The U.S. Food and Drug Administration has said Amgen Inc drug Nplate is safe and effective to treat a rare bleeding disorder called immune thrombocytopenic purpura (ITP). This injectable drug stimulates bone marrow to produce blood platelets which help blood to clot. It received the agency’s approval after other available treatments failed to help.

Dr. Janet Woodcock, head of the FDA's Center for Drug Evaluation and Research said, "This product is important in that it offers a new approach to the treatment of patients with an uncommon blood disorder who are often very ill."

Affecting about 140,000 people in the United States in chronic ITP, it's believed, the body's own immune system destroys platelets, and the bone marrow is unable to produce enough platelets to compensate and low platelet levels can trigger life-threatening bleeding. Approved treatments for it have included steroids, immune-suppressing drugs or surgery to remove the spleen.

Amgen, the Thousand Oaks, California-based biotech company said, "Until now there have been limited FDA-approved treatments available to patients suffering from chronic adult ITP, and the treatment options were often unsuccessful for long-term use."

Clinical testing involving 125 people with ITP showed the drug Nplate significantly increased the platelet counts in the recipients as compared to those who did not get the drug. The FDA said, patients who received Nplate had showed "significantly higher platelet counts and maintained those higher counts compared to those who did not receive the drug." They also found that patients who still had their spleen responded better than those who didn’t.

Doctors who are keen on prescribing Nplate will have to enroll themselves and their patients into a special registry that will track long-term safety. Amgen has said the total cost for patients on Nplate is expected to be "less than or comparable to the total costs of care with standard treatment regimens."

Nplate, also known as romiplostim, is not free from side effects though. These can range from fibrous deposits in the bone marrow, a decrease in platelet count to below pre-treatment levels if the drug is stopped, a form of blood cancer, and blood clots if excessive platelets are produced.

Promacta, or eltrombopag, which are rival drugs by GlaxoSmithKline Plc are up for FDA’s approval decision by September 19. Some analysts expect Nplate to earn anywhere from $66 million to $117 million in 2009 sales and peak around $200 million figures that are small compared with Amgen's 2007 revenue of $14.7 billion.

William Blair & Co analysts said in a research note, "We are encouraged by the approval, but note that the small patient market for this drug will result in a modest contribution to the company's revenues. We continue to believe that the most meaningful revenue addition for Amgen will be pending approval of denosumab in osteoporosis."

Amgen said it was trying for approval for Nplate in Europe, Canada and Switzerland. The Australian authorities approved the drug last month.