Clinical
Amgen study shows romiplostim boosts platelets
Last Updated: 2007-12-10 13:00:39 -0400 (Reuters Health)
By Lisa Baertlein
LOS ANGELES (Reuters) - Amgen Inc said on Saturday that a late-stage trial of its experimental drug AMG 531 showed it boosted and sustained platelet counts in adults with chronic immune thrombocytopenic purpura, a bleeding disorder.
The phase 3 Amgen-sponsored trial included 63 chronic ITP patients, who had their spleens removed after other treatments had failed.
The results, presented at the American Society of Hematology's annual meeting in Atlanta, showed that 38 percent of the 42 patients who received AMG 531, also known as romiplostim, achieved a durable platelet response. There were no responses among the 21 patients who received the placebo.
Researchers also said that AMG 531-treated patients who were also taking ITP medications such as corticosteroids were able to reduce or discontinue use of those medications.
Researchers said the study met its primary endpoint of durable platelet response, defined as a platelet count of greater than or equal to 50,000 platelets per microliter for six of the final eight weeks of the 24-week treatment period.
None of the patients included in the durable response group received rescue medications, such as the corticosteroids, researchers said.
Overall response, defined as either a durable response or a transient response of at least four weeks, was seen in nearly 79 percent of patients in the AMG 531 group. That compared with no responses in the placebo group.
The mean number of weekly platelet responses was significantly greater in patients receiving AMG 531, researchers said.
Data showed that 57 percent of patients in the placebo group required rescue medications, compared with 26 percent in the AMG 531 group.
There were two treatment-related serious adverse events. One patient had elevated bone marrow reticulin that returned to baseline three months after withdrawal of AMG 531. A second developed a clot in a blood vessel, which was successfully treated.
No patient developed neutralizing antibodies against either AMG 531 or endogenous thrombopoietin, the major platelet growth factor promoting platelet production.
Amgen has asked U.S., European Union, Australian and Canadian regulators to approve AMG 531 as a treatment for adults with chronic ITP. Regulatory authorities in the United States, Australia and Canada have granted priority review of Amgen's application.
ITP is a disorder in which the immune system mistakenly targets blood platelets as foreign objects and destroys them. The platelets, which are needed for clotting, are eliminated by the spleen.
The disease can result in dangerously low platelet counts that may result in spontaneous bleeding or bruising.
Amgen on Monday will present data from a phase 3 trial of ITP patients who have not had their spleens removed.
There are an estimated 15,050 to 30,100 new cases of ITP in U.S. adults and children each year, based on a U.S. government population estimate and a disease prevalence estimate from the Annual Review of Medicine.
(Reporting by Lisa Baertlein, editing by Leslie Gevirtz)
