Vascular Endothelial Growth Factor Receptor Tyrosine Kinase Research Articles

VEGF (Vascular Endothelial Growth Factor) Induces NRP1 (Neuropilin-1) Cleavage via ADAMs (a Disintegrin and Metalloproteinase) 9 and 10 to Generate Novel Carboxy-Terminal NRP1 Fragments That Regulate Angiogenic Signaling.

Objective- NRP1(neuropilin-1) acts as a coreceptor for VEGF (vascular endothelial growth factor) with an essential role in angiogenesis. Recent findings suggest that posttranslational proteolytic cleavage of VEGF receptors may be an important mechanism for regulating angiogenesis, but the role of NRP1 proteolysis and the NRP1 species generated by cleavage in endothelial cells is not known. Here, we characterize NRP1 proteolytic cleavage in endothelial cells, determine the mechanism, and investigate the role of NRP1 cleavage in regulation of endothelial cell function. Approach and Results- NRP1 species comprising the carboxy (C)-terminal and transmembrane NRP1 domains but lacking the ligand-binding A and B regions are constitutively expressed in endothelial cells. Generation of these C-terminal domain NRP1 proteins is upregulated by phorbol ester and Ca2+ ionophore, and reduced by pharmacological inhibition of metalloproteinases, by small interfering RNA-mediated knockdown of 2 members of ADAM (a disintegrin and metalloproteinase) family, ADAMs 9 and 10, and by a specific ADAM10 inhibitor. Furthermore, VEGF upregulates expression of these NRP1 species in an ADAM9/10-dependent manner. Transduction of endothelial cells with adenoviral constructs expressing NRP1 C-terminal domain fragments inhibited VEGF-induced phosphorylation of VEGFR2 (VEGF receptor tyrosine kinase)/KDR (kinase domain insert receptor) and decreased VEGF-stimulated endothelial cell motility and angiogenesis in coculture and aortic ring sprouting assays. Conclusions- These findings identify novel NRP1 species in endothelial cells and demonstrate that regulation of NRP1 proteolysis via ADAMs 9 and 10 is a new regulatory pathway able to modulate VEGF angiogenic signaling.

Design, synthesis and biological evaluation of pyrimidine-based derivatives as VEGFR-2 tyrosine kinase inhibitors

Vascular endothelial growth factor receptor-2 (VEGFR-2) plays a crucial role in tumor angiogenesis, and inhibition of the VEGFR-2 signaling pathway has already become an attractive approach for cancer therapy. In this study, a novel pyrimidine-based derivative 7j was designed as lead compound, and three series of potent VEGFR-2 inhibitors were synthesized and biologically evaluated against A549 and HepG2 cell lines. Compounds 7d, 9s and 13n exhibited superior inhibitory activities against A549 cell with IC50 ranged from 9.19 to 13.17 μM and HepG2 cell with IC50 ranged from 11.94 to 18.21 μM compared to those of Pazopanib (IC50 = 21.18 and 36.66 μM). In addition, molecular docking study was performed to investigate the binding capacity and binding mode between target compounds and VEGFR-2.

Preclinical characterization of anlotinib, a highly potent and selective vascular endothelial growth factor receptor-2 inhibitor.

Abrogating tumor angiogenesis by inhibiting vascular endothelial growth factor receptor‐2 (VEGFR2) has been established as a therapeutic strategy for treating cancer. However, because of their low selectivity, most small molecule inhibitors of VEGFR2 tyrosine kinase show unexpected adverse effects and limited anticancer efficacy. In the present study, we detailed the pharmacological properties of anlotinib, a highly potent and selective VEGFR2 inhibitor, in preclinical models. Anlotinib occupied the ATP‐binding pocket of VEGFR2 tyrosine kinase and showed high selectivity and inhibitory potency (IC 50 <1 nmol/L) for VEGFR2 relative to other tyrosine kinases. Concordant with this activity, anlotinib inhibited VEGF‐induced signaling and cell proliferation in HUVEC with picomolar IC 50 values. However, micromolar concentrations of anlotinib were required to inhibit tumor cell proliferation directly in vitro. Anlotinib significantly inhibited HUVEC migration and tube formation; it also inhibited microvessel growth from explants of rat aorta in vitro and decreased vascular density in tumor tissue in vivo. Compared with the well‐known tyrosine kinase inhibitor sunitinib, once‐daily oral dose of anlotinib showed broader and stronger in vivo antitumor efficacy and, in some models, caused tumor regression in nude mice. Collectively, these results indicate that anlotinib is a well‐tolerated, orally active VEGFR2 inhibitor that targets angiogenesis in tumor growth, and support ongoing clinical evaluation of anlotinib for a variety of malignancies.

Establishment of an abnormal vascular patterning model in the mouse retina

Abnormalities in retinal blood vessels and neuronal function persist in eyes undergoing retinopathy of prematurity. In this study, we examined morphological and functional changes in retinal blood vessels and neurons in mice that had undergone short-term interruption of retinal vascular development through inhibition of vascular endothelial growth factor (VEGF) signaling. In mice treated with the VEGF receptor tyrosine kinase inhibitor KRN633 on postnatal day (P) 0 and 1, the vascular density in the retinal surface increased by P12, but development of deep retinal vascular plexus and choroidal vasculature was delayed until P14. Overall retinal morphology was mostly normal in KRN633-treated mice during the observation period (∼P28), with the exception of P8 and P14. On P28, abnormalities in retinal vascular patterns were evident, but electroretinogram and retinal blood perfusion were within the normal range. Abnormal architecture of retinal vasculature disturbs retinal hemodynamics; therefore, mice treated postnatally with VEGF receptor inhibitors could serve as an animal model for studying the regulatory mechanism of local retinal blood flow and the effect of persistent abnormal retinal vascular patterns on the risk of onset of retinal ischemia.

Polymorphisms in the Von Hippel-Lindau Gene Are Associated With Overall Survival in Metastatic Clear-Cell Renal-Cell Carcinoma Patients Treated With VEGFR Tyrosine Kinase Inhibitors.

Clear-cell renal-cell carcinoma (ccRCC) is characterized by loss of a functional Von Hippel-Lindau (VHL) protein. We investigated the potential of 3 single nucleotide polymorphisms (SNPs) in VHL as biomarkers in metastatic ccRCC (m-ccRCC) patients treated with vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors (TKIs). We genotyped 3 VHL SNPs in 199 m-ccRCC patients: rs1642742 T > C, rs1642743 A > G, and rs1678607 C > A. Primary end points were response rate (RR), progression-free survival (PFS), and overall survival (OS) after start of first-line TKI. RR was compared with Fisher's exact test, and PFS and OS with Kaplan-Meier analysis and multivariable Cox regression. Secondary end points were association with VHL promotor hypermethylation, VHL mutation status, VHL loss of heterozygosity,≥ 25% sarcomatoid dedifferentiation, and expression of genes implicated in angiogenesis and immunoresponse (Fisher's exact test and unpaired t tests). The minor alleles of rs1642742 and rs1642743, known to be in close linkage disequilibrium, were associated with poor outcome, following a recessive pattern. For the rs1642742 CC versus TT/TC genotype, OS was 11 versus 26 months (hazard ratio= 2.3; 95% confidence interval, 1.2-6.6; P= .015). For the rs1642743 GG versus AA/AG genotype, OS was 15 versus 28 months (hazard ratio= 2.6; 95% confidence interval, 1.4-5.0; P= .004). After multivariable analysis, both remained linked with poor OS (P= .018 and P= .009, respectively). There was a trend toward shorter PFS and poorer RR. Both SNPs were associated with≥ 25% sarcomatoid dedifferentiation (P= .037 and .006, respectively). No significant results were found for rs1678607. rs1642742 and rs1642743 are candidate biomarkers for poor OS in m-ccRCC patients receiving first-line VEGFR-TKI. They are associated with higher levels of sarcomatoid dedifferentiation.

Retinal neuronal cell loss prevents abnormal retinal vascular growth in a rat model of retinopathy of prematurity

A short-term blockade of the vascular endothelial growth factor (VEGF)-mediated pathway in neonatal rats results in formation of severe retinopathy of prematurity (ROP)-like retinal blood vessels. The present study aimed to examine the role of retinal neurons in the formation of abnormal retinal blood vessels. Newborn rats were treated subcutaneously with the VEGF receptor tyrosine kinase inhibitor, KRN633 (10 mg/kg), or its vehicle (0.5% methylcellulose in water) on postnatal day (P) 7 and P8. To induce excitotoxic loss of retinal neurons, N-methyl-D-aspartic acid (NMDA) was injected into the vitreous chamber of the eye on P9. Changes in retinal morphology, blood vessels, and proliferative status of vascular cells were evaluated on P11 and P14. The number of cells in the ganglion cell layer and the thickness of the inner plexiform layer and inner nuclear layer were significantly decreased 2 days (P11) after NMDA treatment. The pattern and degree of NMDA-induced changes in retinal morphology were similar between vehicle-treated (control) and KRN633-treated (ROP) rats. In ROP rats, increases in the density of capillaries, the tortuosity index of arteries, and the proliferating vascular cells were observed on P14. The expansion of the endothelial cell network was prevented, and the capillary density and the number of proliferating cells were reduced in NMDA-treated retinas of both control and ROP rats. Following NMDA-induced neuronal cell loss, no ROP-like blood vessels were observed in the retinas. These results suggest that retinal neurons play an important role in the formation of normal and ROP-like retinal blood vessels.

An open label, single-armed, exploratory study of apatinib (a novel VEGFR-2 tyrosine kinase inhibitor) in patients with relapsed or refractory non-Hodgkin lymphoma.

BackgroundApatinib, a novel small molecule vascular endothelial growth factor receptor-2 (VEGFR-2) tyrosine kinase inhibitor, have shown remarkable efficacy in many solid cancers. But evidence of antitumor activity in patients with lymphoma is still limited. We conducted an open-label, single-armed, exploratory study in relapse or refractory non-Hodgkin lymphoma patients for the efficacy and safety of apatinib.Experimental designPatients with relapse or refractory non-Hodgkin patients meet the criteria were eligible for enrollment. Treatment comprised of oral apatinib 500 mg once daily with 21 days as a treatment cycle. The primary end point was response rate. Secondary end points included progression-free survival (PFS) and overall survival (OS).ResultsBetween February 2016 and December 2016, 21 patients were enrolled. The ORR (CR plus PR) was 47.6% (10 of 21 patients) included 9.5% CRs and 38.1% PRs. 23.8% patients achieved stable disease made the DCR 71.4% (15/21). The median OS was 7.3 months (95% CI, 7.1 to 7.9) and the median PFS was 7.1 months (95% CI, 4.2 to 7.3). Most patients suffered from grade 1 to grade 2 treatment-related adverse events and the most common nonhematologic adverse events were proteinuria (47.6%), hypertension (42.9%) and hand-foot syndrome (33.3%), respectively.ConclusionsIn our study, the results we presented showed apatinib might have a rapid, safe and high efficacy on relapsed or refractory non-Hodgkin lymphoma patients. Based on the data more clinic trials are expected to be taken to identification the efficacy of apatinib on lymphoma further.

Abstract A132: Deciphering the molecular regulators of tumor resistance to VEGF-receptor tyrosine kinase inhibitors via in vivo genome-wide RNAi screen

Abstract Inhibiting angiogenesis, which is a shared characteristic of all solid tumors, is a promising approach for treating cancer. However, emerging resistance after initial response is still a drawback. We sought to decipher the molecular landscape of tumor resistance to continuous treatment with VEGF-receptor tyrosine kinase inhibitor (RTKi) sunitinib (SU11248, SU). To address that, we performed serial transplantation of a syngeneic LLC tumor model in C57bl6 mice using a genome-wide lentiviral shRNA library targeting about 39,000 transcripts (150K complexity). The abundance of each single knockdown (kd) was longitudinally traced via molecular barcodes towards development of resistant tumors. After three in vivo panning rounds, distinct shRNA constructs were found to be significantly enriched in tumors passaged under SU selection pressure (p3-SU) compared to those passaged without treatment (p3-ctrl). We focused on validation of three candidate shRNA targeting Kdm5c, Csf1, and Cd44. Knockdown of each of these three genes confirmed their role in emerging resistance to sunitinib in vivo in syngeneic model. Furthermore, knockdown of Kdm5c promoted resistance in 786-0 human renal cell carcinoma xenograft model, in which sunitinib is used as the first-line therapy. Transcriptome analysis of shKdm5c, shCsf1, and shCd44 harboring vs. shCtrl cells suggested that the development of resistance is partly due to modulation of cellular pathways as well as alteration of interaction between cells and their microenvironment. In addition, shKdm5c tumors demonstrated resistance towards pazopanib, an VEGF-RTKi with different inhibitory spectrum compared to sunitinib, which suggests a general mechanism of resistance to inhibitors of VEGF signaling after Kdm5c knockdown. Furthermore, cells with shKdm5c showed an increase in survival under hypoxia induced by VEGF-RTKi. Expression profiling of these cells in hypoxia illustrated a network of genes under Kdm5c control, including three components of PRC2 epigenetic modulator, Ezh2, Eed, and Suz12. We found that knockdown of Kdm5c interrupts the imposed break on these genes under hypoxia. In conclusion, we have shown that loss of Kdm5c, CSf1, and Cd44 renders tumor cells resistant to VEGF-RTKi partly through compensatory upregulation of angiogenic factors. In addition, loss of Kdm5c leads to aberrant activation of a gene-regulatory circuitry controlling cellular response to hypoxia. Citation Format: Azadeh Fahim Golestaneh, Maoyun Sun, Christian Schwager, Zili Tang, Lili Ma, Philip Hahnfeldt, Mahmoud Moustafa, Wilko Weichert, Juergen Debus, Lynn Hlatky, Amir Abdollahi. Deciphering the molecular regulators of tumor resistance to VEGF-receptor tyrosine kinase inhibitors via in vivo genome-wide RNAi screen [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A132.

Efficacy and safety of targeting VEGFR drugs in treatment for advanced or metastatic gastric cancer: a systemic review and meta-analysis.

The value of targeting VEGFR (vascular endothelial growth factor receptor) drugs has demonstrated encouraging anti-cancer activity in advanced solid tumors within current clinical trials. This study aimed to serve as the first systemic review to assess their safety and efficacy according to biochemical characteristics of targeting VEGFR drugs in gastric cancer. We analyzed eight clinical trials on targeting VEGFR drugs in gastric cancer. Results showed that targeting VEGFR drugs significantly improved overall survival (OS) [Hazard Ratio (HR) 0.69, 95% confidence interval (CI) (0.55, 0.83), P < 0.001], progression free survival (PFS) [HR 0.50, 95% CI (0.34, 0.66), P < 0.001], disease control rate (DCR) [Odds Ratio (OR) 3.83, 95% CI (2.39, 6.15), P < 0.001] and significantly decreased the progressive disease rate(PDR)[OR 0.45, 95% CI (0.34, 0.59), P < 0.001], but not objective response rate (ORR) [OR 1.46, 95% CI (0.93, 2.29), P = 0.098]. Further subgroup revealed that VEGFR antibody (VEGFR-Ab) drugs were superior to VEGFR tyrosine kinase inhibitor (VEGFR-TKI) drugs in terms of the OS, PFS and PDR. To determine the toxic effect of targeting VEGFR drugs, the relative risk of adverse events (grade ≥ 3) of special interest(AESIs) were estimated. Most of these were predictable and manageable. Furthermore, less AESIs were observed in the VEGFR-Ab than the VEGFR-TKI drugs. In conclusion, VEGFR drugs were effective targeted therapy in advanced or metastatic gastric cancer, and its toxicity is within a controllable range. VEGFR-Ab drugs were more effective than VEGFR-TKI drugs in terms of the OS, PFS and PDR of gastric cancer patients with little toxicity.

Efficient Synthesis and Biological Activity of Novel Indole Derivatives as VEGFR-2 Tyrosine Kinase Inhibitors

A series of novel indole derivatives were synthesized as potent inhibitors for the vascular endothelial growth factor receptor 2 (VEGFR-2) tyrosine kinase. Among those, compound 10b demonstrated the highest growth inhibition rate of 66.7% against the VEGFR-2 tyrosine kinase at 10 μM which indicates that indole-benzothiazole might be the favorable structure. The binding mode of compound 10b with VEGFR-2 tyrosine kinase was evaluated by molecular docking.

Anti-thrombotic and pro-angiogenic effects of Rubia cordifolia extract in zebrafish

Ethnopharmacological relevanceRubia cordifolia is a common traditional Chinese medicine that promotes blood circulation and eliminates blood stasis, and has been used to cure diseases related to blood stasis syndrome (BSS) clinically for many years. It has been previously demonstrated that anti-thrombosis and pro-angiogenesis can improve BSS. However, the anti-thrombotic and pro-angiogenic activities of Rubia cordifolia have not been well investigated. Aim of studyTo determine the potential anti-thrombotic and pro-angiogenic activities of Rubia cordifolia and to elucidate the underlying mechanisms. In addition, the major chemical constituents of Rubia cordifolia extract (QC) were qualitatively analysed by UPLC-Q-TOF/MS to explore the association between pharmacological activity and chemical constituents. Material and methodsThe QC samples were composed of a 95% ethanol extract and an aqueous extract following extraction using 95% ethanol. UPLC-Q-TOF/MS was used to analyse the major chemical constituents of QC. For the anti-thrombotic experiment of QC, a phenylhydrazine (PHZ)-induced AB strain zebrafish thrombosis model was used. The zebrafish larvae were stained using O-dianisidine, and the heart and caudal vein of the zebrafish were observed and imaged with a fluorescence microscope. The staining intensity of erythrocytes in the heart (SI) of each group and the morphology of thrombus in the caudal vein were used to assess the anti-thrombotic effect of QC. For the pro-angiogenic assay of QC, the intersegmental blood vessel (ISV) insufficiency model of Tg(fli-1: EGFP)y1 transgenic zebrafish (Flik zebrafish), which was induced by the VEGF receptor tyrosine kinase inhibitor II (VRI), was used. The morphology of the intact ISVs and defective ISVs was observed to evaluate the pro-angiogenic activity of QC. The mechanism involved in promoting angiogenesis was studied with real-time PCR. ResultsA total of 12 components in QC were identified based on standard compounds and references, including nine anthraquinones and three naphthoquinones. After treatment with QC, the PHZ-induced thrombosis in AB strain zebrafish larvae decreased to a certain degree, which we believe was related to its dosages, and the therapeutic effect within the 50–200 µg/mL QC treatment groups was especially prominent (P < 0.01, P < 0.001) compared to that in the PHZ model group. Similarly, QC also recovered the loss of the ISVs, which was induced by VRI in Flik zebrafish larvae, which have a certain dose-effect relationship. The pro-angiogenic activity of QC was also conspicuous (P < 0.01, P < 0.001) compared to that of the VRI model group. The following real-time PCR assay proved that QC significantly restored the VRI-induced downregulation of vWF, VEGF-A, kdrl, and flt-1 in Flik zebrafish (P < 0.05, P < 0.01, P < 0.001). ConclusionsA total of 12 compounds from QC were analysed by UPLC-Q-TOF/MS. The data of the pharmacological experiments demonstrated that QC presented anti-thrombotic and pro-angiogenic activities in zebrafish, and the principal active components were likely anthraquinones and naphthoquinones. Thus, the current study provided a theoretical basis for the clinical use of Rubia cordifolia as a traditional Chinese medicine in promoting blood circulation and eliminating stasis.

Hypertension and VEGF (Vascular Endothelial Growth Factor) Receptor Tyrosine Kinase Inhibition: Effects on Renal Function.

VEGF (vascular endothelial growth factor) receptor tyrosine kinase inhibitors have become first-line therapy for metastatic renal cell carcinoma. Their use commonly leads to hypertension, but their effects on long-term renal function are not known. In addition, it has been suggested that the development of hypertension is linked to treatment efficacy. The objective of this study was to determine the effects of these drugs on long-term renal function, especially in those with renal dysfunction at baseline, and to examine the role of hypertension on these effects. Serum creatinine measurements were used to calculate the estimated glomerular filtration rate for 130 renal cell carcinoma patients who were treated with this class of tyrosine kinase inhibitors. New or worsening hypertension was defined by documented start or addition of antihypertensive medications. Overall, the use of tyrosine kinase inhibitors in patients with estimated glomerular filtration <60 or ≥60 mL/min per 1.73 m2 was not associated with a decline in long-term renal function. During follow-up, 41 patients developed new or worsening hypertension within 30 days from first drug administration, and this was not linked to further reductions in glomerular filtration. These patients seemed to survive longer than those who did not develop hypertension within 30 days, although this was not statistically significant (P=0.07). Our findings suggest that the use of VEGF tyrosine kinase inhibitors does not adversely affect long-term renal function even in the setting of new-onset hypertension or reduced renal function at baseline.

Phase I dose-escalation study of pazopanib combined with bevacizumab in patients with metastatic renal cell carcinoma or other advanced tumors

BackgroundVascular endothelial growth factor (VEGF) directed therapies are being used in a large number of advanced tumors. Metastatic renal cell carcinoma (mRCC) is highly dependent on the VEGF pathway; VEGF receptor (VEGFR) tyrosine kinase inhibitors (TKI) and humanized VEGF monoclonal antibody have been registered for clinical use in advanced renal cell carcinoma. The VEGFR TKI, pazopanib, with a rather manageable toxicity profile, was preferred to sunitinib by mRCC patients. We investigate the combination of pazopanib and bevacizumab to determine the maximum tolerated dose (MTD) in mRCC and other advanced solid tumors.MethodsIn this bicentric phase I trial with a 3 + 3 + 3 dose-escalation design, patients received oral pazopanib once daily plus intravenous infusion of bevacizumab every 2 weeks from D15, at one of the four dose levels (DL) planned according to the occurrence of dose limiting toxicities (DLT). 400 and 600 mg pazopanib were respectively combined with 7.5 mg/kg bevacizumab in DL1 and DL2, and 600 and 800 mg pazopanib with 10 mg/kg bevacizumab in DL3 and DL4. Tumor response was evaluated every 8 weeks. Blood samples were assayed to investigate pazopanib pharmacokinetics.ResultsTwenty five patients including seven mRCC were enrolled. Nine patients received the DL1, ten received the DL2. No DLT were observed at DL1, five DLT at DL2, and 3 DLT in the six additional patients who received the DL1. A grade 3 microangiopathic hemolytic anemia syndrome was observed in four (16%) patients. Five (22%) patients achieved a partial response. The mean (range) plasmatic concentrations of 400 and 600 pazopanib were respectively 283 (139–427) and 494 (227–761) μg.h/mL at Day 1, and 738 (487–989) and 1071 (678–1464) μg.h/mL at Day 15 i.e. higher than those previously reported with pazopanib, and were not directly influenced by bevacizumab infusion.ConclusionsThe combination of pazopanib and bevacizumab induces angiogenic toxicity in patients without any pre-existing renal or vascular damage. Even if a marginal efficacy was reported with five (22%) patients in partial response in different tumor types, the toxicity profile compromises the development of this combination.Trial registrationThe study was retrospectively registered on ClinicalTrials.gov (number NCT01202032) on 2010, Sept 14th.

Abstract 5599: Soluble PD-L1 as a surrogate biomarker of metastatic progression and resistance to antiangiogenic therapy

Abstract Immune-checkpoint inhibitors are now approved for the treatment of early- and late-stage cancers. These include agents that block the T-cell regulatory protein programmed cell death 1 (PD-1) from being activated by the PD-1 ligand 1 (PD-L1) expressed on cancer cells. There is an urgent need to identify biomarkers of PD-1 pathway inhibition that would predict patient populations responsive to treatment and/or serve as surrogates for drug activity and resistance. PD-L1 expression on tumors is currently a biomarker candidate, but reliable detection and quantification methodologies have proven challenging to standardize. Recently, a soluble PD-L1 (sPD-L1) fragment was identified that can derive from cell-bound PD-L1. Retrospective clinical examinations of sPD-L1 levels in cancer patients suggest a potential use as a surrogate for disease progression and response to treatment; but few preclinical studies have been performed to test this predictive value. We undertook experiments to evaluate plasma sPD-L1 in mouse tumor models during localized primary tumor growth (after orthotopic cell implantation) and spontaneous metastatic disease progression (after surgical removal of the primary). Mouse syngeneic and human xenograft implantation models included breast, kidney, colon, and melanoma cell systems. Our results show that circulating plasma sPD-L1 can correlate with primary and metastatic progression in a stage and model specific manner. Next, we evaluated sPD-L1 following treatment with neutralizing antibodies to PD-1 and PD-L1 in tumor-free mice and found significant dose-dependent sPD-L1 increases, suggesting systemic changes may have utility as a measurement of target saturation and dosing independent of tumor growth. Finally, with current approvals of PD-1 inhibitors in renal cell carcinoma (RCC) patients previously treated with antiangiogenic agents that block vascular endothelial growth factor (VEGF), we evaluated plasma in mouse models of sunitinib resistance - a VEGF receptor tyrosine kinase inhibitor (RTKI). Our results demonstrate that VEGF pathway resistance yields changes in sPD-L1 and may be useful in predicting response to PD-1 pathway inhibition in the refractory setting. Together, these investigations suggest that circulating sPD-L1 changes during disease progression (both local and disseminated) may serve as a potential predictive biomarker for immune-checkpoint and antiangiogenic therapy. Citation Format: Michalis Mastri, Amanda Tracz, Yuhao Shi, Georg Bjarnason, Tran Nguyen, Brian Rini, John M.L. Ebos. Soluble PD-L1 as a surrogate biomarker of metastatic progression and resistance to antiangiogenic therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5599. doi:10.1158/1538-7445.AM2017-5599

Synthesis and Biological Evaluation of Glycyrrhetic Acid Derivatives as Potential VEGFR2 Inhibitors.

Vascular endothelial growth factor receptor 2 (VEGFR2) has been proven to play a major role in the regulation of tumor angiogenesis. A series of novel glycyrrhetic acid derivatives were synthesized and evaluated for their VEGFR2 inhibitory activity as well as their antiproliferative properties against four cancer cell lines (MCF-7, HeLa, HepG2, and A549). In vitro biological evaluations against these human tumor cell lines indicate that most of the prepared compounds have antiproliferative activities; compound 3 a (3β-hydroxy-30-(4-phenyl-1-piperazinyl)olean-12-ene-11,30-dione) exhibited the best inhibitory activity against MCF-7 cells, with an IC50 value of 1.08 μm. Compound 3 a also showed the most potent inhibitory activity against VEGFR2 tyrosine kinase, with an IC50 value of 0.35 μm. Docking simulations were performed with the aim of discovering the binding mode of compound 3 a, and the results indicate that 3 a could bind at the VEGFR2 active site.

CT Intensity Distribution Curve (Histogram) Analysis of Patients Undergoing Antiangiogenic Therapy for Metastatic Renal Cell Carcinoma.

The purpose of this study was to evaluate the median versus mean attenuation obtained from histograms in the response assessment of renal cell carcinoma (RCC) target lesions in patients treated with vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors. Imaging findings of 19 patients with RCC and treated with a VEGFR tyrosine kinase inhibitor that included a baseline study and at least two follow-up studies were retrospectively analyzed. Histograms of target lesions were created from ROI measurements, and mean and median lesion attenuation were obtained. Shift of mean and median was used to classify response of lesions between baseline CT and the first follow-up examination according to the Choi criteria; morphology, attenuation, size, and structure (MASS) criteria; and the Response Evaluation Criteria in Solid Tumors (RECIST). RECIST classification of the last follow-up CT examination was considered the reference standard. Among the 19 patients (six women, 13 men; mean age, 60 ± 8 [SD] years; body mass index, 24.5 ± 4.6 kg/m2), three (16%) had evidence of disease progression; nine (47%), partial response; and seven (37%), stable disease. Temporal change in the shape of the histograms from or to gaussian occurred in 11 of the 19 (58%) lesions, which accounted for a significant difference between mean (64.3 ± 38.5 HU) and median (71.0 ± 36.5 HU) lesion attenuation (p < 0.001). According to the shift of median for outcome analysis, the number of properly classified lesions increased from 12 of 19 (63%) to 13 of 19 (68%) for the Choi criteria and from 14 of 19 (74%) to 15 of 19 (79%) for the MASS criteria. Mean and median attenuation of RCC target lesions differed significantly. Use of shift of median rather than shift of mean increased the number of accurate classifications of lesions at the first follow-up CT examination.

Tivo-3: A phase 3, randomized, controlled, multi-center, open-label study to compare tivozanib hydrochloride to sorafenib in subjects with refractory advanced renal cell carcinoma (RCC).

TPS4600 Background: Tivozanib is a biochemically potent and selective VEGF tyrosine kinase inhibitor in clinical development in RCC. Other agents used for treatment of RCC inhibit multiple tyrosine kinases in addition to the VEGF receptor tyrosine kinase, leading to off-target toxicities such as fatigue, hand-foot syndrome, stomatitis, and neutropenia. The adverse event (AE) profile of tivozanib demonstrates minimal off-target toxicities. TIVO-1 (AV-951-09-301) was an open-label, randomized, controlled, multi-national, multi-center, parallel-arm trial comparing tivozanib to sorafenib in patients with advanced RCC. The blinded independent radiological assessment showed the median progression free survival (mPFS) in the tivozanib arm to be 11.9 months (95% confidence interval (CI) [9.3, 14.7]), compared with 9.1 months (95% CI [7.3, 9.5]) in the sorafenib arm (p = 0.042, HR = 0.797). Overall survival had a negative trend, most likely due to a one-way crossover for patients randomized to sorafenib. This study is designed, in part, to demonstrate that the negative trend in OS was an artifact. Methods: Subjects with metastatic RCC who have failed 2 or 3 prior systemic regimens, one of which includes a VEGFR TKI other than sorafenib or tivozanib, will be randomized in a 1:1 ratio stratified by the IMDC risk category (favorable; intermediate; poor) and prior therapy (two VEGFR TKIs; a prior checkpoint inhibitor plus a prior VEGFR TKI; a prior VEGFR TKI plus any other systemic agent). The primary objective is to compare the progression-free survival (PFS) of subjects randomized to tivozanib with those randomized to sorafenib as assessed by blinded independent radiological review (IRR). Secondary endpoints are overall survival, objective response rate, and duration of response. Clinical trial information: NCT02627963.

The oral VEGF receptor tyrosine kinase inhibitor pazopanib in combination with the MEK inhibitor trametinib in advanced cholangiocarcinoma

Background:Cholangiocarcinoma is an aggressive malignancy with limited therapeutic options. MEK inhibition and antiangiogenic therapies have individually shown modest activity in advanced cholangiocarcinoma, whereas dual inhibition of these pathways has not been previously evaluated. We evaluated the safety and efficacy of combination therapy with the oral VEGF receptor tyrosine kinase inhibitor pazopanib plus the MEK inhibitor trametinib in patients with advanced cholangiocarcinoma.Methods:In this open-label, multicentre, single-arm trial, adults with advanced unresectable cholangiocarcinoma received pazopanib 800 mg daily and trametinib 2 mg daily until disease progression or unacceptable toxicity. The primary end point was progression-free survival (PFS) with secondary end points including overall survival (OS), response rate, and disease control rate (DCR).Results:A total of 25 patients were enrolled and had received a median of 2 prior systemic therapies (range 1–7). Median PFS was 3.6 months (95% CI: 2.7–5.1) and the 4-month PFS was 40% (95% CI: 24.7–64.6%). There was a trend towards increased 4-month PFS as compared with the prespecified null hypothesised 4-month PFS of 25%, but this difference did not reach statistical significance (P=0.063). The median survival was 6.4 months (95% CI: 4.3–10.2). The objective response rate was 5% (95% CI: 0.13–24.9%) and the DCR was 75% (95% CI: 51%, 91%). Grade 3/4 adverse events attributable to study drugs were observed in 14 (56%) and included thrombocytopenia, abnormal liver enzymes, rash, and hypertension.Conclusions:Although the combination of pazopanib plus trametinib had acceptable toxicity with evidence of clinical activity, it did not achieve a statistically significant improvement in 4-month PFS over the prespecified null hypothesised 4-month PFS.

Vandetanib and ADAM inhibitors synergistically attenuate the pathological migration of EBV-infected retinal pigment epithelial cells by regulating the VEGF-mediated MAPK pathway.

The extracellular signals induced by vascular endothelial growth factor (VEGF) are implicated in choroidal neovascularization (CNV) and thus, are associated with vision-limiting complications in the human retina. Vandetanib is an oral anticancer drug that selectively inhibits the activities of VEGF receptor and epidermal growth factor receptor tyrosine kinase; however, the effects of vandetanib on VEGF in retinal pigment epithelial (RPE) cells have not yet been studied. In the present study, a combined treatment of vandetanib and a disintegrin and metalloproteinase (ADAM) protein inhibitors were used to assess the regulation of Epstein-Barr virus (EBV)-infected ARPE19 cells (ARPE19/EBV) migration as a model of CNV. Vandetanib suppressed the expression of the mesenchymal markers ADAM10 and ADAM17 in ARPE19/EBV cells, and also upregulated epithelial cell markers of the RPE cells, E-cadherin and N-cadherin. The migratory activity of ARPE19/EBV induced by VEGF was efficiently blocked by vandetanib. Furthermore, co-treatment with vandetanib and an ADAM10 inhibitor (GI254023X) or ADAM17 inhibitor (Marimastat) synergistically prevented migration and the expression of vimentin, Snail and α-smooth muscle actin by regulating extracellular signal-regulated kinase and p38 mitogen-activated protein kinase. These results suggest that a combination treatment of vandetanib and ADAM inhibitors may be developed as a novel therapeutic regimen to control retina neovascular disease.

Safety and efficacy of fruquintinib in patients with previously treated metastatic colorectal cancer: a phase Ib study and a randomized double-blind phase II study

BackgroundTo assess the efficacy and safety of fruquintinib, a vascular endothelial growth factor receptor (VEGFR) inhibitor, in metastatic colorectal cancer (mCRC) patients.MethodsA phase Ib open-label study and phase II randomized, placebo-controlled trial compared the efficacy of fruquintinib plus best supportive care (BSC) with placebo plus BSC in mCRC patients with ≥2 lines of prior therapies. The primary endpoint was progression-free survival (PFS).ResultsIn the phase Ib study, 42 patients took fruquintinib 5 mg for 3 weeks on/1 week off. The median PFS was 5.80 months, and the median overall survival (OS) was 8.88 months. In the phase II study, 71 patients were randomized (47 to fruquintinib, 24 to placebo). PFS was significantly improved with fruquintinib plus BSC (4.73 months; 95% confidence interval [CI] 2.86–5.59) versus placebo plus BSC (0.99 months; 95% CI 0.95–1.58); (hazard ratio [HR] 0.30; 95% CI 0.15–0.59; P < 0.001). The median OS was 7.72 versus 5.52 months (HR 0.71; 95% CI 0.38–1.34). The most common grade 3–4 adverse events were hypertension and hand-foot skin reaction.ConclusionsFruquintinib showed a significant PFS benefit of 3.7 months in patients with treatment-refractory mCRC. The safety profile was consistent with that of VEGFR tyrosine kinase inhibitors. A randomized phase III confirmatory study in mCRC is underway.Trial registrationNCT01975077 and NCT02196688