Superiority of Rasburicase Versus Allopurinol on Serum Uric Acid Control in Adult Patients with Hematological Malignancies at Risk of Developing Tumor Lysis Syndrome : Results of a Randomized Comparative Phase III Study.

Tumor lysis syndrome (TLS) is a potentially lethal metabolic complication of chemotherapy or cytolytic antibody therapy usually seen in patients with hematologic malignancies, especially those malignancies with a high proliferative rate, large cellular burden and/or sensitivity to chemotherapy. The prevention and management of TLS includes hydration and reduction of serum uric acid (SUA) levels. Although Allopurinol (ALLO) has had longstanding use for TLS prophylaxis, its efficacy in controlling SUA is limited, especially due of its lack of action on pre-existing hyperuricemia. Rasburicase (RAS), a recombinant urate oxidase, effectively reduces SUA due to conversion of UA into allantoin, a readily excretable and soluble substance. RAS has significant activity in the initial management of TLS-associated acute hyperuricemia in pediatric populations, and is currently indicated in the US for this condition in children and adolescents. A prospective, randomized, controlled phase III study was conducted in adult pts to compare the efficacy in SUA control of RAS (0.20 mg/kg/d, IV) days 1–5, versus RAS+ALLO (RAS 0.20 mg/kg/d, IV days 1–3 plus oral ALLO 300 mg/day days 3–5) versus ALLO alone (300 mg/d) days 1–5. 280 pts (275 evaluable) with hematological malignancies at high or potential risk for TLS were enrolled. 92 pts received RAS, 92 pts received RAS+ALLO, and 91 received ALLO. Treatment arms were well balanced in terms of demographics, baseline characteristics, TLS risk, and percentage of pts with baseline hyperuricemia. The SUA response rate - defined as normalization of SUA (≤ 7.5mg/dl) at days 3–7 was 87.0% in the RAS arm, 78.3% in the RAS+ALLO arm and 65.9% in the ALLO arm. RAS was superior over ALLO (p=0.0009) in the overall study population as well as in pts at high risk TLS (89.0% vs. 62.8%, p=0.0012), and in pts with baseline hyperuricemia (89.5% vs. 52.9%, p=0.0151). The time to control SUA in hyperuricemic pts was 4.1 h in the RAS arm and 27 h in the ALLO arm. The mean SUA area under the curve (AUC) results indicated that there was an 8.4-fold increase in UA exposure in the ALLO arm compared to the RAS arm. There were no significant differences in the incidence or severity of adverse events, serious adverse events or deaths. The majority of RAS and/or ALLO-related adverse events were grade 1 and 2, and most of these events were hypersensitivity-related reactions. No cases of anaphylaxis, methemoglobinemia or hemolysis were observed with RAS treatment. In conclusion, RAS is superior to ALLO in normalization of SUA, with a faster effect, in adult pts at risk for TLS. RAS alone or followed by ALLO are two valid options for this patient population.