Ofatumumab in two pediatric nephrotic syndrome patients allergic to rituximab

Obinutuzumab in Frequently Relapsing and Steroid-Dependent Nephrotic Syndrome in Children

BACKGROUND

B-cell depletion with rituximab induces sustained remission in children with steroid-dependent or frequently relapsing nephrotic syndrome. However, most patients relapse after B-cell recovery, and some patients do not achieve B-cell depletion. Obinutuzumab is a second-generation anti-CD20 antibody designed to overcome such situations in B-cell malignancies and was recently reported to be safe and effective in other autoimmune diseases affecting the kidneys.

METHODS

We retrospectively report 41 children with steroid-dependent or frequently relapsing nephrotic syndrome treated with a single low-dose infusion of obinutuzumab at Robert-Debre Hospital between April 2018 and December 2020. Participants were treated because of rituximab resistance or relapse after rituximab and received a single infusion of 300 mg/1.73 m 2 obinutuzumab with cessation of oral immunosuppressors within 2 months.

RESULTS

B-cell depletion was achieved in all participants and lasted a median of 8.3 months (interquartile range, 6.4-11.1), a duration exceeding that for last rituximab treatment. At 12 and 24 months, 92% (38/41) and 68% (28/41) of patients, respectively, were in sustained remission. Mild infusion reactions occurred in five participants (12%) and neutropenia in nine (21%). No significant decrease in IgG level was reported during treatment, and whereas IgM levels decreased in 34 patients (83%), they were normal at last follow-up in 32 (78%).

CONCLUSIONS

These results identified low-dose obinituzumab as a promising treatment option in children with steroid-dependent or frequently relapsing nephrotic syndrome, including those resistant to rituximab. The tolerance profile of obinutuzumab was similar to that of rituximab, but hemogram and immunoglobulin levels should be monitored.

Biologics in steroid resistant nephrotic syndrome in childhood: review and new hypothesis-driven treatment

Nephrotic syndrome affects about 2-7 per 100,000 children yearly and accounts for less than 15% of end stage kidney disease. Steroids still represent the cornerstone of therapy achieving remission in 75-90% of the cases The remaining part result as steroid resistant nephrotic syndrome, characterized by the elevated risk of developing end stage kidney disease and frequently presenting disease recurrence in case of kidney transplant. The pathogenesis of nephrotic syndrome is still far to be elucidated, however, efficacy of immune treatments provided the basis to suggest the involvement of the immune system in the pathogenesis of the disease. Based on these substrates, more immune drugs, further than steroids, were administered in steroid resistant nephrotic syndrome, such as antiproliferative and alkylating agents or calcineurin inhibitors. However, such treatments failed in inducing a sustained remission. In last two decades, the developments of monoclonal antibodies, including the anti-CD20 rituximab and inhibitor of B7-1 abatacept, represented a valid opportunity of treatment. However, also the effectiveness of biologics resulted limited. We here propose a new hypothesis-driven treatment based on the combining administration of rituximab with the anti-CD38 monoclonal antibody daratumumab (NCT05704400), sustained by the hypothesis to target the entire B-cells subtypes pool, including the long-lived plasmacells.

Use of Rituximab in Childhood Idiopathic Nephrotic Syndrome

Rituximab is an established therapy in children with idiopathic nephrotic syndrome to sustain short- to medium-term disease remission and avoid steroid toxicities. Recent trials focus on its use as a first-line agent among those with milder disease severity. Rituximab is used in multidrug refractory nephrotic syndrome and post-transplant disease recurrence, although the evidence is much less substantial. Available data suggest that the treatment response to rituximab depends on various patient factors, dosing regimen, and the concomitant use of maintenance immunosuppression. After repeated treatments, patients are found to have an improving response overall with a longer relapse-free period. The drug effect, however, is not permanent, and 80% of patients eventually relapse and many will require an additional course of rituximab. This underpins the importance of understanding the long-term safety profile on repeated treatments. Although rituximab appears to be generally safe, there are concerns about long-term hypogammaglobulinemia, especially in young children. Reliable immunophenotyping and biomarkers are yet to be discovered to predict treatment success, risk of both rare and severe side effects, e.g. , persistent hypogammaglobulinemia, and guiding of redosing strategy. In this review, we highlight recent advances in the use of rituximab for childhood nephrotic syndrome and how the therapeutic landscape is evolving.

IPNA clinical practice recommendations for the diagnosis and management of children with steroid-sensitive nephrotic syndrome

Idiopathic nephrotic syndrome is the most frequent pediatric glomerular disease, affecting from 1.15 to 16.9 per 100,000 children per year globally. It is characterized by massive proteinuria, hypoalbuminemia, and/or concomitant edema. Approximately 85-90% of patients attain complete remission of proteinuria within 4-6 weeks of treatment with glucocorticoids, and therefore, have steroid-sensitive nephrotic syndrome (SSNS). Among those patients who are steroid sensitive, 70-80% will have at least one relapse during follow-up, and up to 50% of these patients will experience frequent relapses or become dependent on glucocorticoids to maintain remission. The dose and duration of steroid treatment to prolong time between relapses remains a subject of much debate, and patients continue to experience a high prevalence of steroid-related morbidity. Various steroid-sparing immunosuppressive drugs have been used in clinical practice; however, there is marked practice variation in the selection of these drugs and timing of their introduction during the course of the disease. Therefore, international evidence-based clinical practice recommendations (CPRs) are needed to guide clinical practice and reduce practice variation. The International Pediatric Nephrology Association (IPNA) convened a team of experts including pediatric nephrologists, an adult nephrologist, and a patient representative to develop comprehensive CPRs on the diagnosis and management of SSNS in children. After performing a systematic literature review on 12 clinically relevant PICO (Patient or Population covered, Intervention, Comparator, Outcome) questions, recommendations were formulated and formally graded at several virtual consensus meetings. New definitions for treatment outcomes to help guide change of therapy and recommendations for important research questions are given.

Implications of rituximab pharmacokinetic and pharmacodynamic alterations in various immune-mediated glomerulopathies and potential anti-CD20 therapy alternatives

The specific B-cell depleting anti-CD20 monoclonal antibody rituximab (RTX) is effective in terms of the treatment of various immune-mediated glomerulopathies. The administration of RTX has been shown to be reliable and highly effective particularly in patients with ANCA-associated vasculitis, which is manifested predominantly with non-nephrotic proteinuria. Stable long-term B-cell depletion is usually readily attained in such patients using standard dosing regimens. However, in patients with nephrotic syndrome and non-selective proteinuria, the RTX pharmacokinetics is altered profoundly and RTX does not maintain high enough levels for a sufficiently long period, which may render RTX treatment ineffective. Since complement-derived cytotoxicity is one of the important modes of action of RTX, hypocomplementemia, frequently associated with systemic lupus erythematodes, may act to hamper the efficacy of RTX in the treatment of patients with lupus nephritis. This review provides a description of RTX pharmacokinetics and pharmacodynamics in several selected glomerulopathies, as well as the impact of proteinuria, anti-drug antibodies and other clinical variables on the clearance and volume of distribution of RTX. The impact of plasmapheresis and peritoneal dialysis on the clearance of RTX is also discussed in the paper. A review is provided of the potential association between pharmacokinetic and pharmacodynamic alterations in various kidney-affecting glomerular diseases, the sustainability of B-cell depletion and the clinical efficacy of RTX, with proposals for potential dosing implications. The role of therapeutic drug monitoring in treatment tailoring is also discussed, and various previously tested RTX dosing schedules are compared in terms of their clinical and laboratory treatment responses. Since alternative anti-CD20 molecules may prove effective in RTX unresponsive patients, their pharmacokinetics, pharmacodynamics and current role in the treatment of glomerulopathies are also mentioned.

Unexpected Late Response to Ofatumumab in Adult Post-Transplantation Recurrent Focal Segmental Glomerulosclerosis, Case Report

BACKGROUND

Idiopathic focal segmental glomerulosclerosis is an important cause of kidney failure in adults, which is associated with a high risk of disease recurrence after transplantation. Plasmapheresis, rituximab, immunoadsorption, and high-dose cyclosporine are used to treat post-transplant recurrent focal segmental glomerulosclerosis (rFSGS). However, the response rate is variable, and few options remain for unresponsive patients.

CASE REPORT

We present a 44-year-old man with an early post-transplant rFSGS. After peritransplant plasmapheresis, rituximab, and abatacept treatments failed, we employed ofatumumab. After 9 months without apparent benefit, we observed an unexpected partial remission thereafter, without severe side effects. Furthermore, remission has been sustained in 30-month follow-up.

CONCLUSIONS

We believe ofatumumab can be considered an alternative for patients with plasmapheresis and rituximab-resistant post-transplant rFSGS.

New and Old Anti-CD20 Monoclonal Antibodies for Nephrotic Syndrome. Where We Are?

Nephrotic proteinuria is the hallmark of several glomerulonephritis determined by different pathogenetic mechanisms, including autoimmune, degenerative and inflammatory. Some conditions such as Minimal Change Nephropathy (MCN) and Focal Segmental Glomerulosclerosis (FSGS) are of uncertain pathogenesis. Chimeric anti-CD20 monoclonal antibodies have been used with success in a part of proteinuric conditions while some are resistant. New human and humanized monoclonal anti-CD 20 antibodies offer some advantages based on stronger effects on CD20 cell subtypes and have been already administered in hematology and oncology areas as substitutes of chimeric molecules. Here, we revised the literature on the use of human and humanized anti-CD 20 monoclonal antibodies in different proteinuric conditions, resulting effective in those conditions resistant to rituximab. Literature on the use of human anti-CD 20 monoclonal antibodies in different proteinuric diseases is mainly limited to ofatumumab, with several protocols and doses. Studies already performed with ofatumumab given in standard doses of 1,500 mg 1.73m² suggest no superiority compared to rituximab in children and young adults with steroid dependent nephrotic syndrome. Ofatumumab given in very high doses (300 mg/1.73m² followed by five infusion 2,000 mg/1.73 m²) seems more effective in patients who are not responsive to common therapies. The question of dose remains unresolved and the literature is not concordant on positive effects of high dose ofatumumab in patients with FSGS prior and after renal transplantation. Obinutuzumab may offer some advantages. In the unique study performed in patients with multidrug dependent nephrotic syndrome reporting positive effects, obinutuzumab was associated with the anti-CD38 monoclonal antibody daratumumab proposing the unexplored frontier of combined therapies. Obinutuzumab represent an evolution also in the treatment of autoimmune glomerulonephritis, such as membranous nephrotahy and lupus nephritis. Results of randomized trials, now in progress, are awaited to add new possibilities in those cases that are resistant to other drugs. The aim of the present review is to open a discussion among nephrologists, with the hope to achieve shared approaches in terms of type of antibodies and doses in the different proteinuric renal conditions.

Update on the treatment of steroid-sensitive nephrotic syndrome

Steroid-sensitive nephrotic syndrome (SSNS) is a rare condition that develops primarily in preadolescent children after the age of 1 year. Since the 1950s, oral corticosteroids have been the mainstay of treatment of all children presenting with nephrotic syndrome, with most patients responding within 4 weeks to an oral course of prednisone (PDN). However, corticosteroids have important side effects and 60-80 % of patients relapse, developing frequently relapsing or steroid-dependent forms. For these reasons, many patients require second-line steroid-sparing immunosuppressive medications that have considerably improved relapse-free survival, while avoiding many PDN-related toxicities. Since most patients will eventually heal from their disease with a normal kidney function, the morbidity of SSNS is primarily related to side effects of drugs that are used to maintain prolonged remission. Therefore, treatment is essentially based on balancing the use of different drugs to achieve permanent remission with the lowest cumulative number of side effects. Treatment choice is based on the severity of SSNS, on patient age, and on drug tolerability. This review provides an update of currently available therapeutic strategies for SSNS.

UK experience of ofatumumab in recurrence of focal segmental glomerulosclerosis post-kidney transplant

BACKGROUND

Steroid-resistant nephrotic syndrome (SRNS), commonly caused by focal segmental glomerulosclerosis (FSGS), is associated with progression to stage 5 chronic kidney disease, requirement for kidney replacement therapy and a risk of disease recurrence post-kidney transplantation. Ofatumumab (OFA) is a fully humanised monoclonal antibody to CD20, with similar mechanisms of action to rituximab (RTX).

METHODS

We report a case series of seven UK patients (five paediatric, two adult), all of whom developed FSGS recurrence after kidney transplantation and received OFA as part of their therapeutic intervention. All also received concomitant plasmapheresis. The 2-year outcome of these seven patients is reported, describing clinical course, kidney function and proteinuria.

RESULTS

Four patients (all paediatric) achieved complete urinary remission with minimal proteinuria 12 months post-treatment. Three of those four also had normal graft function. Two patients showed partial remission-brief improvement to non-nephrotic proteinuria (197 mg/mmol) in one patient, maintained improvement in kidney function (estimated glomerular filtration rate 76 ml/min/1.73 m²) in the other. One patient did not demonstrate any response.

CONCLUSIONS

OFA may represent a useful addition to therapeutic options in the management of FSGS recurrence post-transplantation, including where RTX has shown no benefit. Concomitant plasmapheresis in all patients prevents any definitive conclusion that OFA was the beneficial intervention.

An updated view of the pathogenesis of steroid-sensitive nephrotic syndrome

Idiopathic nephrotic syndrome is the most common childhood glomerular disease. Most forms of this syndrome respond to corticosteroids at standard doses and are, therefore, defined as steroid-sensitive nephrotic syndrome (SSNS). Immunological mechanisms and subsequent podocyte disorders play a pivotal role in SSNS and have been studied for years; however, the precise pathogenesis remains unclear. With recent advances in genetic techniques, an exhaustive hypothesis-free approach called a genome-wide association study (GWAS) has been conducted in various populations. GWASs in pediatric SSNS peaked in the human leukocyte antigen class II region in various populations. Additionally, an association of immune-related CALHM6/FAM26F, PARM1, BTNL2, and TNFSF15 genes, as well as NPHS1, which encodes nephrin expressed in podocytes, has been identified as a locus that achieves genome-wide significance in pediatric SSNS. However, the specific mechanism of SSNS development requires elucidation. This review describes an updated view of SSNS pathogenesis from immunological and genetic aspects, including interactions with infections or allergies, production of circulating factors, and an autoantibody hypothesis.

Human or Chimeric Monoclonal Anti-CD20 Antibodies for Children with Nephrotic Syndrome: A Superiority Randomized Trial

BACKGROUND

The chimeric anti-CD20 monoclonal antibody rituximab is effective in steroid-dependent and calcineurin inhibitor-dependent forms of nephrotic syndrome, but many patients relapse at 1 year. Because ofatumumab, a fully human anti-CD20 monoclonal antibody, has a more extended binding site and higher affinity to CD20 compared with rituximab, it might offer superior efficacy in these patients.

METHODS

We designed a single-center randomized clinical trial to compare the long-term efficacy of ofatumumab versus rituximab in children and young adults with nephrotic syndrome maintained in remission with prednisone and calcineurin inhibitors. We randomized 140 children and young adults (aged 2-24 years) to receive intravenous ofatumumab (1.50 mg/1.73 m²) or rituximab (375 mg/m²). After infusions, oral drugs were tapered and withdrawn within 60 days. The primary outcome was relapse at 1 year, which was analyzed following the intent-to-treat principle. The secondary endpoint was relapse within 24 months from infusion, on the basis of urine dipstick and confirmed by a urine protein-to-creatinine ratio <200.

RESULTS

At 12 months, 37 of 70 (53%) participants who received ofatumumab experienced relapse versus 36 of 70 (51%) who received rituximab (odds ratio [OR], 1.06; 95% confidence interval [95% CI], 0.55 to 2.06). At 24 months, 53 of 70 (76%) participants who received ofatumumab experienced relapse, versus 46 of 70 (66%) who received rituximab (OR, 1.6; 95% CI, 0.8 to 3.3). The two groups exhibited comparable B cell subpopulation reconstitution and did not differ in adverse events.

CONCLUSIONS

A single dose of ofatumumab was not superior to a single dose of rituximab in maintaining remission in children with steroid-dependent and calcineurin inhibitor-dependent nephrotic syndrome.

CLINICAL TRIAL REGISTRATION NUMBERS

ClinicalTrials.gov (NCT02394119) and https://www.clinicaltrialsregister.eu/ctr-search/search (2015-000624-28).

Steroid-resistant Nephrotic Syndrome in Children: A Mini-review on Genetic Mechanisms, Predictive Biomarkers and Pharmacotherapy Strategies

Steroid-resistant nephrotic syndrome (SRNS) constitutes the second most frequent cause of chronic kidney disease in childhood. The etiology of SRNS remains largely unknown and no standardized treatment exists. Recent advances in genomics have helped to build understanding of the molecular mechanisms and pathogenesis of the disease. The genetic polymorphisms in genes encoding proteins which are involved in the pharmacokinetics and pharmacodynamics of glucocorticoids (GCs) partially account for the different responses between patients with nephrotic syndrome. More importantly, single-gene causation in podocytes-associated proteins was found in approximately 30% of SRNS patients. Some potential biomarkers have been tested for their abilities to discriminate against pediatric patients who are sensitive to GCs treatment and patients who are resistant to the same therapy. This article reviews the recent findings on genetic mechanisms, predictive biomarkers and current therapies for SRNS with the goal to improve the management of children with this syndrome.

Current understandings in treating children with steroid-resistant nephrotic syndrome

Steroid-resistant nephrotic syndrome (SRNS) remains a challenge for paediatric nephrologists. SRNS is viewed as a heterogeneous disease entity including immune-based and monogenic aetiologies. Because SRNS is rare, treatment strategies are individualized and vary among centres of expertise. Calcineurin inhibitors (CNI) have been effectively used to induce remission in patients with immune-based SRNS; however, there is still no consensus on treating children who become either CNI-dependent or CNI-resistant. Rituximab is a steroid-sparing agent for patients with steroid-sensitive nephrotic syndrome, but its efficacy in SRNS is controversial. Recently, several novel monoclonal antibodies are emerging as treatment option, but their efficacy remains to be seen. Non-immune therapies, such as angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, have been proven efficacious in children with SRNS and are recommended as adjuvant agents. This review summarizes and discusses our current understandings in treating children with idiopathic SRNS.

Ofatumumab treatment for nephrotic syndrome recurrence after pediatric renal transplantation

BACKGROUND

Relapsing nephrotic syndrome (NS) after transplantation can be a challenge to treat. The result of the consequent long-lasting proteinuria is the loss of the graft. Disease recurrence after renal transplantation occurs in around half of cases, and the efficacy of therapeutic strategies is often limited. Recently, ofatumumab, a second-generation and fully human anti-CD20 monoclonal antibody, has been shown to be effective in severe situations.

METHODS

We retrospectively collected data from the medical records of children with recurrence of NS after renal transplantation treated with ofatumumab in France, after failure of previous treatments.

RESULTS

Six patients were included in this study in five centers with a median duration of follow-up of 10.5 months. Two different ofatumumab regimens were administered. The primary outcome was proteinuria at 6 months after the last dose of ofatumumab. No patient achieved a complete remission, 3/6 had a partial remission, and 3/6 had no response to ofatumumab. Four patients exhibited a minor allergic reaction with the first infusion. One patient died of infection, as a consequence of multiple factors. No malignancies were observed; however, the time of follow-up was not sufficient to see such disease.

CONCLUSIONS

Altogether, these results suggest ofatumumab has a poor efficacy in treating recurrence of NS after renal transplantation. However, it could be discussed in multidrug-resistant refractory NS, but infectious complications and overimmunosuppression have to be balanced. There is a need for further studies to confirm these findings and safety and to determine a standardized protocol in this indication.

IPNA clinical practice recommendations for the diagnosis and management of children with steroid-resistant nephrotic syndrome

Idiopathic nephrotic syndrome newly affects 1-3 per 100,000 children per year. Approximately 85% of cases show complete remission of proteinuria following glucocorticoid treatment. Patients who do not achieve complete remission within 4-6 weeks of glucocorticoid treatment have steroid-resistant nephrotic syndrome (SRNS). In 10-30% of steroid-resistant patients, mutations in podocyte-associated genes can be detected, whereas an undefined circulating factor of immune origin is assumed in the remaining ones. Diagnosis and management of SRNS is a great challenge due to its heterogeneous etiology, frequent lack of remission by further immunosuppressive treatment, and severe complications including the development of end-stage kidney disease and recurrence after renal transplantation. A team of experts including pediatric nephrologists and renal geneticists from the International Pediatric Nephrology Association (IPNA), a renal pathologist, and an adult nephrologist have now developed comprehensive clinical practice recommendations on the diagnosis and management of SRNS in children. The team performed a systematic literature review on 9 clinically relevant PICO (Patient or Population covered, Intervention, Comparator, Outcome) questions, formulated recommendations and formally graded them at a consensus meeting, with input from patient representatives and a dietician acting as external advisors and a voting panel of pediatric nephrologists. Research recommendations are also given.

B cell modulation strategies in the improvement of transplantation outcomes

Successful transplantation outcome is the final goal in most end stage and nonfunctional organs; however, despite using different therapeutic strategies, antibody-mediated rejection is still a big obstacle. B cells have a key role in transplant rejection by several functions, such as antibody production, antigen presenting, contribution in T cell activation, forming the germinal center, and tertiary lymphoid organs. Therefore, B cells modulation seems to be very crucial in transplant outcome. A double-edged sword function is considered for B cells during transplantation; On the one hand, antibody production against the transplanted organ induces antibody-mediated rejection. On the other hand, IL10 production by regulatory B (Breg) cells induces graft tolerance. Nowadays, several monoclonal antibodies (mAb) are available for B cell modulation that are routinely used in transplant recipients, among which rituximab (anti-CD20 mAb) act in eliminating B cells. However, there are some other monoclonal antibodies, such as epratuzumab and Inotuzumab ozogamicin (IO), which exert anti-CD22 activity, resulting in disruption of B cell functions and induction of tolerance in autoimmune disease or B cell malignancies; that notwithstanding, these mAbs have not yet been tried in transplantation. In this review, we focus on different methods for modulating the activity of B cells as well as induction of Breg cells, aiming to prevent the allograft rejection.

Low-dose ofatumumab for multidrug-resistant nephrotic syndrome in children: a randomized placebo-controlled trial

BACKGROUND

Children with multidrug-resistant nephrotic syndrome (MRNS) are exposed to drug toxicity (steroids/calcineurin inhibitors (CNI)/mycophenolate mofetil (MMF)) and have an increased risk of kidney disease progression. In small case series, the fully humanized anti-CD20 antibody ofatumumab (OFA) induced remission in children with MRNS when at high dose (10,300 mg/1.73 m²) and partial remission at standard dose (1000 mg/1.73 m²).

METHODS

This double-blind randomized placebo-controlled trial tested the efficacy of single infusion OFA in children with proven MRNS and initial chronic renal failure (eGFR [median/range] 119/38-155 ml/min/1.73 m² in Placebo arm vs. 65/19-103 ml/min/1.73 m² Intervention). Children who had been resistant to a combination of CNI and steroids, with or without MMF or rituximab, were randomized to receive single infusion OFA (1500 mg/1.73 m²) (Intervention arm) or normal saline (Placebo arm). We assessed complete or partial remission of proteinuria after 3 months (primary outcome), and after 6 and 12 months (secondary outcomes), as well as progression to end-stage kidney disease.

RESULTS

After 13 of the planned 50 children (25%) were randomized, the data safety and monitoring board recommended study termination for futility. All 13 children remained nephrotic. Renal function worsened in 5 children (2 in Intervention arm, 3 in Placebo arm) who required renal replacement therapy during the study period. Circulating CD20 was reduced following OFA infusion and remained low for > 3 months.

CONCLUSIONS

OFA given in one single infusion of 1500 mg/1.73 m² doses does not induce remission in MRNS. Regimens based on higher OFA doses should be tested in clinical trials.

TRIAL REGISTRATION

https://clinicaltrials.gov: NCT02394106.

Ofatumumab for multirelapsing membranous nephropathy complicated by rituximab-induced serum-sickness

Rituximab (375 mg/m²) achieved remission of the first episode and six relapses of nephrotic syndrome (NS) in a young male patient with podocyte phospholipase A₂ receptor (PLA₂R)-related membranous nephropathy (MN) refractory to steroids and cyclosporine. Between-treatments interval averaged 17.4±4.2 months. The seventh infusion was complicated by delayed serum-sickness, which resolved with steroids. On subsequent relapse, the fully human anti-CD20 monoclonal antibody ofatumumab (300 mg) achieved remission of the NS, without significant side effects. Circulating CD19⁺ B cells were depleted, proteinuria decreased from 10.9 to 1.3 g/day, and serum albumin, immunoglobulin levels and glomerular filtration rate normalised. Twenty-eight months later, despite transient anti-PLA₂R depletion, ofatumumab (100 mg) failed to induce remission of the eighth relapse. Remission was safely achieved 5 months later with repeated ofatumumab infusion (300 mg). This treatment (€723) was less expensive than rituximab (€1801). Ofatumumab could be a safe and cost/effective rescue therapy for patients with MN sensitised against rituximab.

Rituximab-induced serum sickness in a 6-year-old boy with steroid-dependent nephrotic syndrome

Rituximab (RTX) is a murine-human chimeric monoclonal antibody against CD20 that has been proven effective for preventing relapse in frequently-relapsing or steroid-dependent nephrotic syndrome (NS). Serum sickness, a type-3 hypersensitivity reaction resulting from injection of foreign proteins, has been reported in patients treated with RTX. Herein, we describe a case of RTX-induced serum sickness (RISS) in a 6-year-old boy with steroid-dependent NS. He presented to the hospital with fever and polyarthralgia at 10 days after his fourth dose of RTX. Although he was started on empiric intravenous antibiotics, there was no evidence of septic arthritis and his symptoms resolved over the course of 4 days. He was diagnosed with RISS based on the chronology of RTX administration and the acute-onset self-limiting course of the polyarthritis. His serum human anti-chimeric antibody (HACA) level on day 53 exceeded the limit of quantification (5000 ng/mL). The pathogenesis of RISS and the role of HACAs remain unclear. It is important for clinicians to recognize RISS, because further infusions of RTX may cause more severe reactions in patients with a history of RISS.

Ofatumumab in post-transplantation recurrence of focal segmental glomerulosclerosis in a child

FSGS is a potentially devastating form of nephrotic syndrome. Treatment of SRNS can be difficult, especially post-transplantation. The current therapy of post-transplant SRNS includes plasmapheresis, ACE-I, CNI, and monoclonal antibodies (rituximab). Patients who are refractory to these interventions have limited therapeutic alternatives. We present a case of a patient with SRNS secondary to FSGS. He did not respond to immunosuppressive medications prior to transplant, progressed to ESRD, and was started on chronic hemodialysis. He received a DDKT which was complicated by post-transplant FSGS recurrence. A course of plasmapheresis, rituximab, and CNI were administered with some response. Ofatumumab was then given to the patient. As a result, the patient achieved partial remission. Ofatumumab may be a safe and effective option for post-transplant recurrence of FSGS.

Difficult-to-treat idiopathic nephrotic syndrome: established drugs, open questions and future options

The idiopathic nephrotic syndrome in childhood can be classified according to the International Study of Kidney Disease in Children (ISKDC) based on the response to steroids. Typically, steroid-sensitive nephrotic syndrome (SSNS) is characterised by minimal changes in disease (MCD) histology, whereas in steroid-resistant nephrotic syndrome (SRNS) focal segmental glomerulosclerosis (FSGS) is the most prevalent lesion. Patients with SSNS may develop frequent relapses and/or steroid dependency, which can be difficult to treat. New studies confirm the value of calcineurin inhibitors (CNIs) and mycophenolic acid in preventing relapses of SSNS. Rituximab also plays an important role, but many questions regarding initial dosing, repetitions of courses, and long-term side effects remain unclear. SRNS, especially when unresponsive to treatment, can lead to chronic kidney disease. In particular, treatment with CNIs has improved the prognosis and recent data indicate that treatment can even be discontinued in many patients with full remission. In CNI-unresponsive SRNS, rituximab is less effective than in SSNS and the role of other biologicals (such as ofatumumab, abatacept, and others) remains unclear. A significant proportion of children with FSGS have genetic causes and most patients do not respond to immunosuppression, although individual patients with partial and even complete response have been documented. Future studies should evaluate treatments leading to long-term remission without maintenance immunosuppression in SSNS; in both genetic and immune-mediated SRNS, novel options to decrease the number of treatment-unresponsive patients seem mandatory, as they are at a high risk of developing end-stage renal disease.

Successful use of ofatumumab in two cases of early-onset juvenile SLE with thrombocytopenia caused by a mutation in protein kinase C δ

BACKGROUND

We previously described an endogamous Pakistani kindred in whom we identified a novel homozygous missense mutation in the PRKCD gene encoding for protein kinase C δ (PKCδ) as a cause of monogenic systemic lupus erythematosus (SLE). PKCδ has a role in the negative regulation of B cells. Given the nature of the disease, a logical targeted therapeutic approach in these patients is B cell depletion. Indeed, the 3 siblings all had a marked clinical response and resolution of symptoms with rituximab, although 2 of the siblings had severe reactions to rituximab thus precluding further treatment with this. We therefore describe the first successful use of ofatumumab for this rare form of monogenic SLE.

CASE PRESENTATION

All three affected siblings presented with SLE before the age of 3-years with lethargy, intermittent fever, thrombocytopenia, cutaneous involvement, alopecia, and hepatosplenomegaly. Tubulointerstitial nephritis was also present in 1 of the siblings. Homozygosity mapping followed by whole exome sequencing identified a homozygous missense mutation in PRKCD (p.Gly432Trp), subsequently confirmed by Sanger sequencing to be present in all 3 siblings. All 3 patients were initially treated with rituximab, however 2 of the siblings developed severe infusion-related reactions. For subsequent disease flare in these individuals we therefore used an alternative B cell depleting agent, ofatumumab (300 mg/1.73m² on day 1; 700 mg/1.73m² on day 15). This resulted in marked clinical improvement in both patients. To the best of our knowledge, this is the first report describing the successful use of ofatumumab for PKCδ deficiency.

CONCLUSIONS

PKCδ deficiency causes a monogenic form of SLE which responds well to B cell depletion. Ofatumumab is also likely to have a therapeutic role for sporadic juvenile SLE (jSLE) patients intolerant of rituximab.

Adverse events linked with the use of chimeric and humanized anti-CD20 antibodies in children with idiopathic nephrotic syndrome

AIMS

Anti-CD20 antibodies are increasingly being used to treat idiopathic nephrotic syndrome (INS) in children. While they may allow steroid and calcineurin inhibitor withdrawal, repeated infusions of anti-CD20 antibodies are often required to maintain remission. Data on their potential toxicity in INS are needed, to consider repeated infusions.

METHODS

We investigated the side effects associated with the use of rituximab (a chimeric antibody; 130 patients) and ofatumumab (a humanized antibody; 37 patients) in children with INS (steroid-dependent and steroid/calcineurin inhibitor-dependent disease) treated at a national referral centre over a 9-year period (400 treatments; follow-up 1-9 years).

RESULTS

Infusion reactions were mainly absent in children with steroid-dependent disease. Rash, dyspnoea, fever, cough and itchy throat (5% and 18% following rituximab and ofatumumab infusion, respectively) were resolved by using premedication with salbutamol. Other short-term reactions (up to 3 months), including arthritis (2%) and lung injury (1%), were more common with rituximab. Infections were observed 3-9 months following infusion, were similarly common in the two groups and resolved with targeted therapies [antibiotic, fluconazole, immunoglobulins (Igs), etc.]. The number of circulating CD19/20 cells fell to 0 at month 1 and were reconstituted at month 3; circulating IgG antibodies remained within the normal range for 1 year. Tetanus and hepatitis B virus immunization was not modified by either treatment; Epstein-Barr virus and John Cunningham virus activation markers were occasionally observed.

CONCLUSION

Overall, the toxicity of anti-CD20 monoclonal antibodies was limited to post-infusion side effects in children with more complex disease. The relatively safe profile of anti-CD20 antibodies supports their use as steroid-sparing agents in children with INS.

Ofatumumab in post-transplantation recurrence of a pediatric steroid-resistant idiopathic nephrotic syndrome

Treatment of SRNS is a challenge. Antiproliferative agents and depleting antibodies have been reported to be effective. However, these agents are not always successful, and use of ofatumumab could provide a different treatment option. Our patient was diagnosed with a SRNS at 5 years of age. She developed ESRD, with FSGS. This was cause for a first renal transplantation. The NS relapsed, leading to loss of the graft, and a second renal transplantation was performed. Due to the recurrence of the NS, IAds were initiated and led to a complete remission. Our patient remained dependent on IAds, however, despite treatments with calcineurin inhibitors, corticosteroids, rituximab, and abatacept. Ofatumumab was introduced and led to a remission, thus allowing cessation of the IAd treatment. Another infusion of ofatumumab was administered 8 months after the last one, due to the recurrence of the NS and a renewed increase in B cells. Although it did not result in a complete remission, the proteinuria was stabilized in the absence of IAds. Ofatumumab may be an alternative treatment for post-transplantation rituximab-resistant SRNS, although this needs to be confirmed by further studies.

Immunology of idiopathic nephrotic syndrome

The pathogenesis of idiopathic nephrotic syndrome (INS) is as yet unknown, but several lines of evidence indicate that the immune system may play a crucial pathogenic role in non-genetic INS. The most important of these are, first, the effectiveness of therapy based on immunosuppression and, second, a vast body of data derived both from experimental models and from patient studies that implicate T cells and more recently B cells as major players in INS pathogenesis. However, recent findings also suggest a direct role of podocytes as drivers of the disease process, and the interplay between the glomerulus and the immune system is still being elucidated. In this review we provide an overview of current knowledge on the role of different components of the immune system in determining disease. Advances in our understanding of the pathogenesis of INS may help drive new, more tailored therapeutic approaches.

Treatment of membranous nephropathy: time for a paradigm shift

In patients with membranous nephropathy, alkylating agents (cyclophosphamide or chlorambucil) alone or in combination with steroids achieve remission of nephrotic syndrome more effectively than conservative treatment or steroids alone, but can cause myelotoxicity, infections, and cancer. Calcineurin inhibitors can improve proteinuria, but are nephrotoxic. Most patients relapse after treatment withdrawal and can become treatment dependent, which increases the risk of nephrotoxicity. The discovery of nephritogenic autoantibodies against podocyte M-type phospholipase A2 receptor (PLA₂R) and thrombospondin type-1 domain- containing protein 7A (THSD7A) antigens provides a clear pathophysiological rationale for interventions that specifically target B-cell lineages to prevent antibody production and subepithelial deposition. The anti-CD20 monoclonal antibody rituximab is safe and achieves remission of proteinuria in approximately two-thirds of patients with membranous nephropathy. In those with PLA₂R-related disease, remission can be predicted by anti-PLA₂R antibody depletion and relapse by antibody re-emergence into the circulation. Thus, integrated evaluation of serology and proteinuria could guide identification of affected patients and treatment with individually tailored protocols. Nonspecific and toxic immunosuppressive regimens will fall out of use. B-cell modulation by rituximab and second-generation anti-CD20 antibodies (or plasma cell-targeted therapy in anti-CD20 resistant forms of disease) will lead to a novel therapeutic paradigm for patients with membranous nephropathy.

Ofatumumab for the treatment of childhood nephrotic syndrome

BACKGROUND

Ofatumumab is a humanized anti-CD20 monoclonal antibody that has recently garnered interest as a potential therapeutic agent for nephrotic syndrome. We report our center's experience in administering ofatumumab to five pediatric patients with idiopathic nephrotic syndrome.

METHODS

Between March 2015 and November 2016, five patients were treated with ofatumumab. One patient had post-transplant recurrent focal segmental glomerulosclerosis (FSGS) which had been resistant to plasmapheresis and numerous immunosuppressive agents. Four patients had nephrotic syndrome in their native kidneys, one with initial steroid-resistant disease and the others with subsequent development of steroid resistance. Two of the patients were treated with a desensitization protocol after experiencing hypersensitivity reactions to ofatumumab.

RESULTS

One patient did not complete ofatumumab treatment due to infusion reactions. Of the four remaining patients, three achieved complete remission after treatment, and one achieved partial remission. One of the patients achieving complete remission represents the first reported case of successful treatment of post-transplant recurrent FSGS using ofatumumab. Two patients who received ofatumumab with our desensitization protocol were able to complete their treatments after initially experiencing hypersensitivity reactions.

CONCLUSIONS

Ofatumumab may be an effective treatment for refractory childhood nephrotic syndrome and post-transplant recurrent FSGS. A desensitization protocol may be helpful to address hypersensitivity reactions.

Randomised controlled trial comparing ofatumumab to rituximab in children with steroid-dependent and calcineurin inhibitor-dependent idiopathic nephrotic syndrome: study protocol

INTRODUCTION

Oral steroids induce remission in about 90% of children with idiopathic nephrotic syndrome (INS), which is characterised by severe proteinuria and hypoalbuminaemia. Some children become steroid-dependent (SD) and require addition of calcineurin inhibitors (CNI) to maintain remission. Since these oral agents are toxic, alternative interventions are needed for long-term treatment. The anti-CD20 antibody rituximab has shown promising steroid-sparing properties in clinical trials, but benefits are less convincing in complicated forms of SD-INS. Ofatumumab, a new anti-CD20 antibody with stronger affinity to CD20, may be superior to rituximab in maintaining oral steroid-free and CNI-free disease remission in children with SD-INS.

METHODS AND ANALYSIS

This open-label, two-parallel-arm, controlled, phase II randomised clinical trial will enrol children with SD-INS maintained in remission with oral steroids and CNI. Children will be randomised to either ofatumumab or rituximab infusion. After infusion of either antibody, steroids will be maintained for 30 days and then tapered off by 0.3 mg/kg/week until complete withdrawal. 1 week after complete steroid withdrawal, CNI will be decreased by 50% and withdrawn within 2 additional weeks. We will enrol 140 children to detect as significant at the 2-sided p value of 0.01 with a power of >0.8, a reduction in the risk of 1-year relapse (primary end point) of at least 0.3 (ie, from 0.65 to 0.35; (risk ratio 0.54)) in the ofatumumab arm when compared with the rituximab arm. We will compare the amount of steroids required to maintain complete disease remission at 6 and 24 months, relapse-free period, relapse rate per year as secondary end points. Circulating cell populations will be studied as biomarkers or predictors of the anti-CD20 response.

ETHICS AND DISSEMINATION

The trial received ethics approval from the local ethics board. We will publish study results and present them at international scientific meetings.

TRIAL REGISTRATION NUMBERS

NCT02394119; 2015-000624-28; Pre-results.