Impact of pre-emptive rapid testing for glucose-6-phosphate dehydrogenase deficiency prior to rasburicase administration at a tertiary care centre: A retrospective study.

AIMS: Glucose-6-phosphate dehydrogenase (G6PD) deficiency, the most common enzymopathy in humans, can cause acute haemolysis resulting from exposure to certain medications, chemicals, infections and fava beans. Rasburicase, used to manage elevated uric acid levels in the oncologic emergency of tumour lysis syndrome, is one such drug. The US Food and Drug Administration (FDA) recommends testing of G6PD status prior to rasburicase administration for patients at higher risk for G6PD deficiency. METHODS: We performed a retrospective chart review of all oncology patients for whom a semi-quantitative biochemical test for detecting G6PD deficiency was performed prior to rasburicase administration over a 2.5-year period, in a large academic metropolitan hospital. RESULTS: We identified 16 out of 260 tested individuals as G6PD-deficient (6.1%), including six females. On average, test results were electronically available to health care providers within 4 hours of sample collection, with most results available within 2-3 hours. Four G6PD-deficient patients developed elevated uric acid levels. Two of the G6PD-deficient patients were treated with rasburicase, and subsequently developed haemolysis, which was appropriately managed. CONCLUSION: In summary, by providing information about G6PD status with a rapid turnaround time, we have taken a significant step towards personalized medicine in our institution. In spite of the test implementation, two out of four G6PD-deficient patients, who were no longer candidates for rasburicase use, still received the drug, highlighting the need for improved provider education.

Management of Hyperleukocytosis in Childhood Acute Leukemia Without Leukapheresis and Rasburicase Prophylaxis.

Indications of leukapheresis (LPh) and the prophylactic use of rasburicase in tumor lysis syndrome (TLS) of patients with acute leukemia with hyperleukocytosis are not clear. In this retrospective single-center pediatric study, the outcomes of patients with hyperleukocytosis were reviewed. There were 48 patients with acute lymphoblastic leukemia (ALL) and 13 patients with acute myeloblastic leukemia (AML). The treatment strategies included hyperhydration, allopurinol administration, strict monitoring, and early initiation of induction chemotherapy (CT). No patient underwent LPh because it was not available. Rasburicase was used only in 3 ALL patients with hyperuricemia when the drug was available. Laboratory and clinical TLS developed in 54.16% and 14.58% of patients with ALL, respectively. Laboratory and clinical TLS developed in 76.92% and 15.38% of patients with AML, respectively. No patient developed grade III to V TLS requiring dialysis. Thirteen patients (21.3%) had pulmonary leukostasis on admission, but recovered with CT and nasal oxygen. During the first 14 days of presentation, cerebral leukostasis/coagulopathy-related early death (ED) was 4.2% and 7.7% in patients with ALL and AML, respectively, and all of these patients had a white blood cell count ≥400,000/µL. There was also 1 infection-related death. Patients with hyperleukocytosis can be treated without LPh and liberal use of rasburicase. Renal failure is no longer a cause of ED. Intracranial hemorrhage is the main cause of ED, especially in patients already presenting with this complication. LPh may be performed in patients with leukostasis, if it is not possible to start induction CT early. When resources are limited, rasburicase should be administered in patients presenting with or developing hyperuricemia and/or renal dysfunction.

Multivalent Albumin-Neonatal Fc Receptor Interactions Mediate a Prominent Extension of the Serum Half-Life of a Therapeutic Protein.

Human serum albumin (HSA) has been used to extend the serum half-life of therapeutic proteins owing to its exceptionally long serum half-life via the neonatal Fc receptor (FcRn)-mediated recycling mechanism. In most cases, only one HSA molecule was conjugated to a therapeutic protein, leading to a limited extension of the serum half-life. In this study, we hypothesized that conjugation of multiple HSA molecules to a therapeutic protein significantly further extends the serum half-life via multivalent HSA-FcRn interactions. We chose urate oxidase (Uox), a tetrameric therapeutic protein used for the treatment of gout, as a model. In previous studies, only one HSA molecule was site-specifically conjugated to one Uox because of poor conjugation yield of the relatively slow bio-orthogonal chemistry, strain-promoted azide-alkyne cycloaddition (SPAAC). To increase the number of HSA molecules conjugated to one Uox, we employed the faster bio-orthogonal chemistry, inverse electron demand Diels-Alder reaction (IEDDA). We site-specifically introduced the phenylalanine analog with a fast-reacting tetrazine group (frTet) into position 174 of each subunit of Uox. We then achieved site-specific HSA conjugation to each subunit of Uox via IEDDA, generating Uox conjugated to four HSA molecules (Uox-HSA4), with a small portion of Uox conjugated to three HSA molecules (Uox-HSA3). We characterized Uox-HSA4 as well as Uox variants conjugated to one or two HSA molecules prepared via SPAAC (Uox-HSA1 or Uox-HSA2). The enzyme activity of all three Uox-HSA conjugates was comparable to that of unmodified Uox. We found out that an increase in HSA molecules conjugated to Uox (multiple albumin-conjugated therapeutic protein) enhanced FcRn binding and consequently prolonged the serum half-life in vivo. In particular, the conjugation of four HSA molecules to Uox led to a prominent extension of the serum half-life (over 21 h), which is about 16-fold longer than that of Uox-WT.

Rasburicase in hemolytic uremic syndrome related to Shiga toxin-producing Escherichia coli: a report of nine cases.

BACKGROUND: Hyperuricemia might induce additional renal damage in children with hemolytic uremic syndrome related to Shiga toxin-producing Escherichia coli (STEC-HUS). A few case reports have shown rasburicase to be effective in decreasing serum uric acid (UA) and improving renal function. However, there is only one report on the use of rasburicase in a child with STEC-HUS, which shows satisfactory results. We describe here the safety and efficacy of rasburicase in nine additional cases. CASE-DIAGNOSIS/TREATMENT: Data from 9 children (5 females, median age 2 years) who received rasburicase were reviewed. At admission, 6 were dehydrated and 3 euvolemic. Dehydrated patients received saline solution and afterwards, as well as for those initially euvolemic, we aimed to keep a neutral fluid balance. Despite this, urine output did not increase. Baseline creatinine was 3.35 mg/dL (1.47-9.1) and UA 11.4 mg/dL (8.3-19.2). A single dose of rasburicase (0.2 mg/kg) was given 6-8 h after admission, which reduced UA levels to 1.8 mg/dL (0.3-5, p = 0.009) on the next day. However, renal parameters worsen and dialysis had to be initiated. Then, while still on dialysis, a UA rebound occurred in all cases reaching a peak of 8.9 mg/dL (4.5-13.8). Just after a steady increase in urine output, a sustained decline in UA levels concomitantly occurred with an improvement in renal function. At discharge, all patients reached normal UA levels. No side effects were recorded. CONCLUSIONS: Administration of rasburicase in children with STEC-HUS was safe but failed to provide any significant benefit despite fall in serum UA levels.

A retrospective analysis of tumor lysis syndrome management in a quaternary care hospital.

PURPOSE: Due to an increased use of rasburicase, the study's purpose was to evaluate both the management of tumor lysis syndrome and the utilization of rasburicase in the hospital system. Additionally, the efficacy of flat dose rasburicase in lowering uric acid levels was evaluated. Based on the study's findings, the investigators will evaluate the usefulness of implementing a tumor lysis syndrome order set. METHODS: This study evaluated patients from January 2013 through December 2016 for the rasburicase dose and the tumor lysis syndrome therapy administered. RESULTS: Overall, 251 patients were included: prophylactic rasburicase group (n = 125) vs. treatment rasburicase group (n = 126) and of rasburicase 3 mg (R3) group (n = 168) vs. 6 mg (R6) group (n = 83). The prophylactic rasburicase vs. treatment rasburicase group had a significantly lower rate of receiving a xanthine oxidase inhibitor (48.0% vs. 64.3%, p = 0.009), a phosphate binder (6.4% vs. 17.5%, p = 0.007) and an additional dose of rasburicase (20.8% vs. 41.3%, p = 0.001). Intravenous hydration was neither significantly different between the rasburicase groups (p = 0.399) nor between the two rasburicase dosing groups (p = 0.874). Between the rasburicase dosing groups, there was no significant difference in the rate of receiving a xanthine oxidase inhibitor (p = 0.521) or a phosphate binder (p = 0.390). R6 patients had a significantly greater reduction in uric acid change compared to R3 patients (median = -7.9 (-10.1, -5.5) vs. -4.3 (-6.0, -2.7), p < 0.0001). There was no significant difference in uric acid change between the prophylactic rasburicase and treatment rasburicase groups (p = 0.875). CONCLUSION: The study's findings justified the need to implement a tumor lysis syndrome order set. In the study population, utilizing a flat dosing method was effective for hyperuricemia.

Utilization patterns and clinical outcomes of rasburicase administration according to tumor risk stratification.

PURPOSE: Current guidelines for tumor lysis syndrome management recommend rasburicase for high-risk patients. Adherence to guidelines has not been well studied, and the correlation between uric acid reduction and clinically relevant outcomes, such as acute kidney injury, remains unclear. Our study aims to describe rasburicase utilization patterns and outcomes in cancer patients with varying risks for tumor lysis syndrome. METHODS: In this retrospective cohort study, we included cancer inpatients who received rasburicase for tumor lysis syndrome management at two affiliated academic hospitals from 2009 to 2015. Patients were classified by tumor lysis syndrome risk categories prior to drug administration. Primary outcomes included acute kidney injury incidence and renal recovery. Secondary outcomes included uric acid nadir, mortality, and hospital length-of-stay. RESULTS: Among 164 patients, 42 (26%) had high-, 63 (38%) had intermediate-, and 59 (36%) had low-risk for tumor lysis syndrome. A total of 94 patients (57%) had existing renal dysfunction prior to rasburicase use. This occurred more frequently in low- (68%) compared to intermediate- (57%) and high- (43%) risk patients (p = 0.044). A greater proportion of patients in the high-risk group (78%) had renal recovery when compared to the intermediate- (61%) or low- (45%) risk groups (p = 0.056). Despite a similar length of stay, the high-risk group had a significantly lower 30-day mortality (10%) when compared to intermediate- (25%) or low- (32%) risk groups (p = 0.029). CONCLUSIONS: Our results suggest that rasburicase may be frequently prescribed to treat hyperuricemia unrelated to tumor lysis syndrome in cancer patients. Improved education and adherence to guidelines may improve clinical and economic outcomes associated with rasburicase administration.

Bruton's tyrosine kinase inhibitors and the kidney: Focus on ibrutinib.

INTRODUCTION: Tumor lysis syndrome is an oncologic emergency resulting from rapid and massive tumor cell death that may lead to serious clinical complications including acute kidney injury and cardiac arrest. Tumor lysis syndrome most often occurs after the initiation of cytotoxic therapy in patients with high-grade lymphomas and acute lymphoblastic leukemia. CASE REPORT: We present a first case of patient with chemotherapy-resistant chronic lymphocytic leukemia and small lymphocytic lymphoma who developed tumor lysis syndrome upon treatment with ibrutinib (Imbruvica), a novel tyrosine kinase inhibitor. MANAGEMENT AND OUTCOME: The patient showed dramatic improvement in kidney function, uric acid and phosphorus after discontinuation of ibrutinib and a short course of rasburicase (recombinant urate oxidase), and two haemodialysis treatments. DISCUSSION: Clinicians should be aware of this serious side effect and closely monitor kidney function in patients treated with this oral kinase inhibitor.

The value of fixed rasburicase dosing versus weight-based dosing in the treatment and prevention of tumor lysis syndrome.

BACKGROUND: Rasburicase is a recombinant urate oxidase enzyme used for the treatment and prevention of tumor lysis syndrome. Our objective was to assess the efficacy of indication-based, low-dose rasburicase administration compared to the Food and Drug Administration-approved weight-based dosing. METHODS: This was a retrospective cohort study utilizing data from a tertiary medical center including patients admitted from 2012 to 2016, who received at least one dose of rasburicase. The primary outcome was achieving a uric acid level less than 7.5 mg/dl after a single dose of rasburicase in the preprotocol (Food and Drug Administration-approved weight-based dosing) and postprotocol (indication-based, low-dose) groups. Secondary outcomes included the change in uric acid levels between the pre- and postprotocol groups, adherence to the new institutional protocol, need for repeat rasburicase doses, and a cost analysis. RESULTS: Sixty-four patients received at least one dose of rasburicase between 1 January 2012 and 1 December 2016. Twenty-seven (79.4%) doses in the preprotocol group and 28 (82.4%) doses in the postprotocol group successfully achieved a uric acid level less than 7.5 mg/dl after a single dose of rasburicase (p=1.000). The average total monthly cost of rasburicase was reduced by 59.9% after adoption of the new protocol. CONCLUSIONS: Indication-based, low-dose rasburicase displayed significantly more value when compared to weight-based dosing as shown by achieving cost savings without compromising clinical efficacy.

Single 6-mg dose of rasburicase: The experience in a large academic medical center.

BACKGROUND: Tumor lysis syndrome is an oncologic emergency due to the release of tumor cell contents, leading to metabolic derangements. Rasburicase, a recombinant urate oxidase, catabolizes uric acid. At our institution, we administer a single 6-mg dose of rasburicase to patients who are at risk for tumor lysis syndrome. We aimed to assess the efficacy of single 6-mg dose of rasburicase and explore risk factors associated with rasburicase failure. METHODS: We report results in 92 adult patients who had a baseline uric acid greater than 7.5 mg/dL and received a single 6-mg dose of rasburicase for the management of tumor lysis syndrome. Responders were defined as those whose uric acid was less than or equal to 7.5 mg/dL within 24-36 h of rasburicase administration. The primary end point was response based on uric acid level. Secondary end points included response to rasburicase in association with lactate dehydrogenase, serum creatinine, calcium, phosphorus, blood pH, and oncologic diagnosis. RESULTS: Median age was 65 years and 70% were men. Most patients had leukemia (32%) or lymphoma (40%). Eighty-seven of 92 patients (95%), who received single 6-mg dose of rasburicase, achieved a uric acid less than 7.5 mg/dL within 24-36h of dosing. Body mass index was similar between responders and non-responders: 28.6 kg/m2 vs. 26.6 kg/m2, respectively, p = 0.6. Baseline lactate dehydrogenase levels were similar between the groups: 756 U/L vs. 892 U/L, respectively, p = 0.33. Blood pH values documented within 24 h of first dose of rasburicase were also similar between the two groups (n = 30; 7.33 vs. 7.34 respectively, p = 0.6). However, median baseline uric acid was lower in responders than non-responders: 12.3 mg/dL vs. 17.3 mg/dL, respectively, p = 0.012. Baseline serum creatinine and creatinine clearance were similar between responders and non-responders (2.2 mg/dL vs. 3.95 mg/dL; p = 0.12 and 29 mL/min vs. 16 mL/min; p = 0.11, respectively). CONCLUSIONS: Higher baseline uric acid levels were observed in patients who did not respond to the first rasburicase dose. In our study, uric acid levels normalized in 95% of patients after a single 6-mg dose of rasburicase indicating that a single 6-mg dose of rasburicase may be sufficient to manage tumor lysis syndrome, for most patients.

Rasburicase versus intravenous allopurinol for non-malignancy-associated acute hyperuricemia in paediatric cardiology patients.

OBJECTIVES: Limited data exist for management of hyperuricemia in non-oncologic patients, particularly in paediatric cardiac patients. Hyperuricemia is a risk factor for acute kidney injury and may prompt treatment in critically ill patients. The primary objective was to determine if rasburicase use was associated with greater probability normalisation of serum uric acid compared to allopurinol. Secondary outcomes included percent reduction in uric acid, changes in serum creatinine, and cost of therapy. DESIGN: A single-centre retrospective chart review. SETTING: A 20-bed quaternary cardiovascular ICU in a university-based paediatric hospital in California. PATIENTS: Patients admitted to cardiovascular ICU who received rasburicase or intravenous allopurinol between 2015 and 2016. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Data from a cohort of 14 patients receiving rasburicase were compared to 7 patients receiving IV allopurinol. Patients who were administered rasburicase for hyperuricemia were more likely to have a post-treatment uric acid level less than 8 mg/dl as compared to IV allopurinol (100 versus 43%; p = 0.0058). Patients who received rasburicase had a greater absolute reduction in post-treatment day 1 uric acid (-9 mg/dl versus -1.9 mg/dl; p = 0.002). There were no differences in post-treatment day 3 or day 7 serum creatinine or time to normalisation of serum creatinine. The cost of therapy normalised to a 20 kg patient was greater in the allopurinol group ($18,720 versus $1928; p = 0.001). CONCLUSION: In a limited paediatric cardiac cohort, the use of rasburicase was associated with a greater reduction in uric acid levels and associated with a lower cost compared to IV allopurinol.

Comparison of fixed versus traditional weight-based dosing of rasburicase in a pediatric population.

BACKGROUND: The American Society of Clinical Oncology guidelines recommend rasburicase for the treatment of pediatric patients with hyperuricemia at risk of tumor lysis syndrome (TLS) using a weight-based dose of 0.1-0.2 mg/kg once daily for 1-7 days. However, there has been a trend in practice due to recent data showing benefit using a fixed-dose approach. The purpose of this study was to evaluate the efficacy and safety between fixed and weight-based dosing of rasburicase in a pediatric population. PROCEDURE: This was a retrospective chart review of 48 patients from January 1, 2007 to August 31, 2016 at Children's National Health System. Patients less than 18 years old with a documented diagnosis of a malignancy and baseline uric acid level were included; patients less than 30 kg at the time of rasburicase administration were excluded. RESULTS: The primary endpoint of this study was the treatment success of normalization of uric acid level (<5 mg/dl) within 24 hr of rasburicase administration. Eighty-three percent of patients had success with normalization of uric acid post rasburicase dose. Eighty-five percent of patients had success in the weight-based group compared to eighty-one percent in the fixed-dose group (P = 0.715). Mean percent reduction of uric acid at 24 hr was relatively similar between both groups (94% vs. 89%). CONCLUSION: Our results suggest that a fixed-dose strategy of rasburicase is both safe and effective in reducing uric acid levels in the pediatric patient population. A fixed dose of rasburicase 6 mg is a cost-effective treatment option for TLS.

Uricase Inhibits Nitrogen Dioxide-Promoted Allergic Sensitization to Inhaled Ovalbumin Independent of Uric Acid Catabolism.

Nitrogen dioxide (NO2) is an environmental air pollutant and endogenously generated oxidant that contributes to the exacerbation of respiratory disease and can function as an adjuvant to allergically sensitize to an innocuous inhaled Ag. Because uric acid has been implicated as a mediator of adjuvant activity, we sought to determine whether uric acid was elevated and participated in a mouse model of NO2-promoted allergic sensitization. We found that uric acid was increased in the airways of mice exposed to NO2 and that administration of uricase inhibited the development of OVA-driven allergic airway disease subsequent to OVA challenge, as well as the generation of OVA-specific Abs. However, uricase was itself immunogenic, inducing a uricase-specific adaptive immune response that occurred even when the enzymatic activity of uricase had been inactivated. Inhibition of the OVA-specific response was not due to the capacity of uricase to inhibit the early steps of OVA uptake or processing and presentation by dendritic cells, but occurred at a later step that blocked OVA-specific CD4(+) T cell proliferation and cytokine production. Although blocking uric acid formation by allopurinol did not affect outcomes, administration of ultra-clean human serum albumin at protein concentrations equivalent to that of uricase inhibited NO2-promoted allergic airway disease. These results indicate that, although uric acid levels are elevated in the airways of NO2-exposed mice, the powerful inhibitory effect of uricase administration on allergic sensitization is mediated more through Ag-specific immune deviation than via suppression of allergic sensitization, a mechanism to be considered in the interpretation of results from other experimental systems.

Rational use of rasburicase for the treatment and management of tumor lysis syndrome.

Purpose There is a lack of high-level evidence identifying meaningful outcomes and the optimal place in therapy of rasburicase in patients with, or at high risk for tumor lysis syndrome. The primary objective of this study was to evaluate and characterize outcomes resulting from an institution-specific guideline emphasizing supportive care, xanthine oxidase inhibitors, and lower doses of rasburicase. Methods In this retrospective chart review, we compared conservative rasburicase dosing, in accordance with newly developed UMHS tumor lysis syndrome guidelines, with aggressive rasburicase in adult patients (≥ 18 years of age) with hematological or solid tumor malignancies, and a uric acid level between 8 and 15 mg/dL. The primary efficacy outcome assessed the difference in the proportion of patients achieving a uric acid level <8 mg/dL within 48 h using a one-sided noninferiority test. The principle safety outcomes analyzed included incidence of acute kidney injury and hemodialysis requirement. Results One hundred sixty-one patients met inclusion criteria and were included in the study. Within 48 h of an elevated uric acid level, treatment was successful in 97.03% of patients in the conservative group, as compared with 98.33% in the aggressive group (difference, 1.3 percentage points; 95% confidence interval [CI], -3.33 to 5.93). Furthermore, there was no difference in the proportion of patients requiring hemodialysis (2.97% vs. 10.0%, p-value 0.079), or incidence of acute kidney injury (4.0% vs. 12.5%, p-value 1.00) between the treatment group and control group, respectively. Conclusions Conservative rasburicase use was noninferior to aggressive rasburicase use in patients with or at high risk for tumor lysis syndrome.

[Effect of the Administration Period of Rasburicase in Japanese Adult Hematological Malignancy Patients at High-Risk for Tumor Lysis Syndrome].

Tumor lysis syndrome (TLS) is a life-threatening metabolic complication caused by the rapid breakdown of malignant cells. It is an oncologic emergency and occurs spontaneously after the initiation of chemotherapy for hematological malignancies. Therefore, the management of TLS is important. Rasburicase (RSB) has been shown to be effective for the management of TLS. We retrospectively investigated the optimal administration period of RSB (1 to 7 days) for 38 adult patients with a hematological malignancy who were at high risk for TLS. In all patients, the serum uric acid (sUA) value did not increase beyond the upper limit of normal. Clinical TLS did not occur in any patients. Seven patients were administered a single-dose of RSB and sUA remained within normal limits. These results suggested that single-dose RSB administration was efficacious for Japanese adult patients with hematological malignancies who are at high risk for TLS.

Polypeptides with High Zwitterion Density for Safe and Effective Therapeutics.

The commonly used "stealth material" poly(ethylene glycol) (PEG) effectively promotes the pharmacokinetics of therapeutic cargos while reducing their immune response. However, recent studies have suggested that PEG could induce adverse reactions, including the emergence of anti-PEG antibodies and tissue histologic changes. An alternative stealth material with no or less immunogenicity and organ toxicity is thus urgently needed. We designed a polypeptide with high zwitterion density (PepCB) as a stealth material for therapeutics. Neither tissue histological changes in liver, kidney, or spleen, nor abnormal behavior, sickness or death was induced by the synthesized polymer after high-dosage administration for three months in rats. When conjugated to a therapeutic protein uricase, the uricase-PepCB bioconjugate showed significantly improved pharmacokinetics and immunological properties compared with uricase-PEG conjugates.

Single 4.5 mg fixed-dose of rasburicase for hyperuricemia associated with tumor lysis syndrome.

Rasburicase is a recombinant urate oxidase enzyme administered for treatment of hyperuricemia associated with tumor lysis syndrome. Studies demonstrate effectiveness of single fixed-dose rasburicase as compared to the FDA-approved dose of 0.2 mg/kg intravenously daily for up to five days. Doses in these studies range from 1.5 mg to 7.5 mg. Our study evaluated outcomes in patients who received single 4.5 mg fixed-dose rasburicase. This retrospective, IRB-approved chart review evaluated adult oncology subjects who received fixed-dose rasburicase between January 2007 and April 2014. The primary outcome was percentage of patients with normalization of uric acid (level <8 mg/dL within 24 h) after a single 4.5 mg fixed-dose of rasburicase. Secondary objectives were incidence of initial failure of fixed-dose rasburicase and normalization of uric acid in overweight (body mass index ≥25 kg/m2) versus non-overweight patients. Initial failure was defined as need for additional doses or progression to dialysis within one week of the initial fixed-dose. In the 128 patients included, the mean baseline uric acid level was 14.84 mg/dL. Of the 112 patients with a follow-up uric acid level, 68% achieved normalization within 24 h of rasburicase administration. Thirty-eight patients received additional treatment: 10 received additional dose(s) and 28 underwent dialysis. Normalization of uric acid in overweight versus non-overweight patients was 66% and 73%, respectively. Overall, a single 4.5 mg fixed-dose of rasburicase effectively normalized uric acid in 68% of patients within 24 h. Further studies are needed to determine the optimal single fixed-dose necessary for treatment response across all patients.

The optimal single-dose regimen of rasburicase for management of tumour lysis syndrome in children and adults: a systematic review and meta-analysis.

WHAT IS KNOWN AND OBJECTIVE: To perform a meta-analysis exploring the optimal single-dose regimen for managing tumour lysis syndrome (TLS) in children and adults with haematological malignancies. METHODS: We systematically searched PubMed, MEDLINE, Web of Science, the Cochrane Library and the ClinicalTrials.gov website for studies regarding single-dose rasburicase in paediatric and adult patients with TLS. Data were analysed using Open MetaAnalyst statistical software. RESULTS: Fifteen adult studies (fourteen retrospective studies and one randomized controlled trial) and four observational studies using children were extracted, with a total of 906 and 92 subjects, respectively. Single doses of 1·5, 3, 4·5, 6, 7·5 mg and weight-based single doses of 0·05 and 0·15 mg/kg were compared. The response rate for 6, 7·5 mg and 0·15 mg/kg single doses was 90% (95% CI: 0·825-0·974), 98·6% (95% CI: 0·957-1·015) and 93·6% (95% CI: 0·864-1·007), respectively, and higher than other dosing regimens tested. The single doses of 6 mg and 0·15 mg/kg rasburicase decreased uric acid levels more than the other regimens, and the mean uric acid reduction was 8·45 mg/dL (95% CI, 7·51-9·38) and 10 mg/dL (95% CI, 8·58-11·42), respectively. WHAT IS NEW AND CONCLUSION: Our meta-analysis revealed that, for adult patients, a single 6 mg rasburicase dose is sufficient to normalize and sustain lower uric acid and creatinine levels in adults with TLS. This dose, therefore, balances cost and efficacy of treatment. The 3- and 4·5-mg single dose can be considered if the baseline uric acid level <12 mg/dL, with close monitoring of clinical and biochemical parameters, and repeat dosing if required. The 1·5 mg and 0·15 mg/kg single dose were sufficient to manage TLS in children.

Treatment of tumor lysis syndrome in children with leukemia/lymphoma in resource-limited settings-Efficacy of a fixed low-dose rasburicase.

Rasburicase is a novel drug used during the management of tumor lysis syndrome. In countries with limited resources, it is frequently given at a lower dose and only for the treatment of established tumor lysis syndrome and not as prophylaxis. A retrospective study was conducted in the department of pediatric oncology at a tertiary referral oncology center in south India to analyze the use of rasburicase over the past 3 years. Data of all the 18 children (< 14 years of age) who were given rasburicase for the management of hyperuricemia were collected and analyzed. With a mean rasburicase dose of 0.085 mg/kg, hyperuricemia was managed efficiently without the need for a hemodialysis in 16 children (88.8 %). The fall in mean serum uric acid levels after the administration of a single dose of rasburicase at 4, 24, and 48 hours was 31.18 %, 64.8 %, and 74.5 %, respectively. Rasburicase efficiently decreases the uric acid levels to a normal level within a short period. In resource-limited settings, rasburicase at a lower dose is a promising option for managing hyperuricemia in the event of a tumor lysis syndrome.

Prediction of Therapeutic Effect of Rasburicase on Hyperuricemia Associated with Chemotherapy Based on Theoretical Model.

Rasburicase has a strong and fast effect for reducing blood levels of uric acid. However, there have been no reports of theoretical analysis for the rational dose and interval of administration. Thus we constructed a pharmacokinetic and pharmacodynamic model to determine changes in uric acid level after rasburicase administration at various doses and regimens. The time courses of uric acid level predicted using our model were in good agreement with observed data, indicating adequate performance for our model. The therapeutic effects after a single infusion at various rates of generation of uric acid were predicted. The maximum effect was not a large difference, in spite of the generation rate. Then, the therapeutic effects of repeated administrations were predicted. The effect did not change when rasburicase was administered at more than the usual dose. Besides, as the administration interval increased, the difference between minimum and maximum level of uric acid became greater. However, in all doses and regimens, adequate therapeutic effects were obtained. In conclusion, the model was found useful for predicting therapeutic effect of rasburicase and individually determining rational dosage regimen of rasburicase.

Nanocapsule assemblies as effective enzyme delivery systems against hyperuricemia.

The uricase nanocapsule assemblies (UNAs) were developed as effective delivery systems against hyperuricemia following parenteral enzyme therapy. UNAs were characterized in terms of micromorphology, size, catalytic activity, stability, and enzymatic kinetics. The pharmacokinetics/pharmacodynamics in rats after intravenous or subcutaneous injection was investigated. Immunogenicity, hemolysis and stimulation were determined. UNA was composed of many nanocapsules, and thus had higher loading efficiencies and stabilities than a single nanocapsule. The uricase molecules entrapped inside nanocapsules were separated from the circulating bloodstream to retain catalytic activities for a longer time than free uricase. UNAs increased the bioavailability and uric acid-lowering efficacy of uricase, while the immunogenicity and hemolysis rate of uricase were decreased. The superior properties of UNAs might be ascribed to the favorable conformational changes of uricase. Nanocapsule assemblies appeared to be able to deliver uricase effectively. This study also highlighted the importance of suitable systems for therapeutic enzyme delivery.