Nephrology · Medical Literature
Obinutuzumab or Tacrolimus in Primary Membranous Nephropathy
Abstract
New England Journal of Medicine, Ahead of Print.
Clinical relevance
In adults with primary membranous nephropathy, is intravenous obinutuzumab (a type II anti-CD20 monoclonal antibody) superior to oral tacrolimus in inducing complete remission at 104 weeks? __SNAPSHOT__ {"studyDesign":"Randomized, open-label, multicenter, phase 3 superiority trial (MAJESTY; NCT04629248)","setting":"49 sites across 11 countries (multinational); presented at the European Renal Association 2026 Congress and published concurrently in NEJM","sampleSize":"n = 142 (obinutuzumab: ~71, tacrolimus: ~71; 1:1 allocation)","population":"Adults with biopsy-confirmed primary membranous nephropathy and nephrotic syndrome. Patients with prior immunosuppression were eligible if ≥6 months had elapsed since CNI or cyclophosphamide use, or ≥9 months since rituximab use, and provided they had not demonstrated resistance to CNI or rituximab. Exclusion criteria included evidence of spontaneous remission, diabetes, or suspected secondary membranous nephropathy. Randomization was stratified by region and anti-PLA2R antibody level (≥175 U/mL vs. lower).","intervention":"Obinutuzumab 1,000 mg IV on day 1 and at weeks 2, 24, and 26 (4 infusions total), with standard pre-medication (acetaminophen, methylprednisolone, diphenhydramine) to mitigate infusion-related reactions","comparator":"Tacrolimus oral 0.05 mg/kg/day (divided every 12 hours), titrated to serum trough levels of 5–7 ng/mL, maintained through week 52 (or from week 36 in patients achieving complete proteinuric response), then tapered over 8 weeks","primaryOutcome":"Complete remission at week 104, defined as urinary protein-to-creatinine ratio (UPCR) ≤0.3 with stable estimated glomerular filtration rate (eGFR)","followUp":"104 weeks (approximately 2 years)","fundingSource":"Industry (F. Hoffmann–La Roche / Genentech)"}
Key findings
Primary endpoint: Complete remission at week 104 was achieved in 37% of obinutuzumab-treated patients versus 6% of tacrolimus-treated patients — an adjusted absolute difference of 31 percentage points (95% CI, 18 to 44; P < .001), strongly favoring obinutuzumab. The number needed to treat for one additional complete remission is approximately 3.2 (calculated). The complete remission rate in the obinutuzumab arm peaked at week 76 (36%) and was sustained through week 104, consistent with the durable B-cell depletion profile of the drug. Key secondary endpoints: (1) Overall remission (complete or partial) at week 104 was 51% vs. 13% — adjusted difference of 38 percentage points (95% CI, 24 to 52; P < .001). (2) Complete remission at week 76 also significantly favored obinutuzumab (44% vs. 14%; P < .001 per available reporting). Relapse rate at week 104 after achieving complete or partial remission was markedly lower with obinutuzumab (12% vs. 58%), underscoring the durability advantage. Subgroup analyses showed consistent benefit across all prespecified subgroups, including patients stratified by anti-PLA2R antibody level (≥175 U/mL vs. lower). Hierarchical testing halted after the sustained eGFR reduction endpoint showed no significant between-group difference (6% in both arms; HR 1.10, 95% CI 0.18–6.61); consequently, duration of complete remission and PROMIS fatigue score endpoints were not formally tested and their confidence intervals are descriptive only. Safety: Serious adverse events (grade ≥3) occurred in 22% of the obinutuzumab group and 19% of the tacrolimus group. The most common adverse events with obinutuzumab were infusion-related reactions, respiratory tract infections, and neutropenia. No new safety signals were identified beyond the established obinutuzumab profile.
Practice implications
⚠ Only the abstract and secondary reporting are available at this time; the full manuscript data tables, pre-specified statistical analysis plan, definitions of all secondary endpoints, and complete adverse event listings have not been independently reviewed. Findings should be interpreted in this context. The MAJESTY trial establishes that obinutuzumab achieves a substantially higher rate of complete remission and overall remission at 2 years compared with tacrolimus in adults with primary membranous nephropathy — with both a large absolute effect size (~31 percentage points for complete remission) and a marked reduction in post-remission relapse (12% vs. 58%). These findings appear clinically meaningful, not merely statistically significant. The durability of remission with obinutuzumab (requiring only 4 infusions over 6 months vs. a 52-week continuous oral CNI regimen) represents a meaningful practical advantage. Importantly, the comparator (tacrolimus) is a nephrotoxic calcineurin inhibitor with a well-documented propensity for disease relapse after discontinuation — a limitation acknowledged by the high relapse rate in the tacrolimus arm and consistent with prior data. The absence of a rituximab comparator arm limits direct positioning of obinutuzumab relative to the current most common off-label B-cell depletion approach. The trial excluded patients with secondary membranous nephropathy, spontaneous remission, or resistance to prior CNI/rituximab, so generalizability to these subgroups is not established. The no-difference finding on sustained eGFR decline (a more clinically hard endpoint) should be noted, though the study was likely underpowered for this outcome given the sample size and event rate. Given the robustness of the primary and key secondary findings and that FDA Priority Review has been granted (decision anticipated November 2026), this trial is highly likely to be practice-informing pending regulatory approval, particularly if obinutuzumab becomes the first agent with a formal pMN indication. __LIMITATIONS__ Open-label design: absence of blinding introduces risk of ascertainment bias, particularly for subjective outcomes and clinician decisions around rescue therapy or escape criteria.,Small sample size (n=142): adequate for the primary binary endpoint but substantially underpowered for hard renal outcomes such as sustained eGFR decline, as reflected by the wide confidence interval for that endpoint (HR 1.10, 95% CI 0.18–6.61).,No rituximab comparator arm: the study does not establish superiority or equivalence versus rituximab, which is the most commonly used off-label B-cell depleting agent in this disease.,Hierarchical testing stopped at sustained eGFR reduction: formal inference on downstream endpoints (duration of remission, patient-reported fatigue) was not possible; reported intervals are descriptive only.,Active comparator limitation: tacrolimus is a calcineurin inhibitor with a known high relapse rate after cessation and nephrotoxicity concerns — a comparator that may have been selected to maximize the treatment contrast rather than represent equipoise.,Industry sponsorship (F. Hoffmann–La Roche/Genentech): full conflict-of-interest disclosures and data access are not independently verifiable from the abstract alone.,Generalizability: excluded patients with spontaneous remission, secondary membranous nephropathy, diabetes, and those previously resistant to CNI or rituximab — common real-world scenarios.,Duration: 104 weeks is insufficient to assess long-term hard outcomes such as progression to end-stage kidney disease, which may occur over a decade.,Abstract-only review: detailed adverse event tables, sensitivity analyses, handling of missing data, and protocol deviations are not available for critical appraisal. __BOTTOM_LINE_CATEGORY__ potentially_practice_informing __BOTTOM_LINE__ The phase 3 MAJESTY trial demonstrates that obinutuzumab is superior to tacrolimus in inducing complete remission (37% vs. 6%) and overall remission (51% vs. 13%) at 2 years in adults with primary membranous nephropathy, with a dramatically lower post-remission relapse rate and an acceptable safety profile. These represent large, clinically meaningful effect sizes with a favorable NNT. Pending FDA approval (anticipated November 2026), obinutuzumab is positioned to become the first approved therapy for primary membranous nephropathy and to substantially reshape management of this disease, though head-to-head data versus rituximab and long-term hard renal endpoint data are still needed.