Regulators in the USA have finally given the green light to Amgen's Nplate as a treatment for chronic immune thrombocytopenic purpura.

The US Food and Drug Administration has approved Nplate (romiplostim), the first product that directly stimulates the bone marrow to produce needed platelets in patients with ITP. Its decision was based on results from two clinical trials of about 125 patients who had received at least one prior ITP treatment and the findings demonstrated that those who took Nplate achieved significantly higher platelet counts during six months of treatment compared with those who did not take the drug.

Nplate got a strong endorsement from Janet Woodcock, director for the FDA's Center for Drug Evaluation and Research, who said that "this product is important in that it offers a new approach to the treatment of patients”. Still, the drug has been approved for use only for patients with chronic ITP who do not respond sufficiently to current treatments, such as corticosteroids and immunoglobulin.

As part of its review, the FDA raised safety concerns about Nplate, including fibrous deposits in the bone marrow and the possibility that once the drug is stopped, platelet counts could drop below what they were before beginning treatment. Additional risks include blood clots due to excessive increases in platelets and, if Nplate were given to patients with myelodysplasia, a risk for a form of blood cancer known as acute leukaemia.

In response, Amgen has launched the Nplate NEXUS programme as part of the risk evaluation and mitigation strategy developed in partnership with the FDA to assure safe use of the drug. Roger Perlmutter, executive vice president of R&D at the firm said the approval “is the result of more than 15 years of research and represents an important biotechnology milestone as it is the first FDA-approved peptibody protein".

The green light comes a month later than expected and analysts believe that peak sales of the injectable drug will be in the region of $200 million”. The approval also means that Amgen has stolen a march on GlaxoSmithKline/Ligand Pharmaceuticals' rival drug Promacta (eltrombopag), a short-term oral treatment for ITP. The FDA is scheduled to give its decision on the latter on September 19.