Transplantation Reviews xxx (2014) xxx–xxx

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Transplantation Reviews journal homepage: www.elsevier.com/locate/trre

Original contribution

A systematic review of the use of rituximab as induction therapy in renal transplantation☆,☆☆,★ Philip S. Macklin a, Peter J. Morris a,b, Simon R. Knight a,b,⁎ a b

Centre for Evidence in Transplantation (CET), Clinical Effectiveness Unit, The Royal College of Surgeons of England, London, UK Nuffield Department of Surgical Sciences, Oxford University, Oxford, UK

a b s t r a c t Rituximab is a B-lymphocyte depleting agent used to treat lymphoma and autoimmune diseases. There has been recent interest in its use both for management of highly-sensitised and ABO-incompatible recipients but also for induction therapy before transplantation. This systematic review evaluates the evidence for its use as part of induction protocols in ABO-compatible, non-sensitised recipients. 4 databases and 3 trial registries were searched for studies of the use of rituximab as part of induction protocols. The small number of identified studies precluded meta-analysis and thus a narrative review was conducted. 12 manuscripts met the inclusion criteria, relating to 5 individual studies. No significant improvements in patient and graft survival or acute rejection rates were identified with rituximab induction. A single small study reported a trend towards improved graft function with the addition of rituximab induction to a standard immunosuppressive regimen. Rituximab was not found to be associated with increased infectious complications in any study but concerns were raised over possible associations with leukopaenia and cardiovascular mortality. Overall, no convincing benefit of rituximab induction was found and some safety concerns were identified. The results of on-going trials are awaited but further studies may be required before we can draw firm conclusions regarding the efficacy and safety of rituximab in this setting. © 2014 Elsevier Inc. All rights reserved.

1. Introduction Rituximab is a chimeric murine/human monoclonal antibody active against the cell membrane protein CD20 found on the surface of B-lymphocytes prior to their terminal differentiation into plasma cells and responsible for regulating their progression through the cell cycle [1]. Rituximab eliminates B-lymphocytes completely in 88% transplant recipients, an effect that lasts for over 15 months in the majority [2] and thus abrogates antibody-mediated immune responses. When B-lymphocytes begin to reconstitute, they preferentially repopulate as naïve, rather than memory, subsets [3–5]. As B-lymphocytes also function as antigen presenting cells, rituximab is also likely to indirectly ☆ Authorship: PSM performed the database searches, screened search results for inclusion, quality assessed and abstracted data from the included studies and co-wrote the manuscript. This work formed part of his thesis for the Edinburgh Surgical Sciences Qualification (ESSQ), an online Masters programme in surgical sciences at the University of Edinburgh (www.essq.rcsed.ac.uk).SRK suggested the topic of the systematic review, screened search results for inclusion, quality assessed and abstracted data from the included studies and co-wrote the manuscript.PJM provided a third opinion in cases of discordance regarding study inclusion, reviewed the manuscript, supervised PSM's thesis and offered guidance throughout the project. ☆☆ Funding sources: No external funding was received for this study. ★ International Prospective Register of Systematic Reviews [PROSPERO] registration number: CRD42012002101. ⁎ Corresponding author at: Centre for Evidence in Transplantation, Royal College of Surgeons of England, 35-43 Lincoln's Inn Fields, London, UK, WC2A 3PE. Tel.: +44 207 869 6627; fax: +44 207 869 6644. E-mail address: [email protected] (S.R. Knight).

depress T-lymphocyte activity, with both in-vitro and in-vivo evidence supporting this hypothesis [6]. Rituximab has mainly been used to treat haematological malignancies [7] and autoimmune diseases [8,9]. Transplantation is the optimal treatment for end-stage renal failure because of improved patient outcomes and cost efficiency [10–12]. Traditionally, focus has been placed on the prevention of cellular rejection by administration of induction therapy comprising high-dose maintenance immunosuppressants or depleting or non-depleting T-lymphocyte antibodies. Whilst induction therapy directed at T-lymphocytes is known to reduce the incidence of acute graft rejection [13–16], it is uncertain if it actually improves long-term outcomes. Furthermore, there is an increasing appreciation of the importance of B-lymphocytes in the rejection process. The first description of cytotoxic antibodies after renal transplantation [17] and their human leukocyte antigen (HLA) specificity [18] in the late 1960s led to a slowly increasing interest in the role of antibodies in the rejection process. More recently, Terasaki and Ozawa have demonstrated that 20.9% of 2278 kidney transplant recipients had anti-HLA antibodies at 6-month follow-up [19]. Amongst these patients, 6.6% experienced graft loss at 1-year as compared to 3.3% patients without such antibodies (P = 0.0007). In another study, 99/173 (57%) recipients presenting with late-onset graft dysfunction were found to have evidence of antibody-mediated graft injury (defined as the presence of donorspecific antibody [DSA] and/or C4d staining on biopsy) and those with C4d positivity were at increased risk of subsequent graft loss [20]. Thus an interest has developed in induction therapies that deplete B-lymphocytes to prevent both alloantibody production and antigen presentation, which may in turn reduce rates of both humoral and cellular rejection.

http://dx.doi.org/10.1016/j.trre.2014.12.001 0955-470X/© 2014 Elsevier Inc. All rights reserved.

Please cite this article as: Macklin PS, et al, A systematic review of the use of rituximab as induction therapy in renal transplantation, Transplant Rev (2014), http://dx.doi.org/10.1016/j.trre.2014.12.001

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Rituximab has been used as an immunomodulatory agent in renal transplantation, although there appears to be limited evidence to support this practise. Our recent systematic review of the use of rituximab as part of desensitisation protocols identified evidence of limited quality suggesting that rituximab can replace splenectomy in ABO-incompatible renal transplant recipients and may confer some benefit in highlysensitised recipients [21]. In this systematic review, we aim to critically evaluate the use of rituximab as part of induction protocols in ABOcompatible, non-sensitised recipients.

2.4. Study selection Duplicates were discarded from initial search results. The remaining titles and abstracts were reviewed independently by two authors (PSM and SRK) to decide whether they met inclusion criteria. Full articles of potentially relevant studies were reviewed prior to confirming their inclusion. Any discrepancies that could not be resolved were dealt with by discussion with the third author (PJM). 2.5. Data abstraction and analysis

2. Materials and methods 2.1. Protocol and registration This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement [22]. The review is registered with the International Prospective Register of Systematic Reviews (PROSPERO; registration number CRD42012002101).

2.2. Eligibility criteria Inclusion criteria specified all studies of ABO-compatible, nonsensitised adult or paediatric renal transplant recipients in which rituximab-based induction protocols were administered. Exclusion criteria included ABO-incompatible and highly-sensitised study populations, non-renal solid organ and bone marrow transplant studies and case reports. No date or language limits were applied.

Studies are identified by the first author and year of the first full publication (if available) or published abstract or letter. Demographic, outcome and methodological quality data for included studies were abstracted into a database by means of a pro forma. Outcomes and timing of reported outcomes were recorded as specified in each study. When not explicitly stated, outcomes were calculated on the basis of information included within the published record; if this was not possible, ‘not reported’ was recorded in the results tables. All serum creatinine (SCr) values were converted to International System of Units (SI units; μmol/L). Data are presented as the mean (± standard deviation) or median (range) and all values are expressed to one decimal place unless the original article did not provide this degree of accuracy. The exceptions to this are P values which are presented as reported in the published record. Primary study outcomes focus on therapeutic efficacy, including patient and graft survival, incidence of rejection and graft function (SCr or glomerular filtration rate). Secondary outcomes focus on safety. 2.6. Risk of bias in individual studies

2.3. Literature search A systematic literature search was performed in Ovid MEDLINE and Embase, The Cochrane Library and The Transplant Library for studies meeting the inclusion criteria. Search terms included keywords and free text terms for rituximab and its aliases, along with keywords and free text alternatives for renal transplantation (Table 1). The final date for searches was 15th April 2014. Reference lists of identified studies were assessed for potentially relevant records not identified by the initial search. In order to identify unpublished or in-progress studies, we searched ClinicalTrials.gov (http://clinicaltrials.gov), the International Standard Randomised Controlled Trial Number (ISRCTN) Register (http://www. isrctn.org) and the World Health Organisation International Clinical Trials Registry Platform (http://apps.who.int/trialsearch). We also contacted the pharmaceutical companies that manufacture rituximab for details of unpublished trials (Roche [European Union and Canada], Biogen Idec/Genentech [United States of America] and Chugai Pharmaceutical [Japan]).

Table 1 Sample search strategy for OVID Medline. The population – renal transplant recipients 1 TRANSPLANTATION/ 2 ORGAN TRANSPLANTATION/ 3 exp KIDNEY TRANSPLANTATION/ 4 ((kidney$1 or renal$1 or organ$1 or viscera$) adj5 transplant$).ti,ab. 5 ((kidney$1 or renal$1 or organ$1 or viscera$) adj5 graft$).ti,ab. 6 ((kidney$1 or renal$1 or organ$1 or viscera$) adj5 allograft$).ti,ab. 7 or/1-6 The intervention – rituximab 8 (rituximab or mabthera or rituxan or CD20 or C2B8).ti,ab. 9 7 and 8

The risk of bias in the included studies was assessed by use of the Jadad score [23], and also the adequacy of allocation concealment and evidence of analysis by intention-to-treat. The Jadad score has a maximum score of 5, with a score of 3 or greater being considered as good quality. Where studies were only reported in abstract or letter form, quality assessment was not possible. 2.7. Synthesis of results A narrative synthesis was performed because a lack of high-quality comparative studies precluded meta-analysis. Results are presented in a hierarchical order based upon the Oxford Centre for Evidence-Based Medicine 2011 Levels of Evidence [24]. 3. Results Systematic literature search identified 11 records which met our inclusion criteria (1 full article [25], 6 abstracts [26–31] and 4 letters [32–35]), relating to 4 randomised controlled trials (RCTs) (Table 2) and 1 case series. Further information on one of the identified studies was published during manuscript preparation and is included in the review [36]. The flow of trials through the review process is depicted in Fig. 1. Two of the RCTs were double-blind (Tydén et al. [25,26,32,33] and van den Hoogen et al. [27,28,34,36]) whilst two were open label (Clatworthy et al. [30,35] and Tsai et al. [29]). Only one of the studies was reported as a full paper and received a Jadad score of 4/5 [25]. Whilst there was adequate allocation concealment, the study reported a per-protocol analysis. Searching trial registries identified 4 additional ongoing (ClinicalTrials.gov identifiers – NCT01095172 and NCT01318915) or unpublished studies (ClinicalTrials.gov identifiers – NCT00579592 and NCT01312064) that were potentially relevant. Unfortunately, contacting the lead investigators of these studies and the pharmaceutical companies that manufacture rituximab failed to identify any further data for inclusion.

Please cite this article as: Macklin PS, et al, A systematic review of the use of rituximab as induction therapy in renal transplantation, Transplant Rev (2014), http://dx.doi.org/10.1016/j.trre.2014.12.001

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3.1. RCTs (level 2 evidence)

All outcomes are reported for the end of the study period unless stated otherwise. CS – corticosteroids; DAC – daclizumab; IS – immunosuppression; MMF – mycophenolate mofetil; No. – number; PRA – panel reactive antibody; RTX – rituximab; TAC – tacrolimus; Tx – treatment; UK – United Kingdom. ⁎ Full trial report not available. a At 3 years, 128 patients were alive but only 44 RTX and 47 non-RTX patients participated in follow-up. b P = 0.05 for rejection-free survival in group 1 compared to the other study groups. c The addition of RTX induction to baseline IS with MMF, TAC and CS led to significantly better graft function (P = 0.0238) but there was no statistical difference when compared to the RTX, TAC and CS group.

No difference Favours non-RTX No statistical comparison No statistical comparison No difference No difference Favours RTX c No difference No difference No difference No difference b Favours non-RTX No difference No difference Not reported No difference MMF, TAC + CS Favours non-RTX MMF, TAC + CS No difference TAC + CS Not reported MMF + TAC No difference 36 24 6 12

RTX/Placebo RTX/Placebo RTX + MMF/RTX/MMF RTX + CS/DAC 136 (68/68) a 280 (138/142) 46 (15/15/16) 13 (6/7) PRA ≤50% PRA ≤85% PRA b20% Not reported Tydén (2009) Sweden [25,26,32,33] van den Hoogen (2009)⁎ Netherlands [27,28,34,36] Tsai (2012)⁎ Taiwan [29] Clatworthy (2009)⁎ UK [30,35]

Table 2 Outcomes of randomised controlled trials of rituximab as induction therapy.

Patient survival Baseline IS No. of patients Study period Tx regimen (RTX/non-RTX) (months) (RTX/non-RTX) Inclusion criteria Study (year) country

Graft survival

Incidence of rejection

Graft function Adverse effects

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On the basis of the successful prevention of acute rejection in ABOincompatible recipients with rituximab desensitisation [37], Tydén and colleagues conducted the first RCT of rituximab induction in renal transplantation. They compared rituximab induction to placebo amongst recipients with a panel reactive antibody (PRA) less than 50% with initial outcomes reported at 6 months [25,26,33]. 68 patients in each group completed the study and the authors claimed that rituximab induction led to a non-significant tendency to fewer (11.8% vs. 17.6%; P = 0.317) and milder episodes of acute rejection. Amongst these rejection episodes, more C4d positive (4 vs. 1) and steroid-resistant (5 vs. 2) cases occurred in the placebo group. 1 death and 1 graft loss not related to rejection occurred in each group; thus treatment failure (biopsy-proven acute rejection, graft loss or patient death) was 10 in the rituximab group (14.7%) and 14 in the placebo group (20.6%; P = 0.348). There was no difference in graft function or complications between the groups. Importantly, the study's power calculation was based on a reduction in overall treatment failure and not on acute rejection alone. Furthermore, the beneficial effects of rituximab were less profound than the power calculation anticipated. Therefore, the investigators admit that the study was underpowered to detect a statistically significant reduction in acute rejection rate. Three-year outcomes have now been reported [32]. 44/68 patients in the rituximab group and 47/68 patients were available for followup. Within the rituximab group, there was 1 graft loss due to chronic rejection, 8 deaths (6 cardiovascular deaths, 1 pulmonary carcinoma, and 1 fungal pneumonia) and 15 patients refused to participate. Only 1/33 rituximab patients who underwent Luminex antibody testing had developed anti-HLA DSA. In the control group, 1 graft was lost due to recurrence of primary disease and 20 subjects refused to participate. No deaths were stated to have occurred amongst the control subjects, contradicting the group's previous publications. 6/38 control patients who underwent testing had developed anti-HLA DSA. There was a statistically significant increase in mortality (8/68 patients vs. 0/68 patients, P = 0.006) in the rituximab group but no difference between groups regarding rejection episodes (8/44 vs. 12/47; P = 0.31), treatment failure (10/44 vs. 14/47; P = 0.34), DSA positivity or infectious complications. van den Hoogen and colleagues have recently completed an RCT comparing the outcomes of intra-operative rituximab induction therapy to placebo, followed by standard immunosuppression consisting of tacrolimus, mycophenolate mofetil (MMF) and corticosteroids (ClinicalTrials.gov identifier – NCT00565331) [27,28,34,36]. Interim analysis of the first 69 patients to have reached 6-month follow-up demonstrated similar findings to Tydén's initial results, namely a non-significant reduction in the incidence of acute rejection with rituximab (relative risk of acute rejection = 0.53; 95% confidence interval = 0.21–1.32) with no difference in patient and graft survival, graft function or infectious and malignant complications. They did however find that patients receiving rituximab had significantly lower leukocyte counts (6.6 ± 3.0 vs. 8.0 ± 2.5 × 10 9/L; P = 0.04) and a higher incidence of leukopaenia (defined as a leukocyte count b 3.5 × 10 9/l [18% vs. 2.5%; P = 0.03]). A preliminary overview of their final results has recently been published [36]. 280 patients were randomised, with no difference in biopsy-proven acute rejection within the first 6 months after transplant when comparing rituximab (23/138 = 16.7%) to placebo (30/142 = 21.2%; P = 0.25). However, sub-analysis of 62 patients with PRA N6% and/or undergoing re-transplantation demonstrated a trend towards a reduction in biopsy-proven rejection with rituximab (5/28 = 17.9% vs. 13/34 = 38.2%; P = 0.06). There were no differences in patient and graft survival, graft function, levels of proteinuria or infectious and malignant complications between the two groups. However, incidence of neutropaenia (defined as a neutrophil count b1.5 × 10 9/L) was more common in the rituximab group (24.3% vs. 2.2%; P b 0.001). The complete report of this study is still being finalised but has been

Please cite this article as: Macklin PS, et al, A systematic review of the use of rituximab as induction therapy in renal transplantation, Transplant Rev (2014), http://dx.doi.org/10.1016/j.trre.2014.12.001

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accepted for publication in American Journal of Transplantation (personal communication with lead investigator). Tsai and colleagues have published, in abstract form only, the interim findings of a three-arm prospective RCT comparing non-sensitised (PRA b 20%) adult HLA-mismatched renal transplant recipients receiving induction therapy and maintenance immunosuppression with different combinations of rituximab, MMF, tacrolimus and corticosteroids (World Health Organisation International Clinical Trials Registry Platform Main ID – ACTRN12610000420044) [29]. There was a trend towards greater rejection-free survival (P = 0.05) amongst those receiving rituximab induction with MMF, tacrolimus and corticosteroid immunosuppression (15 patients) when compared to the groups that received rituximab induction with only tacrolimus and corticosteroids immunosuppression (15 patients) or MMF, tacrolimus and corticosteroid immunosuppression without rituximab induction (16 patients). All rejection episodes were responsive to corticosteroid pulse therapy except for one episode of antibody-mediated rejection (AMR) that was treated with plasmapheresis and intravenous immunoglobulin (IVIg). Graft function at 6 months was also significantly better in the combined rituximab and MMF group than in the non-rituximab group (P = 0.0238) but there was no statistical difference when compared with the rituximab, tacrolimus and corticosteroid group. No major infective complications occurred amongst patients receiving rituximab whereas one patient died of sepsis and another required fluconazole treatment for Candida pneumonia in the non-rituximab group. The study eventually recruited a total of sixty patients and the final manuscript is in the process of being prepared (personal communication with lead investigator). In contrast to the previous studies, Clatworthy commenced an RCT comparing induction therapy with rituximab and methylprednisolone to daclizumab (a monoclonal antibody antagonist of the interleukin-2 receptor on T-lymphocytes) [30,35], followed by steroid-free maintenance immunosuppression with tacrolimus and MMF. Despite planning

to recruit 120 patients, the study was halted after the first 13 patients due to a high incidence of acute cellular rejection (ACR) in the rituximab group. 5/6 patients treated with rituximab (83.3%) developed an episode of acute rejection within the first 3 months compared to 1/7 in the daclizumab group (14.3%; P = 0.01). All episodes of rejection responded to corticosteroids and there were no differences in patient or graft survival, graft function or adverse events between the groups at 12 months. 3.2. Case series (level 4 evidence) In a report published in abstract form only, Sundberg and colleagues conducted a non-randomised, open-label pilot study to investigate whether induction with rituximab and alemtuzumab (a monoclonal antibody against the cell membrane protein CD52 found on mature lymphocytes) could facilitate calcineurin inhibitor (CNI)-free immunosuppression (maintenance MMF and low-dose prednisone only) [31]. The study included 30 renal transplant recipients and at 2 years, patient and graft survival were 93.3% and 90.0%, respectively. 53% patients experienced rejection, with half of these patients experiencing more than 1 rejection episode. 68.8% (11/16) patients experiencing rejection required CNI treatment, 10 of whom remained on maintenance CNI therapy. The authors concluded that this induction protocol was associated with a high incidence of rejection and that it would take longer-term follow-up to appreciate the true impact of AMR on patient and graft survival. 4. Discussion None of the studies included in this review demonstrate convincing evidence of improved clinical outcomes with the addition of rituximab induction to standard immunosuppression protocols in non-sensitised patients. Trends towards a reduction in the incidence of acute rejection

Fig. 1. Flow diagram to show inclusion and exclusion of articles for this review. RTX = rituximab

Please cite this article as: Macklin PS, et al, A systematic review of the use of rituximab as induction therapy in renal transplantation, Transplant Rev (2014), http://dx.doi.org/10.1016/j.trre.2014.12.001

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are seen, but none of these reach statistical significance and are tempered by safety concerns [29,32,36]. Several studies raised safety concerns regarding rituximab. Whilst initial reports from van den Hoogen's trial reported a significantly lower leukocyte count with rituximab (6.6 ± 3.0 vs. 8.0 ± 2.5 x10 9/L; P = 0.04), the mean value for this group was still within the generally accepted normal range [28]. However, there was still a statistically significant increase in incidence of leukopaenia (6.5% vs. 0%; P b 0.01) [27] and neutropenia (24.3% vs. 2.2%; P b 0.001) [36]. Of particular concern is the excess mortality in the rituximab arm of the Swedish study at 3 years (8 vs. 0 deaths; P = 0.006) [32]. 6 of these deaths were due to cardiovascular events (myocardial infarction/cardiac arrest) and, given published evidence that B-lymphocytes may have an atheroprotective effect [38], the authors raise the possibility that rituximab therapy may have contributed to the excess cardiac mortality seen. There are a number of case reports and series describing cardiac morbidity related to rituximab treatment in the field of oncology [39,40] but evidence from larger studies and clinical trials has not demonstrated excess risk [41,42]. The findings of the studies which reported a high incidence of rejection using rituximab in CNI minimisation [31] and steroid avoidance [35] protocols should be interpreted with caution. In the CNI minimisation case series, patients were administered a second B-lymphocyte depleting agent (alemtuzumab) and received CNI-free maintenance immunosuppression. In Clatworthy's trial investigating steroid avoidance, the high rate of ACR (83%) can in part be explained by the lack of Tlymphocyte directed induction therapy but it was still higher than that seen in a study of patients who received no induction therapy at all (35%) [43]. Interestingly, Tydén also found a higher rate of acute rejection in ABO-compatible patients receiving rituximab induction 24 hours before transplantation than that seen amongst ABO-incompatible patients who received rituximab desensitisation 1 month before surgery [37]. In Clatworthy's trial, post-transplant serum concentrations of the proinflammatory cytokines tumour necrosis factor-α, interleukin-6 and interleukin-10 were increased in some of the rituximab-treated patients; a similar rise in interleukin-10 was also seen in van den Hoogen's trial [36]. This rituximab-induced ‘cytokine storm’ is well recognised [44] and it is possible that these mediators may facilitate antigen presentation, enhance T-lymphocyte activity and predispose to cellular rejection. Other studies, such as those in desensitisation, have administered rituximab some time prior to transplantation along with corticosteroids, potentially normalising this inflammatory milieu by the time of surgery. Whilst administering rituximab in advance of transplantation would be an option for living procedures, this would obviously not be possible in the setting of deceased donor transplants. The differential effects of B-lymphocyte induction therapies on cells with effector and regulatory (BREG) phenotypes are also likely to be important [45]. Depletion of BREG might actually promote an increased immune response and a similar phenomenon has been demonstrated in both animal models of autoimmunity [46–48] and in humans in the non-transplant setting [49]. However, in a recent study of HLAincompatible renal transplant recipients, rituximab reduced the incidence and magnitude of antibody rebound when compared to placebo but did not improve rejection rates, graft function or graft survival [50]. Recent studies have suggested that B-lymphocytes may play an important role in achieving graft tolerance [51–53]. Therefore, rather than attempting to deplete B-lymphocytes, future induction strategies may be designed to manipulate B-lymphocytes towards an immunoregulatory phenotype. Indeed, evidence suggests that B-lymphocyte depletion with alemtuzumab induction is followed by rapid B-lymphocyte repopulation to up to 165% of baseline [54], but these repopulated Blymphocytes have an immature or regulatory phenotype with a higher proportion of BREG and a delayed repopulation of mature memory Blymphocytes [54–56]. This systematic review highlights the paucity of evidence in this area. The data are further limited by the unquantifiable risk of publication bias and with difficulty in assessing methodological quality of the

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identified studies that are presented in abstract form only. Only one study has been published as a full article [25], with good methodological quality. A further concern is that level of acceptable PRA before induction varied widely between studies, meaning that many of the included participants may have had significant levels of pre-formed antibodies and even DSA. Whilst Tydén's RCT only excluded recipients with PRA N50%, the actual mean PRA in both groups was reported as b5% [25]. However, van den Hoogen's study only excluded recipients with PRA N85% and published abstracts have not reported actual levels. Indeed, the authors actually defined 62/280 trial participants as being immunised (PRA N6% or cases of retransplantation) [27]. As rituximab has no activity against differentiated plasma cells, its effect in sensitised patients (without the use of adjunctive antibody removal therapies) may be limited, although a more important observation than its effect on PRA would be the elimination of DSA before transplantation. The lack of evidence suggests adequately powered studies are required before we can draw firm conclusions regarding the efficacy and safety of rituximab in this setting. We believe that a double-blind, randomised trial comparing rituximab to placebo in addition to Tlymphocyte directed induction (e.g. anti-thymocyte globulin or IL2 receptor antibodies) with conventional maintenance immunosuppression, particularly in recipients who have no demonstrable DSA at any time before transplantation, would improve upon the existing evidence. It would also be interesting to study whether rituximab adds anything over induction agents with combined T- and B-lymphocyte activity, such as alemtuzumab. The findings of ongoing trials may also help to answer some of these remaining questions.

Acknowledgments The authors would like to express our gratitude to all investigators who responded to our emails requesting further information relating to their studies of rituximab as induction therapy. PJM has chaired the Data and Safety Monitoring Committee for renal belatacept trials sponsored by Bristol-Myers Squibb during the past 10 years. He currently chairs the Data and Safety Monitoring Committee for the 3C study of alemtuzumab induction and the ONE study of immunoregulatory cells, and chairs the External Advisory Board of the BioDrIM study of biomarkers, all in renal transplantation.

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Please cite this article as: Macklin PS, et al, A systematic review of the use of rituximab as induction therapy in renal transplantation, Transplant Rev (2014), http://dx.doi.org/10.1016/j.trre.2014.12.001