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Clinical Nephrology |




* Clinical Research Centre for Rare Diseases "Aldo e Cele Daccò," Mario Negri Institute for Pharmacological Research, Villa Camozzi, Ranica, and
Unit of Nephrology, Azienda Ospedaliera Ospedali Riuniti, Bergamo, Italy
Address correspondence to: Dr. Piero Ruggenenti, "Mario Negri" Institute for Pharmacological Research, Negri Bergamo Laboratories, Via Gavazzeni, 11-24125 Bergamo, Italy. Phone: +39-035-319-888; Fax: +39-035-319-331; E-mail: manuelap{at}marionegri.it
| Abstract |
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Design, Setting, Participants, & Measurements: In a matched-cohort, single-center, controlled study, the outcome of 12 new incident patients who had idiopathic membranous nephropathy and nephrotic syndrome and received a B cell–driven treatment was compared with that of 24 historical reference patients who were given the standard protocol of four weekly doses of 375 mg/m2.
Results: Only one patient needed a second dose to achieve full CD20 cell depletion. At 1 yr, time course of the components of nephrotic syndrome and the proportion of patients who achieved disease remission (25%) was identical in both groups. Persistent CD20 cell depletion was achieved in all patients. Costs for rituximab treatment and hospitalizations totalled
3770.90 ($4902.20) and
13,977.60 ($18,170.80) with the B cell–driven and the four-dose protocol, respectively. One patient on standard protocol had a severe adverse reaction at second rituximab dose. Thus, B cell titrated as effectively as standard rituximab treatment achieves B cell depletion and idiopathic membranous nephropathy remission but is fourfold less expensive, allowing for more than
10,000, approximately $13,000 in savings per patient.
Conclusions: Avoiding unnecessary reexposure to rituximab is extremely cost-saving and may limit the production of antichimeric antibodies that may increase the risk for adverse reactions and prevent re-treatment of disease recurrences.
| Introduction |
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However, in 29 consecutive patients who were given four weekly doses of 375 mg/m2 to treat IMN and persistent nephrotic syndrome, we observed a full B cell depletion already after the first rituximab administration (5,6). This finding suggested that a single rituximab administration might be sufficient to inhibit fully aberrant B cell clones that produce pathogenic autoantibodies. To test this hypothesis, we designed a treatment protocol titrated to circulating B cells and, in the setting of a prospective matched-cohort study (7), compared the outcome of new incident patients who had IMN and received this novel regimen with that of historical reference patients who were given the standard protocol.
| Materials and Methods |
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3.5 g/24 h for at least 6 mo of angiotensin-converting enzyme inhibitor therapy (ramipril 5 to 10 mg/d), no previous remissions or treatment with steroids or immunosuppressive drugs during the past year, and no circulating hepatitis B surface antigens or anti–hepatitis B core antibodies. Since November 2005, however, we replaced the standard protocol of four weekly doses of 375 mg/m2 with a novel protocol titrated to circulating B cells.
Study Design
In this matched-cohort study, we compared the outcome of each patient who was given the B cell–driven protocol with that of two reference patients who were matched by age (±5 yr), gender, and proteinuria (±1 g/24 h) from the cohort of patients who were given the standard protocol. All patients gave written informed consent according to the Declaration of Helsinki. The study protocol was approved by the Ethical Committee of the Clinical Research Center for Rare Diseases "Aldo & Cele Daccò," Villa Camozzi, of the Mario Negri Institute for Pharmacologic Research. This was a fully academic, internally funded study without involvement of pharmaceutical companies.
Patients were hospitalized the evening before and were discharged the day after each rituximab administration. At admission, 24-h urinary protein excretion (mean of three consecutive measurements), circulating CD20 and CD19 B cells (counted by fluorescence-assisted cell-sorter analysis), and relevant clinical and laboratory parameters (including the tubular-interstitial score [6] at pretreatment biopsies) were recorded. After premedication with 10 mg of chlorphenamine and 500 mg of hydrocortisone, 375 mg/m2 rituximab reconstituted in saline to a concentration of 1 mg/ml was infused at an initial rate of 50 ml/h, progressively increased according to tolerability. An intensivist was alerted in the case of adverse events during the infusion. Baseline parameters were then evaluated weekly for 4 wk and every month up to 1 yr. When
5 B cells/mm3 were detected in the circulation after the first administration, patients who were allocated to the B cell–driven protocol received a second infusion. Reference patients who were allocated to the standard protocol received three additional weekly infusions regardless of B cell counts. All patients were advised to have low sodium and controlled protein intake and received symptomatic treatment to control edema, hypertension, and dyslipidemia. Treatment targets were the same with the two regimens (8).
Cost Analysis
Cost analysis took the perspective of healthy services providers, and the costing method determined the direct health care costs associated with each treatment schedule. All resource use was valued at 2006 Euro prices. Rituximab costs were estimated on the basis of price and amount infused. Costs for hospitalization were obtained from the Hospital Economy Department. Indirect costs were not considered.
Statistical Analyses
Main outcome variable was 24-h urinary protein excretion considered as a continuous variable. Categorical outcomes included complete (24-h proteinuria reduction to <0.3 g in at least two consecutive evaluations and stable or decreasing serum creatinine) or partial (24-h proteinuria reduction to <3 g combined with a reduction of >50% versus baseline in at least two consecutive evaluations and stable or decreasing serum creatinine) remission, respectively, or no response (24-h proteinuria
3.5 g throughout the whole study period and/or increasing serum creatinine). The t test was used for comparisons between continuous variables, and
2 and Fisher exact tests were used for comparisons between categorical variables. Association between variables was measured by means of Pearson correlation coefficient. All statistical tests were two-sided. P < 0.05 was considered statistically significant. Data were expressed as means ± SD or median ± SE as appropriate.
| Results |
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Costs
Overall, patients and reference patients received 13 and 96 infusions, equivalent to a cumulative individual dosage of 9.7 and 36.1 mg/kg, respectively. Considering a cost of
4.13 (equivalent to $5.37) per milligram of rituximab, the individual treatment cost for a patient of 77.6 kg (the average weight of patients included in both cohorts considered as a whole) was of
3108.70 ($4041.30) or
11,569.60 ($15,040.50) with the B cell–driven or standard protocol, respectively.
On average, patients and reference patients were hospitalized for 2.2 and 8.0 d, respectively. Considering a daily hospitalization cost of
301.00 ($391.30), the individual cost was
662.20 ($860.90) and
2408.00 ($3130.40) for patients and reference patients, respectively. Overall, the individual treatment cost was
3770.90 ($4902.20) with the B cell–driven protocol and
13,977.60 ($18,170.80) with the standard treatment. Thus, B cell–driven compared with standard rituximab treatment saved
10,206.70 ($13,268.70) per patient.
| Discussion |
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14,000 (approximately $18,000) per patient. Therefore, we explored whether avoiding repeated drug exposure allowed limitation of adverse effects and costs of rituximab therapy without affecting the efficacy of treatment. Indeed, in this prospective, matched-cohort study, we found that lymphocytolytic rituximab treatment titrated to circulating B cells was as effective as the standard four-dose protocol in inducing IMN remission but showed a better risk/benefit profile, required fewer hospitalizations, and was four-fold less expensive, allowing for more than
10,000 (approximately $13,000) in savings per patient. In the two treatment groups, proteinuria decreased, serum albumin increased, and cholesterol decreased to a similar extent at each time point, and the same proportion of patients achieved complete or partial disease remission. Notably, circulating CD20 B cells were fully depleted already after the first rituximab administration and remained below normal range throughout the whole observation period in both groups. Flow cytometry counts of B cells that carry the CD19 marker—another surface antigen that identifies plasma cell precursors (4)—showed an identical trend. This confirmed that failure to detect CD20+ cells was not due to CD20 antigen masking upon rituximab binding to its specific receptor but rather reflected a true and persistent B cell depletion from the circulation.
These data converge to indicate that in the large majority of cases, three repeated rituximab doses after an initial infusion of 375 mg for m2 body surface area do not provide additional benefit. At most, in a very small minority of cases, a second course may be indicated when full B cell depletion is not achieved by the first dose.
One patient on standard therapy had a severe reaction that, despite steroid and antihistamine premedication, recurred, although with less severe symptoms, during the second infusion despite steroid and antihistamine premedication. One additional patient who received the four-dose course of rituximab had a systemic rash as soon as a second course was attempted to cure a recurrence of the disease. The rash recurred even when rituximab was infused after 1 wk of steroid and antihistamine premedication, and this definitely prevented the execution of treatment. Subsequent analyses revealed that the patient had developed anti-rituximab antibodies. Indeed, repeated or prolonged exposure to rituximab may induce the production of antichimeric antibodies (10,11), which may limit the effect of treatment and increase the risk for hypersensitivity reactions of the immediate type upon drug reexposure. This may prevent re-treatment in those who, after an initial response to therapy, may require a second rituximab course because of disease recurrence. Thus, avoiding unnecessary infusions during the initial course of rituximab may have important clinical implications.
Available studies that evaluated the effect of rituximab in autoimmune diseases are too short and small to assess late and rare complications such as malignancies and opportunistic infections (4,12,13). Moreover, data may be confounded by concomitant immunosuppressive therapy. However, fatal hepatitis B virus reactivation has been reported after rituximab monotherapy with the standard four-dose protocol (14,15), and studies with other lymphocytolytic drugs such as Orthoclone OKT3 (16) and thymoglobulins (8) showed a positive correlation between cumulative drug exposure and risk. Therefore, minimizing exposure to rituximab by titrating treatment to circulating B cells might also improve the safety profile of lymphocytolytic therapy.
An intriguing finding of our study, as well as of previous studies of rituximab in IMN (5,6,17), is that the decrease in proteinuria was already apparent at 3 mo after drug administration. A possible explanation is that in patients with active IMN disease, there is a balance between the production of autoantibodies by activated plasma cells and their continuous clearance from the circulation via ultrafiltration through the abnormally permeant glomerular barrier and concomitant consumption in the kidney at the site where they interact with their specific antigen(s) to form immunocomplexes. This balance is broken after rituximab administration induces a full depletion of the plasma cell precursors. Indeed, chronically activated plasma cells have a faster turnover than quiescent plasma cells and a shorter half-life (17). Thus, their number should start to decline shortly after rituximab treatment, and this should translate into a parallel reduction in antibody production. The new synthesis of autoantibodies is progressively exhausted, the cleared antibodies are not fully replaced any longer, and pathogenic antibodies may progressively disappear from the circulation. This may explain why urinary proteins start to decrease already in the first months after rituximab administration and then progressively decrease over time, in a process that may continue for up to 1 yr (18).
Despite substantial and progressive reduction versus pretreatment levels and regardless of treatment group, residual 24-h proteinuria persistently exceeded 3.5 g in one third of patients who, therefore, remained at increased risk for disease progression and for complications of the nephrotic syndrome (19). We previously found that these patients tend to have more severe chronic, in particular tubulointerstitial, changes at biopsy evaluation and may benefit from dual renin-angiotensin system blockade by combined therapy with angiotensin-converting enzyme inhibitors and angiotensin II blockers (6). The lack of statistical significance in the correlation between proteinuria reduction on follow-up versus baseline and tubulointerstitial score in this study may reflect the relatively small sample size and the spontaneous fluctuations in proteinuria that reduced the power of the analyses.
A strength of our study is that patients were closely monitored with predefined evaluations and that at each time point, proteinuria—the primary efficacy variable—was measured in three consecutive urinary collections and the mean value was considered for statistical analyses. Moreover, we evaluated whether the urine was properly collected by measuring 24-h urinary creatinine excretion and discarded samples with urinary excretions outside the physiologic range. This limited the confounding effect of random fluctuations or of erroneous measurements of proteinuria, which increased the power of the analyses and the reliability of the findings despite the relatively small sample size. On the same line, that all patients were aware of the severity of their disease and showed a remarkably good compliance even before rituximab administration suggests that it is very unlikely that the study findings were confounded by an increased adherence to treatment and diet recommendations. Thus, evidence of benefit provided by this and previous studies of the effects of rituximab in IMN (5,6,18) may provide the background for designing an adequately powered, randomized clinical trial to assess definitively the risk/benefit profile of rituximab as compared with other medications, such as steroids, alkylating agents, and calcineurin inhibitors, that have been extensively used in the past in this clinical setting (20,21). On this regard, finding that at 1 yr of follow-up the reduction in proteinuria versus baseline observed in our study (60%) was comparable to that previously reported in patients who were treated with methylprednisolone and chlorambucil (20) or cyclophosphamide (21) can be taken to suggest that, at least in the short term, rituximab is as effective as aspecific immunosuppressants such as steroids and alkylating agents and, considering its remarkably good risk profile, might offer the advantage of a lower toxicity.
| Conclusions |
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| Disclosures |
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| Acknowledgments |
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| Footnotes |
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P.C. and P.R. contributed equally to this work.
Received March 9, 2007. Accepted June 19, 2007.
| References |
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