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Amgen's Platelet Booster Nplate Gets FDA Nod in ITP Indication(BioWorld Today Via Acquire Media NewsEdge) A month after its original PDUFA date, Amgen Inc.'s Nplate scored an FDA approval as a platelet booster to treat the rare blood disorder chronic immune thrombocytopenic purpura (ITP). The Thousand Oaks, Calif.-based firm's drug is the first of its kind to be approved in the small ITP indication - an estimated 60,000 people in the U.S. have ITP - though potential competitor Promacta (eltrombopag) from San Diego-based Ligand Pharmaceuticals Inc. and partner GlaxoSmithKline plc, of London, is right on its heels with a Sept. 19 PDUFA date. That product has had mixed reviews from regulators so far, getting a thumbs-up from an advisory committee in May but generating concerns from the FDA that it might be no better than placebo while carrying liver safety risks to patients. Existing treatments for ITP include corticosteroids and immunoglobulin, as well as a surgical option, splenectomy. Nplate (romiplostim), which is indicated for patients who do not respond sufficiently to those treatments, is an engineered therapeutic fusion protein designed to work by directly stimulating a patient's bone marrow to produce platelets. Its mechanism is similar to that of thrombopoietin, a natural protein responsible for the growth and maturation of the bone marrow cells that produce platelets. Roger M. Perlmutter, executive vice president of research and development at Amgen, said in a press release that the approval is the "result of more than 15 years of research" and represent the first FDA-approved peptibody protein. In a pivotal trial involving 125 patients who had received at least one prior ITP treatment, those who received Nplate had significantly higher platelet counts and maintained those higher counts compared to those who received placebo. Results presented in June from a long-term study showed that 87 percent of patients achieved a platelet response (defined as a platelet count of 50,000 platelets per microliter) on Nplate. The overall median baseline count was 17,000 platelets per microliter. But, like Promacta, the drug has faced its share of safety concerns. Risks associated with Nplate use include fibrous deposits in the bone marrow and a possible snap-back effect once Nplate treatment is stopped that could result in platelet counts falling below pretreatment baseline levels. Additional risks include blood clots due to excessive increases in platelets, and for patients who have myelodysplasia, an abnormal blood condition, there's a chance Nplate treatment carries a risk of leukemia. In one trial involving 44 patients with myelodysplasia, four developed leukemia after Nplate treatment, and the FDA has said further studies will be needed to determine whether there's a link between the drug's use and leukemia. At the request of the FDA, Amgen is responsible for following a risk evaluation and mitigation strategy, which includes a provision requiring all patients to enroll in a registry to track the drug's long-term safety profile. That program, designated NEXUS (Network of EXperts Understanding and Supporting Nplate and Patients), is aimed at patient education, while collecting further safety data. Nplate also is under review in the European Union, Canada and Switzerland. It previously gained approval in Australia. The drug is not expected to be a huge seller for Amgen, which recorded second-quarter product sales of $3.7 billion, most of that coming from its erythropoiesis-stimulating agent franchise. The firm said Nplate's cost is expected to be less than or comparable to the standard of care for ITP, though analyst Michael Aberman, of Credit Suisse Securities LLC, said the cost is not likely to be "a barrier to adoption." He wrote in a research note that "we believe that Nplate can ramp to sales of over $300 million in ITP globally by 2010." Being able to hit the market first also could give Nplate an advantage over Ligand's Promacta, though Derek Jellinek, an analyst with Susquehanna Financial Group, wrote in a note that Nplate's approval "bodes well" for Ligand's product, as it "alleviates concerns regarding the approvability of thrombopoietin agents." Amgen's stock (NASDAQ:AMGN) barely budged Friday, closing at $64.01, up 20 cents, while shares of Ligand (NASDAQ:LGND) gained 22 cents, or 7.2 percent, to close at $3.28. While the latest approval clearly is good news for Amgen, it's only "a small part of the Amgen story," Aberman said. Investors remained fixed on detailed data from osteoporosis drug denosumab, expected to be presented next month at the American Society of Bone and Mineral Research meeting in Montreal. Top-line data, reported last month, showed that the drug met its primary endpoint in the much-awaited Phase III trial in 7,800 postmenopausal women. (See BioWorld Today, July 29, 2008.) n ? ? Copyright ? 2008 Thomson BioWorld, All Rights Reserved. |