Bone Marrow Cancer Drug Shows Success in Treating Rare Blood Disorder

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A clinical trial supported by NIH was stopped early after researchers found sufficient evidence that a drug used to treat bone marrow cancer and Kaposi sarcoma is safe and effective in treating hereditary hemorrhagic telangiectasia (HHT), a rare bleeding disorder that affects 1 in 5,000 people worldwide.

The trial results, which are published in the New England Journal of Medicine, detail how patients with HHT given the drug, called pomalidomide, experienced a significant reduction in the severity of nosebleeds and needed fewer of the blood transfusions and iron infusions that HHT often demands.

“Finding a therapeutic agent that works in a rare disorder is highly uncommon, so this is a real success story,” said Dr. Andrei Kindzelski of NHLBI. “Before our trial, there was no reliable therapeutic to treat people with HHT. This discovery will give people who suffer with this disease a positive outlook and better quality of life.”

HHT, also known as Osler-Weber-Rendu Syndrome, is characterized by serious defects in the way the body’s blood vessels form. Instead of growing linearly, they become unusually tangled and twisted. The disordered blood vessels are fragile and prone to leaking, which causes excessive nosebleeds or bleeding along the gastrointestinal tract and other mucosal surfaces. These bleeding episodes, which worsen with age, can result in anemia and reduced quality of life. In severe cases, they can be life-threatening.

Researchers speculated that pomalidomide worked by blocking the growth of abnormal blood vessels. It may cause the blood vessels to have a more normal structure or thicker walls so they are less fragile.

Researchers enrolled 144 adults with HHT at 11 U.S. medical centers between 2019 and 2023. All participants had moderate to severe nosebleeds requiring iron infusions or blood transfusions. Researchers gave 95 of the participants pomalidomide daily. The remaining 49 patients received a daily sugar pill in addition to their usual care.

In June 2023, 43 months into the scheduled four-year trial, an interim analysis found pomalidomide had met a prespecified threshold for efficacy, and the trial was closed to further enrollment.

“These findings have broader implications for people with more severe forms of HHT,” said Kindzelski. “In those cases, malformed blood vessels can develop in organs such as the lung, liver and brain, which can lead to hemorrhagic stroke, bleeding in the lungs, or heart failure. A treatment like this could be lifesaving for such patients.”