KDR Kinase Research Articles

Application and SARs of Pyrazolo[1,5-a]pyrimidine as Antitumor Agents Scaffold.

Pyrazolo[1,5-a]pyrimidines are fused heterocycles that have spawned many biologically active antitumor drugs and are important privileged structures for drug development. Pyrazolo[1,5- a]pyrimidine derivatives have played an important role in the development of antitumor agents due to their structural diversity and good kinase inhibitory activity. In addition to their applications in traditional drug targets such as B-Raf, KDR, Lck, and Src kinase, some small molecule drugs with excellent activity against other kinases (Aurora, Trk, PI3K-γ, FLT-3, C-Met kinases, STING, TRPC) have emerged in recent years. Therefore, based on these antitumor drug targets, small molecule inhibitors containing pyrazolo[1,5-a]pyrimidine scaffold and their structure-activity relationships are summarized and discussed to provide more reference value for the application of this particular structure in antitumor drugs.

Mechanisms of VEGF (Vascular Endothelial Growth Factor) Inhibitor-Associated Hypertension and Vascular Disease.

The VEGF (vascular endothelial growth factor) pathway has emerged as an important target for cancer therapy, with VEGF signaling pathway (VSP) inhibitors having been approved for several different malignancies. Less anticipated has been the multitude of cardiovascular and renal effects of these therapies. Hypertension occurs in at least a quarter of patients starting VSP inhibitors, with virtually every patient having an absolute increase in blood pressure. Patients can also develop proteinuria, renal dysfunction, vascular events, or cardiomyopathy. Although these toxicities have been generally manageable, they have introduced cardiovascular and renal considerations for patient care. On the other hand, these sequelae have provided a growing appreciation for the critical role of VEGF in vascular and renal homeostasis in human biology. Although several recent articles have addressed practical considerations with respect to patient care with this class of drugs,1–4 this review will explore mechanisms associated with the vascular toxicities arising from VEGF signaling inhibition in cancer treatment. The human VEGF family consists of 5 related glycoproteins: VEGFA, VEGFB, VEGFC, VEGFD, and PIGF (placental growth factor). These are secreted to form homodimers, which interact with a family of 3 receptor tyrosine kinases: VEGFR1 (VEGF receptor 1), VEGFR2, and VEGFR3 (Figure 1). VEGFA and VEGFB bind to VEGFR1, VEGFA binds to VEGFR2, and VEGFC and VEGFD bind to both VEGFR2 and VEGFR3.1,5 PIGF primarily interacts with VEGFR1. The VEGFRs are found on a wide variety of cell types. VEGFR1, also called Flt-1 (fms-like tyrosine kinase 1), is found on vascular endothelial cells, hematopoietic stem cells, monocytes, and macrophages. VEGFR2, also called KDR (kinase insert domain) or Flk-1 (fetal liver kinase 1), is expressed on vascular and lymphatic endothelial cells; VEGFR3 (also called Flt-4) is restricted to lymphatic endothelial cells.5 On ligand binding, VEGFRs transduce intracellular signals through …

Design, synthesis and activity of novel sorafenib analogues bearing chalcone unit

Two series of sorafenib derivatives (N-methylpicolinamide-4-oxy) chalcones (5a–o, 7a–e) were synthesized and characterized by NMR and MS. All of the target compounds were evaluated for the cytotoxicity against A549, HepG2, MCF-7, and PC-3 cancer cell lines and some selected compounds were further evaluated for the activity against VEGFR-2/KDR and BRAF kinases. The results indicated that all the compounds showed moderate to good antitumor activity, and the compound 5c showed well cytotoxic activity against HepG2, MCF-7 and PC-3 cell lines with IC50 values of 0.56±0.83μM, 3.88±1.03μM and 3.15±0.81μM, which were 1.03–6.14-fold more active than sorafenib (3.44±1.50μM, 3.18±1.43μM, 3.24±0.45μM), respectively. The compound 5b showed good activity on VEGFR-2/KDR kinase, and its IC50 value was 0.72μM. Structure–activity relationships (SARs) and docking studies indicated that replacement of urea group of sorafenib by chalcone ketones improved the cytotoxic activity, and the results suggested that halogen [3-Br, 4-F] and methoxy (substituted on C-3,4,5 or C-2,3,4 position) substitution was benefit for the activity.

Brucine suppresses colon cancer cells growth via mediating KDR signalling pathway.

Angiogenesis plays an important role in colon cancer development. This study aimed to demonstrate the effect of brucine on tumour angiogenesis and its mechanism of action. The anti-angiogenic effect was evaluated on the chicken chorioallantoic membrane (CAM) model and tube formation. The mechanism was demonstrated through detecting mRNA and protein expressions of VEGFR2 (KDR), PKCα, PLCγ and Raf1 by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot (WB), as well as expressions of VEGF and PKCβ and mTOR by ELISA and WB. The results showed that brucine significantly reduced angiogenesis of CAM and tube formation, inhibited the VEGF secretion and mTOR expression in LoVo cell and down-regulated the mRNA and phosphorylation protein expressions of KDR, PKCα, PLCγ and Raf1. In addition, the effects of brucine on KDR kinase activity, viability of LoVo cell and gene knockdown cell were detected with the Lance™ assay, WST-1 assay and instantaneous siRNA. Compared to that of normal LoVo cells, the inhibition on proliferation of knockdown cells by brucine decreased significantly. These results suggest that brucine could inhibit angiogenesis and be a useful therapeutic candidate for colon cancer intervention.

A novel taspine analog, HMQ1611, inhibits growth of non-small cell lung cancer by inhibiting angiogenesis

In the present study, we investigated the antitumor activity of HMQ1611, a novel synthetic taspine derivative, in vivo and evaluated associated potential antiangiogenesis mechanisms. The proliferation of A549 cells was examined by WST-1 assay in vitro. Tube formation and lung tissue vessel models were used to observe the antiangiogenic activity of HMQ1611. In addition, vascular enodthelial growth factor (VEGF) secretion and KDR kinase activities were measured by ELISA and the HTRF(®)KinEASE(™)-TK assay. In vivo, the antitumor activity was assessed by implantation of A549 cells in athymic mice. The results showed that HMQ1611 inhibited A549 cell proliferation and VEGF secretion, while it significantly inhibited tube formation and tissue vascularization. Furthermore, HMQ1611 inhibited A549 xenograft tumor growth. In conclusion, the results of our study suggest that HMQ1611 has latent properties for the inhibition of angiogenesis which are involved in its antitumor activity.

Pharmacophore Modeling and in Silico Screening Studies to Design Potential KDR Kinase Inhibitors

A novel ligand-based pharmacophore model for KDR kinase was generated on the basis of chemical features of 30 KDR kinase inhibitors. This pharmacophore model consists of one hydrogen-bond acceptor, one hydrogen-bond donor and two hydrophobic groups. Several methods have been used to validate the model, suggesting that it can serve as a reliable tool for virtual screening to facilitate the discovery of novel KDR inhibitors. The model was then used as database search query from the National Cancer Institute (NCI) database for the rational design to identify new hit compound.

Discovery of a new potent bisamide FMS kinase inhibitor

FMS is a type III receptor tyrosine kinase that binds to the macrophage or monocyte colony stimulating factor (M-CSF or CSF-1). Signal transduction through that binding results in survival, proliferation, and differentiation of monocyte/macrophage lineage. In this study, we report the discovery of a new potent inhibitor of FMS kinase. The synthesized pyrrolo[3,2-c]pyridine derivative (compound 1) was initially tested at a single concentration of 1μM against 47 different kinases. At this concentration, the% inhibitions of the enzymatic activities of FMS and KDR kinases were 90% and 71%, respectively, while the inhibition in activity was less than 58% for all of the other kinases. For compound 1, the IC50 values against FMS and KDR were 96 and 1058nM, respectively. So, compound 1 was found to be 11 times more selective for FMS kinase than KDR kinase. Compound 1 can be used as a promising lead for the development of new selective inhibitors of FMS kinase, which can be used as useful therapeutic tools for treatment of several inflammatory and cancer disorders.

KDR Kinase Inhibitor Isolated from the Mushroom Boletopsis leucomelas

Three novel p-terphenyl compounds, named boletopsins A (1), B (2), and C (3), and four known analogues (4-7) were isolated from fruiting bodies of the mushroom Boletopsis leucomelas. Compounds 1-7 were tested for KDR kinase inhibitory activity, and boletopsin C (3) was found to have an IC(50) value of 70.7 microM. Compound 3 also showed inhibition of proliferation of human umbilical vein endothelial cells, with an IC(50) value of 9.04 microM.

Autocrine VEGF‐A/KDR loop protects epithelial ovarian carcinoma cells from anoikis

Epithelial ovarian carcinoma (EOC) patients are usually diagnosed at an advanced stage, characterized by interperitoneal carcinomatosis and production of large volumes of ascites. Vascular endothelial growth factor-A (VEGF-A) and its main signaling receptor VEGFR2 (KDR) are coexpressed in primary ovarian tumors, ascitic cells and metastases, suggesting the existence of an autocrine VEGF-A/KDR loop in EOC cells. In the present study, we examined this possibility and explored the role of this autocrine loop in protecting EOC cells from apoptosis under anchorage free growth conditions (anoikis). We found that 3 different EOC cell lines (Caov3, OVCAR3, SKOV3) express both VEGF-A and its receptors, including KDR. In these cells, KDR is constitutively phosphorylated and is detected both in the cell plasma membrane and in the nucleus. Treating EOC cells with specific internal inhibitors of KDR kinase activity or a VEGF-A neutralizing antibody abolished KDR autophosphorylation and resulted in significant increase in apoptosis when cells were grown in single-cell, anchorage-free conditions. By contrast, these blocking reagents had no effect on cell viability when EOC cells were grown in adhesive monolayers. In summary, our results indicate that an autocrine VEGF-A/KDR loop exists in EOC cells and that it plays a role in protecting the cells from anoikis. Our results imply that treating EOC patients with VEGF blocking agents may potentially reduce peritoneal dissemination by decreasing vascular permeability as well as inducing apoptosis of shed ovarian cancer cells in ascites.

Attenuation of edema and infarct volume following focal cerebral ischemia by early but not delayed administration of a novel small molecule KDR kinase inhibitor

Vascular endothelial growth factor (VEGF) may mediate increases in vascular permeability and hence plasma extravasation and edema following cerebral ischemia. To better define the role of VEGF in edema, we examined the effectiveness of a novel small molecule KDR kinase inhibitor Compound-1 in reducing edema and infarct volume following focal cerebral ischemia in studies utilizing treatment regimens initiated both pre- and post-ischemia, and with study durations of 24–72 h. Rats were subjected to 90 min of middle cerebral artery occlusion (MCAO) followed by reperfusion. Pretreatment with Compound-1 (40 mg/kg p.o.) starting 0.5 h before occlusion significantly reduced infarct volume at 72 h post-MCAO (vehicle, 194.1 ± 22.9 mm 3 vs. Compound-1, 127.6 ± 22.8 mm 3 and positive control MK-801, 104.4 ± 22.6 mm 3, both p < 0.05 compared to vehicle control), whereas Compound-1 treatment initiated at 2 h after occlusion did not affect infarct volume. Compound-1 pretreatment also significantly reduced brain water content at 24 h (vehicle, 80.3 ± 0.2% vs. Compound-1, 79.7 ± 0.2%, p < 0.05) but not at 72 h after MCAO. These results demonstrate that early pretreatment administration of a KDR kinase inhibitor elicited an early, transient decrease in edema and subsequent reduction in infarct volume, implicating VEGF as a mediator of stroke-related vascular permeability and ischemic injury.

3D-QSAR Studies of Various Diaryl Urea Derivatives of Multi-targeted Receptor Tyrosine Kinase Inhibitors: Molecular Field Analysis Approach

3D-QSAR analysis has been performed on a series of diaryl urea derivatives of multi-targeted receptor tyrosine kinase inhibitors. Models were developed using the most widely used computational approach molecular field analysis (MFA) from our dataset for the KDR, cKit and FLT3 inhibitors using genetic partial least square (G/PLS) method. These models showed excellent internal predictability and consistency and validation using test set compounds yielded a good predictive power for the activity values of three set of inhibitors. These models would offer utility in guiding the rational design of multi-targeted KDR, cKit and FLT3 receptor tyrosine kinase inhibitors for therapeutic applications. Keywords: QSAR, Receptor tyrosine kinase, MFA, Molecular field analysis, Genetic partial least squares (G/PLS) method

Synthesis of an indole containing KDR kinase inhibitor by tandem Sonogashira coupling-5- endo- dig-cyclization as a key step

An efficient synthesis of the potent KDR kinase inhibitor 3-[5-[[4-(methylsulfonyl)-1-piperazinyl]methyl]-1 H-indol-2-yl]quinoline-2-(1 H)-one using a Sonogashira coupling-5- endo- dig-cyclization strategy is described.

Tandem C-N/Suzuki Coupling as the Key Step in the Syntheses of KDR Kinase Inhibitors

The Pd-catalyzed tandem C-N/Suzuki coupling reaction which offers an easy access to 2-substituted heteroaryl indoles is applied to the syntheses of biologically active KDR kinase inhibitors. The inhibitors can thus be synthesized in only five to seven steps with overall yields up to 63%.

1,4-Dihydroindeno[1,2-c]pyrazoles with Acetylenic Side Chains as Novel and Potent Multitargeted Receptor Tyrosine Kinase Inhibitors with Low Affinity for the hERG Ion Channel

The synthesis of a novel series of 1,4-dihydroindeno[1,2-c]pyrazoles with acetylene-type side chains is described. Optimization of those compounds as KDR kinase inhibitors identified 8, which displayed an oral activity in an estradiol-induced murine uterine edema model (ED50 = 3 mg/kg) superior to Sutent (ED50 = 9 mg/kg) and showed potent antitumor efficacy in an MX-1 human breast carcinoma xenograft tumor growth model (tumor growth inhibition = 90% at 25 mg/kg.day po). The compound was docked into a homology model of the homo-tetrameric pore domain of the hERG potassium channel to identify strategies to improve its cardiac safety profile. Systematic interruption of key binding interactions between 8 and Phe656, Tyr652, and Ser624 yielded 90, which only showed an IC50 of 11.6 microM in the hERG patch clamp assay. The selectivity profile for 8 and 90 revealed that both compounds are multitargeted receptor tyrosine kinase inhibitors with low nanomolar potencies against the members of the VEGFR and PDGFR kinase subfamilies.

Pharmacophore modeling and in silico screening for new KDR kinase inhibitors

In order to elucidate the essential structural features for KDR kinase inhibitors, three-dimensional pharmacophore hypotheses were built on the basis of a set of known KDR kinase inhibitors selected from the literature with CATALYST program. Several methods tools used in validation of pharmacophore hypothsis were presented, and the first hypothesis (Hypo1) was considered to be the best pharmacophore hypothesis. The model (Hypo1) was then employed as 3D search query to screen the Traditional Chinese Medicine Database (TCMD) for other potential lead compounds. One hit illustrated high binding affinity with KDR kinase measured by the surface plasmon resonance biosensor. Docking studies may help elucidate the mechanisms of KDR kinase receptor–ligand interactions.

Efficient Syntheses of KDR Kinase Inhibitors Using a Pd-Catalyzed Tandem C−N/Suzuki Coupling as the Key Step

A family of four potent KDR kinase inhibitors containing an indol-2-yl quinolin-2-one structure was utilizing a Pd-catalyzed tandem C-N and C-C coupling sequence.

Cytotoxic activities of 4 natural products – carnosic acid, xanthohumol, caffeic acid phenethyl ester and (-) eburnamonine

In a cytotoxic or anti-proliferation assay, 20 compounds derived from natural products have been screened for cytotoxic effects against A549 cell line using MTT assay. Among them, carnosic acid, xanthohumol, caffeic acid phenethyl ester and (-) eburnamonine showed activies at concentrations of 50µM and 10µM. These four active compounds were subjected to cytotoxicity studies in two other cell lines (A431 and SK-BR3), using SRB assay. While carnosic acid, xanthohumol and (-) eburnamonine still showed cytotoxic activity, caffeic acid phenethyl ester showed no activity in A431 cell line and low activity against SK-BR3 cell line (IC50=258µM). Xanthohumol possessed the strongest cytotoxic effects against all 3 cell lines with IC50 values of 24.16µM, 16.14µM and 1.68µM in A549, A431 and SK-BR3 cells, respectively. Because A431 and SK-BR3 cells are known to over-express tyrosine kinase receptors, we have studied the four compounds for KDR and Her2 tyrosine kinase receptor inhibitory activity by using fluorescence polarization. The results showed that except caffeic acid phenethyl ester, which showed low inhibitory activity on KDR at a high concentration of 10µM, the other compounds were inactive. In conclusion, carnosic acid, xanthohumol and (-) eburnamonine showed cytotoxic activity in A549, A431 and SK-BR3 cell lines but their activities are not mediated though the inhibition of KDR or Her2 receptors. The cytotoxic activity of caffeic acid phenethyl ester is just limited to A549 cell line, not for the other two cell lines, which suggests a specific activity of this compound.

1,2,3-Thiadiazole substituted pyrazolones as potent KDR/VEGFR-2 kinase inhibitors

KDR kinase inhibition is considered to play an important role in regulating angiogenesis, which is vital for the survival and proliferation of tumor cells. Recently we disclosed a structure-based kinase inhibitor design strategy which led to the identification of a new class of VEGFR-2/KDR kinase inhibitors bearing heterocyclic substituted pyrazolones as the core template. Instability in a rat S9 preparation and poor iv PK profiles for most of these inhibitors necessitated exploration of new pyrazolones to identify new analogs with improved metabolic stability. Optimization of the heterocyclic moiety led to the identification of the thiadiazole series of pyrazolones ( D) as potent VEGFR-2/KDR kinase inhibitors. SAR modifications, kinase selectivity profiling, and structural elements for improved PK properties were explored. Oral bioavailability up to 29% was achieved in the rat. Modeling results based on the Glide XP docking approach supported our postulation regarding the interaction of the lactam segment of the pyrazolones with the hinge region of the KDR kinase.

Thienopyridine urea inhibitors of KDR kinase

A series of substituted thienopyridine ureas was prepared and evaluated for enzymatic and cellular inhibition of KDR kinase activity. Several of these analogs, such as 2, are potent inhibitors of KDR (<10 nM) in both enzymatic and cellular assays. Further characterization of inhibitor 2 indicated that this analog possessed excellent in vivo potency (ED 50 2.1 mg/kg) as measured in an estradiol-induced mouse uterine edema model.

3D QSAR studies on a series of potent and high selective inhibitors for three kinases of RTK family

For targets belonging to the same family of receptors, inhibitors often act at more than one biological target and produce a synergistic effect. Separate CoMFA and CoMSIA models were developed from our data set for the KDR, cKit and Tie-2 inhibitors. These models showed excellent internal predictability and consistency, and validation using test-set compounds yielded a good predictive power for the pIC 50 value. The field contour maps (CoMFA and CoMSIA) corresponding to the KDR, cKit and Tie-2 kinase subtypes reflected the characteristic similarities and differences between these types. These maps provided valuable information to facilitate structural modifications of the inhibitor to increase selectivity for the KDR over cKit and Tie-2.