According to results recently presented at the 2007 annual meeting of the American Society of Hematology (ASH), the investigative agent romiplostim (AMG531) continues to significantly improve platelet levels. Results from previous trials have indicated that romiplostim is highly effective at improving platelet levels among patients with cancer and patients with idiopathic thrombocytic purpura (ITP). These results provide further evidence that romiplostim is an effective therapeutic agent for treatment of low platelet levels in various diseases.
Platelets are essential for blood to clot when necessary (such as when skin is cut or bruised). Thrombocytopenia occurs when platelet levels fall below normal. Thrombocytopenia can often occur as a direct result of cancer, from cancer treatment, or from other diseases such as ITP. Adult chronic ITP is an autoimmune disorder that results in low levels of platelets. The immune system of patients with ITP either attacks mature platelets or attacks the cells in the body that produce platelets. As a result, patients with chronic ITP constantly suffer from thrombocytopenia. For specific questions about chronic ITP and recommendations concerning treatment, it's recommended that patients contact their physicians
Patients with thrombocytopenia may require transfusions of platelets from donors-a procedure associated disadvantages such as medical costs, time, a potential reaction to the donor platelets, and potential infection. In order to avoid these undesirable consequences, researchers have been evaluating ways to stimulate the body to produce platelets and reverse thrombocytopenia among patients with cancer.
The only agent approved for the treatment of thrombocytopenia is Neumega® (oprelvekin). Neumega, however, is not widely used for the treatment of thrombocytopenia because overall results have not been promising.
Romiplostim is an agent that stimulates the production of platelets using a different pathway from Neumega. Romiplostim has demonstrated a significant reduction in thrombocytopenia among patients with cancer. It continues to be evaluated in various diseases for both its effectiveness and long-term safety.
Researchers from several U.S. and European medical centers recently conducted several clinical trials to further evaluate romiplostim's ability to improve platelet levels. These trials included patients with chronic ITP. Results were presented at ASH.
The first clinical trial included 63 patients with chronic ITP who were treated with either romiplostim or placebo (inactive substitute) for six months. These patients had suffered from chronic ITP for approximately eight to nine years.
- Significant improvements in platelet levels were achieved in 79% of patients treated with romiplostim.
- In contrast, no patients who received placebo had improvements in platelet levels.
- Patients treated with romiplostim experienced a reduction in use of therapies necessary for treatment of chronic ITP.
The second clinical trial included 62 patients with chronic ITP who were also treated with either romiplostim or placebo.
- Significant improvements in platelet levels that were sustained for more than six weeks occurred in 61% of patients treated with romiplostim and 4.8% of patients who received placebo.
- Significant improvements in platelet levels for any amount of time were achieved in 88% of patients treated with romiplostim compared with 14% of patients who received placebo.
- Romiplostim was considered very well tolerated.
The third clinical trial included 136 patients with chronic ITP who were evaluated for side effects associated with long-term treatment with romiplostim.
- The most frequent side effects associated with long-term treatment with romiplostim included headache, fatigue, diarrhea, nosebleeds, sore throat, sore joints, and bruising.
- Only three patients withdrew from treatment due to side effects.
- There was no association between side effects and increased duration of therapy with romiplostim.
- Significantly increased levels of platelets were achieved in 82% of patients.
- After just two doses of romiplostim, at least half of the patients experienced increased levels of platelets.
- 30 patients were receiving therapy in addition to romiplostim when they started the trial; 13 of these patients could discontinue the additional therapy once treated with romiplostim.
The fourth study evaluated the association between use of romiplostim and need for additional treatment including immunoglobulins (therapy for ITP) in patients with chronic ITP. Patients were treated with either romiplostim or placebo and were compared regarding need for additional immunoglobulin therapy.
- Only 10% of patients treated with romiplostim received additional immunoglobulin therapy.
- 50% of patients who received placebo needed additional immunoglobulin therapy.
Taken together, results from these four trials indicate that romiplostim significantly improves platelet levels among thrombocytopenic patients, is well tolerated-even when used long-term-and reduces the need for additional immunoglobulin therapy in patients with ITP. These promising results may provide significant benefit to cancer patients with thrombocytopenia. Clinical trials are underway to further evaluate romiplostim in this group of patients.
Patients with ITP may wish to speak with their physician regarding their individual risks and benefits of participation in a clinical trial further evaluating romiplostim or other promising therapeutic agents.
 Gersheimer TB, Pullarkat V, Senecal FM, et al. Evaluation of AMG 531 efficacy in splenectomized patients with chronic immune thrombocytopenic purpura (ITP) in a randomized placebo-controlled phase 3 study. Blood. 2007;110:8a, abstract number 2.
 Kuter DJ, Bussel JB, Senecal FM, et al. Evaluation of AMG 531 in nonsplenectomized patients with chronic immune thrombocytopenic. Blood 2007;110. abstract number 565.
 Bussel JB, Kuter DJ, de Wolf JThM, et al. Long-term dosing of AMG 531 in thrombocytopenic patients with immune thrombocytopenic purpura: 2-year update. Blood. 2007;110:174a, abstract number 568.
 Pullarkat V, Gersheimer TB, de Wolf JThM, et al. Reduction in immunoglobulin (VIG or Anti D) use in patients with chronic immune thrombocytopenic purpura (ITP) receiving AMG 531. Blood. 2007;110:313a, abstract number 1034.