The effects of ponatinib, a multi-targeted tyrosine kinase inhibitor, against human U87 malignant glioblastoma cells

Intranasal administration of molecular-gated mesoporous nanoparticles to increase ponatinib delivery to the brain

Background: Glioblastoma is the most common and lethal brain cancer. New treatments are needed. However, the presence of the blood-brain barrier is limiting the development of new treatments directed toward the brain, as it restricts the access and distribution of drugs to the CNS. Materials & methods: In this work, two different nanoparticles (i.e., mesoporous silica nanoparticles and magnetic mesoporous silica nanoparticles) loaded with ponatinib were prepared. Results & conclusion: Both particles were characterized and tested in vitro and in vivo, proving that they are not toxic for blood-brain barrier cells and they increase the amount of drug reaching the brain when administered intranasally in comparison with the results obtained for the free drug.

Receptor-Tyrosine Kinase Inhibitor Ponatinib Inhibits Meningioma Growth In Vitro and In Vivo

To date, there is no standard-of-care systemic therapy for the treatment of aggressive meningiomas. Receptor tyrosine kinases (RTK) are frequently expressed in aggressive meningiomas and are associated with poor survival. Ponatinib is a FDA- and EMA-approved RTK inhibitor and its efficacy in meningioma has not been studied so far. Therefore, we investigated ponatinib as a potential drug candidate against meningioma. Cell viability and cell proliferation of ponatinib-treated meningioma cells were assessed using crystal violet assay, manual counting and BrdU assay. Treated meningioma cell lines were subjected to flow cytometry to evaluate the effects on cell cycle and apoptosis. Meningioma-bearing mice were treated with ponatinib to examine antitumor effects in vivo. qPCR was performed to assess the mRNA levels of tyrosine kinase receptors after ponatinib treatment. Full-length cDNA sequencing was carried out to assess differential gene expression. IC50 values of ponatinib were between 171.2 and 341.9 nM in three meningioma cell lines. Ponatinib induced G0/G1 cell cycle arrest and subsequently led to an accumulation of cells in the subG1-phase. A significant induction of apoptosis was observed in vitro. In vivo, ponatinib inhibited meningioma growth by 72.6%. Mechanistically, this was associated with downregulation of PDGFRA/B and FLT3 mRNA levels, and mitochondrial dysfunction. Taken together, ponatinib is a promising candidate for targeted therapy in the treatment of aggressive meningioma.

DECIPHER pooled shRNA library screen identifies PP2A and FGFR signaling as potential therapeutic targets for diffuse intrinsic pontine gliomas

BACKGROUND

Diffuse intrinsic pontine gliomas (DIPGs) are highly aggressive pediatric brain tumors that are characterized by a recurrent mutation (K27M) within the histone H3 encoding genes H3F3A and HIST1H3A/B/C. These mutations have been shown to induce a global reduction in the repressive histone modification H3K27me3, which together with widespread changes in DNA methylation patterns results in an extensive transcriptional reprogramming hampering the identification of single therapeutic targets based on a molecular rationale.

METHODS

We applied a large-scale gene knockdown approach using a pooled short hairpin (sh)RNA library in combination with next-generation sequencing in order to identify DIPG-specific vulnerabilities. The therapeutic potential of specific inhibitors of candidate targets was validated in a secondary drug screen.

RESULTS

We identified fibroblast growth factor receptor (FGFR) signaling and the serine/threonine protein phosphatase 2A (PP2A) as top depleted hits in patient-derived DIPG cell cultures and validated their lethal potential by FGF ligand depletion and genetic knockdown of the PP2A structural subunit PPP2R1A. Further, pharmacological inhibition of FGFR and PP2A signaling through ponatinib and LB-100 treatment, respectively, exhibited strong tumor-specific anti-proliferative and apoptotic activity in cultured DIPG cells.

CONCLUSIONS

Our findings suggest FGFR and PP2A signaling as potential new therapeutic targets for the treatment of DIPGs.

Targeting the Extra-Cellular Matrix-Tumor Cell Crosstalk for Anti-Cancer Therapy: Emerging Alternatives to Integrin Inhibitors

The extracellular matrix (ECM) is a complex network composed of a multitude of different macromolecules. ECM components typically provide a supportive structure to the tissue and engender positional information and crosstalk with neighboring cells in a dynamic reciprocal manner, thereby regulating tissue development and homeostasis. During tumor progression, tumor cells commonly modify and hijack the surrounding ECM to sustain anchorage-dependent growth and survival, guide migration, store pro-tumorigenic cell-derived molecules and present them to enhance receptor activation. Thereby, ECM potentially supports tumor progression at various steps from initiation, to local growth, invasion, and systemic dissemination and ECM-tumor cells interactions have long been considered promising targets for cancer therapy. Integrins represent key surface receptors for the tumor cell to sense and interact with the ECM. Yet, attempts to therapeutically impinge on these interactions using integrin inhibitors have failed to deliver anticipated results, and integrin inhibitors are still missing in the emerging arsenal of drugs for targeted therapies. This paradox situation should urge the field to reconsider the role of integrins in cancer and their targeting, but also to envisage alternative strategies. Here, we review the therapeutic targets implicated in tumor cell adhesion to the ECM, whose inhibitors are currently in clinical trials and may offer alternatives to integrin inhibition.

Novel Gene Fusions in Glioblastoma Tumor Tissue and Matched Patient Plasma

Sequencing studies have provided novel insights into the heterogeneous molecular landscape of glioblastoma (GBM), unveiling a subset of patients with gene fusions. Tissue biopsy is highly invasive, limited by sampling frequency and incompletely representative of intra-tumor heterogeneity. Extracellular vesicle-based liquid biopsy provides a minimally invasive alternative to diagnose and monitor tumor-specific molecular aberrations in patient biofluids. Here, we used targeted RNA sequencing to screen GBM tissue and the matched plasma of patients (n = 9) for RNA fusion transcripts. We identified two novel fusion transcripts in GBM tissue and five novel fusions in the matched plasma of GBM patients. The fusion transcripts FGFR3-TACC3 and VTI1A-TCF7L2 were detected in both tissue and matched plasma. A longitudinal follow-up of a GBM patient with a FGFR3-TACC3 positive glioma revealed the potential of monitoring RNA fusions in plasma. In summary, we report a sensitive RNA-seq-based liquid biopsy strategy to detect RNA level fusion status in the plasma of GBM patients.

Phase II trial of ponatinib in patients with bevacizumab-refractory glioblastoma

Background

Responses to bevacizumab in glioblastoma (GBM) are not durable. Plasma levels of basic fibroblast growth factor (bFGF) increase at the time of tumor progression. By targeting vascular endothelial growth factor receptor (VEGFR), platelet‐derived growth factor receptor, Src, and FGF receptor pathways, ponatinib may potentially help to overcome some of the putative mechanisms of adaptive resistance.

Methods

We performed a phase II trial of ponatinib in patients with bevacizumab‐refractory GBM and variants. Adult patients with Karnofsky performance score (KPS) ≥60, measurable disease, and normal organ and marrow function received 45 mg ponatinib daily. No limit on the number of prior therapies but only one prior bevacizumab‐containing regimen was allowed. Primary endpoint was 3‐month progression‐free survival. Plasma biomarkers of angiogenesis and inflammation were evaluated before and after treatment.

Results

The study closed after the first stage. Fifteen patients enrolled: median age 61 [27‐74]; median KPS 80 [70‐90]; median number of prior relapses 2 [2‐4]. Three‐month progression‐free survival rate was 0, median overall survival was 98 days [95% CI 56, 257], and median PFS was 28 days [95% CI 27, 30]. No responses were seen. The most common grade ≥3 adverse events included fatigue (n = 3), hypertension (2), and lipase elevation (2). Ponatinib treatment significantly increased plasma VEGF, soluble (s)VEGFR1, sVEGFR2, sTIE2, interferon gamma (IFNγ), tumor necrosis factor alpha (TNF‐α), interleukin (IL)‐6, IL‐8, and IL‐10 and decreased sVEGFR2.

Conclusions

Ponatinib was associated with minimal activity in bevacizumab‐refractory GBM patients. Circulating biomarker data confirmed pharmacodynamic changes and suggested that resistance to ponatinib may be related to an increase in inflammatory cytokines.

Ponatinib: a novel multi-tyrosine kinase inhibitor against human malignancies

Human malignancies are often the result of overexpressed and constitutively active receptor and non-receptor tyrosine kinases, which ultimately lead to the mediation of key tumor-driven pathways. Several tyrosine kinases (ie, EGFR, FGFR, PDGFR, VEGFR), are aberrantly activated in most common tumors, including leukemia, glioblastoma, gastrointestinal stromal tumors, non-small-cell lung cancer, and head and neck cancers. Iclusig™ (ponatinib, previously known as AP24534) is an orally active multi-tyrosine kinase inhibitor and is currently approved by the US Food and Drug Administration for patients with chronic myeloid leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia, specifically targeting the BCR-ABL gene mutation, T315I. Due to ponatinib's unique multi-targeted characteristics, further studies have demonstrated its ability to target other important tyrosine kinases (FGFR, PDGFR, SRC, RET, KIT, and FLT1) in other human malignancies. This review focuses on the available data of ponatinib and its molecular targets for treatment in various cancers, with a discussion on the broader potential of this agent in other cancer indications.

Recent Studies on Ponatinib in Cancers Other Than Chronic Myeloid Leukemia

Ponatinib is a third line drug for the treatment of chronic myeloid leukemia patients, especially those that develop the gatekeeper mutation T315I, which is resistant to the first and the second line drugs imatinib, nilotinib, dasatinib and bosutinib. The compound was first identified as a pan Bcr-Abl and Src kinase inhibitor. Further studies have indicated that it is a multitargeted inhibitor that is active on FGFRs, RET, AKT, ERK1/2, KIT, MEKK2 and other kinases. For this reason, the compound has been evaluated on several cancers in which these kinases play important roles, including thyroid, breast, ovary and lung cancer, neuroblastoma, rhabdoid tumours and in myeloproliferative disorders. Ponatinib is also being tested in clinical trials to evaluate its activity in FLT3-ITD acute myelogenous leukemia, head and neck cancers, certain type of lung cancer, gastrointestinal stromal tumours and other malignancies. In this review we report the most recent preclinical and clinical studies on ponatinib in cancers other than CML, with the aim of giving a complete overview of this interesting compound.

Gene Fusion in Malignant Glioma: An Emerging Target for Next-Generation Personalized Treatment

Malignant gliomas are heterogeneous diseases in genetic basis. The development of sequencing techniques has identified many gene rearrangements encoding novel oncogenic fusions in malignant glioma to date. Understanding the gene fusions and how they regulate cellular processes in different subtypes of glioma will shed light on genomic diagnostic approaches for personalized treatment. By now, studies of gene fusions in glioma remain limited, and no medication has been approved for treating the malignancy harboring gene fusions. This review will discuss the current characterization of gene fusions occurring in both adult and pediatric malignant gliomas, their roles in oncogenesis, and the potential clinical implication as therapeutic targets.

Blood-brain barrier-adapted precision medicine therapy for pediatric brain tumors

Targeted chemotherapeutics provide a promising new treatment option in neuro-oncology. The ability of these compounds to penetrate the blood-brain barrier is crucial for their successful incorporation into patient care. "CNS Targeted Agent Prediction" (CNS-TAP) is a multi-institutional and multidisciplinary translational program established at the University of Michigan for evaluating the central nervous system (CNS) activity of targeted therapies in neuro-oncology. In this report, we present the methodology of CNS-TAP in a series of pediatric and adolescent patients with high-risk brain tumors, for which molecular profiling (academic and commercial) was sought and targeted agents were incorporated. Four of five of the patients had potential clinical benefit (partial response or stable disease greater than 6 months on therapy). We further describe the specific drug properties of each agent chosen and discuss characteristics relevant in their evaluation for therapeutic suitability. Finally, we summarize both tumor and drug characteristics that impact the ability to successfully incorporate targeted therapies into CNS malignancy management.

Identification and targeting of an FGFR fusion in a pediatric thalamic "central oligodendroglioma"

Approximately 1–5% of pediatric intracranial tumors originate in the thalamus. While great strides have been made to identify consistent molecular markers in adult oligodendrogliomas, such as the 1p/19q co-deletion, it is widely recognized that pediatric oligodendrogliomas have a vastly different molecular make-up. While pediatric thalamic or “central oligodendrogliomas” are histologically similar to peripheral pediatric oligodendrogliomas, they are behaviorally distinct and likely represent a cohesive, but entirely different entity. We describe a case of a 10-year-old girl who was diagnosed with an anaplastic glioma with features consistent with the aggressive entity often diagnosed as central or thalamic oligodendroglioma. We performed whole-exome (paired tumor and germline DNA) and transcriptome (tumor RNA) sequencing, which demonstrated an FGFR3-PHGDH fusion. We describe this fusion and our rationale for pursuing personalized, targeted therapy for the patient’s tumor that may potentially play a role in the treatment of similar cases.

The novel kinase inhibitor ponatinib is an effective anti-angiogenic agent against neuroblastoma

Background High-risk neuroblastoma has poor outcomes with high rates of relapse despite aggressive treatment, and novel therapies are needed to improve these outcomes. Ponatinib is a multi-tyrosine kinase inhibitor that targets many pathways implicated in neuroblastoma pathogenesis. We hypothesized that ponatinib would be effective against neuroblastoma in preclinical models. Methods We evaluated the effects of ponatinib on survival and migration of human neuroblastoma cells in vitro. Using orthotopic xenograft mouse models of human neuroblastoma, we analyzed tumors treated with ponatinib for growth, gross and histologic appearance, and vascularity. Results Ponatinib treatment of neuroblastoma cells resulted in decreased cell viability and migration in vitro. In mice with orthotopic xenograft neuroblastoma tumors, treatment with ponatinib resulted in decreased growth and vascularity. Conclusions Ponatinib reduces neuroblastoma cell viability in vitro and reduces tumor growth and vascularity in vivo. The antitumor effects of ponatinib suggest its potential as a novel therapeutic agent for neuroblastoma, and further preclinical testing is warranted.

Beyond standard therapy: drugs under investigation for the treatment of gastrointestinal stromal tumor

INTRODUCTION

Gastrointestinal stromal tumor (GIST) is the most common nonepithelial malignancy of the GI tract. With the discovery of KIT and later platelet-derived growth factor α (PDGFRA) gain-of-function mutations as factors in the pathogenesis of the disease, GIST was the quintessential model for targeted therapy. Despite the successful clinical use of imatinib mesylate, a selective receptor tyrosine kinase (RTK) inhibitor that targets KIT, PDGFRA and BCR-ABL, we still do not have treatment for the long-term control of advanced GIST.

AREAS COVERED

This review summarizes the drugs that are under investigation or have been assessed in trials for GIST treatment. The article focuses on their mechanisms of actions, the preclinical evidence of efficacy, and the clinical trials concerning safety and efficacy in humans.

EXPERT OPINION

It is known that KIT and PDGFRA mutations in GIST patients influence the response to treatment. This observation should be taken into consideration when investigating new drugs. RECIST was developed to help uniformly report efficacy trials in oncology. Despite the usefulness of this system, many questions are being addressed about its validity in evaluating the true efficacy of drugs knowing that new targeted therapies do not affect the tumor size as much as they halt progression and prolong survival.