promising radiosensitizers. Specifically, we highlight small molecules and immunotherapy agents that have been studied in conjunction with RT in clinical trials. Recent preclinical studies involving GBM radiosensitizers are also discussed.

Targeting Glioblastoma Stem Cells to Overcome Chemoresistance: An Overview of Current Therapeutic Strategies

Glioblastoma (GBM) is the most malignant primary brain tumor. The current standard approach in GBM is surgery, followed by treatment with radiation and temozolomide (TMZ); however, GBM is highly resistant to current therapies, and the standard of care has not been revised over the last two decades, indicating an unmet need for new therapies. GBM stem cells (GSCs) are a major cause of chemoresistance due to their ability to confer heterogeneity and tumorigenic capacity. To improve patient outcomes and survival, it is necessary to understand the properties and mechanisms underlying GSC chemoresistance. In this review, we describe the current knowledge on various resistance mechanisms of GBM to therapeutic agents, with a special focus on TMZ, and summarize the recent findings on the intrinsic and extrinsic mechanisms of chemoresistance in GSCs. We also discuss novel therapeutic strategies, including molecular targeting, autophagy inhibition, oncolytic viral therapy, drug repositioning, and targeting of GSC niches, to eliminate GSCs, from basic research findings to ongoing clinical trials. Although the development of effective therapies for GBM is still challenging, this review provides a better understanding of GSCs and offers future directions for successful GBM therapy.

Galvanotactic Migration of Glioblastoma and Brain Metastases Cells

Galvanotaxis, the migration along direct current electrical fields, may contribute to the invasion of brain cancer cells in the tumor-surrounding tissue. We hypothesized that pharmacological perturbation of the epidermal growth factor (EGF) receptor and downstream phosphatidylinositol 3-kinase (PI3K)/AKT pathway prevent galvanotactic migration. In our study, patient-derived glioblastoma and brain metastases cells were exposed to direct current electrical field conditions. Velocity and direction of migration were estimated. To determine the effects of EGF receptor antagonist afatinib and AKT inhibitor capivasertib, assays of cell proliferation, apoptosis and immunoblot analyses were performed. Both inhibitors attenuated cell proliferation in a dose-dependent manner and induced apoptosis. We found that most of the glioblastoma cells migrated preferentially in an anodal direction, while brain metastases cells were unaffected by direct current stimulations. Afatinib presented only a mild attenuation of galvanotaxis. In contrast, capivasertib abolished the migration of glioblastoma cells without genetic alterations in the PI3K/AKT pathway, but not in cells harboring PTEN mutation. In these cells, an increase in the activation of ERK1/2 may in part substitute the inhibition of the AKT pathway. Overall, our data demonstrate that glioblastoma cells migrate in the electrical field and the PI3K/AKT pathway was found to be highly involved in galvanotaxis.

Genomic Analysis of Tumors from Patients with Glioblastoma with Long-Term Response to Afatinib

Glioblastoma is an aggressive form of central nervous system tumor. Recurrence rates following primary therapy are high, and few second-line treatment options provide durable clinical benefit. Aberrations of the epidermal growth factor receptor (EGFR) gene are observed in up to 57% of glioblastoma cases and EGFR overexpression has been identified in approximately 60% of primary glioblastomas. In preclinical studies, afatinib, a second-generation ErbB blocker, inhibited cell proliferation in cells harboring mutations commonly found in glioblastoma. In two previous Phase I/II studies of afatinib plus temozolomide in patients with glioblastoma, limited efficacy was observed; however, there was notable benefit in patients with the EGFR variant III (EGFRvIII) mutation, EGFR amplification, and those with loss of phosphatase and tensin homolog (PTEN). This case series report details treatment histories of three long-term responders from these trials. Next-generation sequencing of tumor samples identified alterations in a number of cancer-related genes, including mutations in, and amplification of, EGFR. Tumor samples from all three patients shared favorable prognostic factors, eg O⁶-methylguanine-DNA methyl-transferase (MGMT) gene promoter methylation; however, negative prognostic factors were also observed, suggesting that these shared genetic features did not completely account for the favorable responses. The genetic profile of the tumor from Patient 1 showed clear differences from the other two tumors: lack of involvement of EGFR aberrations but with a mutation occurring in PTPN11. Preclinical studies showed that single-agent afatinib and temozolomide both separately inhibit the growth of tumors with a C-terminal EGFR truncation, thus providing further rationale for combining these two agents in the treatment of glioblastomas harboring EGFR aberrations. These findings suggest that afatinib may provide treatment benefit in patients with glioblastomas that harbor ErbB family aberrations and, potentially, other genetic aberrations. Further studies are needed to establish which patients with newly diagnosed/recurrent glioblastomas may potentially benefit from treatment with afatinib.

Evolving management of HER2+ breast cancer brain metastases and leptomeningeal disease

Patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer are at a particularly high risk of breast cancer brain metastasis (BCBM) and leptomeningeal disease (LMD). Improvements in systemic therapy have translated to improved survival for patients with HER2-positive BCBM and LMD. However, the optimal management of these cases is rapidly evolving and requires a multidisciplinary approach. Herein, a team of radiation oncologists, medical oncologists, neuro-oncologists, and breast surgeon created a review of the evolving management of HER2-positive BCBM and LMD. We assess the epidemiology, diagnosis, and evolving treatment options for patients with HER2-positive BCBM and LMD, as well as the ongoing prospective clinical trials enrolling these patients. The management of HER2-positive BCBM and LMD represents an increasingly common challenge that involves the coordination of local and systemic therapy. Advances in systemic therapy have resulted in an improved prognosis, and promising targeted therapies currently under prospective investigation have the potential to further benefit these patients.

Glioblastoma pharmacotherapy: A multifaceted perspective of conventional and emerging treatments (Review)

Due to its localisation, rapid onset, high relapse rate and resistance to most currently available treatment methods, glioblastoma multiforme (GBM) is considered to be the deadliest type of all gliomas. Although surgical resection, chemotherapy and radiotherapy are among the therapeutic strategies used for the treatment of GBM, the survival rates achieved are not satisfactory, and there is an urgent need for novel effective therapeutic options. In addition to single-target therapy, multi-target therapies are currently under development. Furthermore, drugs are being optimised to improve their ability to cross the blood-brain barrier. In the present review, the main strategies applied for GBM treatment in terms of the most recent therapeutic agents and approaches that are currently under pre-clinical and clinical testing were discussed. In addition, the most recently reported experimental data following the testing of novel therapies, including stem cell therapy, immunotherapy, gene therapy, genomic correction and precision medicine, were reviewed, and their advantages and drawbacks were also summarised.

Receptor tyrosine kinases as druggable targets in glioblastoma: Do signaling pathways matter?

Glioblastoma (GBM) is the most malignant primary brain tumor without effective therapies. Since bevacizumab was FDA approved for targeting vascular endothelial growth factor receptor 2 (VEGFR2) in adult patients with recurrent GBM, targeted therapy against receptor tyrosine kinases (RTKs) has become a new avenue for GBM therapeutics. In addition to VEGFR, the epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor (PDGFR), hepatocyte growth factor receptor (HGFR/MET), and fibroblast growth factor receptor (FGFR) are major RTK targets. However, results from clinical Phase II/III trials indicate that most RTK-targeting therapeutics including tyrosine kinase inhibitors (TKIs) and neutralizing antibodies lack clinical efficacy, either alone or in combination. The major challenge is to uncover the genetic RTK alterations driving GBM initiation and progression, as well as to elucidate the mechanisms toward therapeutic resistance. In this review, we will discuss the genetic alterations in these 5 commonly targeted RTKs, the clinical trial outcomes of the associated RTK-targeting therapeutics, and the potential mechanisms toward the resistance. We anticipate that future design of new clinical trials with combination strategies, based on the genetic alterations within an individual patient’s tumor and mechanisms contributing to therapeutic resistance after treatment, will achieve durable remissions and improve outcomes in GBM patients.

Afatinib and radiotherapy, with or without temozolomide, in patients with newly diagnosed glioblastoma: results of a phase I trial

Background

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor in adults. Amplification or overexpression of the epidermal growth factor receptor gene, part of the ErbB family, occur in approximately 40% and 60% of patients with GBM, respectively. We present data from a dose-finding study of the ErbB inhibitor afatinib in combination with radiotherapy (RT), with or without temozolomide (TMZ), in patients with GBM.

Methods

This was a phase I, open-label, 3 + 3 dose-escalation trial in patients with newly-diagnosed, histologically-confirmed grade 4 malignant glioma and proven O⁶-methylguanine-DNA methyltransferase gene promoter methylation status. The primary endpoint was the maximum tolerated dose (MTD) of continuous daily afatinib when given in combination with RT, with (regimen M) or without (regimen U) concomitant TMZ treatment.

Results

Fifty-five patients were enrolled; 36 received ≥ 1 dose of trial medication (regimen M, n = 20, regimen U, n = 16). Afatinib was discontinued by all patients during the study. Reasons for afatinib discontinuation (regimen M/U) included disease progression (45%/50%), dose-limiting toxicity (10%/0%), and other adverse events (AEs; 35%/38%). The most frequently reported AEs with either regimen were diarrhea and rash, with no new safety signals identified. The MTD was determined as afatinib 30 mg in combination with daily TMZ and RT, and afatinib 40 mg in combination with RT alone.

Conclusions

This study identified the MTD for afatinib in combination with RT, with and without TMZ, in patients with GBM. Further studies of afatinib in patients with GBM are warranted and should be based on appropriate biomarker-based preselection.

Trial registration

NCT00977431 (first posted September 15, 2009).

Supplementary Information

The online version contains supplementary material available at 10.1007/s11060-021-03877-6.

Imposing Phase II and Phase III Clinical Trials of Targeted Drugs for Glioblastoma: Current Status and Progress

The most common primary intracranial tumor is glioma, among which glioblastoma (GBM) has the worst prognosis. Because of the high degree of malignancy of GBM and frequent recurrence after surgery, postoperative therapy, including chemotherapy, radiotherapy, targeted therapy, and immunotherapy, is particularly important. A wide variety of targeted drugs have undergone phase III clinical trials for patients with GBM, but these drugs do not work for all patients, and few patients in these trials have prolonged overall survival. In this review, some imposing phase III clinical trials of targeted drugs for glioma are introduced, and some prospective phase II clinical trials that have been completed or are in progress are summarized. In addition, the mechanisms of these drugs are briefly introduced, and deficiencies of these clinical trials are analyzed. This review aims to provide a comprehensive overview of current research on targeted drugs for glioma to clarify future research directions.

Primary Cilia-Related Pathways Moderate the Development and Therapy Resistance of Glioblastoma

As microtubule-based structures, primary cilia are typically present on the cells during the G0 or G1-S/G2 phase of the cell cycle and are closely related to the development of the central nervous system. The presence or absence of this special organelle may regulate the central nervous system tumorigenesis (e.g., glioblastoma) and several degenerative diseases. Additionally, the development of primary cilia can be regulated by several pathways. Conversely, primary cilia are able to regulate a few signaling transduction pathways. Therefore, development of the central nervous system tumors in conjunction with abnormal cilia can be regulated by up- or downregulation of the pathways related to cilia and ciliogenesis. Here, we review some pathways related to ciliogenesis and tumorigenesis, aiming to provide a potential target for developing new therapies at genetic and molecular levels.

Novel Receptor Tyrosine Kinase Pathway Inhibitors for Targeted Radionuclide Therapy of Glioblastoma

Glioblastoma (GB) remains the most fatal brain tumor characterized by a high infiltration rate and treatment resistance. Overexpression and/or mutation of receptor tyrosine kinases is common in GB, which subsequently leads to the activation of many downstream pathways that have a critical impact on tumor progression and therapy resistance. Therefore, receptor tyrosine kinase inhibitors (RTKIs) have been investigated to improve the dismal prognosis of GB in an effort to evolve into a personalized targeted therapy strategy with a better treatment outcome. Numerous RTKIs have been approved in the clinic and several radiopharmaceuticals are part of (pre)clinical trials as a non-invasive method to identify patients who could benefit from RTKI. The latter opens up the scope for theranostic applications. In this review, the present status of RTKIs for the treatment, nuclear imaging and targeted radionuclide therapy of GB is presented. The focus will be on seven tyrosine kinase receptors, based on their central role in GB: EGFR, VEGFR, MET, PDGFR, FGFR, Eph receptor and IGF1R. Finally, by way of analyzing structural and physiological characteristics of the TKIs with promising clinical trial results, four small molecule RTKIs were selected based on their potential to become new therapeutic GB radiopharmaceuticals.

Depatuxizumab Mafodotin (Depatux-M) Plus Temozolomide in Recurrent Glioblastoma Patients: Real-World Experience from a Multicenter Study of Italian Association of Neuro-Oncology (AINO)

Simple Summary

Depatux-M is an antibody-drug conjugate against activated EGFR. The efficacy and tolerability of the Depatux-M and temozolomide combination in recurrent glioblastoma patients were recently analyzed in the INTELLANCE-2/EORTC 1410 phase 2 trial. Despite the trial was negative, it showed interesting results for patients received this combination therapy versus standard treatment. For the first time worldwide, we investigated this treatment in a real-life population. Interestingly, we reported encouraging clinical benefits close to that reported in the previous randomized INTELLANCE 2 trial. Ocular toxicity was manageable. Likely, a subgroup of patients could benefit of this treatment and so, significant molecular predictors of treatment efficacy such as EGFR SNVs should be better investigated in a larger prospective study.

Abstract

Background: Depatuxizumab Mafodotin (Depatux-M; ABT-414) is an antibody-drug conjugate consisting of a specific antibody against activated EGFR and a cytotoxic agent with antimicrotubule activity. The INTELLANCE 2/EORTC 1410 phase 2 trial produced interesting results for the combination regimen of Depatux-M and temozolomide in EGFR-amplified glioblastoma patients at first recurrence. For the first time worldwide, our work investigated the clinical outcome and safety of this combination in a real-life population. Materials and Methods: Patients were enrolled from seven AINO (Italian Association of Neuro-Oncology) Institutions. The major inclusion criteria were: histologically confirmed diagnosis of glioblastoma, EGFR-amplified, one or more prior systemic therapies and ECOG PS ≤ 2. According to the original schedule, patients received Depatux-M 1.25 mg/kg every 2 weeks combined with temozolomide. The primary endpoints of the study were overall survival and safety. Results: A total of 36 patients were enrolled. The median age was 57 years, ECOG PS was 0–1 in 28 patients (88%), MGMT methylated status was found in 22 (64%), 15 patients (42%) received the combined treatment as second-line therapy. The median OS was 8.04 months (95% CI, 5.3–10.7), the 12 month-OS was 37%. On univariate and multivariate analyses, the MGMT methylation status was the only factor resulting significantly associated with survival. Grade 3 ocular toxicity occurred in 11% of patients; no grade 4 ocular toxicity was reported. No death was considered to be drug-related. Conclusions: The study reported the first “real world” experience of Depatux-M plus temozolomide in recurrent glioblastoma patients. Encouraging clinical benefits were demonstrated, even though most patients were treated beyond second-line therapy. Overall, the results are close to those reported in the previous phase 2 trial. Toxicity was moderate and manageable.

Targeting RTK-PI3K-mTOR Axis in Gliomas: An Update

Gliomas are the most common and challenging malignancies of the central nervous system (CNS), due to their infiltrative nature, tendency to recurrence, and poor response to treatments. Indeed, despite the advances in neurosurgical techniques and in radiation therapy, the modest effects of therapy are still challenging. Moreover, tumor recurrence is associated with the onset of therapy resistance; it is therefore critical to identify effective and well-tolerated pharmacological approaches capable of inducing durable responses in the appropriate patient groups. Molecular alterations of the RTK/PI3K/Akt/mTOR signaling pathway are typical hallmarks of glioma, and several clinical trials targeting one or more players of this axis have been launched, showing disappointing results so far, due to the scarce BBB permeability of certain compounds or to the occurrence of resistance/tolerance mechanisms. However, as RTK/PI3K/mTOR is one of the pivotal pathways regulating cell growth and survival in cancer biology, targeting still remains a strong rationale for developing strategies against gliomas. Future rigorous clinical studies, aimed at addressing the tumor heterogeneity, the interaction with the microenvironment, as well as diverse posology adjustments, are needed-which might unravel the therapeutic efficacy and response prediction of an RTK/PI3K/mTOR-based approach.

Treatment options for progression or recurrence of glioblastoma: a network meta-analysis

BACKGROUND

Glioblastoma (GBM) is a highly malignant brain tumour that almost inevitably progresses or recurs after first line standard of care. There is no consensus regarding the best treatment/s to offer people upon disease progression or recurrence. For the purposes of this review, progression and recurrence are considered as one entity.

OBJECTIVES

To evaluate the effectiveness of further treatment/s for first and subsequent progression or recurrence of glioblastoma (GBM) among people who have received the standard of care (Stupp protocol) for primary treatment of the disease; and to prepare a brief economic commentary on the available evidence.

SEARCH METHODS

We searched MEDLINE and Embase electronic databases from 2005 to December 2019 and the Cochrane Central Register of Controlled Trials (CENTRAL, in the Cochrane Library; Issue 12, 2019). Economic searches included the National Health Service Economic Evaluation Database (NHS EED) up to 2015 (database closure) and MEDLINE and Embase from 2015 to December 2019.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and comparative non-randomised studies (NRSs) evaluating effectiveness of treatments for progressive/recurrent GBM. Eligible studies included people with progressive or recurrent GBM who had received first line radiotherapy with concomitant and adjuvant temozolomide (TMZ).

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies and extracted data to a pre-designed data extraction form. We conducted network meta-analyses (NMA) and ranked treatments according to effectiveness for each outcome using the random-effects model and Stata software (version 15). We rated the certainty of evidence using the GRADE approach.

MAIN RESULTS

We included 42 studies: these comprised 34 randomised controlled trials (RCTs) and 8 non-randomised studies (NRSs) involving 5236 participants. We judged most RCTs to be at a low risk of bias and NRSs at high risk of bias. Interventions included chemotherapy, re-operation, re-irradiation and novel therapies either used alone or in combination. For first recurrence, we included 11 interventions in the network meta-analysis (NMA) for overall survival (OS), and eight in the NMA for progression-free survival (PFS). Lomustine (LOM; also known as CCNU) was the most common comparator and was used as the reference treatment. No studies in the NMA evaluated surgery, re-irradiation, PCV (procarbazine, lomustine, vincristine), TMZ re-challenge or best supportive care. We could not perform NMA for second or later recurrence due to insufficient data. Quality-of-life data were sparse. First recurrence (NMA findings) Median OS across included studies in the NMA ranged from 5.5 to 12.6 months and median progression-free survival (PFS) ranged from 1.5 months to 4.2 months. We found no high-certainty evidence that any treatments tested were better than lomustine. These treatments included the following. Bevacizumab plus lomustine: Evidence suggested probably little or no difference in OS between bevacizumab (BEV) combined with lomustine (LOM) and LOM monotherapy (hazard ratio (HR) 0.91, 0.75 to 1.10; moderate-certainty evidence), although BEV + LOM may improve PFS (HR 0.57, 95% confidence interval (CI) 0.44 to 0.74; low-certainty evidence). Bevacizumab monotherapy: Low-certainty evidence suggested there may be little or no difference in OS (HR 1.22, 95% CI 0.84 to 1.76) and PFS (HR 0.90, 95% CI 0.58 to 1.38; low-certainty evidence) between BEV and LOM monotherapies; more evidence on BEV is needed. Regorafenib (REG): REG may improve OS compared with LOM (HR 0.50, 95% CI 0.33 to 0.76; low-certainty evidence). Evidence on PFS was very low certainty and more evidence on REG is needed. Temozolomide (TMZ) plus Depatux-M (ABT414): For OS, low-certainty evidence suggested that TMZ plus ABT414 may be more effective than LOM (HR 0.66, 95% CI 0.47 to 0.92) and may be more effective than BEV (HR 0.54, 95% CI 0.33 to 0.89; low-certainty evidence). This may be due to the TMZ component only and more evidence is needed. Fotemustine (FOM): FOM and LOM may have similar effects on OS (HR 0.89, 95% CI 0.51 to 1.57, low-certainty evidence). Bevacizumab and irinotecan (IRI): Evidence on BEV + irinotecan (IRI) versus LOM for both OS and PFS is very uncertain and there is probably little or no difference between BEV + IRI versus BEV monotherapy (OS: HR 0.95, 95% CI 0.70 to 1.30; moderate-certainty evidence). When treatments were ranked for OS, FOM ranked first, BEV + LOM second, LOM third, BEV + IRI fourth, and BEV fifth. Ranking does not take into account the certainty of the evidence, which also suggests there may be little or no difference between FOM and LOM. Other treatments Three studies evaluated re-operation versus no re-operation, with or without re-irradiation and chemotherapy, and these suggested possible survival advantages with re-operation within the context of being able to select suitable candidates for re-operation. A cannabinoid treatment in the early stages of evaluation, in combination with TMZ, merits further evaluation. Second or later recurrence Limited evidence from three heterogeneous studies suggested that radiotherapy with or without BEV may have a beneficial effect on survival but more evidence is needed. Evidence was insufficient to draw conclusions about the best radiotherapy dosage. Other evidence suggested that there may be little difference in survival with tumour-treating fields compared with physician's best choice of treatment. We found no reliable evidence on best supportive care. Severe adverse events (SAEs) The BEV+LOM combination was associated with significantly greater risk of SAEs than LOM monotherapy (RR 2.51, 95% CI 1.72 to 3.66, high-certainty evidence), and ranked joint worst with cediranib + LOM (RR 2.51, 95% CI 1.29 to 4.90; high-certainty evidence). LOM ranked best and REG ranked second best. Adding novel treatments to BEV was generally associated with a higher risk of severe adverse events compared with BEV alone.

AUTHORS' CONCLUSIONS

For treatment of first recurrence of GBM, among people previously treated with surgery and standard chemoradiotherapy, the combination treatments evaluated did not improve overall survival compared with LOM monotherapy and were often associated with a higher risk of severe adverse events. Limited evidence suggested that re-operation with or without re-irradiation and chemotherapy may be suitable for selected candidates. Evidence on second recurrence is sparse. Re-irradiation with or without bevacizumab may be of value in selected individuals, but more evidence is needed.

Clinical Experience using Osimertinib in Patients with Recurrent Malignant Gliomas Containing EGFR Alterations

Background

EGFR alterations are commonly observed in malignant gliomas (MG). Osimertinib, an irreversible EGFR-tyrosine kinase inhibitor, effectively penetrates the blood brain barrier and achieves therapeutic concentrations in brain tissue.

Materials and Methods

This retrospective chart review identified six patients with recurrent MG and EGFR alterations who received osimertinib.

Results

Four patients were assessed for response. One patient had a partial response, two patients achieved stable disease and one was refractory. One patient with an EGFR vIII rearrangement remained on treatment for 236 days and a second patient with an EGFR vIII mutation remained on treatment for 294 days and continued on treatment at the time of analysis. Thrombocytopenia occurred in two patients, one patient developed grade 1 diarrhea and pneumonia, and another patient developed grade 1 mucositis.

Conclusion

Osimertinib had a tolerable safety profile in this heavily pretreated brain tumor population. Osimertinib may benefit select patients with recurrent MG containing EGFR alterations.

INTELLANCE 2/EORTC 1410 randomized phase II study of Depatux-M alone and with temozolomide vs temozolomide or lomustine in recurrent EGFR amplified glioblastoma

Background

Depatuxizumab mafodotin (Depatux-M) is a tumor-specific antibody–drug conjugate consisting of an antibody (ABT-806) directed against activated epidermal growth factor receptor (EGFR) and the toxin monomethylauristatin-F. We investigated Depatux-M in combination with temozolomide or as a single agent in a randomized controlled phase II trial in recurrent EGFR amplified glioblastoma.

Methods

Eligible were patients with centrally confirmed EGFR amplified glioblastoma at first recurrence after chemo-irradiation with temozolomide. Patients were randomized to either Depatux-M 1.25 mg/kg every 2 weeks intravenously, or this treatment combined with temozolomide 150–200 mg/m² day 1–5 every 4 weeks, or either lomustine or temozolomide. The primary endpoint of the study was overall survival.

Results

Two hundred sixty patients were randomized. In the primary efficacy analysis with 199 events (median follow-up 15.0 mo), the hazard ratio (HR) for the combination arm compared with the control arm was 0.71 (95% CI = 0.50, 1.02; P = 0.062). The efficacy of Depatux-M monotherapy was comparable to that of the control arm (HR = 1.04, 95% CI = 0.73, 1.48; P = 0.83). The most frequent toxicity in Depatux-M treated patients was a reversible corneal epitheliopathy, occurring as grades 3–4 adverse events in 25–30% of patients. In the long-term follow-up analysis with median follow-up of 28.7 months, the HR for the comparison of the combination arm versus the control arm was 0.66 (95% CI = 0.48, 0.93).

Conclusion

This trial suggests a possible role for the use of Depatux-M in combination with temozolomide in EGFR amplified recurrent glioblastoma, especially in patients relapsing well after the end of first-line adjuvant temozolomide treatment. (NCT02343406)

A Systematic Review of Glioblastoma-Targeted Therapies in Phases II, III, IV Clinical Trials

Glioblastoma (GBM), the most frequent and aggressive glial tumor, is currently treated as first line by the Stupp protocol, which combines, after surgery, radiotherapy and chemotherapy. For recurrent GBM, in absence of standard treatment or available clinical trials, various protocols including cytotoxic drugs and/or bevacizumab are currently applied. Despite these heavy treatments, the mean overall survival of patients is under 18 months. Many clinical studies are underway. Based on clinicaltrials.org and conducted up to 1 April 2020, this review lists, not only main, but all targeted therapies in phases II-IV of 257 clinical trials on adults with newly diagnosed or recurrent GBMs for the last twenty years. It does not involve targeted immunotherapies and therapies targeting tumor cell metabolism, that are well documented in other reviews. Without surprise, the most frequently reported drugs are those targeting (i) EGFR (40 clinical trials), and more generally tyrosine kinase receptors (85 clinical trials) and (ii) VEGF/VEGFR (75 clinical trials of which 53 involving bevacizumab). But many other targets and drugs are of interest. They are all listed and thoroughly described, on an one-on-one basis, in four sections related to targeting (i) GBM stem cells and stem cell pathways, (ii) the growth autonomy and migration, (iii) the cell cycle and the escape to cell death, (iv) and angiogenesis.

Optimal Therapies for Recurrent Glioblastoma: A Bayesian Network Meta-Analysis

The optimal treatment of recurrent glioblastoma (GBM) remains controversial. Therefore, our study aimed to compare and rank active therapies in recurrent GBM. We performed a systematic review and a Bayesian network meta-analysis. We obtained a treatment hierarchy using the surface under the cumulative ranking curve and mean ranks. A cluster analysis was conducted to aggregate the separated results of three outcomes. The protocol was registered in PROSPERO (CRD42019146794). A total of 1,667 citations were identified, and 15 eligible articles with 17 treatments remained in the final network meta-analysis. Pairwise comparison showed no significant difference on the 6-month progression-free survival (6-m PFS) rate, objective response rate (ORR), and overall survival (OS). Among the reports, cediranib plus lomustine (CCNU) corresponded to the highest rates of grade 3-4 adverse events. Ranking and cluster analysis indicated that bevacizumab (BEV) plus CCNU and regorafenib had a higher efficacy on the ORR, 6-m PFS rate and OS, and that BEV monotherapy or BEV combined with active drug therapies was advantageous for the ORR and 6-m PFS rate. Additionally, tumor treatment fields (TTF) plus BEV showed a relatively higher SUCRA value in OS. According to ranking and cluster analysis, BEV plus CCNU and regorafenib are the primary recommendations for treatment. BEV monotherapy alone or combined with active drug therapies are recommended in patients with severe neurological symptoms. Advanced therapy, such as TTF and immunotherapy, remain to be investigated in future studies.

Receptor Tyrosine Kinase Signaling and Targeting in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is amongst the deadliest of human cancers, with a median survival rate of just over one year following diagnosis. Characterized by rapid proliferation and diffuse infiltration into the brain, GBM is notoriously difficult to treat, with tumor cells showing limited response to existing therapies and eventually developing resistance to these interventions. As such, there is intense interest in better understanding the molecular alterations in GBM to guide the development of more efficient targeted therapies. GBM tumors can be classified into several molecular subtypes which have distinct genetic signatures, and they show aberrant activation of numerous signal transduction pathways, particularly those connected to receptor tyrosine kinases (RTKs) which control glioma cell growth, survival, migration, invasion, and angiogenesis. There are also non-canonical modes of RTK signaling found in GBM, which involve G-protein-coupled receptors and calcium channels. This review uses The Cancer Genome Atlas (TCGA) GBM dataset in combination with a data-mining approach to summarize disease characteristics, with a focus on select molecular pathways that drive GBM pathogenesis. We also present a unique genomic survey of RTKs that are frequently altered in GBM subtypes, as well as catalog the GBM disease association scores for all RTKs. Lastly, we discuss current RTK targeted therapies and highlight emerging directions in GBM research.

Efficacy of Afatinib in the Treatment of Patients with Non-Small Cell Lung Cancer and Head and Neck Squamous Cell Carcinoma: A Systematic Review and Meta-Analysis

Simple Summary

Evidence from randomized controlled trials about the efficacy of monotherapy of afatinib on survival of patients with advanced non-small cell lung cancer (NSCLC) and recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC) has been not yet rigorously reviewed, which needs to be systemically reviewed and meta-analyzed in terms of overall survival and progression-free survival endpoints. The evidence from randomized controlled trials indicated that first- or second-line afatinib monotherapy has improved the survival of patients with NSCLC. Second-line monotherapy afatinib is well-tolerated and could be a promising monotherapy for recurrent/metastatic HNSCCs; however, further randomized controlled trials should be conducted to collect extra survival data regarding the efficacy of afatinib in R/M HNSCC.

Abstract

Several randomized controlled trials (RCTs) evaluated the afatinib efficacy in patients with advanced non-small cell lung cancer (NSCLC) and recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC). This review systemically outlined and meta-analyzed the afatinib efficacy in NSCLC and R/M HNSCC in terms of overall survival (OS) and progression-free survival (PFS) endpoints. Records were retrieved from PubMed, Web of Science, and ScienceDirect from 2011 to 2020. Eight afatinib RCTs were included and assessed for the risk of bias. In meta-analysis, overall pooled effect size (ES) of OS in afatinib group (AG) significantly improved in all RCTs and NSCLC-RCTs [hazard ratios (HRs): 0.89 (95% CI: 0.81–0.98, p = 0.02); I² = 0%, p = 0.71/ 0.86 (95% CI: 0.76–0.97; p = 0.02); I² = 0%, p = 0.50, respectively]. ES of PFS in AG significantly improved in all RCTs, NSCLC-RCTs, and HNSCC-RCTs [HRs: 0.75 (95% CI: 0.68–0.83; p < 0.00001); I² = 26%, p = 0.24; 0.75 (95% CI: 0.66–0.84; p < 0.00001); I² = 47%, p = 0.15/0.76 (95% CI: 0.65–88; p = 0.0004); I² = 34%, p = 0.0004, respectively]. From a clinical viewpoint of severity, interstitial lung disease, dyspnea, pneumonia, acute renal failure, and renal injury were rarely incident adverse events in the afatinib group. In conclusion, first- and second-line afatinib monotherapy improved the survival of patients with NSCLC, while second-line afatinib monotherapy could be promising for R/M HNSCC. The prospective protocol is in PROSPERO (ID = CRD42020204547).

Therapeutic strategies of recurrent glioblastoma and its molecular pathways 'Lock up the beast'

Glioblastoma multiforme (GBM) has a poor prognosis-despite aggressive primary treatment composed of surgery, radiotherapy and chemotherapy, median survival is still around 15 months. It starts to grow again after a year of treatment and eventually nothing is effective at this stage. Recurrent GBM is one of the most disappointing fields for researchers in which their efforts have gained no benefit for patients. They were directed for a long time towards understanding the molecular basis that leads to the development of GBM. It is now known that GBM is a heterogeneous disease and resistance comes mainly from the regrowth of malignant cells after eradicating specific clones by targeted treatment. Epidermal growth factor receptor, platelet derived growth factor receptor, vascular endothelial growth factor receptor are known to be highly active in primary and recurrent GBM through different underlying pathways, despite this bevacizumab is the only Food and Drug Administration (FDA) approved drug for recurrent GBM. Immunotherapy is another important promising modality of treatment of GBM, after proper understanding of the microenvironment of the tumour and overcoming the reasons that historically stigmatise GBM as an 'immunologically cold tumour'. Radiotherapy can augment the effect of immunotherapy by different mechanisms. Also, dual immunotherapy which targets immune pathways at different stages and through different receptors further enhances immune stimulation against GBM. Delivery of pro-drugs to be activated at the tumour site and suicidal genes by gene therapy using different vectors shows promising results. Despite using neurotropic viral vectors specifically targeting glial cells (which are the cells of origin of GBM), no significant improvement of overall-survival has been seen as yet. Non-viral vectors 'polymeric and non-polymeric' show significant tumour shrinkage in pre-clinical trials and now at early-stage clinical trials. To this end, in this review, we aim to study the possible role of different molecular pathways that are involved in GBM's recurrence, we will also review the most relevant and recent clinical experience with targeted treatments and immunotherapies. We will discuss trials utilised tyrosine receptor kinase inhibitors, immunotherapy and gene therapy in recurrent GBM pointing to the causes of potential disappointing preliminary results of some of them. Additionally, we are suggesting a possible future treatment based on recent successful clinical data that could alter the outcome for GBM patients.

Updated Insights on EGFR Signaling Pathways in Glioma

Nowadays, due to recent advances in molecular biology, the pathogenesis of glioblastoma is better understood. For the newly diagnosed, the current standard of care is represented by resection followed by radiotherapy and temozolomide administration, but because median overall survival remains poor, new diagnosis and treatment strategies are needed. Due to the quick progression, even with aggressive multimodal treatment, glioblastoma remains almost incurable. It is known that epidermal growth factor receptor (EGFR) amplification is a characteristic of the classical subtype of glioma. However, targeted therapies against this type of receptor have not yet shown a clear clinical benefit. Many factors contribute to resistance, such as ineffective blood-brain barrier penetration, heterogeneity, mutations, as well as compensatory signaling pathways. A better understanding of the EGFR signaling network, and its interrelations with other pathways, are essential to clarify the mechanisms of resistance and create better therapeutic agents.

Current evidence and challenges of systematic therapies for adult recurrent glioblastoma: Results from clinical trials

Recurrence is a major concern for adult patients with glioblastomas (GBMs), and the prognosis remains poor. Although several therapies have been assessed, most of them have not achieved satisfactory results. Therefore, there is currently no standard treatment for adult recurrent GBM (rGBM). Here, we review the results of clinical trials for the systematic therapy of rGBM. Regorafenib, rindopepimut and neoadjuvant programmed death 1 (PD-1) inhibitors are promising agents for rGBM, while regorafenib is effective in both O⁶-methylguanine DNA methyltransferase (MGMT) promoter methylated and unmethylated patients. Temozolomide rechallenge and alkylating agents combined with bevacizumab can be useful for patients with MGMT methylation, and patients with isocitrate dehydrogenase (IDH) mutations or second recurrence can benefit from vocimagene amiretrorepvec (Toca 511). Some phase I trials on targeted therapy and immunotherapy have shown positive results, and results from further studies are expected. In addition to the analysis of existing clinical trial results, forthcoming trials should be well designed, and patients are encouraged to participate in appropriate clinical trials.

Lessons learned from contemporary glioblastoma randomized clinical trials through systematic review and network meta-analysis: part 2 recurrent glioblastoma

BACKGROUND

There exists no consensus standard of treatment for patients with recurrent glioblastoma (GB). Here we used a network meta-analysis on treatments from randomized control trials (RCTs) to assess the effect on overall survival (OS) and progression-free survival (PFS) to determine if any consensus treatment can be determined for recurrent GB.

METHODS

We included all recurrent GB RCTs with at least 20 patients in each arm, and for whom patients underwent standard of care at the time of their GB initial diagnosis. Our primary outcome was OS, with secondary outcomes including PFS and adverse reactions. Hazard ratio (HR) and its 95% confidence interval (CI) of the comparison of study arms regarding OS and PFS were extracted from each paper. For comparative efficacy analysis, we utilized a frequentist network meta-analysis, an extension of the classic pair-wise meta-analysis. We followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses.

RESULTS

Fifteen studies were included representing 29 separate treatment arms and 2194 patients. In our network meta-analysis, combination treatment with tumor-treating field and Vascular endothelial growth factor (VEGF) inhibitor ranked first in improving OS (P = .80). Concomitant anti-VEGF and Lomustine treatment was superior to Lomustine alone for extending PFS (HR 0.57, 95% CI 0.41-0.79) and ranked first in improving PFS compared to other included treatments (P = .86).

CONCLUSIONS

Our analysis highlights the numerous studies performed on recurrent GB, with no proven consensus treatment that is superior to the current SOC. Intertrial heterogeneity precludes drawing strong conclusions, and confidence analysis was low to very low. Further confirmation by future trials is recommended for our exploratory results.

Nanodelivery Systems Targeting Epidermal Growth Factor Receptors for Glioma Management

A paradigm shift in treating the most aggressive and malignant form of glioma is continuously evolving; however, these strategies do not provide a better life and survival index. Currently, neurosurgical debulking, radiotherapy, and chemotherapy are the treatment options available for glioma, but these are non-specific in action. Patients invariably develop resistance to these therapies, leading to recurrence and death. Receptor Tyrosine Kinases (RTKs) are among the most common cell surface proteins in glioma and play a significant role in malignant progression; thus, these are currently being explored as therapeutic targets. RTKs belong to the family of cell surface receptors that are activated by ligands which in turn activates two major downstream signaling pathways via Rapidly Accelerating Sarcoma/mitogen activated protein kinase/extracellular-signal-regulated kinase (Ras/MAPK/ERK) and phosphatidylinositol 3-kinase/a serine/threonine protein kinase/mammalian target of rapamycin (PI3K/AKT/mTOR). These pathways are critically involved in regulating cell proliferation, invasion, metabolism, autophagy, and apoptosis. Dysregulation in these pathways results in uncontrolled glioma cell proliferation, invasion, angiogenesis, and cancer progression. Thus, RTK pathways are considered a potential target in glioma management. This review summarizes the possible risk factors involved in the growth of glioblastoma (GBM). The role of RTKs inhibitors (TKIs) and the intracellular signaling pathways involved, small molecules under clinical trials, and the updates were discussed. We have also compiled information on the outcomes from the various endothelial growth factor receptor (EGFR)-TKIs-based nanoformulations from the preclinical and clinical points of view. Aided by an extensive literature search, we propose the challenges and potential opportunities for future research on EGFR-TKIs-based nanodelivery systems.

The Landscape of Novel Therapeutics and Challenges in Glioblastoma Multiforme: Contemporary State and Future Directions

BACKGROUND

Glioblastoma multiforme is a malignant intracranial neoplasm that constitutes a therapeutic challenge because of the associated high morbidity and mortality given the lack of effective approved medication and aggressive nature of the tumor. However, there has been extensive research recently to address the reasons implicated in the resistant nature of the tumor to pharmaceutical compounds, which have resulted in several clinical trials investigating promising treatment approaches.

METHODS

We reviewed literature published since 2010 from PUBMED and several annual meeting abstracts through 15 September 2020. Selected articles included those relevant to topics of glioblastoma tumor biology, original basic research, clinical trials, seminal reviews, and meta-analyses. We provide a discussion based on the collected evidence regarding the challenging factors encountered during treatment, and we highlighted the relevant trials of novel therapies including immunotherapy and targeted medication.

RESULTS

Selected literature revealed four main factors implicated in the low efficacy encountered with investigational treatments which included: (1) blood-brain barrier; (2) immunosuppressive microenvironment; (3) genetic heterogeneity; (4) external factors related to previous systemic treatment that can modulate tumor microenvironment. Investigational therapies discussed in this review were classified as immunotherapy and targeted therapy. Immunotherapy included: (1) immune checkpoint inhibitors; (2) adoptive cell transfer therapy; (3) therapeutic vaccines; (4) oncolytic virus therapy. Targeted therapy included tyrosine kinase inhibitors and other receptor inhibitors. Finally, we provide our perspective on future directions in treatment of glioblastoma.

CONCLUSION

Despite the limited success in development of effective therapeutics in glioblastoma, many treatment approaches hold potential promise including immunotherapy and novel combinational drugs. Addressing the molecular landscape and resistant immunosuppressive nature of glioblastoma are imperative in further development of effective treatments.

Mechanisms of EGFR Resistance in Glioblastoma

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults. Despite numerous efforts to target epidermal growth factor receptor (EGFR), commonly dysregulated in GBM, approaches directed against EGFR have not achieved the same degree of success as seen in other tumor types, particularly as compared to non-small cell lung cancer (NSCLC). EGFR alterations in glioblastoma lie primarily in the extracellular domain, unlike the kinase domain alterations seen in NSCLC. Small molecule inhibitors are difficult to develop for the extracellular domain. Monoclonal antibodies can be developed to target the extracellular domain but must contend with the blood brain barrier (BBB). We review the role of EGFR in GBM, the history of trialed treatments, and the potential paths forward to target the pathway that may have greater success.

Discrete Coiled Coil Rotamers Form within the EGFRvIII Juxtamembrane Domain

Mutations in the epidermal growth factor receptor (EGFR) extracellular domain (ECD) are implicated in the development of glioblastoma multiforme (GBM), which is a highly aggressive form of brain cancer. Of particular interest to GBM is the EGFR variant known as EGFRvIII, which is distinguished by an in-frame deletion of exons 2-7, which encode ECD residues 6-273. Included within the deleted region is an autoinhibitory tether, whose absence, alongside unique disulfide interactions within the truncated ECD, supports assembly of a constitutively active asymmetric kinase dimer. Previous studies have shown that the binding of growth factors to the ECD of wild-type EGFR leads to the formation of two distinct coiled coil dimers in the cytoplasmic juxtamembrane (JM) segment, whose identities correlate with the downstream phenotype. One coiled coil contains leucine residues at the interhelix interface (EGF-type), whereas the other contains charged and polar side chains (TGF-α-type). It has been proposed that growth-factor-dependent structural changes in the ECD and adjacent transmembrane helix are transduced into distinct JM coiled coils. Here, we show that, in the absence of this growth-factor-induced signal, the JM of EGFRvIII adopts both EGF-type and TGF-α-type structures, providing direct evidence for this hypothesis. These studies confirm that the signals that define JM coiled coil identity begin within the ECD, and support a model in which growth-factor-induced conformational changes are transmitted from the ECD through the transmembrane helix to favor different coiled coil isomers within the JM.

Reduced EGFR and increased miR-221 is associated with increased resistance to temozolomide and radiotherapy in glioblastoma

Despite aggressive treatment with temozolomide and radiotherapy and extensive research into alternative therapies there has been little improvement in Glioblastoma patient survival. Median survival time remains between 12 and 15 months mainly due to treatment resistance and tumor recurrence. In this study, we aimed to explore the underlying mechanisms behind treatment resistance and the lack of success with anti-EGFR therapy in the clinic. After generating a number of treatment resistant Glioblastoma cell lines we observed that resistant cell lines lacked EGFR activation and expression. Furthermore, cell viability assays showed resistant cells were significantly less sensitive to the anti-EGFR agents when compared to parental cell lines. To further characterise the resistance mechanism in our cells microRNA prediction software identified miR-221 as a negative regulator of EGFR expression. miR-221 was up-regulated in our resistant cell lines, and this up-regulation led to a significant reduction in EGFR expression in both our cultured cell lines and a large cohort of glioblastoma patient tumor tissue.

Novel Treatment Strategies for Glioblastoma

Glioblastoma (GBM) is the most common primary central nervous system tumor in adults. It is a highly invasive disease, making it difficult to achieve a complete surgical resection, resulting in poor prognosis with a median survival of 12–15 months after diagnosis, and less than 5% of patients survive more than 5 years. Surgical, instrument technology, diagnostic and radio/chemotherapeutic strategies have slowly evolved over time, but this has not translated into significant increases in patient survival. The current standard of care for GBM patients involving surgery, radiotherapy, and concomitant chemotherapy temozolomide (known as the Stupp protocol), has only provided a modest increase of 2.5 months in median survival, since the landmark publication in 2005. There has been considerable effort in recent years to increase our knowledge of the molecular landscape of GBM through advances in technology such as next-generation sequencing, which has led to the stratification of the disease into several genetic subtypes. Current treatments are far from satisfactory, and studies investigating acquired/inherent resistance to current therapies, restricted drug delivery, inter/intra-tumoral heterogeneity, drug repurposing and a tumor immune-evasive environment have been the focus of intense research over recent years. While the clinical advancement of GBM therapeutics has seen limited progression compared to other cancers, developments in novel treatment strategies that are being investigated are displaying encouraging signs for combating this disease. This aim of this editorial is to provide a brief overview of a select number of these novel therapeutic approaches.

Development of a Potent Brain-Penetrant EGFR Tyrosine Kinase Inhibitor against Malignant Brain Tumors

The epidermal growth factor receptor (EGFR) is genetically altered in nearly 60% of glioblastoma tumors; however, tyrosine kinase inhibitors (TKIs) against EGFR have failed to show efficacy for patients with these lethal brain tumors. This failure is attributed to the inability of clinically tested EGFR TKIs to cross the blood-brain barrier (BBB) and achieve adequate pharmacological levels to inhibit various oncogenic forms of EGFR that drive glioblastoma. Through SAR analysis, we developed compound 5 (JCN037) from an anilinoquinazoline scaffold by ring fusion of the 6,7-dialkoxy groups to reduce the number of rotatable bonds and polar surface area and by introduction of an ortho-fluorine and meta-bromine on the aniline ring for improved potency and BBB penetration. Relative to the conventional EGFR TKIs erlotinib and lapatinib, JCN037 displayed potent activity against EGFR amplified/mutant patient-derived cell cultures, significant BBB penetration (2:1 brain-to-plasma ratio), and superior efficacy in an EGFR-driven orthotopic glioblastoma xenograft model.

Multiomics profiling of paired primary and recurrent glioblastoma patient tissues

Background

Despite maximal therapy with surgery, chemotherapy, and radiotherapy, glioblastoma (GBM) patients have a median survival of only 15 months. Almost all patients inevitably experience symptomatic tumor recurrence. A hallmark of this tumor type is the large heterogeneity between patients and within tumors itself which relates to the failure of standardized tumor treatment. In this study, tissue samples of paired primary and recurrent GBM tumors were investigated to identify individual factors related to tumor progression.

Methods

Paired primary and recurrent GBM tumor tissues from 8 patients were investigated with a multiomics approach using transcriptomics, proteomics, and phosphoproteomics.

Results

In the studied patient cohort, large variations between and within patients are observed for all omics analyses. A few pathways affected at the different omics levels partly overlapped if patients are analyzed at the individual level, such as synaptogenesis (containing the SNARE complex) and cholesterol metabolism. Phosphoproteomics revealed increased STMN1(S38) phosphorylation as part of ERBB4 signaling. A pathway tool has been developed to visualize and compare different omics datasets per patient and showed potential therapeutic drugs, such as abobotulinumtoxinA (synaptogenesis) and afatinib (ERBB4 signaling). Afatinib is currently in clinical trials for GBM.

Conclusions

A large variation on all omics levels exists between and within GBM patients. Therefore, it will be rather unlikely to find a drug treatment that would fit all patients. Instead, a multiomics approach offers the potential to identify affected pathways on the individual patient level and select treatment options.