Weiss, Clifford R.

Abstract Hereditary hemorrhagic telangiectasia (HHT) results in recurrent severe epistaxis, chronic gastrointestinal bleeding, and other morbid manifestations. Pomalidomide was recently demonstrated to be efficacious for bleeding in HHT in the landmark PATH-HHT trial. Given that the vascular remodeling that results in bleeding improvement may require several months, characteristics associated with treatment response would be invaluable to plan treatment. Using data from PATH-HHT (NCT03910244), we identified characteristics associated with change from baseline in Epistaxis Severity Score (ESS; a well-validated 10-point HHT bleeding scale and the trial’s primary end point) using multivariable-adjusted repeated-measures models. Characteristics associated with a better response to pomalidomide at weeks 16 to 24 of the trial included a higher (more severe) baseline ESS (change from baseline, −0.76 [95% confidence interval (CI), −0.99 to −0.54] points per 1-point higher baseline score, P< .001) and concomitant antifibrinolytic therapy (−0.73 [95% CI, −1.48 to 0.01] vs no therapy, P = .05). Characteristics associated with a less robust response were older age (0.29 [95% CI, 0.05-0.53] per 10 years older, P = .02) and underlying ACVRL1 germ line mutation (0.62 [95% CI, −0.04 to 1.27] vs ENG, SMAD4, or mutation not known, P = .06]. Characteristics notably associated with placebo response (placebo effect) were patient-reported outcome measures, such that those experiencing more severe disease at baseline had less placebo effect. In conclusion, several baseline patient and disease characteristics were associated with pomalidomide response, findings that may help guide patient selection for the use of pomalidomide in HHT. This trial was registered at www.Clinicaltrials.gov as NCT03910244.

Introduction Hereditary hemorrhagic telangiectasia (HHT), the second most common bleeding disorder worldwide, affects 1 in 5000 people and is characterized by extensive formation of telangiectasia and arteriovenous malformations (AVM) in mucosa, lung, brain, and liver. The primary clinical manifestation is recurrent, often severe epistaxis which commonly results in iron deficiency anemia, emergency room visits, hospitalizations, and reduced quality of life (QOL). Though non-randomized and/or underpowered studies have suggested that systemic bevacizumab or thalidomide may be effective in treating HHT, there have been no pivotal studies and therefore no FDA or EMA approved therapies. Methods PATH-HHT was an NHLBI-funded, randomized, placebo-controlled clinical trial conducted at 13 centers in the US to determine the safety and efficacy of pomalidomide for bleeding in HHT. Pomalidomide was supplied by Celgene and Bristol Myers Squibb. Patients were randomized in a 2:1 ratio to receive pomalidomide 4 mg daily or matching placebo for 6 months. Dose reductions were allowed for toxicity. The primary endpoint was the change in the Epistaxis Severity Score (ESS), a well-validated bleeding score in HHT, from baseline (randomization) to the end of the six-month treatment period, analyzed using a mixed model for repeated measures with adjustment for baseline value, center, treatment, visit, and treatment by visit interaction. Key secondary endpoints included 1) change in the average daily self-reported epistaxis duration from the four weeks preceding the baseline visit to weeks 20-24 of treatment, 2) amount of parenteral iron infused or blood transfused, and 3) change in QOL measurements, including an HHT-specific QOL score. Results PATH-HHT opened in November 2019 and was closed to enrollment by the NHLBI in June 2023 after a planned 75% interim analysis met a prespecified threshold for efficacy. A total of 144 patients were randomized and treated (95 pomalidomide, 49 placebo). Early study discontinuation was 25% in pomalidomide: 14% AE, 11% withdrawn, 1 unrelated death, compared with placebo (4% withdrawn). Across groups, 8% were terminated after 12 weeks for early study closure. Participants included 48% females, 11% non-white race; mean (± SD) age was 58.8±12.2 years. The mean ESS at baseline was 5.0±1.5 (4.9 pomalidomide, 5.2 placebo), consistent with moderate to severe epistaxis. At 24 weeks, the ESS in patients treated with pomalidomide decreased by a mean [95% CI] of -1.84 [-2.24, -1.44] and in the placebo group decreased by -0.89 [-1.39, -0.39] (mean difference -0.95 [-1.58, -0.32], p = 0.003) (Figure, Panel A). Difference between groups was apparent by 12 weeks (mean difference -0.52, 95% CI [-1.04, -0.01], p = 0.045). The HHT-specific QOL score, which ranges from 0 to 16 with higher scores indicating more limitations, also decreased more in the pomalidomide (mean -2.6, 95% CI [-3.3, -1.9]) vs the placebo group at 24 weeks (mean -1.2, 95% CI [-2.1, -0.3], p = 0.015) (Figure, Panel B). Adverse events that occurred more in the pomalidomide group included mild to moderate neutropenia (45% vs. 10%), constipation/diarrhea (60% vs. 37%), and rash (36% vs. 10%). Venous thrombosis occurred in 2% of patients in each group. Conclusion PATH-HHT is the largest and the first adequately powered, randomized trial of systemic therapy in HHT. The study demonstrated a significant and highly clinically relevant reduction in epistaxis in pomalidomide-treated patients as well as an improvement in the HHT-specific QOL score. Pomalidomide may offer a novel approach to management of HHT. Since plasma was collected from patients in this study before and at the end of treatment, additional studies may identify biomarkers predicting pomalidomide responses.

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<11, N=104) had an increase in mean Hgb from 8.6 g/dL to 11.9 g/dL at 3 months (P<0.0001) up to 12.5 g/dL at 12 months (P<0.0001) (Table 2, Figure 1). For patients with epistaxis as an indication for treatment (N=119), mean ESS dropped from 6.8 at baseline to ≤3.5 on treatment (P<0.0001) (Table 2, Figure 2). In patients requiring RBC transfusion prior to bevacizumab (N=81), transfusion requirements decreased from a median of 8 units in the 6 months before treatment to a median of 0 units in the first 6 months after treatment (P<0.0001); similarly, in patients requiring iron infusion prior to bevacizumab (N=99), requirements decreased from a median of 4 infusions to 2 infusions (P<0.0001) (Table 2). RBC transfusion and iron infusion requirements continued to improve with ongoing bevacizumab treatment (Table 2) and improvement occurred regardless of baseline bleeding severity; Figure 3 illustrates the dramatic reduction in RBC transfusion and iron infusion requirements in a severe patient sub-cohort. Overall, compared with pretreatment, RBC transfusion and iron infusion requirements decreased by 86% and 66%, respectively, on bevacizumab. On subgroup analysis by underlying mutation (ENG vs. ACVRL1), there were no significant differences in baseline parameters or bevacizumab response. Bevacizumab was well-tolerated; TEAEs felt to be likely or possibly related to bevacizumab occurred in 36% of patients (Table 3), with new or worsened hypertension (16%) and fatigue (9%) most common. No patient developed venous thromboembolism on bevacizumab. Only 5 patients (4%) discontinued bevacizumab for TEAEs and only 3 patients (2%) discontinued bevacizumab for lack of effectiveness. 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.