Romiplostim for Prevention of Severe Chemotherapy-Induced Thrombocytopenia in Lymphoma Patients—Phase I Study

<b>Background/Objectives:</b> Intensive chemotherapy is the cornerstone of lymphoma treatment but often leads to severe chemotherapy-induced thrombocytopenia (sCIT), resulting in treatment delays, reduced dose intensity, and the need for transfusions. While granulocyte colony-stimulating factors (G-CSFs) are commonly used to manage neutropenia, the use of thrombopoietic growth factors has not been adequately studied. <b>Methods:</b> This phase I dose-finding study evaluated the use of weekly romiplostim as prophylaxis for recurrent sCIT in patients undergoing chemotherapy for lymphoma. Eligible patients were those treated with a 21-day chemotherapy cycle who previously experienced sCIT, thus serving as their own "controls". sCIT was defined as one of the following: (A) a platelet count (PLT) <50 × 10⁹/L on day 1 of the subsequent cycle, leading to delay or dose reduction in chemotherapy, or (B) grade 4 thrombocytopenia (<25 × 10⁹/L) and/or (C) platelet transfusion for bleeding. The primary endpoints were the incidence of sCIT and the rate of romiplostim-associated-adverse-events, with thromboembolic complications being an event of special interest. <b>Results:</b> Nine patients with sCIT requiring a PLT transfusion on the prior treatment cycle were treated across three dose schedules. The phase 2 recommended schedule was defined as a starting dose of 3-5 mcg/kg based on the baseline PLT count, with weekly adjustments for counts <150 × 10⁹/L and >450 × 10⁹/L. Romiplostim prevented recurrent grade 4 thrombocytopenia in 47% of the chemotherapy cycles and averted recurrent transfusion in 65% of cycles. Notably, low starting doses, as used in solid malignancies, were insufficient, leading to recurrent thrombocytopenia. <b>Conclusions:</b> Romiplostim was well-tolerated, with no thromboembolic events, and allowed most patients to complete their chemotherapy on schedule at full dose intensity.