ASH: Oral Drug Boosts Platelet Counts for ITP

December 12, 2006

ORLANDO -- An investigational oral platelet growth factor increased platelet levels in patients with chronic idiopathic thrombocytopenic purpura (ITP) reported investigators here.

ORLANDO, Dec. 12 -- An investigational oral platelet growth factor increased platelet counts in patients with chronic idiopathic thrombocytopenic purpura (ITP) reported investigators here.

In multinational randomized controlled trials, Promacta (eltrombopag) increased counts by about a factor of 10 when delivered at the highest dose to patients with ITP, said James B. Bussel, M.D., director of the Platelet Disorders Center at the Weill Cornell Medical Center in New York.

"We believe that this will be a major new advance in the management of ITP," Dr. Bussel said at the American Society of Hematology meeting here.

"It confirms a previous study that you can treat ITP by stimulating the platelet count," he added. "Previous studies had all basically focused on slowing down the rate of platelet destruction, and the advantage of this particular agent is that it can be given orally once a day."

Promacta is a thrombopoeitin receptor agonist that has been shown in both preclinical studies and clinical trials to stimulate proliferation and differentiation of megakaryocytes. Because it is a relatively small molecule therapeutic, it has less potential than large peptides to evoke an immune reaction, according to investigators.

The Phase II trial was an international randomized, double-blind, placebo-controlled study in 117 adult patients with chronic ITP (more than six months), with baseline platelet counts of less than 30,000/?L.

The patients were randomly assigned to Promacta orally once daily in doses of 30, 50 or 75 mg, or to placebo, for six weeks. The investigators assessed bleeding events weekly during treatment and biweekly after treatment using adverse event reporting and the WHO bleeding scale, which measures bleeding severity from Grade 0 (no bleeding) through to Grade 4 (debilitating blood loss).

The study was planned to have an enrollment of 270 patients, but was stopped at the first interim analysis for efficacy, of both the 50- and 75-mg doses (P

The most common adverse event was mild to moderate headache, which occurred in 21% of patients both on placebo and the 75-mg dose of Promacta, in 13% of patients on the 30 mg dose, and in 10% of those on the 50 mg dose.

There was no apparent relationship between the dose and incidence of adverse events in the study.

Clinical trials of Promacta are continuing for ITP and other conditions where thrombocytopenia is of concern, such as chemotherapy and liver disease.