Effect of an Endothelin B Receptor Agonist on the Tumor Accumulation of Nanocarriers.

Enhancing blood flow to tumors is a prominent strategy for improving the tumor accumulation of macromolecular drugs through the enhanced permeability and retention (EPR) effect. IRL-1620 is an agonist of the endothelin B receptor, and is a promising molecule to enhance tumor blood flow by activating endothelial nitric oxide synthase. However, contradictory effects on tumor blood flow modulation have been reported because the effects of IRL-1620 may differ in different animal models. Here, we examined for the first time the effect of IRL-1620 on the EPR effect for PEGylated liposomes in a CT-26 murine colon cancer model. Co-injection of IRL-1620 at an optimum dose (3 nmol/kg) nearly doubled the tumor accumulation of liposomes compared with controls, indicating that IRL-1620 enhanced the EPR effect in the present colon cancer model. Co-injection of IRL-1620 is a promising strategy to improve the therapeutic effects of macromolecular drugs while reducing their side effects.

Endothelin receptor-A mediates degradation of the glomerular endothelial surface layer via pathologic crosstalk between activated podocytes and glomerular endothelial cells.

Emerging evidence of crosstalk between glomerular cells in pathological settings provides opportunities for novel therapeutic discovery. Here we investigated underlying mechanisms of early events leading to filtration barrier defects of podocyte and glomerular endothelial cell crosstalk in the mouse models of primary podocytopathy (podocyte specific transforming growth factor-ß receptor 1 signaling activation) or Adriamycin nephropathy. We found that glomerular endothelial surface layer degradation and albuminuria preceded podocyte foot process effacement. These abnormalities were prevented by endothelin receptor-A antagonism and mitochondrial reactive oxygen species scavenging. Additional studies confirmed increased heparanase and hyaluronoglucosaminidase gene expression in glomerular endothelial cells in response to podocyte-released factors and to endothelin-1. Atomic force microscopy measurements showed a significant reduction in the endothelial surface layer by endothelin-1 and podocyte-released factors, which could be prevented by endothelin receptor-A but not endothelin receptor-B antagonism. Thus, our studies provide evidence of early crosstalk between activated podocytes and glomerular endothelial cells resulting in loss of endothelial surface layer, glomerular endothelial cell injury and albuminuria. Hence, activation of endothelin-1-endothelin receptor-A and mitochondrial reactive oxygen species contribute to the pathogenesis of primary podocytopathies in experimental focal segmental glomerulosclerosis.

Electroacupuncture induces antihyperalgesic effect through endothelin-B receptor in the chronic phase of a mouse model of complex regional pain syndrome type I.

Complex regional pain syndrome (CRPS) is a disorder that involves abnormal inflammation and nerve dysfunction frequently resistant to a broad range of treatments. Peripheral nerve stimulation with electroacupuncture (EA) has been widely used in different clinical conditions to control pain and inflammation; however, the use of EA in the treatment of CRPS is under investigation. In this study, we explore the effects of EA on hyperalgesia and edema induced in an animal model of chronic post-ischemia pain (CPIP model) and the possible involvement of endothelin receptor type B (ETB) in this effect. Female Swiss mice were subjected to 3 h hind paw ischemia/reperfusion CPIP model. EA treatment produced time-dependent inhibition of mechanical and cold hyperalgesia, as well as edema in CPIP mice. Peripheral administration (i.pl.) of BQ-788 (10 nmol), an ETB antagonist, prevented EA-induced antihyperalgesia while intrathecal administration prolonged EA's effect. Additionally, peripheral pre-treatment with sarafotoxin (SRTX S6c, 30 pmol, ETB agonist) increased EA anti-hyperalgesic effect. Furthermore, the expression of peripheral ETB receptors was increased after EA treatments, as measured by western blot. These results may suggest that EA's analgesic effect is synergic with ETB receptor activation in the periphery, as well as central (spinal cord) ETB receptor blockade. These data support the use of EA as a nonpharmacological approach for the management of CRPS-I, in an adjuvant manner to ETB receptor targeting drugs.

Endothelin and diabetic complications: a brain-centric view.

The global epidemic of diabetes is of significant concern. Diabetes associated vascular disease signifies the principal cause of morbidity and mortality in diabetic patients. It is also the most rapidly increasing risk factor for cognitive impairment, a silent disease that causes loss of creativity, productivity, and quality of life. Small vessel disease in the cerebral vasculature plays a major role in the pathogenesis of cognitive impairment in diabetes. Endothelin system, including endothelin-1 (ET-1) and the receptors (ET(A) and ET(B)), is a likely candidate that may be involved in many aspects of the diabetes cerebrovascular disease. In this review, we took a brain-centric approach and discussed the role of the ET system in cerebrovascular and cognitive dysfunction in diabetes.

Modeling of pharmacokinetics, efficacy, and hemodynamic effects of macitentan in patients with pulmonary arterial hypertension.

BACKGROUND: Macitentan is the first endothelin receptor antagonist with demonstrated efficacy on morbidity and mortality in pulmonary arterial hypertension (PAH) in the pivotal study SERAPHIN. METHODS: The pharmacokinetics (PK) of macitentan and its active metabolite, ACT-132577, were characterized in a population model. Efficacy and hemodynamics (pharmacodynamics, PD) were related to PK based on PK/PD modeling. RESULTS: Sex, age, and body weight influenced the PK to a statistically significant extent. Model-based simulations showed that these variables are clinically not relevant. Concomitant use of PAH medication (PDE-5 inhibitors) did not influence macitentan trough concentration to a relevant extent. Efficacy and hemodynamics showed clear differences from placebo for macitentan concentrations on 3 and 10 mg with consistent superior effects for 10 mg. After 6 months, PAH patients showed model-predicted 6-min walk distance (6-MWD) improvements of 1.0 m on placebo compared to 29.8 and 34.1 m on 3 and 10 mg of macitentan, respectively. Higher macitentan concentrations were associated with reductions in pulmonary vascular resistance (PVR), mean right atrial and pulmonary arterial pressure, and total pulmonary resistance (TPR) and increases in cardiac index (CI) and mixed venous oxygen saturation. Statistical significance was determined for PVR, TPR, and CI but not for 6-MWD. In addition, PVR showed more pronounced differences between active treatment and placebo than 6-MWD. CONCLUSIONS: Modeling identified statistically significant inter-patient differences; simulations to assess the magnitude of the effects permitted clinical judgment. The same approach will allow for extrapolation to children. Hemodynamic markers might be better markers of treatment effects than 6-MWD. TRIAL REGISTRATION: The SERAPHIN study and its open-label extension are registered with ClinicalTrials.gov with identifiers NCT00660179 (https://www.clinicaltrials.gov/ct2/show/NCT00660179) and NCT00667823 (https://clinicaltrials.gov/ct2/show/NCT00667823) and with EudraCT with identifiers 2007-002440-14 (https://www.clinicaltrialsregister.eu/ctr-search/search?query=2007-002440-14) and 2007-003694-27 (https://www.clinicaltrialsregister.eu/ctr-search/search?query=2007-003694-27).

Macitentan Improves Health-Related Quality of Life for Patients With Pulmonary Arterial Hypertension: Results From the Randomized Controlled SERAPHIN Trial.

BACKGROUND: Pulmonary arterial hypertension (PAH) leads to reduced health-related quality of life (HRQoL). The objectives of this analysis were to evaluate the effect of macitentan on HRQoL in patients with PAH in the Study with an Endothelin Receptor Antagonist in Pulmonary Arterial Hypertension to Improve Clinical Outcome (SERAPHIN) study. The association between baseline HRQoL and long-term outcomes was also investigated. METHODS: Patients were randomized to placebo, macitentan 3 mg, or macitentan 10 mg once daily. Patients aged 14 years or older completed the 36-Item Short Form Survey (SF-36) at baseline, at month 6 and month 12, and at the end of treatment (EOT). The absolute change from baseline to month 6 in SF-36 scores was calculated. The time to a clinically meaningful deterioration in the SF-36 physical component summary and mental component summary (PCS and MCS) scores and associations between baseline PCS/MCS scores and time to morbidity/mortality events were also assessed. RESULTS: At month 6, macitentan 10 mg significantly improved seven of eight SF-36 domains and the PCS and MCS scores vs placebo. Macitentan 10 mg significantly reduced the risk of a three-point or greater deterioration in PCS (hazard ratio [HR], 0.60; 95% CI, 0.47-0.76; P < .0001) and MCS scores (HR, 0.76; 95% CI, 0.61-0.95; P = .0173) until EOT vs placebo. Patients with a baseline PCS score greater than the median baseline value had a significantly reduced risk of morbidity/mortality compared with patients with a PCS score less than the median; a similar result was observed for the MCS score. CONCLUSIONS: Macitentan significantly improved HRQoL in patients with PAH compared with placebo and significantly reduced the risk of a clinically meaningful HRQoL deterioration. An association between better baseline HRQoL and improved long-term outcomes was shown. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT00660179; URL: clinicaltrials.gov.

First-in-Human Proof-of-Concept Study: Intralesional Administration of BQ788, an Endothelin Receptor B Antagonist, to Melanoma Skin Metastases.

BACKGROUND: This first-in-human proof-of-concept study aimed to check whether safety and preclinical results obtained by intratumoral administration of BQ788, an endothelin receptor B (EDNRB) antagonist, can be repeated in human melanoma patients. METHODS: Three patients received a single intralesional BQ788 application of 3 mg. After 3-7 days, the lesions were measured and removed for analysis. The administered dose was increased to a cumulative dosage of 8 mg in patient 4 (4 × 2.0 mg, days 0-3; lesion removed on day 4) and to 10 mg in patient 5 (3 × 3.3 mg, days 0, 3, and 10; lesion removed after 14 days). Control lesions were simultaneously treated with phosphate-buffered saline (PBS). All samples were processed and analyzed without knowledge of the clinical findings. RESULTS: No statistical evaluation was possible because of the number of patients (n = 5) and the variability in the mode of administration. No adverse events were observed, regardless of administered dose. All observations were in accordance with results obtained in preclinical studies. Accordingly, no difference in degree of tumor necrosis was detected between BQ788- and PBS-treated samples. In addition, both EDNRB and Ki67 showed decreased expression in patients 2 and 5 and, to a lesser extent, in patient 1. Similarly, decreased expression of EDNRB mRNA in patients 2 and 5 and of BCL2A1 and/or PARP3 in patients 2, 3, and 5 was found. Importantly, semiquantitatively scored immunohistochemistry for CD31 and CD3 revealed more blood vessels and lymphocytes, respectively, in BQ788-treated tumors of patients 2 and 4. Also, in all patients, we observed inverse correlation in expression levels between EDNRB and HIF1A. Finally, in patient 5 (the only patient treated for longer than 1 week), we observed inhibition in lesion growth, as shown by size measurement. CONCLUSION: The intralesional applications of BQ788 were well tolerated and showed signs of directly and indirectly reducing the viability of melanoma cells.

Improvement of cold injury-induced mouse brain edema by endothelin ETB antagonists is accompanied by decreases in matrixmetalloproteinase 9 and vascular endothelial growth factor-A.

Brain edema is a potentially fatal pathological state that often occurs after brain injuries such as ischemia and trauma. However, therapeutic agents that fundamentally treat brain edema have not yet been established. We previously found that endothelin ETB receptor antagonists attenuate the formation and maintenance of vasogenic brain edema after cold injury in mice. In this study, the effects of ETB antagonists on matrixmetalloproteinase (MMP)9 and vascular endothelial growth factor (VEGF)-A expression were examined in the cold injury model. Cold injury was performed in the left brain of male ddY mice (5-6 weeks old) for the induction of vasogenic edema. Expression of MMP9 and VEGF-A mRNA in the mouse cerebrum was increased by cold injury. Immunohistochemical observations showed that the MMP9 and VEGF-A were mainly produced in reactive astrocytes in the damaged cerebrum. Intracerebroventricular administration of BQ788 (10 µg) or IRL-2500 (10 µg) (selective ETB antagonists) attenuated brain edema and disruption of the blood-brain barrier after cold injury. BQ788 and IRL-2500 reversed the cold injury-induced increases in MMP9 and VEGF-A expression. The induction of reactive astrocytes producing MMP9 and VEGF-A in the damaged cerebrum was attenuated by BQ788 and IRL-2500. These results suggest that attenuations of astrocytic MMP9 and VEGF-A expression by ETB antagonists may be involved in the amelioration of vasogenic brain edema.

Novel dual endothelin receptor antagonist macitentan reverses severe pulmonary arterial hypertension in rats.

The efficacy of endothelin (ET) receptor antagonist bosentan in patients with severe pulmonary arterial hypertension (PAH) remains limited, partly because its higher doses for potential blockade of ET receptors have never been tested due to liver dysfunction. We hypothesized that rigorous blockade of ET receptors using the novel dual ET receptor antagonist macitentan would be effective in treating severe PAH without major side effects in a preclinical model appropriately representing the human disorder. In normal rats, 30 mg·kg·d of macitentan completely abolished big ET-1-induced increases in right ventricle (RV) systolic pressure. Adult male rats were injected with SU5416, a vascular endothelial growth factor blocker, and exposed to hypoxia for 3 weeks and then to normoxia for an additional 5 weeks (total 8 weeks). In intrapulmonary arterial rings isolated from rats with severe PAH, macitentan concentration dependently inhibited ET-1-induced contraction. Long-term treatment with macitentan (30 mg·kg·d, from week 3 to 8) reversed the high RV systolic pressure with preserved cardiac output. Development of RV hypertrophy, luminal occlusive lesions and medial wall thickening were also significantly improved without increasing serum levels of liver enzymes by macitentan. In conclusion, efficacious blockade of ET receptors with macitentan would reverse severe PAH without major adverse effects.

MAPK pathway inhibition enhances the efficacy of an anti-endothelin B receptor drug conjugate by inducing target expression in melanoma.

Therapies targeting the mitogen-activated protein (MAP) kinase pathway in melanoma have produced significant clinical responses; however, duration of response is limited by acquisition of drug resistance. Rational drug combinations may improve outcomes in this setting. We assessed the therapeutic combination of an antibody-drug conjugate (ADC) targeting the endothelin B receptor (EDNRB) with small-molecule inhibitors of the MAP kinase signaling pathway in melanoma. Cell lines and tumor models containing either mutant BRAF or NRAS, or wild-type for both, were exposed to small-molecule inhibitors of BRAF and MEK. Expression of EDNRB was analyzed and the therapeutic impact of combining the anti-EDNRB ADC with the BRAF and MEK inhibitors was assessed. Increased expression of EDNRB in response to inhibition of BRAF and/or MEK was observed and augmented the antitumor activity of the ADC. Enhanced target expression and ADC antitumor activity were realized irrespective of the response of the tumor model to the BRAF or MEK inhibitors alone and could be achieved in melanoma with mutant NRAS, BRAF, or neither mutation. Cells that acquired resistance to BRAF inhibition through long-term culture retained drug-induced elevated levels of EDNRB expression. Expression of EDNRB was not enhanced in normal human melanocytes by inhibition of BRAF and the combination of the ADC with MAPK inhibitors was well-tolerated in mice. The anti-EDNRB ADC combines well with BRAF and MEK inhibitors and could have therapeutic use in the majority of human melanoma cases.