US FDA staff seeks input on Amgen clot drug risks

By Lisa Richwine

WASHINGTON (Reuters) - U.S. drug reviewers will ask an advisory panel if an experimental Amgen Inc medicine for a rare blood disorder may carry a risk of clotting, cancer or other problems, documents released on Monday said.

An analysis from Food and Drug Administration staff said the drug, called Nplate, appeared effective but the agency wanted advice about five possible safety concerns.

Amgen is seeking FDA approval to sell the injectable drug for adults with a clotting disorder called chronic immune thrombocytopenia purpura, or chronic ITP, which puts patients at risk for serious bleeding. A panel of outside experts meets Wednesday to review the medicine, known generically as romiplostim.

Data submitted by Amgen so far "indicate that (Nplate) is safe and effective" for increasing levels of platelets, the cells that help the blood clot, and reducing the rate of serious bleeding, an FDA medical reviewer wrote.

But experience with the drug was limited and "may be inadequate to detect important safety concerns" that could arise based on the way it works to boost platelet production, the reviewer added.

Amgen, in a separate summary, said "the overall profile of romiplostim can be considered favorable" for patients who do not respond to other treatments. The company said risks could be managed through labeling and post-approval monitoring.

About 60,000 U.S. adults have chronic ITP, Amgen said. Current treatments, including removing the spleen or giving immune-suppressing drugs, do not help all patients and may have serious side effects, Amgen said.

About half of 83 patients treated with Nplate had their platelets boosted for at least six of the final eight weeks of treatment, the company said. That compared with 2.4 percent of patients receiving a placebo.