WEDNESDAY, Nov. 28 , 2007 (HealthDay News) -- An experimental drug can boost the number of clotting cells, called platelets, in patients suffering from a dangerous deficiency of these cells, researchers report.
The new drug is called eltrombopag, and in one study, patients with the autoimmune disorder idiopathic thrombocytopenic purpura (ITP) were able to use the medication to boost their platelet levels and cut their risk for bleeding.
In a second study, patients with hepatitis C (HCV)-related cirrhosis of the liver were able to begin antiviral therapy for their condition after eltrombopag raised their platelet counts.
"Eltrombopag is not just used in one disease," explained Dr. John McHutchison, lead author of the hepatitis study and an associate director of the Duke Clinical Research Institute in Durham, N.C. "It could be used in cancer/chemotherapy, ITP; it could have a very, very broad use across many different diseases," said McHutchison, who is also professor of medicine at Duke University.
But the trials, both of which are published in the Nov. 29 issue of the New England Journal of Medicine, reported only short-term results and should be considered carefully, experts cautioned.
"I stress the preliminary nature of these reports," said Dr. Robert S. Schwartz, deputy editor of the New England Journal of Medicine and author of an accompanying editorial on the studies. "We thought that these preliminary results were promising, but they will have to be confirmed in bigger trials."
Thrombocytopenia, which refers to any disorder in which there are not enough platelets, can prevent people from receiving necessary treatments.
With ITP, the body destroys its own platelets or not enough platelets are produced.
"This is a condition in which there's a low platelet count, and if it drops very low, usually below 30,000, the clinical manifestations are principally bleeding and bruising," Schwartz explained.
Eltrombopag is thought to stimulate megakaryocytes, the bone marrow cells that produce blood platelets. The drug, also called Promacta, is being developed by GlaxoSmithKline, which funded both studies.
For the first study, 118 people with ITP and low platelet counts were randomized to receive 30, 50 or 75 milligrams of eltrombopag or a placebo. All participants had failed at least one previous treatment.
A platelet count of 50,000 or more per cubic millimeter on day 43 was achieved in 28 percent, 70 percent and 81 percent of participants who received 30, 50 and 75 milligrams of eltrombopag respectively.
Only 11 percent of those in the placebo group reached this level.
By day 15 of the trial, more than 80 percent of patients receiving 50 or 75 milligrams of eltrombopag daily had an increased platelet count. These individuals also experienced decreased bleeding.
For the second study, 74 patients with HCV-related cirrhosis and low platelet counts were randomly assigned to receive 30, 50 or 75 milligrams of eltrombopag daily or a placebo for four weeks.
"Hepatitis C is clearly a big problem. It's the most common cause for liver transplantation and the commonest cause of cirrhosis," McHutchison said. "We have treatments out there approved but people with more advanced liver disease and low platelet counts were excluded from the registration trial [for FDA approval]."
By week four, 75 percent of those receiving 30 milligrams of eltrombopag, 79 percent of those receiving 50 milligrams and 95 percent of those receiving 75 milligrams of eltrombopag had platelet counts of 100,000 per cubic millimeter or more. By contrast, none of those receiving the placebo saw their counts increase to that level.
Twelve weeks of antiviral therapy with peginterferon - used to fight hepatitis C -- was successfully completed by 36 percent, 53 percent and 65 percent of patients receiving 30 milligrams, 50 milligrams or 75 milligrams of eltrombopag, and only 6 percent of those in the placebo group.
"We deal with people on the [liver] transplant list with low platelet counts all the time. We've never had a drug we could give them, particularly by mouth," McHutchison said.
Two larger trials are planned which, if successful, could form the basis for FDA approval of the drug, the researchers said.
More information
There's more on ITP at the U.S. National Heart, Lung and Blood Institute .
