Romiplostim: a guide to its use in immune (idiopathic) thrombocytopenic purpura
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Romiplostim: a guide to its use in immune (idiopathic) thrombocytopenic purpura Adapted from Drugs 2009; 69 (3): 307-17[1]
What is the rationale for developing the drug? Immune (idiopathic) thrombocytopenic purpura (ITP) is a relatively common acquired haemorrhagic disorder in adults (incidence ≈2 per 100 000 adults).[1] It is characterized by a low platelet count (typically 25% during weeks 1–12. The corresponding placebo results were two of ten nonsplenectomized and one of six splenectomized patients.[6] Rescue medications were administered to significantly (p ≤ 0.02) fewer romiplostim than placebo recipients, both in nonsplenectomized (17% vs 62%) and splenectomized (26% vs 57%) patients.[6] Romiplostim improved some measures of diseaserelated quality of life.[12] Relative to placebo, romiplostim was associated with significant (p ≤ 0.05) improvements in ITP-patient assessment questionnaire scores for activity in nonsplenectomized patients, and symptoms, bother, social activity and women’s reproductive health in splenectomized patients.[12] Drugs Ther Perspect 2009; Vol. 25, No. 6
Is it effective long term? Platelet response was maintained by most patients during longer-term treatment with romiplostim in 3-year (n = 142)[7] or 4-year (n = 215)[8] updates of an ongoing, open-label extension of the placebo-controlled trials. Patients were eligible for the open-label, multicentre extension if they had completed a prior romiplostim trial for the treatment of ITP and had a platelet count ≤50 × 109/L.[7] Most patients treated with romiplostim (87%[7] and 74%[8] in the 3-year[7] and 4-year[8] updates) had at least one platelet response (defined as a platelet count at a scheduled weekly visit that was ≥50 × 109/L and double the platelet count at baseline for the extension, in the absence of rescue medication in the preceding 8 weeks). Between weeks 4 through 144, the platelet response rate was 47–74%.[7] The proportion of patients responding was lower in splenectomized versus nonsplenectomized patients, as was the magnitude of the response. Platelet responses occurred, on average, for two-thirds of the time on treatment in responding patients.[7] Twothirds of the patients treated with romiplostim had a platelet count ≥50 × 109/L for ≥25 consecutive weeks; 41% had a platelet count ≥50 × 109/L for ≥52 consecutive weeks.[8] The mean romiplostim weekly dose increased over the first 24 weeks, but remained relatively stable thereafter.[7,8] The mean weekly dose was 5.9 μg/kg;[7] in three-quarters of the patients, the romiplostim weekly dose remained within 2 μg/kg of their most frequent dose for at least 90% of the time. One-half of the patients receiving concurrent ITP therapy at baseline discontinued such therapy altogether.[7,8] An additional one-third[7] or one-quarter[8] reduced the dose of this medication by ≥25%.
What is its tolerability profile? Romiplostim was generally well tolerated in the phase III studies. Almost all adverse events were mild to moderate in intensity; most were related to the underlying low pla
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