Dose - response relationship of bevacizumab in hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia: from signaling insights to therapeutic advances

Hereditary hemorrhagic telangiectsia (HHT) is an inherited vascular disorder with highly variable expressivity, affecting up to 1 in 5,000 individuals. This disease is characterized by small arteriovenous malformations (AVMs) in mucocutaneous areas (telangiectases) and larger visceral AVMs in the lungs, liver, and brain. HHT is caused by loss-of-function mutations in the BMP9-10/ENG/ALK1/SMAD4 signaling pathway. This Review presents up-to-date insights on this mutated signaling pathway and its crosstalk with proangiogenic pathways, in particular the VEGF pathway, that has allowed the repurposing of new drugs for HHT treatment. However, despite the substantial benefits of these new treatments in terms of alleviating symptom severity, this not-so-uncommon bleeding disorder still currently lacks any FDA- or European Medicines Agency-approved (EMA-approved) therapies.

Case report: Diagnosis of hereditary hemorrhagic telangiectasia (Osler Weber Rendu Syndrome) in a 23-year-old male presented with anemia and thrombocytopenia and its response to bevacizumab

Osler Weber Rendu Syndrome (OWS) is characterized by the development of abnormally dilated blood vessels, which manifest as arteriovenous shunts (pulmonary, gastrointestinal, hepatic, and cerebral) and mucocutaneous telangiectasias (lips, tongue, and fingertips). It is an autosomal dominant disease with a defect in transforming growth factor beta superfamily genes. This defect results in increased angiogenesis and disruption of vessel wall integrity. The disease remains underreported, with occasional history of recurrent epistaxis, iron deficiency anemia, and gastrointestinal bleeding in moderate to severe cases. Diagnosis is based on clinical presentation and confirmed by genetic testing. Various local (nasal saline, air humidification, laser ablation, and electric cauterization for epistaxis and endoscopic Argon Plasma Coagulation-APC for active GI bleeding), surgical, and systemic (tranexamic acid and antiangiogenic agents like bevacizumab and thalidomide) treatment options are used depending upon disease severity. Here, we present a case with recurrent gastrointestinal bleeding refractory to endoscopic APC ablation and thalidomide and severe symptomatic anemia requiring multiple packed red cell transfusions. The patient was ultimately started on bevacizumab, to which he had a good response and has remained in remission for 8 months as of now. This case emphasizes the need to have a low threshold of suspicion to diagnose HHT and start targeted therapy like bevacizumab early on in moderate to severe cases of HHT rather than just relying on temporizing palliative measures like ablation, cauterization, and tranexamic acid.

Hereditary Hemorrhagic Telangiectasia: The Convergence of Genotype, Phenotype, and Imaging in Modern Diagnosis and Management of a Multisystem Disease

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disease that manifests as vascular malformations in the brain, lung, liver, gastrointestinal tract, nasal mucosa, and skin. Diagnosis and management of HHT is guided in large part by imaging studies, making it a condition with which the radiology community needs familiarity. Proper screening and care lead to improved morbidity and mortality in patients with HHT. International guidelines were recently updated and form the basis for a detailed discussion of the role of imaging and image-guided therapy in HHT. © RSNA, 2021 Online supplemental material is available for this article.

High output cardiac failure in 3 patients with hereditary hemorrhagic telangiectasia and hepatic vascular malformations, evaluation of treatment

BACKGROUND

This report addresses how patients with hereditary hemorrhagic telangiectasia (HHT) and high output cardiac failure (HOCF) due to hepatic vascular malformations, should be evaluated and could be treated. HHT is a genetic disorder, leading to vascular abnormalities with potentially serious clinical implications. In the liver, arteriovenous malformations occur in more than 70% of patients, but only about 8% present clinical symptoms such as HOCF with pulmonary hypertension and less commonly portal hypertension, biliary ischemia and hepatic encephalopathy.

RESULTS

Three female patients with HHT type 2 and HOCF caused by severe arteriovenous malformations in the liver are presented in this case series. The patients were seen at the HHT-Centre at Odense University Hospital. Treatment with either orthotopic liver transplantation (one patient) or bevacizumab (two patients) was initiated. All patients experienced marked symptom relief and objective improvement. New York Heart Association-class were improved, ascites, peripheral edema and hence diuretic treatment was markedly reduced or discontinued in all three patients. Bevacizumab also resulted in notable effects on epistaxis and anemia.

CONCLUSION

Our findings substantiate the importance of identification of symptomatic arteriovenous malformations in the liver in patients with HHT. Bevacizumab may possibly, as suggested in this case series and supported by previous case studies, postpone the time to orthotopic liver transplantation or even make it unnecessary. Bevacizumab represents a promising new treatment option, which should be investigated further in clinical trials.

Influence of Antigen Mass on the Pharmacokinetics of Therapeutic Antibodies in Humans

Therapeutic antibodies are increasingly used to treat various diseases, including neoplasms and chronic inflammatory diseases. Antibodies exhibit complex pharmacokinetic properties, notably owing to the influence of antigen mass, i.e. the amount of antigenic targets to which the monoclonal antibody binds specifically. This review focuses on the influence of antigen mass on the pharmacokinetics of therapeutic antibodies quantified by pharmacokinetic modelling in humans. Out of 159 pharmacokinetic studies, 85 reported an influence of antigen mass. This influence led to non-linear elimination decay in 50 publications, which was described using target-mediated drug disposition or derived models, as quasi-steady-state, irreversible binding and Michaelis-Menten models. In 35 publications, the pharmacokinetics was apparently linear and the influence of antigen mass was described as a covariate of pharmacokinetic parameters. If some reported covariates, such as the circulating antigen level or tumour size, are likely to be correlated to antigen mass, others, such as disease activity or disease type, may contain little information on the amount of antigenic targets. In some cases, antigen targets exist in different forms, notably in the circulation and expressed at the cell surface. The influence of antigen mass should be soundly described during the early clinical phases of drug development. To maximise therapeutic efficacy, sufficient antibody doses should be administered to ensure the saturation of antigen targets by therapeutic antibodies in all patients. If necessary, antigen mass should be taken into account in routine clinical practice.

[Determining the dose to be injected in the first clinical trials with monoclonal antibodies: not so easy!]

Monoclonal antibodies are a therapeutic tool frequently used in oncology, as they allow the specific targeting of molecules expressed by cancer cells and, in most cases, induce minimal toxic effects on healthy tissues. Because monoclonal antibodies frequently lack significant toxicity and are not associated to a direct relationship between dose and effect, the methods of clinical development traditionally used for chemotherapy agents are scarcely useful for this class of drugs. In addition, no consensus exists on the definition of parameters different from toxicity that could assist the process of dose selection of monoclonal antibody in early clinical trials.

Pazopanib may reduce bleeding in hereditary hemorrhagic telangiectasia

Pazopanib (Votrient) is an orally administered tyrosine kinase inhibitor that blocks VEGF receptors potentially serving as anti-angiogenic treatment for hereditary hemorrhagic telangiectasia (HHT). We report a prospective, multi-center, open-label, dose-escalating study [50 mg, 100 mg, 200 mg, and 400 mg], designed as a proof-of-concept study to demonstrate efficacy of pazopanib on HHT-related bleeding, and to measure safety. Patients, recruited at 5 HHT Centers, required ≥ 2 Curacao criteria AND [anemia OR severe epistaxis with iron deficiency]. Co-primary outcomes, hemoglobin (Hgb) and epistaxis severity, were measured during and after treatment, and compared to baseline. Safety monitoring occurred every 1.5 weeks. Seven patients were treated with 50 mg pazopanib daily. Six/seven showed at least 50% decrease in epistaxis duration relative to baseline at some point during study; 3 showed at least 50% decrease in duration during Weeks 11 and 12. Six patients showed a decrease in ESS of > 0.71 (MID) relative to baseline at some point during study; 3/6 showed a sustained improvement. Four patients showed > 2 gm improvement in Hgb relative to baseline at one or more points during study. Health-related QOL scores improved on all SF-36 domains at Week 6 and/or Week 12, except general health (unchanged). There were 19 adverse events (AE) including one severe AE (elevated LFTs, withdrawn from dosing at 43 days); with no serious AE. In conclusion, we observed an improvement in Hgb and/or epistaxis in all treated patients. This occurred at a dose much lower than typically used for oncologic indications, with no serious AE. Further studies of pazopanib efficacy are warranted.

Strategies for clinical development of monoclonal antibodies beyond first-in-human trials: tested doses and rationale for dose selection

BACKGROUND

Our previous survey on first-in-human trials (FIHT) of monoclonal antibodies (mAbs) showed that, due to their limited toxicity, the recommended phase II dose (RP2D) was only tentatively defined.

METHODS

We identified, by MEDLINE search, articles on single-agent trials of mAbs with an FIHT included in our previous survey. For each mAb, we examined tested dose(s) and dose selection rationale in non-FIHTs (NFIHTs). We also assessed the correlation between doses tested in the registration trials (RTs) of all FDA-approved mAbs and the corresponding FIHT results.

RESULTS

In the 37 dose-escalation NFIHTs, the RP2D indication was still poorly defined. In phase II-III NFIHTs (n=103 on 37 mAbs), the FIHT RP2D was the only dose tested for five mAbs. For 16 mAbs, only doses different from the FIHT RP2D or the maximum administered dose (MAD) were tested and the dose selection rationale infrequently indicated. In the 60 RTs on 27 FDA-approved mAbs with available FIHT, the FIHT RP2D was tested only for two mAbs, and RT doses were much lower than the FIHT MAD.

CONCLUSIONS

The rationale beyond dose selection in phase II and III trials of mAbs is often unclear in published articles and not based on FIHT data.

Intra-venous bevacizumab in hereditary hemorrhagic telangiectasia (HHT): A retrospective study of 46 patients

Background

Bevacizumab, an anti-VEGF monoclonal antibody, has recently emerged as a new option for severe forms of hereditary hemorrhagic telangiectasia (HHT). Its utilization in this orphan disease has rapidly spread despite the lack of randomized trials and international guidelines. The objective of this study is to report the main clinical data (baseline characteristics, dose schedule, efficacy, adverse events and deaths) of HHT patients treated by intravenous bevacizumab in France.

Methods

Retrospective observational study of HHT patients treated with bevacizumab for a severe form of the disease in the 14 centers of the French HHT network.

Results

Forty-six patients (median age: 68 years) were treated between March 2009 and May 2015. Ten patients were treated for high output cardiac failure, 20 patients for severe hemorrhages and 16 for both indications. The standard protocol (6 infusions of 5mg/kg every 2 weeks) was initially used in 89% of the cases but diverse strategies were subsequently applied. A clinical improvement was noted by the referent physician for 74% of the patients with a median effect’s duration of 6 months. Wound healing complications led to 2 amputations. Arthralgia/arthritis and arterial hypertension occurred in 5 patients each. One third of the patients were dead at the time of the final update, coherently with age and the poor prognosis of these highly symptomatic patients.

Conclusion

Intravenous bevacizumab seems to provide a clinical benefice in severe HHT patients. Precautions concerning wound healing and vascular pathologies must be respected. Prospective double blinded versus placebo trials are needed.

Deregulated TGF-β/BMP Signaling in Vascular Malformations

Correct organization of the vascular tree requires the balanced activities of several signaling pathways that regulate tubulogenesis and vascular branching, elongation, and pruning. When this balance is lost, the vessels can be malformed and fragile, and they can lose arteriovenous differentiation. In this review, we concentrate on the transforming growth factor (TGF)-β/bone morphogenetic protein (BMP) pathway, which is one of the most important and complex signaling systems in vascular development. Inactivation of these pathways can lead to altered vascular organization in the embryo. In addition, many vascular malformations are related to deregulation of TGF-β/BMP signaling. Here, we focus on two of the most studied vascular malformations that are induced by deregulation of TGF-β/BMP signaling: hereditary hemorrhagic telangiectasia (HHT) and cerebral cavernous malformation (CCM). The first of these is related to loss-of-function mutation of the TGF-β/BMP receptor complex and the second to increased signaling sensitivity to TGF-β/BMP. In this review, we discuss the potential therapeutic targets against these vascular malformations identified so far, as well as their basis in general mechanisms of vascular development and stability.

Nintedanib as a novel treatment option in hereditary haemorrhagic telangiectasia

A 70-year-old patient with known hereditary haemorrhagictelangiectasia (HHT) was seen regularly in our outpatient clinic. He underwent multiple therapeutical interventions, including both surgical and medical, for the treatment of recurrent epistaxis without sustained success. Due to a concurrent diagnosis of idiopathic pulmonary fibrosis, treatment with the tyrosine kinase inhibitor nintedanib was initiated, after which point the patient reported a dramatic and unanticipated improvement in his epistaxis and skin telangiectasia. On the basis of this case report, we propose that nintedanib may be a potential treatment option for refractory epistaxis in HHT.

Intravenous Bevacizumab Therapy in a Patient with Hereditary Hemorrhagic Telangiectasia, ENG E137K, Alcoholic Cirrhosis, and Portal Hypertension

Intravenous bevacizumab decreased mucosal bleeding in some patients with hereditary hemorrhagic telangiectasia (HHT). We treated a 47-year-old male who had HHT, severe epistaxis, and gastrointestinal bleeding, alcoholic cirrhosis, and portal hypertension with intravenous bevacizumab 2.5 mg/kg every 2 weeks. We tabulated these measures weekly during weeks 1–33 (no bevacizumab); 34–57 (bevacizumab); and 58–97 (no bevacizumab): hemoglobin (Hb) levels; platelet counts; units of transfused packed erythrocytes (PRBC units); and quantities of iron infused as iron dextran to support erythropoiesis. We performed univariate and multivariable analyses. We sequenced his ENG and ACVRL1 genes. Epistaxis and melena decreased markedly during bevacizumab treatment. He reported no adverse effects due to bevacizumab. Mean weekly Hb levels were significantly higher and mean weekly PRBC units and quantities of intravenous iron were significantly lower during bevacizumab treatment. We performed a multiple regression on weekly Hb levels using these independent variables: bevacizumab treatment (dichotomous); weekly platelet counts; weekly PRBC units; and weekly quantities of intravenous iron. There was 1 positive association: (bevacizumab treatment; p = 0.0046) and 1 negative association (PRBC units; p = 0.0004). This patient had the novel ENG mutation E137K (exon 4; c.409G→A). Intravenous bevacizumab treatment 2.5 mg/kg every 2 weeks for 24 weeks was well-tolerated by a patient with HHT due to ENG E137K and was associated with higher weekly Hb levels and fewer weekly PRBC units.

Targeting BMP signalling in cardiovascular disease and anaemia

Bone morphogenetic proteins (BMPs) and their receptors, known to be essential regulators of embryonic patterning and organogenesis, are also critical for the regulation of cardiovascular structure and function. In addition to their contributions to syndromic disorders including heart and vascular development, BMP signalling is increasingly recognized for its influence on endocrine-like functions in postnatal cardiovascular and metabolic homeostasis. In this Review, we discuss several critical and novel aspects of BMP signalling in cardiovascular health and disease, which highlight the cell-specific and context-specific nature of BMP signalling. Based on advancing knowledge of the physiological roles and regulation of BMP signalling, we indicate opportunities for therapeutic intervention in a range of cardiovascular conditions including atherosclerosis and pulmonary arterial hypertension, as well as for anaemia of inflammation. Depending on the context and the repertoire of ligands and receptors involved in specific disease processes, the selective inhibition or enhancement of signalling via particular BMP ligands (such as in atherosclerosis and pulmonary arterial hypertension, respectively) might be beneficial. The development of selective small molecule antagonists of BMP receptors, and the identification of ligands selective for BMP receptor complexes expressed in the vasculature provide the most immediate opportunities for new therapies.