Rogaratinib: A potent and selective pan-FGFR inhibitor with broad antitumor activity in FGFR-overexpressing preclinical cancer models

Aberrant activation in fibroblast growth factor signaling has been implicated in the development of various cancers, including squamous cell lung cancer, squamous cell head and neck carcinoma, colorectal and bladder cancer. Thus, fibroblast growth factor receptors (FGFRs) present promising targets for novel cancer therapeutics. Here, we evaluated the activity of a novel pan‐FGFR inhibitor, rogaratinib, in biochemical, cellular and in vivo efficacy studies in a variety of preclinical cancer models. In vitro kinase activity assays demonstrate that rogaratinib potently and selectively inhibits the activity of FGFRs 1, 2, 3 and 4. In line with this, rogaratinib reduced proliferation in FGFR‐addicted cancer cell lines of various cancer types including lung, breast, colon and bladder cancer. FGFR and ERK phosphorylation interruption by rogaratinib treatment in several FGFR‐amplified cell lines suggests that the anti‐proliferative effects are mediated by FGFR/ERK pathway inhibition. Furthermore, rogaratinib exhibited strong in vivo efficacy in several cell line‐ and patient‐derived xenograft models characterized by FGFR overexpression. The observed efficacy of rogaratinib strongly correlated with FGFR mRNA expression levels. These promising results warrant further development of rogaratinib and clinical trials are currently ongoing (ClinicalTrials.gov Identifiers: NCT01976741, NCT03410693, NCT03473756).

What's new?

Deregulated fibroblast growth factor receptor (FGFR) signaling is involved in tumorigenesis and cancer progression. Here, the authors report on a novel pan‐FGFR inhibitor, rogaratinib, that potently and highly selectively prevents the activity of FGFRs 1, 2, 3, and 4. Rogaratinib inhibits cell proliferation in various FGFR‐addicted cancers in vitro, including colon, lung, and bladder cancer. Rogaratinib also exhibits strong in vivo efficacy in several cell line‐ and patient‐derived xenograft models characterized by FGFR mRNA overexpression with good tolerability. Altogether, these data warrant the further development of rogaratinib for treatment of cancers with FGFR alterations, and clinical trials are currently ongoing.

Abstract 4332: Discovery of BAY 1163877 - A pan-FGFR inhibitor: De novo structure-based design and lead optimization of benzothiophenyl-pyrrolotriazines

Fibroblast growth factors (FGFs) orchestrate a variety of cellular functions by binding to their transmembrane tyrosine-kinase receptors (FGFR1-4) and activating downstream signaling pathways. Alterations in FGFR encoding genes are frequently observed in a variety of solid tumors including lung, gastric, breast and urothelial cancer. Therefore, targeting FGFRs using selective FGFR inhibitors is an attractive therapeutic approach to treat cancer patients.

BAY 1163877 is an orally active, highly potent and selective small molecule FGFR-1, -2 and -3 kinase inhibitor. We disclose for the very first time its discovery and chemical structure. BAY 1163877 was derived from a de novo structure-based design approach and medicinal chemistry optimization. Data on the structure activity relationship and the pharmacokinetic profile of the benzothiophenyl-pyrrolotriazine structure class will be presented. Based on its favorable preclinical profile, BAY 1163877 is currently being investigated in a Phase 1 clinical trial (NCT01976741).

Citation Format: Marie-Pierre L. Collin, Mario Lobell, Walter Huebsch, Dirk Brohm, Mélanie Héroult, Klemens Lustig, Sylvia Gruenewald, Ulf Boemer, Rolf Jautelat, Holger Hess-Stump, Stefan Jaroch, Michael Brands, Karl Ziegelbauer. Discovery of BAY 1163877 - A pan-FGFR inhibitor: De novo structure-based design and lead optimization of benzothiophenyl-pyrrolotriazines. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4332.

Abstract 4746: Pharmacological characterization of BAY-876, a novel highly selective inhibitor of glucose transporter (GLUT)-1 in vitro and in vivo

One hallmark of cancer is the accelerated metabolism, high energy requirements, and increased glucose uptake by the tumor cells, the latter being the first and rate-limiting step for glucose metabolism. Glucose transport into the tumor cell is mediated by facilitative high-affinity glucose transporter (GLUT) proteins. Among the 14 GLUT proteins, expression of GLUT1 in normal organs is nearly exclusively restricted to the blood brain barrier, while other GLUTs are also expressed in a wide variety of vital organs such as liver and heart. Interestingly, GLUT1 expression is highly regulated by hypoxia-inducible factor (HIF)-1α, a key driver of tumor progression. In line with this finding, GLUT1 over-expression was found to be associated with tumor progression and poor overall survival in various tumor indications. Consequently, GLUT1 represents a potential target for cancer treatment. Therefore, we have developed a highly-selective GLUT1 inhibitor, namely BAY-876, with selectivity over GLUT2, 3, and 4 of 4700-, 800-, and 135-fold, respectively. We here show for the first time the pharmacological characterization of BAY-876, comprising inhibition of glucose-uptake, anti-proliferative activity in vitro, and anti-tumor efficacy in vivo in models of different tumor indications in monotherapy as well as first results on the combinability of BAY-876. Furthermore, at the therapeutic dose, BAY-876 treatment did not show any relevant finding on the behavior of treated mice in the Irwin test, assuming no or only minor effects on brain function. In conclusion, BAY-876 is the first GLUT1-selective inhibitor which reduces glucose uptake and growth of tumor cells with sufficient tolerability at the efficacious dose in preclinical models.

Citation Format: Charlotte Kopitz, Luisella Toschi, Carolyn Algire, Mélanie Héroult, Anna-Lena Frisk, Kirstin Meyer, Arndt Schmitz, Eleni Lagkadinou, Heike Petrul, Iring Heisler, Roland Neuhaus, Bernd Buchmann, Herbert Himmel, Marcus Bauser, Andrea Haegebarth, Karl Ziegelbauer. Pharmacological characterization of BAY-876, a novel highly selective inhibitor of glucose transporter (GLUT)-1 in vitro and in vivo. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4746.

Neuropilin-1 mediates vascular permeability independently of vascular endothelial growth factor receptor-2 activation

Neuropilin-1 (NRP1) regulates developmental and pathological angiogenesis, arteriogenesis, and vascular permeability, acting as a coreceptor for semaphorin 3A (Sema3A) and the 165-amino acid isoform of vascular endothelial growth factor A (VEGF-A165). NRP1 is also the receptor for the CendR peptides, a class of cell- and tissue-penetrating peptides with a specific R-x-x-R carboxyl-terminal motif. Because the cytoplasmic domain of NRP1 lacks catalytic activity, NRP1 is mainly thought to act through the recruitment and binding to other receptors. We report here that the NRP1 intracellular domain mediates vascular permeability. Stimulation with VEGF-A165, a ligand-blocking antibody, and a CendR peptide led to NRP1 accumulation at cell-cell contacts in endothelial cell monolayers, increased cellular permeability in vitro and vascular leakage in vivo. Biochemical analyses, VEGF receptor-2 (VEGFR-2) silencing, and the use of a specific VEGFR blocker established that the effects induced by the CendR peptide and the antibody were independent of VEGFR-2. Moreover, leakage assays in mice expressing a mutant NRP1 lacking the cytoplasmic domain revealed that this domain was required for NRP1-induced vascular permeability in vivo. Hence, these data define a vascular permeability pathway mediated by NRP1 but independent of VEGFR-2 activation.

Targeting mitochondrial complex I using BAY 87-2243 reduces melanoma tumor growth

Background

Numerous studies have demonstrated that functional mitochondria are required for tumorigenesis, suggesting that mitochondrial oxidative phosphorylation (OXPHOS) might be a potential target for cancer therapy. In this study, we investigated the effects of BAY 87-2243, a small molecule that inhibits the first OXPHOS enzyme (complex I), in melanoma in vitro and in vivo.

Results

BAY 87-2243 decreased mitochondrial oxygen consumption and induced partial depolarization of the mitochondrial membrane potential. This was associated with increased reactive oxygen species (ROS) levels, lowering of total cellular ATP levels, activation of AMP-activated protein kinase (AMPK), and reduced cell viability. The latter was rescued by the antioxidant vitamin E and high extracellular glucose levels (25 mM), indicating the involvement of ROS-induced cell death and a dependence on glycolysis for cell survival upon BAY 87-2243 treatment. BAY 87-2243 significantly reduced tumor growth in various BRAF mutant melanoma mouse xenografts and patient-derived melanoma mouse models. Furthermore, we provide evidence that inhibition of mutated BRAF using the specific small molecule inhibitor vemurafenib increased the OXPHOS dependency of BRAF mutant melanoma cells. As a consequence, the combination of both inhibitors augmented the anti-tumor effect of BAY 87-2243 in a BRAF mutant melanoma mouse xenograft model.

Conclusions

Taken together, our results suggest that complex I inhibition has potential clinical applications as a single agent in melanoma and also might be efficacious in combination with BRAF inhibitors in the treatment of patients with BRAF mutant melanoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s40170-015-0138-0) contains supplementary material, which is available to authorized users.

Abstract 665: Inhibition of mitochondrial complex I enhances the therapeutic benefit of BRAF inhibition in mutant melanoma cell lines

Metabolic reprogramming is considered to be one of the major hallmarks of cancer. Selective inhibitors of mutant BRAFV600E, are a widely used targeted therapy for melanoma. Unfortunately, acquired drug resistance, which commonly occurs, represents a major limitation to clinical efficacy. Recent studies have highlighted the role of BRAF inhibition in promoting oxidative phosphorylation (OXPHOS), over glycolysis, in BRAFV600E melanomas, a switch commonly seen in conjunction with development of drug resistance. This metabolic switch occurs at the transcriptional level, indicated by the up-regulation of PGC1α through the lineage-specific transcription factor MITF. Based on these data, we propose that increased OXPHOS is required for melanoma cells to acquire resistance against the BRAF inhibition, which supports our investigation of the therapeutic benefit of combining BRAF and OXPHOS inhibitors. For the latter, respiratory Complex I, an essential enzyme in the mitochondrial respiratory chain, is a logical target for OXPHOS inhibition.

We investigated the molecular, metabolic and bioenergetic effects of a selective mutant BRAF inhibitor (Vemurafenib/PLX4032) and BAY 87-2243, a small molecule inhibiting respiratory Complex I, in vitro using various BRAF-mutant melanoma cell lines. First, our study revealed that BRAF inhibition increased the expression of mitochondrial genes and mitochondrial respiration, which is associated with elevated mitochondrial oxidative stress, independent of the expression of PGC1α. Furthermore, BAY 87-2243 inhibited OXPHOS, down-regulated the expression of mitochondrial genes and increased reactive oxygen species (ROS) production. We also demonstrated that inhibition of BRAF increased the OXPHOS phenotype and therefore enhanced the effect of BAY 87-2243 on mitochondrial metabolism; the combination of both inhibitors showed synergistic effects in vitro.Interestingly, long term BRAF inhibition resulted in BRAFV600E melanoma cells to become resistant to BAY 87-2243. Preliminary studies suggest that melanoma cells pretreated with a BRAF inhibitor, with higher rates of mitochondrial respiration and elevated ROS levels, are prone to cell death when targeted by pro-oxidants. Further studies are currently ongoing to understand this resistance phenotype as well as the underlying mechanism which drives the synergistic drug effect.

Citation Format: Laura Schoeckel, Katharina Bitschar, Mélanie Héroult, Charlotte Kopitz, Andrea Hägebarth. Inhibition of mitochondrial complex I enhances the therapeutic benefit of BRAF inhibition in mutant melanoma cell lines. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 665. doi:10.1158/1538-7445.AM2015-665

Involvement of endothelial ephrin-B2 in adhesion and transmigration of EphB-receptor-expressing monocytes

The vascular endothelium is a crucial interface that controls the recruitment of circulating leukocytes. Based on the luminal expression of the ephrin-B2 ligand by endothelial cells (ECs) and the expression of EphB receptors (EphBRs) by circulating monocytes, we hypothesized that EphBR-ephrinB interactions are involved in monocyte adhesion. Adhesion experiments with monocytic cells were performed on ECs that overexpressed either full-length ephrin-B2 or cytoplasmically truncated ephrin-B2 (DeltaC-ephrin-B2). Atomic force microscopy confirmed similar adhesive strengths of EphBR-expressing J774 cells to ECs that either overexpressed full-length ephrin-B2 or truncated DeltaC-ephrin-B2 (1-minute interaction). Yet, adhesion experiments under static or flow conditions for 30 minutes demonstrated the preferential adhesion of monocytic cells to ECs that overexpressed full-length ephrin-B2 but not to DeltaC-ephrin-B2 or to ECs that had been mock transduced. Adhesion was blocked by ephrin-B2-specific and EphBR-specific antibodies. Correspondingly, adhesion of EphB4-receptor-overexpressing monocytes to ephrin-B2-positive ECs was further augmented. Trafficking experiments of cell-surface molecules revealed that, prior to internalization, the resulting EphB4-receptor-ephrin-B2 complex translocated from the luminal surface to inter-endothelial junctions. Lastly, full-length ephrin-B2 in ECs was also involved in monocyte transmigration. Collectively, our study identifies a role of EphBR-ephrinB interactions as a new step in the cascade of events leading to monocyte adhesion and transmigration through the vascular endothelium.

Neuropilin-1-VEGFR-2 complexing requires the PDZ-binding domain of neuropilin-1

Vascular endothelial growth factor (VEGF) acts as a hierarchically high switch of the angiogenic cascade by interacting with its high affinity VEGF receptors and with neuropilin co-receptors. VEGF(165) binds to both Neuropilin-1 (NP-1) and VEGFR-2, and it is believed that ligand binding forms an extracellular bridge between both molecules. This leads to complex formation, thereby enhancing VEGFR-2 phosphorylation and subsequent signaling. We found that inhibition of VEGF receptor (VEGFR) phosphorylation reduced complex formation between NP-1 and VEGFR-2, suggesting a functional role of the cytoplasmic domain of VEGFR-2 for complex formation. Correspondingly, deleting the PDZ-binding domain of NP-1 decreased complex formation, indicating that extracellular VEGF(165) binding is not sufficient for VEGFR-2-NP-1 interaction. Synectin is an NP-1 PDZ-binding domain-interacting molecule. Experiments in Synectin-deficient endothelial cells revealed reduced VEGFR-2-NP-1 complex formation, suggesting a role for Synectin in VEGFR-2-NP-1 signaling. Taken together, the experiments have identified a novel mechanism of NP-1 interaction with VEGFR-2, which involves the cytoplasmic domain of NP-1.

Eph receptor and ephrin ligand-mediated interactions during angiogenesis and tumor progression

Eph receptors comprise the largest family of receptor tyrosine kinases. They are classified into an A family and a B family on the basis of the characteristic properties of the corresponding ephrin ligands which are either GPI-anchored peripheral membrane molecules (A class ephrins) or transmembrane molecules (B class ephrins). Eph receptors and ephrin ligands were originally identified as neuronal pathfinding molecules. Yet, gene targeting experiments in mice have identified the EphB/ephrinB system as critical and rate-limiting determinant of arterio-venous differentiation during embryonic vascular development. Identification of vascular EphB/ephrinB functions has in the last few years stimulated two emerging fields of vascular biology research, namely (1) the molecular analysis of the structural and functional mechanisms of arterio-venous differentiation, and (2) the molecular study of the commonalities between vascular and neuronal guidance and patterning mechanisms. This review summarizes the current understanding of vascular Eph receptor and ephrin ligand functions and provides an overview of emerging roles of the Eph/ephrin system in controlling tumor and vascular functions during tumorigenesis and tumor progression.

Heparin affin regulatory peptide binds to vascular endothelial growth factor (VEGF) and inhibits VEGF-induced angiogenesis

Heparin affin regulatory peptide (HARP) is an heparin-binding molecule involved in the regulation of cell proliferation and differentiation. Here, we report that HARP inhibited the biological activity induced by the 165-amino-acid form of vascular endothelial growth factor (VEGF165) on human umbilical vein endothelial cells. Endothelial-cell proliferation induced by VEGF165 showed about 50% inhibition in the presence of HARP in a concentration of 3 nM. In similar range of concentrations, HARP blocked tube formation induced by VEGF165 in three-dimensional angiogenesis assay. In vivo studies showed that HARP inhibited the VEGF165-induced Matrigel trade mark infiltration of endothelial cells. We then investigated the mechanisms of this inhibition and shown that HARP inhibited the binding of 125I-VEGF165 to the VEGF receptors of endothelial cells. Additional studies using VEGF soluble receptors indicated that binding of 125I-VEGF165 to kinase insert domain-containing receptor and neuropilin receptor was inhibited by HARP, but conversely the binding of 125I-VEGF165 to fms-like tyrosine kinase I receptor was unaffected. A competitive affinity-binding assay demonstrated that HARP interacted directly with VEGF165 with a dissociation coefficient of 1.38 nM. Binding assay using deletion mutants of HARP revealed that the thrombospondin type-1 repeats domains were involved in this interaction. These data demonstrate for the first time that the angiogenic factor HARP can also negatively regulates the angiogenic activity of VEGF165.

Correlation of elevated plasma levels of two structurally related growth factors, heparin affin regulatory peptide and midkine, in advanced solid tumor patients

Heparin affin regulatory peptide (HARP) and midkine (MK) are growth factors, expressed in carcinomas, neuroblastomas and gliomas. In this study, we measured the levels of HARP and MK in plasma samples from 77 cancer patients. The patients had advanced tumors with loco-regional (n=18) or metastatic (n=49) diseases and 10 patients have their diseases limited to the primary site. HARP and MK plasma concentrations were significantly higher in all of these different subgroups of cancer patients (P<0.05 in all cases), when compared to healthy controls (n=30). Neither HARP nor MK levels were significantly different between patients with loco-regional and metastatic tumors (P=0.203 and 0.242, respectively). Moreover, a strong correlation between the elevations of the plasma levels of these two proteins (r2=0.546) in these cancer patients was found. Measurements of these secreted angiogenic growth factors may be useful for evaluation of cancer diagnosis.

Immunoassay for measuring the heparin-binding growth factors HARP and MK in biological fluids

Heparin-affin regulatory peptide (HARP) and Midkine (MK) belong to a family of growth/differentiation factors that have a high affinity for heparin. The involvement of these molecules in various proliferative diseases prompted us to develop an assay for measuring the concentrations of these factors in biological fluids and culture media. This report describes an immunoassay that uses only commercially available materials, based on the high affinity of certain molecules for heparin. It consists of adsorbing heparin-BSA covalent complexes to microtiter plate wells and to quantify the heparin bound HARP or MK by using appropriate antibody. The method is specific and measures concentrations ranging from 40-1200 pg/mL HARP and from 25-1200 pg/mL MK and various parameters are investigated. The within-assay coefficient of variation was less than 5% for both assays. The method was checked by measuring the concentrations of these growth factors in the sera of healthy humans and in patients with cancer. As previously reported, we confirmed that the serum concentrations of MK are higher in patients with tumours (n = 139) than in controls (n = 19). The synthesis of HARP and MK by various cells in culture was also analysed.

Glycosaminoglycans promote HARP/PTN dimerization

Heparin affin regulatory peptide (HARP), also called pleiotrophin (PTN), is a secreted polypeptide which binds to heparin and plays a key role in cellular growth and differentiation. In order to assess the determinants potentially important to its biological activity, we tested the ability of HARP to oligomerize, a process involved in mitogenic activity of the heparin-binding fibroblast growth factor. Using dissuccinimidyl suberate cross-linking experiments and affinity chromatography, we report that human HARP forms noncovalent dimers. Dimerization is dependent on the presence of heparin or other sulfated glycosaminoglycans, as chlorate treatment of cells inhibits this process. In vitro, different glycosaminoglycans, such as dermatan sulfate and chondroitin sulfate-C, also induce a dimer assembly of HARP. The relevance of this process was supported by experiments demonstrating that HARP is secreted as a dimer in conditioned medium of NIH-3T3 cells that overexpressed this growth factor and is also associated to the cell surface or to the extracellular matrix.