The LPS induced pyroptosis exacerbates BMPR2 signaling deficiency to potentiate SLE-PAH.

Pulmonary arterial hypertension (PAH) is a common and fatal complication of systemic lupus erythematosus (SLE). Whether the BMP receptor deficiency found in the genetic form of PAH is also involved in SLE-PAH patients remains to be identified. In this study, we employed patient-derived samples from SLE-associated PAH (SLE-PAH) and established comparable mouse models to clarify the role of BMP signaling in the pathobiology of SLE-PAH. Firstly, serum levels of LPS and autoantibodies (auto-Abs) directed at BMP receptors were significantly increased in patients with SLE-PAH compared with control subjects, measured by ELISA. Mass cytometry was applied to compare peripheral blood leukocyte phenotype in patients prior to and after treatment with steroids, which demonstrated inflammatory cells alteration in SLE-PAH. Furthermore, BMPR2 signaling and pyroptotic factors were examined in human pulmonary arterial endothelial cells (PAECs) in response to LPS stimulation. Interleukin-8 (IL-8) and E-selectin (SELE) expressions were up-regulated in autologous BMPR2+/R899X endothelial cells and siBMPR2-interfered PAECs. A SLE-PH model was established in mice induced with pristane and hypoxia. Moreover, the combination of endothelial specific BMPR2 knockout in SLE mice exacerbated pulmonary hypertension. Pyroptotic factors including gasdermin D (GSDMD) were elevated in the lungs of SLE-PH mice, and the pyroptotic effects of serum samples isolated from SLE-PAH patients on PAECs were analyzed. BMPR2 signaling upregulator (BUR1) showed anti-pyroptotic effects in SLE-PH mice and PAECs. Our results implied that deficiencies of BMPR2 signaling and proinflammatory factors together contribute to the development of PAH in SLE.

Activin receptor-like kinase 1 is associated with immune cell infiltration and regulates CLEC14A transcription in cancer.

Cancer cells sustain their metabolic needs through nutrients and oxygen supplied by the bloodstream. The requirement for tumor angiogenesis has been therapeutically exploited in the clinical setting mainly by means of inhibition of the vascular endothelial growth factor family of ligands and receptors. Despite promising results in preclinical models, the benefits for patients proved to be limited. Inadequate efficacy similarly halted the development of agents impinging on the activity of the activin receptor-like kinase (ALK)1, a member of the transforming growth factor-ß superfamily. Notwithstanding its characterization as an endothelial cell marker, the full spectrum of biological processes associated with ALK1 is essentially unexplored. Here, we present data revealing the genetic network associated with ACVRL1 (the gene encoding for ALK1) expression in human cancer tissues. Computational analysis unveiled a hitherto unknown role for ACVRL1 in relation to genes modulating the functionality of the immune cell compartment. Moreover, we generated a signature of 8 genes co-expressed with ACVRL1 across different tumor types and characterized the c-type lectin domain containing protein (CLEC)14A as a potential downstream target of ACVRL1. Considering the lack of reagents for ALK1 detection that has hampered the field to date, our work provides the opportunity to validate the 8-gene signature and CLEC14A as biomarkers for ALK1 activity. Ultimately, this may help revisit the clinical development of already existing ALK1-blocking compounds as precision medicines for cancer.

TGF-ß1, but not bone morphogenetic proteins, activates Smad1/5 pathway in primary human macrophages and induces expression of proatherogenic genes.

Macrophages are responsible for the control of inflammation and healing, and their malfunction results in cardiometabolic disorders. TGF-ß is a pleiotropic growth factor with dual (protective and detrimental) roles in atherogenesis. We have previously shown that in human macrophages, TGF-ß1 activates Smad2/3 signaling and induces a complex gene expression program. However, activated genes were not limited to known Smad2/3-dependent ones, which prompted us to study TGF-ß1-induced signaling in macrophages in detail. Analysis of Id3 regulatory sequences revealed a novel enhancer, located between +4517 and 4662 bp, but the luciferase reporter assay demonstrated that this enhancer is not Smad2/3 dependent. Because Id3 expression is regulated by Smad1/5 in endothelial cells, we analyzed activation of Smad1/5 in macrophages. We demonstrate here for the first time, to our knowledge, that TGF-ß1, but not BMPs, activates Smad1/5 in macrophages. We show that an ALK5/ALK1 heterodimer is responsible for the induction of Smad1/5 signaling by TGF-ß1 in mature human macrophages. Activation of Smad1/5 by TGF-ß1 induces not only Id3, but also HAMP and PLAUR, which contribute to atherosclerotic plaque vulnerability. We suggest that the balance between Smad1/5- and Smad2/3-dependent signaling defines the outcome of the effect of TGF-ß on atherosclerosis where Smad1/5 is responsible for proatherogenic effects, whereas Smad2/3 regulate atheroprotective effects of TGF-ß.

Phase I study of PF-03446962, a fully human monoclonal antibody against activin receptor-like kinase-1, in patients with hepatocellular carcinoma.

BACKGROUND: This expansion cohort of a multicenter, dose-escalation, phase I study (NCT00557856) evaluated safety, tolerability, antitumor activity, pharmacokinetics, and pharmacodynamic effects of the anti-activin receptor-like kinase-1 (ALK-1) monoclonal antibody PF-03446962 in advanced hepatocellular carcinoma (HCC). PATIENTS AND METHODS: Patients with HCC and disease progression after prior antiangiogenic therapy or intolerance to treatment received PF-03446962 7 mg/kg intravenously biweekly, as recommended in the dose-escalation part of the study. RESULTS: Twenty-four patients received PF-03446962. The most frequent treatment-related adverse events (AEs) were thrombocytopenia (33.3%), asthenia (29.2), and chills (16.7%). Two patients experienced treatment-related telangiectasia, suggesting an in vivo knockout of ALK-1 function through ALK-1 pathway inhibition. Overall, treatment-related grade 3-4 AEs were reported in eight patients (33.3%). Treatment-related grade 3-4 thrombocytopenia was noted in four patients. No complete or partial responses were reported. Twelve (50%) patients achieved stable disease, which lasted ≥12 weeks in seven (29.2%) patients. The median time to progression was 3 months. Biomarker analyses showed higher mean tumor expression of c-tumor mesenchymal-epithelial transition factor and higher mean serum levels of bone morphogenetic protein-9 in patients with disease control (DC) for ≥12 weeks versus patients with disease progression. Conversely, lower mean serum transforming growth factor-ß and vascular endothelial growth factor receptor-3 levels were detected in patients with DC versus patients with progression. CONCLUSIONS: The observed safety, tolerability, pharmacokinetic profile, and clinical activity support further evaluation of PF-03446962 in patients with HCC and other solid malignancies, as single agent or in combination with other antiangiogenic, chemotherapeutic, or immunotherapeutic agents. TRIAL REGISTRATION NUMBER: NCT00557856.

PF-03446962, a fully-human monoclonal antibody against transforming growth-factor ß (TGFß) receptor ALK1, in pre-treated patients with urothelial cancer: an open label, single-group, phase 2 trial.

Despite a compelling preclinical rationale for the use of anti-angiogenic drugs in urothelial cancer (UC), short-living responses have been observed in clinical trials. PF-03446962 is a novel monoclonal antibody against Activin Receptor-Like Kinase-1 (ALK1), a type I subclass of the TGFß receptor, with dose-dependent anti-angiogenic activity. An open label, single-group, phase 2 trial of PF-03446962 was conducted in salvage setting. Patients failing at least one chemotherapy regimen were eligible. Design provided PF-03446962 10 mg/Kg intravenously fortnightly until disease progression (PD) or unacceptable toxicity. Two-month progression-free survival (PFS) was the primary endpoint. The trial was registered with ClinicalTrials.gov, number NCT01620970. Fourteen patients were enrolled from October 2012 to July 2013. Median age was 64 years (interquartile range [IQR]: 58.2-69.5), 9 patients had a Bellmunt score of 1-2, median number of prior drugs was 3. One stable disease and 13 PD were recorded and the study met the futility stopping rule of interim analysis. Median PFS was 1.8 months (95 %CI, 1.4-2.0). After a median follow up of 7.4 months (IQR 4.5-10.9), 8 patients are alive. Median overall survival (OS) was 8 months (95 %CI, 2.9-not estimable). Most common toxicities were thrombocytopenia (G1-2 in 5 cases, persistent G3 in one, with 3 dose delays and 1 dose interruption), fatigue and abdominal pain (G1-2 in 4 cases each). Impairment of quality of life (ESAS score) was observed as well as an increase from baseline to +2 month median levels of vascular endothelial growth factor (VEGF) and interleukin-8. PF-03446962 had no activity as single drug in refractory UC and we do not recommend further investigation outside of the combination with agents targeting the VEGF receptor axis.

Anti-human activin receptor-like kinase 1 (ALK1) antibody attenuates bone morphogenetic protein 9 (BMP9)-induced ALK1 signaling and interferes with endothelial cell sprouting.

Genetic and molecular studies suggest that activin receptor-like kinase 1 (ALK1), a transforming growth factor ß (TGF-ß) type I receptor, and endoglin, a TGF-ß co-receptor, play an essential role in vascular development and pathological angiogenesis. Several agents that interfere with ALK1 and endoglin function are currently in clinical trials for antiangiogenic activity in cancer therapy. One of these agents, PF-03446962 (anti-hALK1 antibody), shows promising results in the clinic. However, its effects on endothelial cell function and mechanism of action are unclear. Here we demonstrate that anti-hALK1 antibody selectively recognizes human ALK1. The anti-hALK1 antibody interfered with bone morphogenetic protein 9 (BMP9)-induced signaling in endothelial cells. Consistent with this notion, anti-hALK1 antibody was found to compete highly efficiently with the binding of the ALK1 ligand BMP9 and TGF-ß to ALK1. Moreover, it prevented BMP9-dependent recruitment of co-receptor endoglin into this angiogenesis-mediating signaling complex. In addition, we demonstrated that anti-hALK1 antibody inhibited endothelial cell sprouting but did not directly interfere with vascular endothelial growth factor (VEGF) signaling, VEGF-induced proliferation, and migration of endothelial cells. Finally, we demonstrated that BMP9 in serum is essential for endothelial sprouting and that anti-hALK1 antibody inhibits this potently. Our data suggest that both the VEGF/VEGF receptor and the BMP9/ALK1 pathways are essential for stimulating angiogenesis, and targeting both pathways simultaneously may be an attractive strategy to overcome resistance to antiangiogenesis therapy.

Identification of Acvr2a as a Th17 cell-specific gene induced during Th17 differentiation.

IL-17-producing T lymphocytes have been found to comprise a distinct lineage of T helper cells (Th17 cells) that are major causes of autoimmune diseases such as EAE, RA, and IBD. In this study, we found that activin receptor type-2A (Acvr2a) is a gene induced during the differentiation of this effector cell lineage as compared with naïve T cells. The transcript of Acvr2a was not induced in Th1 and Th2 cells, and both TGF-ß and IL-6 were required for the induction of Acvr2a. When the differentiation of Th17 cells was inhibited by all tarans retinoic acid (ATRA) which induces regulatory T cell (Treg) differentiation under Th17 differentiation conditions, expression of Acvr2a was also inhibited. Hence we propose that Acvr2a is a Th17 specific gene making Th17 cells distinct from other helper T cells, Th1, Th2, and Treg.

Activin and transforming growth factor-beta signaling pathways are activated after allergen challenge in mild asthma.

BACKGROUND: Both transforming growth factor (TGF)-beta(1) and activin-A have been implicated in airway remodeling in asthma, but the modulation of their specific signaling pathways after disease activation remains undefined. OBJECTIVE: To define the expression kinetics of TGF-beta(1), activin-A ligands, and follistatin (a natural activin inhibitor), their type I and type II receptors (activin-like kinase[ALK]-1, ALK-5, ALK-4, TbetaRII, and ActRIIA/RIIB) and activation of signaling (via phosphorylated (p) Smad2), in the asthmatic airway after allergen challenge. METHODS: Immunohistochemistry was performed on bronchial biopsies from 15 mild atopic patients with asthma (median age, 25 years; median FEV(1)% predicted, 97%) at baseline and 24 hours after allergen inhalation. Functional effects of activin-A were evaluated by using cultured normal human bronchial epithelial (NHBE) cells. RESULTS: pSmad2(+) epithelial cells increased at 24 hours (P = .03), and pSmad2 was detected in submucosal cells. No modulation of activin-A, follistatin, or TGF-beta(1) expression was demonstrated. Activin receptor(+) cells increased after allergen challenge: ALK-4 in epithelium (P = .04) and submucosa (P = .04), and ActRIIA in epithelium (P = .01). The TGF-beta receptor ALK-5 expression was minimal in the submucosa at baseline and after challenge and was downregulated in the epithelium after challenge (P = .02), whereas ALK-1 and TbetaRII expression in the submucosa increased after allergen challenge (P = .03 and P = .004, respectively). ALK-1 and ALK-4 expression by T cells was increased after allergen challenge. Activin-A induced NHBE cell proliferation, was produced by NHBE cells in response to TNF-alpha, and downregulated TNF-alpha and IL-13-induced chemokine production by NHBE cells. CONCLUSION: Both TGF-beta and activin signaling pathways are activated on allergen provocation in asthma. Activin-A may contribute to resolution of inflammation.

Proteomic identification and functional validation of activins and bone morphogenetic protein 11 as candidate novel muscle mass regulators.

Myostatin is a secreted TGF-beta family member that controls skeletal muscle growth. Humans, cattle, and dogs carrying natural loss-of-function mutations in the myostatin gene and myostatin knockout mice exhibit significant increases in skeletal muscle mass. Treatment of adult mice with antimyostatin antibodies also resulted in significant muscle mass increases. However, myostatin-knockout mice that were treated with a soluble form of the activin type II receptor (ActRII) B increased their muscle mass by an additional 15-25%, indicating that there is at least one additional ligand, in addition to myostatin, that functions to limit muscle growth. Here, both soluble ActRII and -IIB fragment-crystallizable proteins were used to affinity purify their native ligands from human and mouse sera. Using mass spectrometry-based proteomics and in vitro binding assays we have identified and confirmed that a number of TGF-beta family members, including myostatin, activins-A, -B, and -AB, bone morphogenetic proteins (BMPs) -9, -10, and -11, bind to both ActRIIs. Many of these factors, such as BMPs-11, -9, and -10 were discovered in systemic circulation for the first time, indicating that these ligands may also act in an endocrine fashion. Using a promoter-specific gene reporter assay, we demonstrated that soluble ActRIIB fragment-crystallizable proteins can inhibit the canonical signaling induced by these ligands. In addition, like myostatin, these factors were able to block the differentiation of myoblast cells into myotubes. However, in addition to myostatin, only BMP-11, and activins-A, -B, and -AB could be blocked from inhibiting the myoblast-to-myotube differentiation with both soluble ActRIIs, thus implicating them as potential novel regulators of muscle growth.

Combined immuno-purification and detection of recombinant erythropoietins and activin receptor type II-Fc fusion proteins by isoelectric focusing for application in doping control.

Iso-electric focusing (IEF) was the first method established to discriminate endogenous and recombinant erythropoietins (rEPOs). It is still approved by the World Anti-Doping Agency (WADA) as an initial testing procedure to detect erythropoiesis stimulating agents (ESAs) in doping control samples. However EPO-Fc, one of the prohibited rEPOs designated by WADA, is not detectable with the actual IEF conditions. Other newly developed ESAs - luspatercept and sotatercept, both activin receptor type II-Fc fusion proteins (ActRII-Fc) - are also now prohibited and could be used in combination with rEPOs. Methods of identification of ActRII-Fc in blood by SAR/SDS-PAGE have been described, but not by IEF. Here we detail improvements in blood sample preparation and IEF analysis: A combined immuno-purification of EPOs and ActRII-Fc proteins in a single procedure, an appropriate isoforms separation for all proteins using new pre-loading and gel conditions, and a single detection of all rEPOs and ActRII-Fc proteins after successive incubation with anti-EPO and anti-ActRII antibodies. With these changes, distinctive profiles for all the ESAs were obtained by IEF. Therefore, IEF could be used as a screening method to detect a wide spectrum of prohibited ESAs in blood samples prior to specific confirmation for the identified rEPO or ActRII-Fc.

Detection of the Human Anti-ActRII Antibody Bimagrumab in Serum by Means of Affinity Purification, Tryptic Digestion, and LC-HRMS.

PURPOSE: Inhibitors of the ActRII signaling pathways represent promising therapeutics for the treatment of muscular diseases, but also pose risks as performance-enhancing agents in sports. Bimagrumab is a human anti-ActRII antibody which was found to increase muscle mass and function by blocking ActRII signaling. As it has considerable potential for being misused as doping agent in sports, the aim of this study was to develop a mass spectrometric detection assay for doping control serum samples. EXPERIMENTAL DESIGN: Within this study, a detection method for Bimagrumab in human serum was developed, which combines ammonium sulfate precipitation and affinity purification with proteolytic digestion and LC-HRMS. To facilitate the unambiguous identification of the diagnostic peptides, an orthogonal IM separation was additionally performed. RESULTS: The assay was successfully validated and the analysis of clinical samples demonstrated its fitness for purpose for an application in routine doping control analysis. CONCLUSIONS AND CLINICAL RELEVANCE: Although no myostatin inhibitors have obtained clinical approval yet, the proactive development of detection methods for emerging doping agents represents a key aspect of preventive doping research. The presented approach will expand the range of available tests for novel protein therapeutics and can readily be modified to include further target analytes.

A Phase I Study of the Anti-Activin Receptor-Like Kinase 1 (ALK-1) Monoclonal Antibody PF-03446962 in Patients with Advanced Solid Tumors.

PURPOSE: Objectives of this dose-finding study were to determine the MTD and recommended phase II dose (RP2D) of the first-in-class anti-activin receptor-like kinase 1 (ALK-1) monoclonal antibody PF-03446962, and assess safety and antitumor activity in patients with advanced solid tumors. EXPERIMENTAL DESIGN: This open-label, multicenter study was based on a 3+3 design. PF-03446962 was administered biweekly by intravenous infusion, at doses ranging from 0.5 to 15 mg/kg. RESULTS: Forty-four patients received treatment with PF-03446962. Dose-limiting toxicities observed during dose escalation included grade 3 increased amylase, grade 3/4 increased lipase, and grade 3/4 thrombocytopenia. The MTD was determined to be 10 mg/kg. The RP2D was set at 7 mg/kg for patients with advanced solid tumors, based on the observed safety, pharmacokinetics, and antitumor activity. The most-frequent treatment-related, all-grade adverse events included thrombocytopenia (20.5%), fatigue (15.9%), and nausea, increased amylase, and increased lipase (each 11.4%). Treatment-related telangiectasia was noted in 7% of patients, suggesting in vivo inhibition of the ALK-1 pathway. None of the deaths was deemed to be treatment-related. Three (6.8%) patients with advanced hepatocellular carcinoma, renal cell carcinoma, or non-small cell lung cancer achieved a partial response, and 12 (27.3%) patients had stable disease, across dose levels. Contrast-enhanced ultrasound analysis of tumor vascularity showed reduction in tumor perfusion in 2 patients with stable disease following treatment with PF-03446962. CONCLUSIONS: The clinical activity demonstrated in this study points to PF-03446962 as a novel approach to antiangiogenic therapy, with manageable safety profile and single-agent, antitumor activity in patients with advanced solid tumors. Clin Cancer Res; 22(9); 2146-54. ©2015 AACR.

ActRII blockade protects mice from cancer cachexia and prolongs survival in the presence of anti-cancer treatments.

BACKGROUND: Cachexia affects the majority of patients with advanced cancer and is associated with reduced treatment tolerance, response to therapy, quality of life, and life expectancy. Cachectic patients with advanced cancer often receive anti-cancer therapies against their specific cancer type as a standard of care, and whether specific ActRII inhibition is efficacious when combined with anti-cancer agents has not been elucidated yet. METHODS: In this study, we evaluated interactions between ActRII blockade and anti-cancer agents in CT-26 mouse colon cancer-induced cachexia model. CDD866 (murinized version of bimagrumab) is a neutralizing antibody against the activin receptor type II (ActRII) preventing binding of ligands such as myostatin and activin A, which are involved in cancer cachexia. CDD866 was evaluated in association with cisplatin as a standard cytotoxic agent or with everolimus, a molecular-targeted agent against mammalian target of rapamycin (mTOR). In the early studies, the treatment effect on cachexia was investigated, and in the additional studies, the treatment effect on progression of cancer and the associated cachexia was evaluated using body weight loss or tumor volume as interruption criteria. RESULTS: Cisplatin accelerated body weight loss and tended to exacerbate skeletal muscle loss in cachectic animals, likely due to some toxicity of this anti-cancer agent. Administration of CDD866 alone or in combination with cisplatin protected from skeletal muscle weight loss compared to animals receiving only cisplatin, corroborating that ActRII inhibition remains fully efficacious under cisplatin treatment. In contrast, everolimus treatment alone significantly protected the tumor-bearing mice against skeletal muscle weight loss caused by CT-26 tumor. CDD866 not only remains efficacious in the presence of everolimus but also showed a non-significant trend for an additive effect on reversing skeletal muscle weight loss. Importantly, both combination therapies slowed down time-to-progression. CONCLUSIONS: Anti-ActRII blockade is an effective intervention against cancer cachexia providing benefit even in the presence of anti-cancer therapies. Co-treatment comprising chemotherapies and ActRII inhibitors might constitute a promising new approach to alleviate chemotherapy- and cancer-related wasting conditions and extend survival rates in cachectic cancer patients.

An antibody blocking activin type II receptors induces strong skeletal muscle hypertrophy and protects from atrophy.

The myostatin/activin type II receptor (ActRII) pathway has been identified to be critical in regulating skeletal muscle size. Several other ligands, including GDF11 and the activins, signal through this pathway, suggesting that the ActRII receptors are major regulatory nodes in the regulation of muscle mass. We have developed a novel, human anti-ActRII antibody (bimagrumab, or BYM338) to prevent binding of ligands to the receptors and thus inhibit downstream signaling. BYM338 enhances differentiation of primary human skeletal myoblasts and counteracts the inhibition of differentiation induced by myostatin or activin A. BYM338 prevents myostatin- or activin A-induced atrophy through inhibition of Smad2/3 phosphorylation, thus sparing the myosin heavy chain from degradation. BYM338 dramatically increases skeletal muscle mass in mice, beyond sole inhibition of myostatin, detected by comparing the antibody with a myostatin inhibitor. A mouse version of the antibody induces enhanced muscle hypertrophy in myostatin mutant mice, further confirming a beneficial effect on muscle growth beyond myostatin inhibition alone through blockade of ActRII ligands. BYM338 protects muscles from glucocorticoid-induced atrophy and weakness via prevention of muscle and tetanic force losses. These data highlight the compelling therapeutic potential of BYM338 for the treatment of skeletal muscle atrophy and weakness in multiple settings.

Blockade of the activin receptor IIb activates functional brown adipogenesis and thermogenesis by inducing mitochondrial oxidative metabolism.

Brown adipose tissue (BAT) is a key tissue for energy expenditure via fat and glucose oxidation for thermogenesis. In this study, we demonstrate that the myostatin/activin receptor IIB (ActRIIB) pathway, which serves as an important negative regulator of muscle growth, is also a negative regulator of brown adipocyte differentiation. In parallel to the anticipated hypertrophy of skeletal muscle, the pharmacological inhibition of ActRIIB in mice, using a neutralizing antibody, increases the amount of BAT without directly affecting white adipose tissue. Mechanistically, inhibition of ActRIIB inhibits Smad3 signaling and activates the expression of myoglobin and PGC-1 coregulators in brown adipocytes. Consequently, ActRIIB blockade in brown adipose tissue enhances mitochondrial function and uncoupled respiration, translating into beneficial functional consequences, including enhanced cold tolerance and increased energy expenditure. Importantly, ActRIIB inhibition enhanced energy expenditure only at ambient temperature or in the cold and not at thermoneutrality, where nonshivering thermogenesis is minimal, strongly suggesting that brown fat activation plays a prominent role in the metabolic actions of ActRIIB inhibition.

Effects of dilution and prolonged storage with preservative in a polyethylene container on Bevacizumab (Avastin™) for topical delivery as a nasal spray in anti-hereditary hemorrhagic telangiectasia and related therapies.

BACKGROUND: Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular dysplasia and severe, recurrent epistaxis is a common clinical phenotype associated with HHT. An intranasal treatment regime of diluted Avastin™ (Bevacizumab; recombinant humanized anti-vascular epithelial growth factor immunoglobin G1) using apulsatile nasal irrigator has proven efficacious in clinical practice. However, concerns regarding the stability of Avastin™ following dilution and prolonged storage in standard containers used for drug delivery, such as polyethylene bottles, have so far prevented a more widespread clinical use. Compatibility with the preservative benzalkonium chloride was also unknown. OBJECTIVE: This study aimed at determining, whether dilution, prolonged refrigerated storage and the presence of the preservative benzalkonium chloride - as required for novel Avastin™ formulations - affected the biochemical and electrochemical properties of the drug. METHODS: We performed a detailed biochemical and electrochemical analysis of Avastin™, including native and sodium dodecyl sulfate polyacrylamide gel electrophoresis, enzyme-linked immunosorbent assay and isoelectric focusing. RESULTS: We did not detect any evidence of degeneration or aggregation following dilution and prolonged, refrigerated storage or from the presence of benzalkonium chloride. All biochemical and electrochemical properties of Avastin™ after dilution and prolonged, refrigerated storage were undistinguishable from control. CONCLUSIONS: Our data provide important insight into the stability of Avastin™ and allow the consideration of novel Avastin™ formulations, including its use in a metered-dose nasal spray for the treatment of HHT and other applications.