Anti-rituximab Antibodies Research Articles

A novel dosing approach for rituximab in glomerular diseases based on a population pharmacokinetic analysis

ObjectivesRituximab is being increasingly prescribed for the treatment of autoimmune glomerular diseases. While it is highly effective for some diseases, the response is less predictable for others, which may be due to differing requirements in terms of the dosing according to the disease type and variations concerning exposure to the drug. MethodsWe compiled novel rituximab dosing schedules according to pharmacokinetic analysis of data gathered from rituximab treated patients in a tertiary referral nephrology centre between May 2020 and June 2023. The population-pharmacokinetic analysis was based on the rituximab dosing, the patients’ characteristics, rituximab levels and anti-rituximab antibodies. ResultsThe analysis, which was based on data from 185 patients, clearly highlighted differing rituximab dosing requirements for patients with ANCA associated vasculitis and minimal change disease compared to those with membranous nephropathy, focal-segmental glomerulosclerosis and lupus nephritis. This corresponded to the good treatment response of the first two diseases and the unreliable efficacy for the others. The model predicts the rituximab pharmacokinetics with high degree of accuracy when body weight, proteinuria, type of glomerulonephritis, treatment length and anti-rituximab antibodies formation are used as covariates. We proposed a dosing schedule with shortened dosing intervals for difficult-to-treat diagnoses with high proteinuria. ConclusionIn order to ensure reliable and comparable exposure of rituximab with respect to the full range of glomerular diseases, the dosing schedule should be adjusted for membranous nephropathy, focal-segmental glomerulosclerosis and lupus nephritis. This is largely, but not solely, due to the enhanced level of unselective proteinuria in these diseases.

Using real-world data to inform dosing strategies of rituximab for pediatric patients with frequent-relapsing or steroid-dependent nephrotic syndrome: a prospective pharmacokinetic-pharmacodynamic study.

Objectives: Rituximab is frequently used off-label for the treatment of frequent-relapsing/steroid-dependent nephrotic syndrome (FRNS/SDNS). However, the optimal dosing schedules remain undetermined. The objective of this study was to establish a population pharmacokinetic-pharmacodynamic (PK-PD) model in pediatric patients with FRNS/SDNS, and to investigate dosing regimens that provide adequate suppression of B lymphocytes. Methods: A prospective, open-label, single-center study was conducted in Nephrology Department at Children's Hospital of Fudan University, and a two-compartment PK model of rituximab in pediatric FRNS/SDNS has been developed previously by our group. CD19+ lymphocyte count profiles were obtained from these patients. The presence of anti-rituximab antibodies was assessed prior to medication in children who had previously received rituximab or during follow-up at the last sampling point for PK analysis. PK-PD analyses were performed to describe the changes of CD19+ lymphocytes, with rituximab assumed to increase their death rate. Monte Carlo simulation was conducted to evaluate different dosing regimens. Results: In total, 102 measurements of CD19+ lymphocyte counts were available for PK-PD analysis. No detectable levels of anti-rituximab antibodies were observed during the PK follow-up period. A turnover model with saturable stimulatory action of rituximab on the removal of lymphocytes best characterized the relationship between rituximab concentration and CD19+ lymphocyte counts, where the Emax and EC50 were estimated to be 99.6*106/L and 5.87μg/mL, respectively. Simulations indicated that a single infusion of 750mg/m2 and 2 infusions of 375mg/m2 both yielded a 10-week suppression of CD19+ lymphocytes. Conclusion: This study represents a first attempt to quantitatively describe the PK-PD relationship of rituximab in pediatric patients with FRNS/SDNS, and provide a potential pathway for future precision dosing strategy for rituximab therapy. Further clinical studies are warranted to evaluate the efficacy and safety of different dosing schemes.

Acquired thrombotic thrombocytopenic purpura with rituximab-induced serum sickness

The patient was a 38-year-old man who was admitted to our hospital with fever, vomiting and unclear speech. Blood tests showed hemolytic anemia, thrombocytopenia, and elevated creatinine, and a Coombs test was negative. ADAMTS13 activity was <1% and ADAMTS13 inhibitor was 0.7 BU/ml, so we diagnosed acquired thrombotic thrombocytopenic purpura (aTTP). We started plasma exchange and prednisolone 1 mg/kg on the day of admission (day 1). The platelet count recovered to normal on day 5, and hemolytic findings improved. However, symptoms worsened again, and thus we started rituximab for refractory aTTP on day 24. After rituximab administration, the patient showed no signs of infusion reaction (IR) or recurrence. On day 31, he received the second dose of rituximab and was discharged. On day 38, he had knee pain, fever, erythema, and difficulty moving. CRP was elevated and CH50 slightly decreased. Imaging findings were normal. Anti-rituximab antibody was positive (197 ng/ml), leading to the diagnosis of rituximab-induced serum sickness. Rituximab administration was discontinued, and the serum sickness has not recurred. The presence of anti-rituximab antibodies may aid diagnosis in patients with suspected symptoms of serum sickness or recurring IR-like symptoms.

#5348 THE EFFECTS OF RITUXIMAB IN NON-HCV-RELATED MIXED CRYOGLOBULINEMIC VASCULITIS

Abstract Background and Aims Remarkable results in severe HCV-related cryoglobulinemic vasculitis have been obtained with Rituximab. Details of the clinical characteristics and effective treatment of non HCV-related cryogloulinemic syndromes are presently lacking. Method This paper reports on a prospective single-Center open study aimed at evaluating the clinical presentation and effects of Rituximab administered alone in patients with severe non HCV-related cryoglobulinemic syndrome Results The study group included 11 patients followed for at least 6 months. Three patients had type I cryoglobulinemia, 6 had type II and the remaining 2 patients had type III. Mean cryocrit was 2.5%. Four out of 11 patients had symptomatic sicca complex with anti-SSA (Ro)/anti SSB (La) antibodies. All 11 patients presented with biopsy-proven renal involvement, 4 out of 11 with leukocytoclastic vasculitis, and 8 with involvement of the peripheral nervous system. Renal biopsy revealed diffuse membranoproliferative glomerulonephritis (MPGN) in 9 out of 11 patients. Extracapillary proliferation and necrosis of the glomerular tuft was observed in 1 of these 9 cases. Interstitial nephritis together with mesangial expansion and capillary immune deposits were observed in 1 patient. Prevalent interstitial fibrosis and glomerular sclerosis were detected in the remaining case. Patients underwent treatment with rituximab alone. After 6 months we observed a remarkable improvement in the necrotizing skin ulcers and a substantial amelioration of the electrophysiological parameters of motor and sensory peripheral neuropathy. Improvement in both renal function (from 2.8 to 1.4 mg/dl, p &amp;lt; 0.001) and proteinuria (from 4.2 g/24 to 0.4 g/24 h, p &amp;lt; 0.001) was found in 10 out of 11 patients, while 1 could not be fully treated because of a severe infusion reaction and sudden development of anti-Rituximab antibodies. Good renal response was confirmed at the end of follow-up (38.4 months). Three patients had a relapse at 6, 12, and 48 months, respectively. Conclusion In our cohort the administration of 4 once-weekly infusions of Rituximab followed by 2 more infusions after 1 and 2 months proved to be effective in the management of these rare patients.

Risk Factors Associated with the Occurrence of Anti-rituximab Antibodies in Membranous Nephropathy.

Teisseyre, Maxime2,3,4; Brglez, Vesna1,2,4; Cremoni, Marion1,2,4; Fernandez, Celine1,2,4; Graça, Daisy1,2,4; Boyet-Suavet, Sonia2,4; Benzaken, Sylvia1; Esnault, Vincent L.M.2,3; Seitz-Polski, Barbara1,2,3,4,a Author Information

Anti-rituximab antibodies demonstrate neutralizing capacity, associate with lower circulating drug levels and earlier relapse in lupus.

High rates of anti-drug antibodies (ADA) to rituximab have been demonstrated in patients undergoing treatment for SLE. However, little is known with regard to their long-term dynamics, impact on drug kinetics and subsequent implications for treatment response. In this study, we aimed to evaluate ADA persistence over time, impact on circulating drug levels, assess clinical outcomes and whether they are capable of neutralizing rituximab. Patients with SLE undergoing treatment with rituximab were recruited to this study (n = 35). Serum samples were collected across a follow-up period of 36 months following treatment (n = 114). Clinical and laboratory data were collected pre-treatment and throughout follow-up. ADA were detected via electrochemiluminescent immunoassays. A complement dependent cytotoxicity assay was used to determine neutralizing capacity of ADA in a sub-cohort of positive samples (n = 38). ADA persisted over the 36-month study period in 64.3% of patients undergoing treatment and titres peaked earlier and remained higher in those who had previously been treated with rituximab when compared with than those who were previously treatment naive. ADA-positive samples had a significantly lower median drug level until six months post rituximab infusion (P = 0.0018). Patients with persistent ADA positivity showed a significant early improvement in disease activity followed by increased rates of relapse. In vitro analysis confirmed the neutralizing capacity of ADA to rituximab. ADA to rituximab were common and persisted over the 36-month period of this study. They associated with earlier drug elimination, an increased rate of relapse and demonstrated neutralizing capacity in vitro.

Evaluation of Clinical Relevance and Biological Effects of Antirituximab Antibodies in Patients With Pemphigus

The clinical relevance of antirituximab antibodies (ARAs) in patients with pemphigus who are treated with rituximab (RTX) is currently unknown. To determine the prevalence of ARAs in patients with pemphigus who are treated with RTX and their association with complete remission (CR) and relapse. This post hoc analysis of the Ritux3 trial was conducted from January 2010 to December 2015 in 25 dermatology departments in France and included 42 patients with moderate-to-severe pemphigus who were randomized to receive treatment with RTX. Five additional patients were recruited for an ancillary study. The proportions of patients who achieved CR or relapsed after an initial treatment cycle of RTX were compared depending on whether patients had ARAs. Patients were treated with 1000 mg of RTX on days 1 and 15 and 2 maintenance infusions of 500 mg at months 12 and 18. Rates of relapse and sustained CR at month 36. Levels of ARAs, antidesmoglein 1/3 antibodies, RTX serum concentrations, and peripheral blood CD19+ B-cell frequency were measured. Of 42 participants with vs without ARAs, the mean (SD) age was 55 (17) years and 56 (17) years, respectively; 25 (59.5%) were women. Antirituximab antibodies were detected in the serum samples of 13 of 42 patients (31%) during the first year. Nine patients who experienced relapse before month 12 were excluded because they received additional infusions and could not be further analyzed. Among the 33 remaining patients, 2 patients (6.1%) experienced relapse after month 12, and 31 (95.9%) maintained a sustained CR until month 36. The rate of sustained CR was not different whether patients had ARAs (11 of 13 [85%]) or not (20 of 20 [100%]) (P = .15). Both groups (ARA+ vs ARA-) also had similar CD19+ B-cell depletion and RTX levels, but patients with ARAs had higher anti-desmoglein 3 antibody (DSG3 Abs) levels compared with those without ARAs (mean [SD], 30.1 [50.9] AU/mL vs 4.0 [4.3] AU/mL; P = .03). The 2 patients with ARAs who experienced relapse after month 12 had an undetectable RTX level, incomplete B-cell depletion, and higher anti-DSG3 Abs level than the 11 patients who maintained a sustained CR with ARAs (RTX mean [SD] concentration, 0 ug/mL vs 12.5 [2.2] ug/mL; P = .03; incomplete B-cell depletion, 2 of 2 vs 4 of 11; P = .19; mean [SD] anti-DSG3 Abs levels, 103.5 [61.5] AU/mL vs 19.5 [11.0] AU/mL; P = .001) or patients without ARAs (mean [SD] RTX concentration, 0 ug/mL vs 13.5 [1.8] ug/mL; P = .02; incomplete B-cell depletion, 2 of 2 vs 5 of 20; P = .09; mean [SD] anti-DSG3 Abs level, 103.5 [61.5] AU/mL vs 4.0 [1.0] AU/mL; P < .001). The results of this cohort study suggest that ARAs are frequently detected in patients with pemphigus who are treated with RTX and generally are not associated with patient outcomes. Only a few patients with the combination of ARAs, low RTX concentration, incomplete B-cell depletion, and persistent serum anti-DSG3 Abs seem at high risk of relapse.

Interference in a Neutralizing Antibody Assay for Odronextamab, a CD20xCD3 Bispecific mAb, from Prior Rituximab Therapy and Possible Mitigation Strategy

A cell-based assay was developed to detect neutralizing anti-drug antibodies (NAbs) against odronextamab, a CD20xCD3 bispecific monoclonal antibody (mAb) under investigation for treatment of CD20+ B cell malignancies. In this assay, odronextamab bridges between two cell types, CD20-expressing HEK293 cells and CD3-expressing Jurkat T cells that generate a luciferase signal upon CD3 clustering. Patient samples containing NAbs directed to either arm of the bispecific drug block the odronextamab bridge formation between the cell lines thus preventing the generation of the luciferase signal. We determined that other anti-CD20 therapeutics also block bridge formation, resulting in false-positive results. In patient samples from odronextamab clinical trials, approximately 30% of baseline samples had a strong false-positive NAb signal that correlated with the presence of prior rituximab (anti-CD20) therapy. We determined that rituximab interference can be minimized by the addition of anti-rituximab antibodies in the NAb assay. Understanding and mitigating the impact of prior biologic exposure is increasingly important for implementing a successful bioanalytical strategy to support clinical drug development, especially in the immuno-oncology field.Graphical Odronextamab neutralizing antibody assay, interference, and mitigation. A Design of the odronextamab neutralizing antibody (NAb) assay where anti-CD20xCD3 drug bridges between CD20-expressing HEK293 cells and Jurkat T cells expressing an NFAT response element and luciferase reporter. True NAb prevents odronextamab from bridging between target and effector cells, thus preventing the expression of luciferase. B Interference with odronextamab from other anti-CD20 therapeutic antibodies (e.g., rituximab) from prior disease treatment generates a false-positive NAb result. Assay interference can be mitigated with an anti-idiotypic antibody against the interfering therapy.

Predicting Sustained Clinical Response to Rituximab in Moderate to Severe Systemic Manifestations of Primary Sjögren Syndrome.

ObjectiveTo assess outcomes of repeat rituximab cycles and identify predictors of sustained clinical response in systemic manifestations of primary Sjögren syndrome (pSS).MethodsAn observational study was conducted in 40 rituximab‐treated patients with pSS. Clinical response was defined as a 3‐point or more reduction in the European League Against Rheumatism (EULAR) Sjögren Disease Activity Index (ESSDAI) at 6 months from baseline. Peripheral blood B cells were measured using highly sensitive flow cytometry. Predictors of sustained response (within two rituximab cycles) were analyzed using penalized logistic regression.ResultsThirty‐eight out of 40 patients had moderate to severe systemic disease (ESSDAI >5). Main domains were articular (73%), mucocutaneous (23%), hematological (20%), and nervous system (18%). Twenty‐eight out of 40 (70%) patients were on concomitant immunosuppressants. One hundred sixty‐nine rituximab cycles were administered with a total follow‐up of 165 patient‐years. In cycle 1 (C1), 29/40 (73%) achieved ESSDAI response. Of C1 responders, 23/29 received retreatment on clinical relapse, and 15/23 (65%) responded. Of the 8/23 patients who lost response, these were due to secondary non‐depletion and non‐response (2NDNR; 4/23 [17%] as we previously observed in systemic lupus erythematosus with antirituximab antibodies, inefficacy = 2/23, and other side effects = 2/23). Within two cycles, 13/40 (33%) discontinued therapy. In multivariable analysis, concomitant immunosuppressant (odds ratio 7.16 [95% confidence interval: 1.37–37.35]) and achieving complete B‐cell depletion (9.78 [1.32–72.25]) in C1 increased odds of response to rituximab. At 5 years, 57% of patients continued on rituximab.ConclusionOur data suggest that patients with pSS should be co‐prescribed immunosuppressant with rituximab, and treatment should aim to achieve complete depletion. About one in six patients develop 2NDNR in repeat cycles. Humanized or type 2 anti‐CD20 antibodies may improve clinical response in extra‐glandular pSS.

FC066: Circulating Anti-Rituximab Antibodies Do Not Affect Response to Rituximab in Steroid-Dependent Nephrotic Syndrome

Abstract BACKGROUND AND AIMS Previous studies reported that the chimeric anti-CD20 monoclonal rituximab may lead to the production of anti-rituximab antibodies (Anti-RTX-Abs), due to the chimeric nature, impairing the efficacy of further infusions. In the context of glomerulonephritis, recent findings have described that the incidence of anti-RTX-Abs development may affect the efficacy of rituximab in paediatric steroid dependent nephrotic syndrome (SDNS) [Fujinaga et al. Pediatr Nephrol. 2020 Oct; 35(10): 2003–2008] and in membranous nephropathy [Boyer-Suavet et al. Front Immunol. 2020 Jan 13; 10: 3069]. The improved patient outcomes and cost-effectiveness have led to the development of a new generation of fully human anti-B cell agents in haematological and autoimmune diseases [Klomjit et al. Am J Kidney Dis. 2020 Dec; 76(6): 883–888]. Therefore, elucidating the role of Anti-RTX-Abs with the aim to develop personalized therapies is mandatory. In a randomized clinical trial, we compared the efficacy of fully humanized anti-CD20 antibody ofatumumab versus rituximab in children and young adults with SDNS [Ravani et al. JASN Oct 2021, 32 (10) 2652–2663]. METHOD We randomized 140 subjects to single infusion of rituximab or ofatumumab. Follow-up was of 24 months. We measured anti-rituximab IgG antibodies (LISA- TRACKER, Theradiag© Croissy Beaubourg, France) at the enrollment in 64/140 (46%) patients who previously received rituximab, regardless of the randomization arm, and at 6 months in 54/70 of the patients in the rituximab arm. (Fig. 1) Median time of last rituximab treatment was 36 months (13–54) before enrollment. RESULTS Anti-RTX-Abs were detected in none of the patients receiving more than or equal to one rituximab infusion before enrollment. At 6 months, Anti-RTX-Abs are detected in 14/54 patients (26%) who received rituximab (Fig. 2A). Patients developing anti-RTX-Abs or not had similar characteristics at enrollment. At T6, anti-RTX-Abs was not statistically different comparing who received rituximab before enrollment and who did not (Fig. 2B). Of the 54 patients treated with rituximab, 35 (65%) relapsed in 12 months of follow-up. Incidence of patients with anti-RTX-Abs at T6 was not statistically different comparing who experienced relapse with who did not (Fig. 2C). Time to relapse is reported in Fig. 2D. According to the protocol study, the 35 relapsing received a further infusion of rituximab. In this subgroup, incidence of patients with anti-RTX-Abs at T6 was not statistically different comparing who experienced further relapses with who did not (Fig. 2E). Both patients with and without anti-RTX-Abs had similar levels of total B-cell counts before rituximab therapy and at month 6 and 12 thereafter, showing similar B-cell reconstitution (Fig. 2F). We found similar percentages for memory B-cells comparing patients with and without Anti-RTX-Abs at enrollment, at month 6 and at month 12 of follow-up (Fig. 2G). CONCLUSION We evaluated the impact of Anti-RTX-Abs in a prospective study considering a large cohort of SDNS patients who received additional rituximab in case of relapse after a single infusion (375 mg/m2). According to the literature, we reported the development of Anti-RTX-Abs after a single infusion, which seems to persist for limited time. However, in contrast to previous findings, the development of Anti-RTX-Abs does not represent an unfavourable factor, which may limit the efficacy and the safety of further infusions. The prospective design of our study, in contrast to previous ones, represents one of the major strength of the present work. Moreover, Anti-RTX-Abs did not affect total and memory B-cell reconstitution following rituximab treatment.

P243 Anti-rituximab antibodies demonstrate neutralising capacity, associate with lower circulating drug levels and early relapse in patients undergoing treatment for systemic lupus erythematosus

Abstract Background/Aims A major limitation of biologic therapy is formation of anti-drug antibodies (ADA). We previously demonstrated that ADA to rituximab are more prevalent in patients undergoing treatment for systemic lupus erythematosus (SLE) than rheumatoid arthritis and vasculitis, and predict subsequent infusion reactions. However, little is known regarding the long-term dynamics of ADA to rituximab. In this study we evaluated the longitudinal impact of ADA positivity in terms of drug kinetics, treatment response and neutralising capacity in SLE. Methods Patients with SLE undergoing treatment with rituximab were recruited to this study (n = 35). Serum samples were collected at the following intervals post-treatment; 1-3 months, 6 months, 12 months, 36 months (n = 114). Clinical and laboratory data was collected pre-treatment and at each time point. ADA were detected using an electrochemiluminescent immunoassay. Serum rituximab levels were measured via ELISA. A complement dependent cytotoxic assay was used to determine neutralising capability of ADA in a subgroup of positive samples (n = 38). Results ADA were found to be persistently positive over the 36-month follow-up period in 64.3% of patients. There was no significant difference in baseline disease activity (BILAG / SLEDAI-2K) between those who were subsequently ADA positive vs negative. ADA positive patients were younger at diagnosis compared with ADA negative (mean 22.50 ± 9.10 vs 37.29 ± 11.31 years, p = 0.002). Multivariate logistic regression found older age at diagnosis was associated with reduced incidence of persistent ADA with a 22% decrease in risk for each addition year after diagnosis (p = 0.03). ADA positive patients had a significantly lower C3 level at baseline (mean 0.61 ± 0.23 vs 0.87 ± 0.30, p = 0.026), which remained lower at each subsequent time point post-treatment up to 12 months. ADA titres peaked earlier and remained higher in those who had been treated with rituximab previously compared with those who were rituximab naive (median 132 AU/ml vs 7 AU/ml at 1-3 months). At 6 months post-treatment, patients with detectable ADA had a significantly lower circulating drug level than ADA negative (p = 0.0018). In terms of clinical response, ADA positive patients had an initial significant improvement in disease activity (SLEDAI-2K) by 3 months (p &amp;lt; 0.001). However, response was not maintained at 12 months. In comparison, ADA-negative patients showed a significant improvement in SLEDAI-2K at 6 months and this was maintained across the 36-month follow-up period. BILAG defined relapse within 12 months of treatment was only seen in ADA positive patients. Finally, all ADA positive samples were found to neutralise rituximab in vitro. Conclusion ADA to rituximab were common and persisted over the 36 month period of this study. ADA associated with earlier drug elimination, increased relapse rates and demonstrated neutralising capacity suggesting that ADA could be a significant limitation to sustained response to treatment. Disclosure C. Wincup: Grants/research support; Lupus UK, Versus Arthritis, British Society for Rheumatology. N. Dunn: None. C. Ruetsch-Chelli: None. A. Manouchehrinia: None. N. Kharlamova: None. M. Naja: None. B. Seitz-Polski: None. D. Isenberg: None. A. Fogdell-Hahn: None. C. Ciurtin: None. E. Jury: None.

Non HCV-Related Mixed Cryoglobulinemic Vasculitis With Biopsy-Proven Renal Involvement: The Effects of Rituximab.

In the countries where HCV infection is still endemic, about 90% of subjects with mixed cryoglobulinemia had previously been infected with HCV and about 80% are RNA positive. Remarkable results in severe HCV-related cryoglobulinemic vasculitis have been obtained with Rituximab. Details of the clinical characteristics and effective treatment of non HCV-related cryogloulinemic syndromes are presently lacking. This paper reports on a prospective single-Center open study aimed at evaluating the clinical presentation and effects of Rituximab administered alone in patients with severe non HCV-related cryoglobulinemic syndrome. The study group included 11 patients followed for at least 6 months. Three patients had type I cryoglobulinemia, 6 had type II and the remaining 2 patients had type III. Mean cryocrit was 2.5%. Four out of 11 patients had symptomatic sicca complex with anti-SSA (Ro)/anti SSB (La) antibodies. All 11 patients presented with biopsy-proven renal involvement, 4 out of 11 with leukocytoclastic vasculitis, and 8 with involvement of the peripheral nervous system. Renal biopsy revealed diffuse membranoproliferative glomerulonephritis (MPGN) in 9 out of 11 patients. Extracapillary proliferation and necrosis of the glomerular tuft was observed in 1 of these 9 cases. Interstitial nephritis together with mesangial expansion and capillary immune deposits were observed in 1 patient. Prevalent interstitial fibrosis and glomerular sclerosis were detected in the remaining case. Patients underwent treatment with rituximab alone. After 6 months we observed a remarkable improvement in the necrotizing skin ulcers and a substantial amelioration of the electrophysiological parameters of motor and sensory peripheral neuropathy. Improvement in both renal function (from 2.8 to 1.4 mg/dl, p < 0.001) and proteinuria (from 4.2 g/24 to 0.4 g/24 h, p < 0.001) was found in 10 out of 11 patients, while 1 could not be fully treated because of a severe infusion reaction and sudden development of anti-Rituximab antibodies. Good renal response was confirmed at the end of follow-up (38.4 months). Three patients had a relapse at 6, 12, and 48 months, respectively. In our cohort the administration of 4 once-weekly infusions of Rituximab followed by 2 more infusions after 1 and 2 months proved to be effective in the management of these rare patients.

Anti-rituximab antibodies affect pharmacokinetics and pharmacodynamics of rituximab in children with immune-mediated diseases.

Rituximab (RTX) is a chimeric monoclonal CD20-antibody. Lack of efficacy has been suggested to be related to the presence of anti-drug antibodies (ADA). The aims of this study were to determine if ADA impact the pharmacokinetics (PK) and pharmacodynamics (PD) of RTX in children, whether the formation of ADA differs between various immune-mediated diseases and if it is related to the occurrence of infusion-related reactions (IRR). All children <18 years who had received RTX treatment in our centre between December 2006 and February 2020 with known ADA/RTX-levels, were retrospectively included. The presence of ADA was defined as a titre >8 AU/ml. Of twenty-six children treated with RTX for various immune-mediated diseases, six patients were ADA-positive (23.1%). In all ADA-positive patients, RTX concentrations were undetectable in contrast to ADA-negative patients (median RTX concentration 3.1 μg/ml; IQR 0.57-12.0; p<0.001). Failure of B cell depletion was found in 5/6 ADA-positive and 1/19 ADA-negative patients (p=0.003). In SLE-patients, 50.0% (n=4/8) had developed RTX-ADA. Severe anaphylaxis (n=3) occurred only in the ADA-positive group. In our cohort of paediatric patients, undetectable RTX concentrations were found in ADA-positive patients, indicative that these ADA have a PK impact. RTX-ADA also seem to affect the PD, as in the majority of these patients, B cell depletion failed. ADA were most present in SLE-patients and anaphylactic reactions occurred only in ADA-positive patients. With this knowledge, a change of drug might be considered in the presence of RTX-ADA.

Anti-Rituximab Antibodies in Idiopathic Nephrotic Children Treated with Rituximab: A Prospective Single Centre Study

Corticosteroids have been the main treatment of nephrotic syndrome (NS) for decades however many patients fail to respond. In such children, alternative immunosuppressive medications such as rituximab is used to maintain remission of NS. However, antibodies to rituximab develops during treatment reduces its efficacy. Therefore, this study aimed to measure anti-rituximab antibody (ARA) levels and efficacy of rituximab in children treated for NS. This prospective observational study was conducted among children with difficult to treat nephrotic syndrome. After baseline assessment, patients received single dose of intravenous infusion of 375 mg/m² rituximab. ARA levels were determined at base line, 3-month, 6-month, and 12-month interval. Thirty-four patients with a mean age of 7 years were evaluated in this study. During follow up visits five patients developed ARA; two patients detected ARA of 23.7 IU/ µL at 3-month, one patient had ARA level of 53.2 IU/µL at 6-month and during last follow up visit (at 12 month) two patients had mean ARA level of 24.1 IU/µL. The number of relapses per person year before rituximab was 1.5 (Incidence density) which changed to 0.14 per person year after the rituximab administration in the study subjects. Twenty-Nine patients became relapse-free during rituximab treatment. Out of five patients with ARA, one had relapse during follow up. There was no major adverse effect observed during and post-rituximab therapy. In conclusion, the study demonstrated ARA levels in few patients who were treated with rituximab having sustained clinical outcomes without any major adverse events.

Anti-rituximab antibodies in pediatric steroid-dependent nephrotic syndrome.

Rituximab is a chimeric anti-CD20 monoclonal antibody that induces sustained remission in children with steroid-dependent nephrotic syndrome. However, there is no consensus on the optimal regimen and monitoring of rituximab. In other autoimmune diseases, anti-rituximab antibodies (ARA) have been reported in 10-40% of patients, but their clinical relevance remains unclear. In nephrotic syndrome, data are scarce. We report a single-center retrospective study with immuno- and pharmacological monitoring of rituximab treatment in children with frequent relapsing (FR) or steroid-dependent nephrotic syndrome (SDNS). We analyzed the monthly monitoring of 24 children, receiving a dose of rituximab (375 mg/m2) between December 2017 and April 2018 at the Pediatric Nephrology Department of Robert-Debré hospital, Paris. ARA were detected in 7/24 patients (29%), sometimes after the first infusion of rituximab. ARA were present at baseline in two patients previously treated with rituximab. Both displayed no B-cell depletion. ARA were also reported in 5/22 patients during follow-up, with antibodies always detected in the first month following B-cell recovery. An incomplete CD19+CD20- B-cell depletion at M1 (5-25/mm3) and low serum rituximab levels was predictive of developing ARA. The development of de novo ARA during follow-up was not associated with shorter B-cell depletion. This study shows that ARA are frequent in children with FR/SDNS and that close immuno- and pharmacological monitoring may help personalizing rituximab treatment in patients needing repeated injections.

Immunomonitoring du rituximab appliqué aux maladies auto-immunes : une aide pour la pratique clinique ?

IntroductionImmune monitoring of monoclonal antibodies is a helpful tool in optimizing the management of patients treated with TNF blockers, especially in gastroenterology. In contrast, studies evaluating the interest of such monitoring are lacking for other monoclonal antibodies used in autoimmune diseases, including rituximab despite its widespread use in the field for almost 15 years. Hence, we conducted a study whose goal was to describe the clinical and biological characteristics of all patients who had a rituximab immune monitoring. MethodsAll the clinical, biological and therapeutic data attached to the demands (from 2015 onwards) we received for immune monitoring of rituximab (measurements of rituximab serum levels and anti-rituximab antibodies using the drug-sensitive assay LISA-TRACKER Duo Rituximab®), were retrospectively reviewed. Suspected cases of hypersensitivity and secondary non-response were included. ResultsSeveral medical specialities (nephrology, haematology, neurology, rheumatology, internal medicine) were represented among the 18 records included in the study (out of 23 demands), 10 being suspected cases of hypersensitivity and 8 secondary non-responders. All 6 patients whose symptoms were consistent with the classical presentation of serum sickness, as well as half of the secondary non-responders, were positive for antirituximab antibodies. ConclusionThis detailed real world case study illustrates the potential benefits of rituximab immune monitoring (especially anti-rituximab antibodies) in autoimmune diseases, suggesting it could be helpful in suspected cases of serum sickness, as well as secondary non-response (B-cell non-depletion being an early red flag). Larger and disease-specific studies are warranted to support these findings.

Ofatumumab or Rituximab for Children with Steroid- and Calcineurin Inhibitor -Dependent Nephrotic Syndrome - &lt;i&gt;A Superiority Randomized Controlled Trial (OFA2)&lt;/i&gt;

Background: The chimeric anti-CD20 monoclonal antibody rituximab has been successfully used in steroid- and calcineurin inhibitor-dependent forms of nephrotic syndrome to maintain oral-drug-free remission, but almost half of patients relapse at one year. Ofatumumab, a fully human anti-CD20 monoclonal antibody, may be superior to rituximab in maintaining remission in these patients. Here, we compared head-to head ofatumumab and rituximab in a randomized controlled clinical trial. Methods: In this single center superiority clinical trial, 140 children and young adults (age 2-24 years) with nephrotic syndrome in remission with steroids and calcineurin-inhibitors were randomized to receive intravenous ofatumumab (1.500 mg/1.73 m2; intervention) or rituximab (375 mg/m2; control). Following infusions, oral drugs were tapered and withdrawn within 60 days. Participants were followed for 36 months. The primary analysis followed an intent-to-treat approach. The primary outcome was relapse at one year, defined by proteinuria (creatinine ratio ≥2000 mg/g). The secondary endpoint included the occurrence of a disease relapse within 24 months from infusion. Cellular and safety data were assessed. Findings: At 12 months, 37 participants relapsed in the ofatumumab arm (52.8%) vs. 36 in the rituximab arm (51.4%; Odds Ratio [OR] 1.06; 95% confidence interval [CI] 0.55 to 2.06). At 24 months, 53 participants relapsed in the ofatumumab arm (75.7%) vs. 46 in the rituximab arm (65.7%; [OR] 1.6 [Cl] 0.8 to 3.3). Analyses stratified by age ≤9 and >9 years supported the same conclusion. Anti-rituximab antibodies did not modify the effects of the intervention. No important side effects occurred during infusion nor during follow up. Higher pretreatment levels of memory and IgM-memory B cells predicted relapse. Interpretation: Ofatumumab is not superior to rituximab in maintaining oral-drug-free remission in children with steroid-and calcineurin inhibitor-dependent nephrotic syndrome. Anti-CD20 antibodies may alter the course of the disease by interfering with memory B cell populations. Clinical Trial Registration Details: Clinical Trials.gov (identifier: NCT02394119) and Eudract.ema.europe.eu (identifier: 2015-000624-28). Funding Information: PR, FL, FM and GMG were supported by the Italian Ministry of Health, Ricerca Finalizzata, grant: WFR:PE-2016-02361576. MC and MV are supported by the Associazione per la Cura del Bambino Nefropatico ONLUS. GMG, MB, and MC are supported by ‘’Fondazione Malattie Renali del Bambino” ONLUS. The Institute Giannina Gaslini (trial sponsor) provided logistic and financial through grant ‘Cinque per mille of IRPEF-Finanziamento della ricerca sanitaria’. The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication. Declaration of Interest: Authors declare no competing interests. Ethical Approval: We obtained study approval from the local Independent Ethics Committee (ComitatoEticoRegione Liguria), the Italian Drug Agency (AgenziaItaliana del Farmaco, AIFA).

Rituximab Hypersensitivity: From Clinical Presentation to Management

Rituximab is a chimeric monoclonal antibody (mAb) against CD20 molecule which is expressed on human B cells. It has been used for the treatment of various lymphoid malignancies, lymphoproliferative diseases, and rheumatologic disorders. Rituximab is generally well tolerated. However, increased use of rituximab has been associated with hypersensitivity reactions (HSRs), which can be classified as infusion-related, cytokine-release, type I (IgE/non-IgE), mixed, type III, and type IV reactions. Immediate infusion-related reactions to rituximab are quite common and decrease in frequency with subsequent infusions. However, in about 10% of patients, severe infusion-related reactions develop, which prevent its use. Some of the immediate infusion reactions are due to a cytokine-release but some reactions raise concerns for type I (IgE/non-IgE) hypersensitivity. Recent studies have shown the presence of serum anti-rituximab antibodies, either represented by the IgG or IgE isotype. In some cases, clinical manifestations of IgE-mediated reactions and cytokine-release reactions partially overlap, which is called a mixed reaction. Classified as Type III reaction, rituximab-induced serum sickness reactions have been reported in patients with autoimmune diseases and hematological malignancies. The classic serum sickness triad (fever, rash, and arthralgia) has been observed in patients mainly with an underlying rheumatologic condition. Severe delayed type IV hypersensitivity reactions including non-severe maculopapular rash to severe reactions such as Stevens–Johnson syndrome and toxic epidermal necrolysis have been rarely reported following rituximab injection. Comprehensive reviews focused on rituximab-induced HSRs are scarce. We aimed to review clinical presentations, underlying mechanisms of rituximab hypersensitivity, as well as management including rapid drug desensitization.

Personalized Medicine for PLA2R1-Related Membranous Nephropathy: A Multicenter Randomized Control Trial.

Background: Membranous Nephropathy (MN) is a rare autoimmune disease related to PLA2R1 antibodies in 70% of cases. One third of patients enter in spontaneous remission. PLA2R1 epitopes in MN have been characterized in four different domains of PLA2R1 and a mechanism of epitope spreading from the immunodominant CysR domain to CTLD1 and/or CTLD7 and/or CTLD8 domains has been associated with poor prognosis. Epitope spreading could predict spontaneous remission (45% in non-spreader patients vs. 0.05% in spreader patients). The comparison of different regimens of rituximab dosing showed that: (i) early remission rate depends on rituximab dosing, (ii) low dose could be enough for patients with anti-PLA2R1 activity restricted to CysR, (iii) high dose may be required for spreader patients. This study aims to evaluate the efficacy of personalized treatment in PLA2R1-related MN depending on the epitope spreading status, in comparison to the established GEMRITUX protocol.Methods: A multicenter, randomized, controlled, prospective clinical trial will be conducted in 22 French hospitals. Sixty-four consecutive patients with PLA2R1-related MN will be randomly assigned to either the control group following the GEMRITUX protocol (symptomatic treatment for 6 months, if the nephrotic syndrome (NS) persists at month-6, two 375 mg/m2 rituximab infusions at 1 week interval) or the personalized treatment group (patients with no epitope spreading at month-0 will be treated with symptomatic treatment for 6 months, if NS persists at month-6, two 375 mg/m2 rituximab infusions at 1 week interval; patients with epitope spreading at month-0 or month-6 with persistent NS will be treated immediately with two 1 g rituximab infusions at 2 week interval). The primary study outcome is the rate of clinical remission at month-12. The secondary outcomes include complete and partial remissions, immunological remissions, relapses, proteinuria, albuminuria, serum creatinine, eGFR, PLA2R1 antibody titers, severe infections, lymphocyte counts and lymphocyte phenotype, residual rituximab levels at month-3 and neutralizing anti-rituximab antibodies at month-6 and month-12 after rituximab treatment.Discussion: The results of this trial will confirm whether personalized treatment of PLA2R1-driven nephrotic MN is more efficient to induce clinical remission than the established GEMRITUX protocol, and may thus contribute to improved remission rates and reduced relapse rates.Trial registration: NCT 03804359 trial number. Registered on 15th January 2019.

Unfavorable impact of anti-rituximab antibodies on clinical outcomes in children with complicated steroid-dependent nephrotic syndrome.

Anti-rituximab antibodies (ARA) are associated not only with adverse events, such as infusion reactions (IR) and serum sickness, but also with rituximab efficacy. However, the clinical relevance of ARA in children with steroid-dependent nephrotic syndrome (SDNS) remains unknown. We retrospectively reviewed clinical outcomes of 13 children with complicated SDNS receiving repeated single-dose rituximab treatments at 375 mg/m2 to assess whether ARA formation could impact toxicity and efficacy of additional rituximab. Pre-rituximab 22 samples collected from patients who developed IR during the second or subsequent rituximab doses were measured by electrochemiluminescence analysis. ARA were identified in 5 of 13 patients (9 of 22 samples). Median time to recovery of CD19+ B cells to > 1% of total lymphocytes and median relapse-free time after rituximab treatment were significantly shorter in the 9 ARA-positive samples than the 13 ARA-negative samples (41 vs. 100 days, p < 0.01 and 119 vs. 308 days, p < 0.05, respectively). Kaplan-Meier analysis showed that time to CD19+ B cell recovery after rituximab was significantly shorter in ARA-positive samples than in ARA-negative samples (p < 0.005). Severe IR developed in two ARA-positive patients and serum sickness in one ARA-positive patient. The incidence of ARA formation was high in the pre-rituximab samples of patients with complicated SDNS who developed IR during the second or subsequent rituximab doses, suggesting that ARA formation might have an unfavorable impact on the toxicity and efficacy of additional rituximab doses in these patients.