US FDA staff seeks input on Amgen clot drug risks
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.
The FDA staff said safety concerns with Nplate include whether it may increase clotting too much or boost production of abnormal cells seen in blood cancers.
Other issues FDA staff highlighted for panel discussion include a drop in platelets if Nplate is stopped, development of antibodies that might neutralize the drug's effects, and an increase in bone-marrow fibers known as reticulin, which was seen in 4 percent of patients.
Dietmar Berger, leader of Amgen's Nplate development, said in an interview the increased reticulin did not lead to any health problems in patients studied. The company has not seen any rise in cancers or blood clots, he added.
The FDA will consider the advisory panel's input before deciding whether to approve Nplate sales.
Rodman & Renshaw analyst Michael King put the odds of a favorable panel recommendation at 60 percent. The outcome may hinge on whether panel members believe platelets were increased enough to provide a meaningful benefit for patients.
"This is definitely not a slam dunk," King said.
He projected 2009 sales of $117 million for Nplate if it wins approval. While that makes the drug small for a giant biotech company such as Amgen, a positive recommendation could help the company's stock this week as it faces a closely watched FDA panel review on Thursday of the risks from its $3.6-billion-a-year anemia drug Aranesp, King said.
If Nplate wins the panel's backing and Amgen "comes away on Thursday without getting their heads taken off, I think people will breathe a sigh of relief," King said.
Nplate could face competition from a rival GlaxoSmithKline Plc drug called Promacta, which comes in pill form. That drug also is under FDA review.
(Reporting by Lisa Richwine, editing by Dave Zimmerman and Tim Dobbyn)
