Novel 6-aminofuro[3,2-c]pyridines as potent, orally efficacious inhibitors of cMET and RON kinases

Targeting MET: Discovery of Small Molecule Inhibitors as Non-Small Cell Lung Cancer Therapy

MET has been considered as a promising drug target for the treatment of MET-dependent diseases, particularly non-small cell lung cancer (NSCLC). Small molecule MET inhibitors with mainly three types of binding modes (Ia/Ib, II, and III) have been developed. In this Review, we provide an overview of the structural features, activation mechanism, and dysregulation pathway of MET and summarize progress on the development and discovery strategies utilized for MET inhibitors as well as mechanisms of acquired resistance to current approved inhibitors. The insights will accelerate discovery of new generation MET inhibitors to overcome clinical acquired resistance.

Design, synthesis and antitumor evaluation of novel 5-methylpyrazolo[1,5-a]pyrimidine derivatives as potential c-Met inhibitors

A series of novel 5-methylpyrazolo[1,5-a]pyrimidine derivatives (10a-10x) were designed, synthesized, and evaluated for their in vitro inhibitory activities against c-Met kinase and antiproliferative activities against the SH-SY5Y, MDA-MB-231, A549, and HepG2 cell lines. Most of the compounds remarkably inhibited c-Met kinase and showed moderate to good cytotoxicity and selectivity toward the four cancer cell lines. Among them, compounds 10b and 10f were the two most potent selective c-Met inhibitors with half-maximal inhibitory concentration (IC₅₀) values of 5.17 ± 0.48 nM and 5.62 ± 0.78 nM, respectively, and suppression abilities comparable with the positive control cabozantinib. Cell proliferation assay further demonstrated that the two most promising compounds 10a and 10b also showed good cytotoxicity and selectivity toward MDA-MB-231 cells, with IC₅₀ values of 26.67 ± 2.56 μM and 26.83 ± 2.41 μM, respectively. Compounds 10f and 10g showed cytotoxicity and selectivity toward A549 cells, with IC₅₀ values of 20.20 ± 2.04 μM and 21.65 ± 1.58 μM, respectively. All antiproliferative activities were within the range of those of cabozantinib. Notably, these compounds presented relatively low hepatotoxicity compared with reference drugs. Moreover, the preliminary structure-activity relationship and docking studies revealed that replacement of a nitrogen-containing heterocycle on the R₂ (block A) group might improve the c-Met kinase inhibitory and antiproliferative effects in MDA-MB-231 cells, whereas displacement by a substituted benzene ring, especially for the p-fluorophenyl or 4-fluoro-3-methoxyphenyl moiety, on the R₂ group enhanced cytotoxicity toward A549 cells. Together, these results suggest that 10b and 10f are promising compounds and provide a basis for their development as new antitumor agents.

A novel bispecific c-MET/CTLA-4 antibody targetting lung cancer stem cell-like cells with therapeutic potential in human non-small-cell lung cancer

A novel paradigm in tumor biology suggests that non-small-cell lung cancer (NSCLC) growth is driven by lung cancer stem cell (LCSC) like cells, but t here are still not any effective strategies to remove LCSCs. The bispecific antibody (BsAb) is a novel antibody, which can target two different antigens and mediate specific killing effects by selectively redirecting effector cells to the target cells. Here, we designed and synthesized a new BsAb, BsAb-5, that can target cellular mesenchymal-to-epithelial transition factor (c-MET) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) in CD166⁺ LCSCs with high affinity and specificity, for the first time. We showed that BsAb-5 could inhibit hepatocyte growth factor (HGF) mediated tumor development, including proliferation, migration, and apoptosis, serving as an inhibitory c-MET antibody. Moreover, we demonstrated that mechanisms responsible for BsAb-5 in CD166⁺ LCSCs included inducing c-MET degradation and inhibition of HGF-stimulated c-MET-Notch pathway by using AdHGF infection, nuclei location, and Western blot assays. In vivo, xenograft analysis revealed that mice on BsAb-5 group showed significantly reduced tumor volume. At the meantime, the observed antitumor effects of BsAb-5 were dependent on considerably suppressing T-regulatory cells (T_regs) and up-regulating effector T cells. On the basis of these results, we have identified a potential BsAb drug, which can effectively target c-MET and CTLA-4 in CD166⁺ LCSCs for the treatment of human NSCLC.

A novel bispecific c-MET/PD-1 antibody with therapeutic potential in solid cancer

The bispecific antibody is a novel antibody, which can target two different antigens and mediate specific killing effects by selectively redirecting effector cells to the target cells. Here, we designed and synthesized a bispecific antibody (BsAb) that can bind cellular-mesenchymal to epithelial transition factor (c-MET, overexpressed in several human solid tumor), and programmed death-1 (PD-1, involved in cancer cell immune evasion) with high affinity and specificity. We found that BsAb can induce the degradation of c-MET protein in cancer cells, including MKN45, a gastric cancer cell line, and A549, a lung cancer cell line. BsAb inhibited hepatocyte growth factor (HGF)-mediated proliferation, migration, and antiapoptosis, and downregulated HGF-stimulated phosphorylation of c-MET, protein kinase B (AKT), and extracellular signal-regulated kinase (ERK1/2). BsAb can also rescue T cell activation. Furthermore, xenograft analysis revealed that BsAb markedly inhibits the growth of subcutaneously implanted tumors and chronic inflammation. On the basis of these results, we have identified a potential bispecific drug, which can effectively target c-MET and PD-1 for the treatment of human solid cancers.

RON kinase: A target for treatment of cancer-induced bone destruction and osteoporosis

Bone destruction occurs in aging and numerous diseases, including osteoporosis and cancer. Many cancer patients have bone osteolysis that is refractory to state-of-the-art treatments, which block osteoclast activity with bisphosphonates or by inhibiting the receptor activator of nuclear factor κB ligand (RANKL) pathway. We previously showed that macrophage-stimulating protein (MSP) signaling, which is elevated in about 40% of breast cancers, promotes osteolytic bone metastasis by activation of the MSP signaling pathway in tumor cells or in the bone microenvironment. We show that MSP signals through its receptor, RON tyrosine kinase, expressed on host cells, to activate osteoclasts directly by a previously undescribed pathway that is complementary to RANKL signaling and converges on proto-oncogene, non-receptor tyrosine kinase SRC (SRC). Genetic or pharmacologic inhibition of RON kinase blocked cancer-mediated bone destruction and osteoporosis in several mouse models. Furthermore, the RON kinase inhibitor BMS-777607/ASLAN002 altered markers of bone turnover in a first-in-human clinical cancer study, indicating the inhibitor's potential for normalizing bone loss in patients. These findings uncover a new therapeutic target for pathogenic bone loss and provide a rationale for treatment of bone destruction in various diseases with RON inhibitors.

Strategies of targeting the extracellular domain of RON tyrosine kinase receptor for cancer therapy and drug delivery

PURPOSE

Cancer is one of the most important life-threatening diseases in the world. The current efforts to combat cancer are being focused on molecular-targeted therapies. The main purpose of such approaches is based on targeting cancer cell-specific molecules to minimize toxicity for the normal cells. RON (Recepteur d'Origine Nantais) tyrosine kinase receptor is one of the promising targets in cancer-targeted therapy and drug delivery.

METHODS

In this review, we will summarize the available agents against extracellular domain of RON with potential antitumor activities.

RESULTS

The presented antibodies and antibody drug conjugates against RON in this review showed wide spectrum of in vitro and in vivo antitumor activities promising the hope for them entering the clinical trials.

CONCLUSION

Due to critical role of extracellular domain of RON in receptor activation, the development of therapeutic agents against this region could lead to fruitful outcome in cancer therapy.

Preclinical Efficacy of Ron Kinase Inhibitors Alone and in Combination with PI3K Inhibitors for Treatment of sfRon-Expressing Breast Cancer Patient-Derived Xenografts

PURPOSE

Recent studies have demonstrated that short-form Ron (sfRon) kinase drives breast tumor progression and metastasis through robust activation of the PI3K pathway. We reasoned that upfront, concurrent inhibition of sfRon and PI3K might enhance the antitumor effects of Ron kinase inhibitor therapy while also preventing potential therapeutic resistance to tyrosine kinase inhibitors (TKI).

EXPERIMENTAL DESIGN

We used patient-derived breast tumor xenografts (PDX) as high-fidelity preclinical models to determine the efficacy of single-agent or dual Ron/PI3K inhibition. We tested the Ron kinase inhibitor ASLAN002 with and without coadministration of the PI3K inhibitor NVP-BKM120 in hormone receptor-positive [estrogen receptor (ER)(+)/progesterone receptor (PR)(+)] breast PDXs with and without PIK3CA gene mutation.

RESULTS

Breast PDX tumors harboring wild-type PIK3CA showed a robust response to ASLAN002 as a single agent. In contrast, PDX tumors harboring mutated PIK3CA demonstrated partial resistance to ASLAN002, which was overcome with addition of NVP-BKM120 to the treatment regimen. We further demonstrated that concurrent inhibition of sfRon and PI3K in breast PDX tumors with wild-type PIK3CA provided durable tumor stasis after therapy cessation, whereas discontinuation of either monotherapy facilitated tumor recurrence.

CONCLUSIONS

Our work provides preclinical rationale for targeting sfRon in patients with breast cancer, with the important stipulation that tumors harboring PIK3CA mutations may be partially resistant to Ron inhibitor therapy. Our data also indicate that tumors with wild-type PIK3CA are most effectively treated with an upfront combination of Ron and PI3K inhibitors for the most durable response. Clin Cancer Res; 21(24); 5588-600. ©2015 AACR.

Prognostic Value of Hepatocyte Growth Factor Receptor Expression in Patients with Perihilar Cholangiocarcinoma

BACKGROUND

Although an aggressive surgical approach to perihilar cholangiocarcinoma (PHC) has improved survival, a prognosis of advanced PHC remains unsatisfactory. The overexpression of mesenchymal-epithelial transition factor (MET) and recepteur d'origine nantais (RON) has been shown to be associated with poor prognosis in some types of cancer.

METHODS

One hundred sixty-nine patients who underwent histologically curative resection for PHC were subjected to immunohistochemical analysis for MET and RON. The association between a positive expression of MET or RON and clinicopathologic features as well as the patients' prognosis were analyzed.

RESULTS

There were 27 patients (16 %) who had a positive expression for both MET and RON. Although clinicopathologic features in the either MET- or RON-negative group were not significantly different compared to the both MET- and RON-positive group, the prognosis tended to be worse in the patients with both MET and RON positivity. When the analysis was limited to patients with advanced-stage disease (stage III and IVa), a multivariate analysis revealed that both MET and RON positivity and lymph node metastasis were identified as independent poor prognostic factors.

CONCLUSIONS

The overall survival rate for patients with both MET and RON positivity was worse than that with either MET or RON negativity in patients with advanced PHC. The poor prognosis in these patients was not associated with unfavorable clinicopathologic features. The examination of MET and RON expression in PHC may enable a tailored method for patient classification that could not otherwise be achieved using the conventional pathologic classification system.

The RON receptor tyrosine kinase promotes metastasis by triggering MBD4-dependent DNA methylation reprogramming

Metastasis is the major cause of death in cancer patients, yet the genetic and epigenetic programs that drive metastasis are poorly understood. Here, we report an epigenetic reprogramming pathway that is required for breast cancer metastasis. Concerted differential DNA methylation is initiated by the activation of the RON receptor tyrosine kinase by its ligand, macrophage stimulating protein (MSP). Through PI3K signaling, RON/MSP promotes expression of the G:T mismatch-specific thymine glycosylase MBD4. RON/MSP and MBD4-dependent aberrant DNA methylation results in the misregulation of a specific set of genes. Knockdown of MBD4 reverses methylation at these specific loci and blocks metastasis. We also show that the MBD4 glycosylase catalytic residue is required for RON/MSP-driven metastasis. Analysis of human breast cancers revealed that this epigenetic program is significantly associated with poor clinical outcome. Furthermore, inhibition of Ron kinase activity with a pharmacological agent blocks metastasis of patient-derived breast tumor grafts in vivo.

Targeting receptor tyrosine kinase MET in cancer: small molecule inhibitors and clinical progress

The HGF/MET signaling pathway is critical in mediating a wide range of normal physiological functions including embryological development, wound healing, and tissue regeneration. Aberrant activation of the pathway has frequently been found in human cancers via protein overexpression, mutation, gene amplification, and also paracrine or autocrine up-regulation. In addition, the activation of HGF/MET signaling confers resistance to the effects of cancer treatments. Therefore, inhibition of the HGF/MET signaling pathway has great potential for therapeutic intervention in cancer. Currently, there are three approaches toward modulating HGF/MET signaling in human clinical studies of cancer: anti-HGF monoclonal antibodies, MET monoclonal antibodies, and small molecule MET inhibitors. Preliminary clinical benefit from inhibition of HGF or MET has been reported. This Perspective will provide an overview of the HGF/MET signaling pathway in cancer and then will review the development of small molecule MET inhibitors and their progress in clinical applications.