Hereditary hemorrhagic telangiectasia (HHT) is an angiogenesis-dependent genetic disorder characterized by small vascular malformations (telangiectasia) in the skin and mucosal linings, and symptoms including nosebleeds, gastrointestinal bleeding, and iron-deficiency anemia. Internal organs can harbor malformations in larger vessels, called arteriovenous malformations (AVMs), which can result in serious bleeding episodes. HHT is a disorder of unbalanced angiogenesis. Patients have elevated plasma and tissue expression of vascular endothelial growth factor (VEGF)—the primary mediator of angiogenesis—and transforming growth factor-beta (TGF-b), which stimulates production of VEGF.
In a letter in the May 14, 2009 issue of the New England Journal of Medicine, Prithviraj Bose, M.D., and colleagues from the University of Oklahoma Health Science Center reported on the treatment of a 42-year old man with HHT using the antiangiogenic drug bevacizumab (Avastin), a humanized monoclonal antibody designed to neutralize VEGF. After treatment with 4000 mg of intravenous iron over a 6-month period, the patient received 4 cycles of bevacizumab every 2 weeks at a dose of 10 mg/kg for the first 2 cycles, and 5 mg/kg for the second two. After bevacizumab therapy was initiated, the patient’s nosebleeds decreased from 3-4 episodes per day pre-therapy to only 1-2 episodes per week. After completion of 12 weeks of treatment, the number of nosebleeds stabilized at 1-2 per day, but were of much shorter duration than pre-treatment (~10 min. vs. 30-45 min.). Serum ferritin (iron) levels increased from an average of 33 ng per mL in the 6 months prior to bevacizumab treatment to an average of 315 ng per mL in the 9 months after treatment was started. One-year follow-up of the patient indicates that the beneficial effects of bevacizumab in HHT may require maintenance therapy.
Two other cases of bevacizumab use in HHT have been reported. A patient with the condition receiving the agent for malignant mesothelioma had a dramatic reduction in GI bleeding due to AVMs; a second patient with severe hepatic HHT who received 6 courses of bevacizumab no longer required liver transplant and was doing well 6 months after completing treatment.
It should be noted that bevacizumab is not approved for the treatment of HHT or mesothelioma, and the cases described in these research reports represent off-label use of the agent. For more information on HHT, visit www.HHT.org.