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Introduction : Hereditary hemorrhagic telangiectasia (HHT, Osler-Weber-Rendu disease) is a rare hereditary multisystem vascular disease of disordered angiogenesis. Pathologic elevations in vascular endothelial growth factor (VEGF) result in fragile, abnormal vessels in nasal and gastrointestinal (GI) mucosa causing recurrent epistaxis, chronic GI bleeding, and anemia that is often transfusion-dependent. Bevacizumab is a monoclonal IgG1 antibody that neutralizes circulating VEGF and is a potential targeted anti-angiogenic treatment in HHT, which has no FDA-approved therapy. Data for use of intravenous (IV) bevacizumab in HHT is currently limited to case reports and small single-center retrospective case series. The International HHT Intravenous Bevacizumab Investigative Team study of Bleeding (InHIBIT-Bleed) is an international collaboration of HHT Centers seeking to more definitively describe the safety and effectiveness of systemic bevacizumab to treat chronic bleeding and anemia in HHT. Methods : The following data was retrospectively collected at each participating center for all HHT patients treated for at least 3 months with off-label systemic bevacizumab for chronic bleeding: demographics, baseline HHT characteristics, epistaxis severity score (ESS, a validated 10-point scale to evaluate epistaxis in HHT), bevacizumab dosing, treatment-emergent adverse events (TEAEs), hemoglobin (Hgb), red blood cell (RBC) transfusions, and IV iron infusions. Hgb and ESS at baseline were compared with post-bevacizumab values at 3, 6, 9, and 12 months with the paired t-test. RBC transfusion and iron infusion requirements before and after bevacizumab treatment were compared with the Wilcoxon signed rank test. Results : 140 HHT patients were treated with IV bevacizumab for chronic bleeding for a median of 23 (range, 3-96) months with a median of 12 (range, 2-74) total infusions. Bevacizumab was dosed at 5 mg/kg every 2 weeks for the first 2 months, then monthly for 4 months; following this, maintenance dosing practices varied depending on center. Baseline patient characteristics are given in Table 1. After bevacizumab initiation, patients with baseline anemia (Hgb Conclusions : We present results of IV bevacizumab treatment of chronic bleeding and anemia in a large cohort of 140 HHT patients, demonstrating that bevacizumab was highly effective, with an improvement in mean Hgb of 3.9 g/dL, dramatic reduction in ESS, and decrease in RBC transfusion and iron infusion requirements by 86% and 66%, respectively. Effectiveness was maintained over time. Safety analysis included a total of 194 patient-years of IV bevacizumab administration to HHT patients and had low TEAE rates with only 4% discontinuing treatment due to TEAEs. Disclosures Al-Samkari: Agios: Consultancy, Research Funding; Moderna: Consultancy; Dova: Consultancy, Research Funding. Kuter:Caremark: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Dova: Consultancy, Honoraria; Kyowa-Kirin: Consultancy, Honoraria; Zafgen: Consultancy, Honoraria; Platelet Disorder Support Association: Consultancy, Honoraria; Shinogi: Consultancy, Honoraria; Up-to-Date: Consultancy, Honoraria, Patents & Royalties: 3 Up-to-Date chapters; Agios: Consultancy, Honoraria, Research Funding; Platelet Disorder Support Association: Consultancy, Honoraria; Bristol Myers Squibb (BMS): Consultancy, Honoraria, Research Funding; Caremark: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Merck Sharp Dohme: Consultancy, Honoraria; Merck Sharp Dohme: Consultancy, Honoraria; Daiichi Sankyo: Consultancy, Honoraria; Argenx: Consultancy, Honoraria, Research Funding; Bristol Myers Squibb (BMS): Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Kezar: Research Funding; Shire: Consultancy, Honoraria; Kezar: Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Agios: Consultancy, Honoraria, Research Funding; Principia: Consultancy, Honoraria, Research Funding; Zafgen: Consultancy, Honoraria; Alnylam: Consultancy, Honoraria, Research Funding; Actelion (Syntimmune): Consultancy, Honoraria, Research Funding; Actelion (Syntimmune): Consultancy, Honoraria, Research Funding; Principia: Consultancy, Honoraria, Research Funding; Protalex: Consultancy, Honoraria, Research Funding; Protalix: Consultancy, Honoraria; Protalix: Consultancy, Honoraria; Rigel: Consultancy, Honoraria, Research Funding; Rigel: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; UCB: Consultancy, Honoraria; Takeda (Bioverativ): Consultancy, Honoraria, Research Funding; Up-to-Date: Consultancy, Honoraria, Patents & Royalties: 3 Up-to-Date chapters; UCB: Consultancy, Honoraria; Kyowa-Kirin: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Genzyme: Consultancy, Honoraria; Genzyme: Consultancy, Honoraria; Protalex: Consultancy, Honoraria, Research Funding; Argenx: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Shinogi: Consultancy, Honoraria; Takeda (Bioverativ): Consultancy, Honoraria, Research Funding; Shire: Consultancy, Honoraria; Alnylam: Consultancy, Honoraria, Research Funding; Dova: Consultancy, Honoraria; Daiichi Sankyo: Consultancy, Honoraria; Momenta: Consultancy, Honoraria; Momenta: Consultancy, Honoraria. OffLabel Disclosure: The presentation will discuss off-label use of systemic bevacizumab for the treatment of chronic bleeding and anemia in hereditary hemorrhagic telangiectasia.

The Hereditary Hemorrhagic Telangiectasia (HHT) is a rare autosomal dominant vascular dysplasia that affects 1-5000 individuals worldwide. Is characterized by fragile mucocutaneous telangiectasia and vascular malformations in organs such as brain, lungs, liver and the gastrointestinal tract. Nose and gastrointestinal bleeding are remarkable, leading to frequent iron deficiency anemia (IDA) or life threatening bleeding episodes. Venous thromboembolic events (VTE) in HHT are probably more frequent than general population due to high plasmatic levels of FVIII specially in clinical conditions like long time immobilization due to brain abscesses or severe anemia. Additionally, in those patients with pulmonary fistula, the thromboembolic events can produce paradoxal strokes. On the other hand, almost all HHT medical treatments usually used to treat HHT related bleeding could produce thromboembolic disease. Anticoagulation (ACO) in this bleeding condition is a challenge, nevertheless, almost 50% can tolerate it well. Objective: To report the incidence of VTE in the HHT population. Methods: Ambispective cohort of adult based on the Institutional Registry of HHT. VTE was defined as the first episode of pulmonary embolism (PE), deep venous thrombosis (VTE) or thrombosis in the fistula sac or the progression of a prior event after its first 48 hs despite anticoagulation. Result: Over 524 patients 394 adults with HHT confirmed by Curazao criteria or positive genetic test and complete data were included. There were 18 VTE events 4.6% (CI95% 2.7-6.8%), 9 DVT (2.3% IC95% 1.2-4.4%) and 3 PE (0.7% IC95% 0.13-2%). The female gender represents 72%. The median age at the event was 67 years (IIQ 25-75% 56-73). Five patients (27%) were on ACO prior to the event, mainly for atrial fibrillation, and 3(18%) suffered a previous VTE. The most frequent risk factors were recent hospitalization (44%) and iron deficiency anemia (44%), immobility (33%), recent surgery (18%), as well as cancer (5%) and recent travel (5%) patient each.Fifteen (83%) patients received ACO, 10(55%) received LMH followed by acenocumarol, 3(30%) of which had to be stopped due to nose or gastrointestinal bleeding.In 5 (27%) a cava vein filter were inserted, of which 3 are under anticoagulation therapy. Conclusion: VTE incidence in our study was significantly higher than reported in general population at similar age. However, the inclusion of more symptomatic and serious HHT patients could be selection bias. The low number of patients, may influence the results. IDA and hospitalization were the most important associated conditions. Most patients tolerated well the anticoagulation therapy. Disclosures No relevant conflicts of interest to declare.