Pharmacokinetics of rituximab and clinical outcomes in patients with anti-neutrophil cytoplasmic antibody associated vasculitis

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

OBJECTIVES

Rituximab 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.

METHODS

We 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.

RESULTS

The 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.

CONCLUSION

In 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.

Sustained post-rituximab B-cell depletion is common in ANCA-associated vasculitis and is affected by sex and renal function

OBJECTIVE

Despite the increasing use of rituximab in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), it remains unclear what the optimal dosing is, especially for maintenance of remission. A deeper understanding of post-rituximab B-cell repopulation patterns may aid better-tailored treatment.

METHODS

This is a monocentric, retrospective study including ANCA-positive AAV patients receiving a single course of rituximab induction. CD19+ B cells were longitudinally monitored with flow cytometry. B-cell repopulation was defined as CD19+ >10 cells/μL.

RESULTS

Seventy-one patients were included, the majority with microscopic polyangiitis (75%), myeloperoxidase-ANCA positivity (75%) and with renal involvement (79%). During a median follow-up of 54 months since the first rituximab infusion, 44 patients (62%) repopulated B cells, with a median time to repopulation of 39 months (range 7-102). Patients experiencing B-cell depletion lasting longer than the overall median time to repopulation (39 months) exhibited a lower risk of flare and higher risk of serious infection. In multivariate Cox regression, higher estimated glomerular filtration rate (eGFR) [hazard ratio (HR) 1.84, 95% confidence interval (CI) 1.13-2.98 per 30 mL/min/1.73 m2 eGFR] and female sex (HR 2.70, 95% CI 1.37-5.31) were independent predictors of increased rate of B-cell repopulation.

CONCLUSION

A subset of AAV patients develop sustained post-rituximab B-cell depletion, which associates with reduced risk of flare and increased risk of serious infection in the long term. Preserved renal function and female sex are associated with faster B-cell repopulation. These observations further highlight the need to personalize immunosuppression to improve clinical outcomes.

Antibody Drug Clearance: An Underexplored Marker of Outcomes with Checkpoint Inhibitors

Immune-checkpoint inhibitor (ICI) therapy has dramatically changed the clinical landscape for several cancers, and ICI use continues to expand across many cancer types. Low baseline clearance (CL) and/or a large reduction of CL during treatment correlates with better clinical response and longer survival. Similar phenomena have also been reported with other monoclonal antibodies (mAb) in cancer and other diseases, highlighting a characteristic of mAb clinical pharmacology that is potentially shared among various mAbs and diseases. Though tempting to attribute poor outcomes to low drug exposure and arguably low target engagement due to high CL, such speculation is not supported by the relatively flat exposure-response relationship of most ICIs, where a higher dose or exposure is not likely to provide additional benefit. Instead, an elevated and/or increasing CL could be a surrogate marker of the inherent resistant phenotype that cannot be reversed by maximizing drug exposure. The mechanisms connecting ICI clearance, therapeutic efficacy, and resistance are unclear and likely to be multifactorial. Therefore, to explore the potential of ICI CL as an early marker for efficacy, this review highlights the similarities and differences of CL characteristics and CL-response relationships for all FDA-approved ICIs, and we compare and contrast these to selected non-ICI mAbs. We also discuss underlying mechanisms that potentially link mAb CL with efficacy and highlight existing knowledge gaps and future directions where more clinical and preclinical investigations are warranted to clearly understand the value of baseline and/or time-varying CL in predicting response to ICI-based therapeutics.

Association Between Plasma Rituximab Concentration and the Risk of Major Relapse in Antineutrophil Cytoplasmic Antibody-Associated Vasculitides During Rituximab Maintenance Therapy

OBJECTIVE

Interindividual variability in response to rituximab remains unexplored in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides. Rituximab pharmacokinetics (PK) and pharmacodynamics (PD) as well as genetic polymorphisms could contribute to variability. This ancillary study of the MAINRITSAN 2 trial aimed to explore the relationship between rituximab plasma concentration, genetic polymorphisms in PK/PD candidate genes, and clinical outcomes.

METHODS

Patients included in the MAINRITSAN2 trial (ClinicalTrials.gov identifier: NCT01731561) were randomized to receive a 500-mg fixed-schedule rituximab infusion or an individually tailored regimen. Rituximab plasma concentrations at month 3 (CM3) were assessed. DNA samples (n = 53) were genotyped for single-nucleotide polymorphisms within 88 putative PK/PD candidate genes. The relationship between PK/PD outcomes and genetic variants was investigated using logistic linear regression in additive and recessive genetic models.

RESULTS

One hundred and thirty-five patients were included. The frequency of underexposed patients (<4 μg/ml) in the fixed-schedule group was statistically lower compared to that in the tailored-infusion group (2.0% versus 18.0%; P = 0.02, respectively). Low rituximab plasma concentration at 3 months (CM3 <4 μg/ml) was an independent risk factor for major relapse (odds ratio 6.56 [95% confidence interval (95% CI) 1.26-34.09]; P = 0.025) at month 28 (M28). A sensitivity survival analysis also identified CM3 <4 μg/ml as an independent risk factor for major relapse (hazard ratio [HR] 4.81 [95% CI 1.56-14.82]; P = 0.006) and relapse (HR 2.70 [95% CI 1.02-7.15]; P = 0.046). STAT4 rs2278940 and PRKCA rs8076312 were significantly associated with CM3 but not with major relapse onset at M28.

CONCLUSION

These results suggest that drug monitoring could be useful to individualize the schedule of rituximab administration within the maintenance phase.

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.

Low dose versus standard dose rituximab for the treatment of antiphospholipid syndrome: A pilot study from a tertiary medical center

BACKGROUND

To investigate the therapeutic effects and safety of low-dose and standard-dose rituximab (RTX) in the treatment of antiphospholipid syndrome (APS).

METHODS

In this real-world study, we included 22 consecutive patients with APS who received RTX. Standard dose (SD) was defined as an overall dosage of RTX ≥ 1000mg in the induction period, and low dose (LD) was defined as an overall dosage of RTX <1000mg.

RESULTS

Of included patients, 1 patients died, 2 patients withdrew and 19 patients completed 6-month follow-up. Nine patients received SD-RTX and 13 patients received LD-RTX, and elder patients [LD-RTX vs. SD-RTX: (49.1 ± 15.5) vs. (35.8 ± 12.3) years, p = 0.044] and patients with later-onset [LD-RTX vs. SD-RTX: (46.8 ± 16.3) vs. (31.3 ± 13.6) years, p = 0.029] were more frequently included in LD-RTX than SD-RTX. Following 6 month RTX treatment, 8 patients (42.1%) achieved complete remission, 8 patients (42.1%) achieved partial remission and 3 patients (15.8%) showed no remission. The titers of anticardiolipin antibodies [baseline vs. 6 months: 30.8 (10.7, 90) vs. 19.5 (2.45, 69.10) U/L, p = 0.023] and the levels of erythrocyte sedimentation rate [baseline vs. 6 months: 29 (6, 63) vs. '6 (3, 14) mm/h, p = 0.021] exhibited a significantly decrease in all APS patients. Remission rate and titers of anti-β2-glycoprotein I and lupus anticoagulant did not differ significantly between two groups.

CONCLUSION

RTX might be a safe and effective option for patients with APS, and low dose confers equal efficacy as standard dose. Further cohort studies are needed to confirm our findings.

Relationship Between Gender and 1-Year Mortality in ANCA-Associated Vasculitis Patients: A Single-Center Retrospective Analysis and Meta-Analysis

Objective

The relationship between gender and short-term prognosis of patients with anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV) is unclear, hence single-center retrospective analysis and meta-analysis were conducted to determine the relationship.

Methods

Initially treated patients with AAV were retrospectively enrolled. Data of clinical manifestation, laboratory indicators, Birmingham vasculitis activity score (BVAS), therapeutic treatments, and the patients' situations within 1 year were recorded. First, we compared the basic characteristics between male and female patients. Second, the risk factors associated with a 1-year mortality rate of patients with AAV were evaluated. Finally, a meta-analysis was performed to explore the effect of gender on 1-year mortality in patients with AAV.

Results

The study involved 84 patients with AAV, including 33 female and 51 male participants. In total, 14 people died (12 males and 2 females) and 70 survived in the 1st year. Statistical differences were noted in the age of onset, the course of the disease, WBC, HB, N, ESR, CRP, BUN, ALT and ALB, BVAS, and 1-year mortality rate between male and female participants. In male patients, elevated Scr, NLR, PLT, and RDW-CV were associated with poor AAV (P < 0.05) prognosis. The meta-analysis verified that male gender was an independent risk factor for the 1-year mortality of patients with AAV(OR = 1.54).

Conclusion

Significant sex-specific differences were found in patients with AAV. Male patients contributed to 1.54-fold of 1-year mortality risk in patients with AAV by meta-analysis. More attention should be paid to the mortality risk of male patients with AAV in the early stage.

The Influence of Underlying Disease on Rituximab Pharmacokinetics May be Explained by Target-Mediated Drug Disposition

BACKGROUND AND OBJECTIVES

Rituximab is an anti-CD20 monoclonal antibody approved in several diseases, including chronic lymphocytic leukemia (CLL), diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), rheumatoid arthritis (RA), and anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV). The influence of underlying disease on rituximab pharmacokinetics has never been investigated for several cancer and non-cancer diseases simultaneously. This study aimed at assessing this influence using an integrated semi-mechanistic model accounting for target-mediated elimination of rituximab.

METHODS

Rituximab concentration-time data from five studies previously published in patients with CLL, DLBCL, FL, RA, and AAV were described using a two-compartment model with irreversible binding of rituximab to its target antigen. Both underlying disease and target antigen measurements were assessed as covariates.

RESULTS

Central volume of distribution was [95% confidence interval] 1.7-fold [1.6-1.9] higher in DLBCL than in RA, FL, and CLL, and it was 1.8-fold [1.6-2.1] higher in RA, FL, and CLL than in AAV. First-order elimination rate constants were 1.8-fold [1.7-2.0] and 1.3-fold [1.2-1.5] higher in RA, DLBCL, and FL than in CLL and AAV, respectively. Baseline latent antigen level (L₀) was 54-fold [30-94], 20-fold [11-36], and 29-fold [14-64] higher in CLL, DLBCL, and FL, respectively, than in RA and AAV. In lymphoma, L₀ increased with baseline total metabolic tumor volume (p = 6.10^-7). In CLL, the second-order target-mediated elimination rate constant (k_deg) increased with baseline CD20 count on circulating B cells (CD20_cir, p = 0.0081).

CONCLUSIONS

Our results show for the first time that rituximab pharmacokinetics is strongly influenced by underlying disease and disease activity. Notably, neoplasms are associated with higher antigen amounts that result in decreased exposure to rituximab compared to inflammatory diseases. Our model might be used to estimate unbound target amounts in upcoming studies.

Dose-dependent Pharmacological Response to Rituximab in the Treatment of Antineutrophil Cytoplasmic Antibody-Associated Vasculiti

OBJECTIVE

Rituximab (RTX) is effective in induction and maintenance of remission in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). However, uncertainty remains regarding the optimal maintenance dosing regimen. This work evaluates the relationship between variability in RTX dosing and pharmacological response in AAV.

METHODS

A prospective cohort of AAV patients (n=28) with either GPA (n=23) or MPA (n=5) receiving maintenance RTX therapy were followed in a single tertiary care academic medical center over a 2-year period. Patient demographics, RTX dosing information, and trough plasma RTX levels were collected along with laboratory measures of pharmacologic response, including B-cell counts and ANCA titers.

RESULTS

RTX dosing information from 94 infusions with 59 trough samples were collected with a mean±SD dose of 640±221 mg, dosing interval of 210±88 days, and trough plasma RTX concentration of 622±548 ng/mL. RTX trough concentrations were associated with RTX dose (ρ=0.60, p<0.0001) and dosing interval (ρ=-0.55, p<0.0001). RTX dosing intensity (mg/d) was associated with RTX trough concentrations (ρ=0.57, p<0.0001). Higher dosing intensities were associated with undetectable B-cell repopulation (p<0.0001), but not negative ANCA titers (p=0.6). Stratification of dosing intensities based on the standard dosing regimen of 500 mg every six months (2.4 to 3.3 mg/d) demonstrated that this regimen was associated with B-cell repopulation in 8 of 17 doses (47%) compared to 0 of 23 doses (0%) with the high-dose regimen (>3.3 mg/d) (p<0.0001).

CONCLUSION

RTX maintenance dosing of 500 mg every six months may be inadequate to maintain B-cell depletion in the treatment of AAV.

Defining a Therapeutic Window for Rituximab Maintenance Therapy in ANCA-Associated Vasculitis: A Longitudinal Observational Study

Background/Objective:

Rituximab (RTX) has been shown to be effective at maintaining remission in patients with granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA), however, the optimal regimen has not been established. The objective of this study was to determine the association between RTX exposure and pharmacological response.

Methods:

Thirty patients with GPA (25) and MPA (5) receiving maintenance therapy with RTX were longitudinally followed in a single tertiary care center. Peripheral blood samples were collected at the trough of RTX therapy and plasma RTX concentrations were measured by ELISA.

Results:

Trough plasma RTX levels greater than 550 ng/mL were associated with B-cell depletion in 100% of the samples analyzed, compared to 51% of samples with levels less than 550 ng/mL (p<0.0001). Trough plasma RTX levels greater than 1,000 ng/mL were associated with hypogammaglobulinemia in 100% of the samples analyzed, compared to 60% of samples with levels less than 1000 ng/mL (p=0.03). There was no association between the peripheral RTX and anti-RTX antibodies. However, the presence of anti-RTX antibodies was associated with a lower risk of hypogammaglobulinemia (83% versus 56%; p=0.04).

Conclusions:

Plasma trough RTX level between 550 ng/mL and 1,000 ng/mL is associated with a higher rate of B-cell depletion while minimizing hypogammaglobulinemia in GPA and MPA patients on maintenance RTX therapy. Establishment of target RTX trough levels would allow for a personalized approach to dosing RTX. However, larger and longer-term studies will be necessary to confirm these initial findings.

Non-Linear Rituximab Pharmacokinetics and Complex Relationship between Rituximab Concentrations and Anti-Neutrophil Cytoplasmic Antibodies (ANCA) in ANCA-Associated Vasculitis: The RAVE Trial Revisited

BACKGROUND AND OBJECTIVES

Rituximab is approved in patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and leads to a decrease of ANCA levels. The objectives of this study were to investigate the non-linear pharmacokinetics of rituximab and the relationship between its concentrations and ANCA levels in AAV patients.

METHODS

Ninety-two AAV patients from the RAVE (Rituximab in ANCA-Associated Vasculitis) trial were assessed. Both ANCA anti-myeloperoxidase (MPO-ANCA) and anti-proteinase 3 (PR3-ANCA) levels were used as biomarkers. The pharmacokinetics of rituximab were described using a semi-mechanistic two-compartment model that included a latent target antigen turnover and allowed the estimation of specific target-mediated elimination in addition to its non-specific elimination of rituximab. The effect of rituximab on the ANCA level was described using a semi-mechanistic compartment model with a negative feedback (Friberg) model with no transit compartment. A population modeling approach was used.

RESULTS

Our pharmacokinetic and pharmacokinetic-pharmacodynamic (PK-PD) models satisfactorily described both concentration-time and concentration-effect relationship data. The mean (inter-individual standard deviation) estimated non-specific clearance was 0.15 L/day (0.30%) and the target-mediated elimination rate constant was 2.4 × 10^-5 nmol/day. The elimination half-lives for MPO-ANCA and PR3-ANCA were 24 and 18 days, respectively.

CONCLUSIONS

A non-linear target-mediated elimination of rituximab was detected in AAV patients. Our PK-PD model allowed quantification of the association between rituximab concentrations and ANCA levels. This decrease was deep but delayed, and more sustained in patients with MPO-ANCA than in those with PR3-ANCA. Our results suggest that repeating courses of rituximab might improve the clinical response to rituximab.

Rituximab Associated Hypogammaglobulinemia in Autoimmune Disease

Objective

To evaluate the characteristics of patients with autoimmune disease with hypogammaglobulinemia following rituximab (RTX) and describe their long-term outcomes, including those who commenced immunoglobulin replacement therapy.

Methods

Patients received RTX for autoimmune disease between 2003 and 2012 with immunoglobulin G (IgG) <7g/L were included in this retrospective series. Hypogammaglobulinemia was classified by nadir IgG subgroups of 5 to <7g/L (mild), 3 to <5g/L (moderate) and <3g/L (severe). Characteristics of patients were compared across subgroups and examined for factors associated with greater likelihood of long term hypogammaglobulinemia or immunoglobulin replacement.

Results

142 patients were included; 101 (71%) had anti-neutrophil cytoplasm antibody (ANCA) associated vasculitis (AAV), 18 (13%) systemic lupus erythematosus (SLE) and 23 (16%) other conditions. Mean follow-up was 97.2 months from first RTX. Hypogammaglobulinemia continued to be identified during long-term follow-up. Median time to IgG <5g/L was 22.5 months. Greater likelihood of moderate hypogammaglobulinemia (IgG <5g/L) and/or use of immunoglobulin replacement therapy at 60 months was observed in patients with prior cyclophosphamide exposure (odds ratio (OR) 3.60 [95% confidence interval (CI) 1.03 – 12.53], glucocorticoid use at 12 months [OR 7.48 (95% CI 1.28 – 43.55], lower nadir IgG within 12 months of RTX commencement [OR 0.68 (95% CI 0.51 – 0.90)] and female sex [OR 8.57 (95% CI 2.07 – 35.43)]. Immunoglobulin replacement was commenced in 29/142 (20%) and associated with reduction in infection rates, but not severe infection rates.

Conclusion

Hypogammaglobulinemia continues to occur in long-term follow-up post-RTX. In patients with recurrent infections, immunoglobulin replacement reduced rates of non-severe infections.

[Rituximab immunomonitoring in autoimmune diseases: a support tool in clinical practice?]

INTRODUCTION

Immune 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.

METHODS

All 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.

RESULTS

Several 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.

CONCLUSION

This 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.

Variability of rituximab and tocilizumab trough concentrations in patients with rheumatoid arthritis

Patients with rheumatoid arthritis (RA) are eligible for treatment with therapeutic monoclonal antibodies (mAbs) that target tumor necrosis factor α (TNFα), as well as others, such as rituximab (RTX) and tocilizumab (TCZ). Although pharmacokinetic variability and the link between concentration-clinical response of anti-TNFα mAbs have been well-described, little is known about RTX and TCZ. We aimed to evaluate the variability of RTX and TCZ serum concentrations in RA patients treated in second-line and the relationship between RTX/TCZ concentrations and the clinical response. Serum mAb trough concentrations of RA patients treated with RTX (n = 35) or TCZ (n = 46) were determined at week 24 by liquid chromatography-tandem mass spectrometry. The clinical response was assessed at week 24 by the change in the disease activity score in the 28 joints-erythrocyte sedimentation rate from baseline (ΔDAS28-Erythrocyte Sedimentation Rate) and according to the European League Against Rheumatism (EULAR) recommendations. RTX and TCZ trough concentrations were highly variable, with a coefficient of variation of 171.3% for RTX (median [10th-90th percentiles]: <1.0 µg/mL [<1.0-5.1]) and 132.6% for TCZ (median [10th-90th percentiles]: 5.4 µg/mL [<1.0-27.8]). Univariate analysis did not identify any determinants of such variability, except cotreatment with methotrexate, which was associated with lower RTX concentrations (P = 0.03). The response to treatment was not related to the RTX or TCZ trough concentration. RTX and TCZ trough concentrations at 24 weeks were highly variable in RA patients treated in the second line, without any link concentration-clinical response having been demonstrated.

The Influence of Different Disease States on Rituximab Pharmacokinetics

BACKGROUND

The anti-CD20 antibody rituximab, which promotes the selective depletion of CD20 positive B cells, was the first targeted therapy that was approved for the treatment of B-cell malignancies, and it is now widely prescribed in both malignant and non-malignant, immune-related diseases. However, the cause of its various clinical responses in certain diseases, have not been clearly elucidated. The variabilities in inter-individual pharmacokinetic and the emerging evidence of the relationships between pharmacokinetic and pharmacodynamic may provide a better understanding of this drug.

METHODS

We searched and summarized the latest published articles on rituximab pharmacokinetic profiles and the pharmacokinetic/pharmacodynamic models in different patient populations, including B-cell malignancies, rheumatoid arthritis, ANCA-associated vasculitis, and glomerular kidney diseases.

RESULTS

Most pharmacokinetic data are drawn from clinical studies in oncology clinical practice. Body weight, gender, and antigen-related factors are proven to be the key factors affecting rituximab pharmacokinetics. In addition, the positive exposure-response relations were reported, which provide encouraging evidence for individualized therapies. While in immune disorders, especially in the off-labeled indications, pharmacokinetic studies are quite limited. Compared with that in B-cell malignancies, the differences in the pharmacokinetic parameters may be attributed to the different pathogeneses of diseases, mechanisms of action and dosing strategies. However, the correlation between drug exposure and clinical outcomes remains unclear.

CONCLUSION

Here, we provide an overview of the complexities associated with rituximab pharmacokinetics and pharmacodynamics in different diseases. Although many influencing factors need to be verified in future studies, a better understanding of the relationships between pharmacokinetic and pharmacodynamic may assist in optimizing rituximab clinical practice.

Updates for the treatment of EGPA

Eosinophilic granulomatosis with polyangiitis (EGPA, formerly Churg-Strauss syndrome) is the least frequent antineutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV). Major advances of our knowledge on its pathophysiology have revealed features of both AAV and eosinophilic disorders. The development of targeted biotherapies for both diseases opened new possibilities for EGPA management. In this review, we highlight the rationale underlying the routine treatment strategy, which relies mainly on corticosteroids, with immunosuppressant adjunction for severe disease. However, novel therapies are still needed for refractory/relapsing disease and to alleviate the corticosteroid-dependence of asthma and chronic rhinosinusitis. At present, the most promising biotherapies target either eosinophil biology, like mepolizumab, an anti-interleukin-5, or the B-cell compartment, with rituximab. Recent clinical data on new treatment options are discussed and therapeutic strategies are proposed.

Rituximab treatment of ANCA-associated vasculitis

INTRODUCTION

Rituximab, an anti-B-cell biological therapy, has been investigated in several clinical trials on antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs).

AREAS COVERED

In this paper, the clinical trials and open-label studies on rituximab efficacy and safety in treating AAVs are reviewed.

EXPERT OPINION

Rituximab achieved high remission-induction and sustained-maintenance rates for patients with these severe diseases, thereby challenging the cornerstone treatment of corticosteroids and cyclophosphamide followed by azathioprine. Rituximab should be used as first-line therapy with corticosteroids to induce remission of severe AAVs, especially in situations in which cyclophosphamide may be problematic (relapse after cyclophosphamide, women of childbearing age, risk of malignancy). Cyclophosphamide indications are likely to be restricted in the future. Whenever possible, rituximab should be preferred to azathioprine to maintain remission. The current maintenance regimen has been extended to at least 18 months but its optimal duration remains unknown and recent data suggest the possibility to extend treatment to 4 years. Future challenges include defining the best dose regimen: at present, different schedules are used as alternatives to those recognized as standards by health authorities. In addition, it remains to identify which patients will benefit the most from long-term retreatment: potentially those with relapsing disease or anti-proteinase-3 ANCA-positivity.

Interventions for renal vasculitis in adults

BACKGROUND

Renal vasculitis presents as rapidly progressive glomerulonephritis and comprises of a group of conditions characterised by acute kidney injury (AKI), haematuria and proteinuria. Treatment of these conditions involve the use of steroid and non-steroid agents in combination with plasma exchange. Although immunosuppression overall has been very successful in treatment of these conditions, many questions remain unanswered in terms of dose and duration of therapy, the use of plasma exchange and the role of new therapies. This 2019 publication is an update of a review first published in 2008 and updated in 2015.

OBJECTIVES

To evaluate the benefits and harms of any intervention used for the treatment of renal vasculitis in adults.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 21 November 2019 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

Randomised controlled trials investigating any intervention for the treatment of renal vasculitis in adults.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study quality and extracted data. Statistical analyses were performed using a random effects model and results expressed as risk ratio (RR) with 95% confidence intervals (CI) for dichotomous outcomes or mean difference (MD) for continuous outcomes.

MAIN RESULTS

Forty studies (3764 patients) were included. Studies conducted earlier tended to have a higher risk of bias due to poor (or poorly reported) study design, broad inclusion criteria, less well developed disease definitions and low patient numbers. Later studies tend to have improved in all areas of quality, aided by the development of large international study groups. Induction therapy: Plasma exchange as adjunctive therapy may reduce the need for dialysis at three (2 studies: RR 0.43, 95% CI 0.23 to 0.78; I2 = 0%) and 12 months (6 studies: RR 0.45, 95% CI 0.29 to 0.72; I2 = 0%) (low certainty evidence). Plasma exchange may make little or no difference to death, serum creatinine (SCr), sustained remission or to serious or the total number of adverse events. Plasma exchange may increase the number of serious infections (5 studies: RR 1.26, 95% CI 1.03 to 1.54; I2 = 0%; low certainty evidence). Remission rates for pulse versus continuous cyclophosphamide (CPA) were equivalent but pulse treatment may increase the risk of relapse (4 studies: RR 1.79, 95% CI 1.11 to 2.87; I2 = 0%) (low certainty evidence) compared with continuous cyclophosphamide. Pulse CPA may make little or no difference to death at final follow-up, or SCr at any time point. More patients required dialysis in the pulse CPA group. Leukopenia was less common with pulse treatment; however, nausea was more common. Rituximab compared to CPA probably makes little or no difference to death, remission, relapse, severe adverse events, serious infections, or severe adverse events. Kidney function and dialysis were not reported. A single study reported no difference in the number of deaths, need for dialysis, or adverse events between mycophenolate mofetil (MMF) and CPA. Remission was reported to improve with MMF however more patients relapsed. A lower dose of steroids was probably as effective as high dose and may be safer, causing fewer infections; kidney function and relapse were not reported. There was little of no difference in death or remission between six and 12 pulses of CPA. There is low certainty evidence that there were less relapses with 12 pulses (2 studies: RR 1.57, 95% CI 0.96 to 2.56; I2 = 0%), but more infections (2 studies: RR 0.79, 95% CI 0.36 to 1.72; I2 = 45%). One study reported severe adverse events were less in patients receiving six compared to 12 pulses of CPA. Kidney function and dialysis were not reported. There is limited evidence from single studies about the effectiveness of intravenous immunoglobulin, avacopan, methotrexate, immunoadsorption, lymphocytapheresis, or etanercept. Maintenance therapy: Azathioprine (AZA) has equivalent efficacy as a maintenance agent to CPA with fewer episodes of leucopenia. MMF resulted in a higher relapse rate when tested against azathioprine in remission maintenance. Rituximab is an effective remission induction and maintenance agent. Oral co-trimoxazole did not reduce relapses in granulomatosis with polyangiitis. There were fewer relapses but more serious adverse events with leflunomide compared to methotrexate. There is limited evidence from single studies about the effectiveness of methotrexate versus CPA or AZA, cyclosporin versus CPA, extended versus standard AZA, and belimumab.

AUTHORS' CONCLUSIONS

Plasma exchange was effective in patients with severe AKI secondary to vasculitis. Pulse cyclophosphamide may result in an increased risk of relapse when compared to continuous oral use but a reduced total dose. Whilst CPA is standard induction treatment, rituximab and MMF were also effective. AZA, methotrexate and leflunomide were effective as maintenance therapy. Further studies are required to more clearly delineate the appropriate place of newer agents within an evidence-based therapeutic strategy.