GP2013 Treatment in Patients With Active Rheumatoid Arthritis, Previously Treated With Rituxan® or MabThera®: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for GP2013 Treatment in Patients With Active Rheumatoid Arthritis, Previously Treated With Rituxan® or MabThera® (NCT02514772), a randomized phase 3 study. The primary outcome is Number of Patients Experiencing Anaphylactic Reactions.

2. Clinical Question

3. Trial Design

This was a Phase 3, randomized, double-blind, controlled, parallel-group, multicenter study. The registry record lists enrollment of 107 and status as completed. It identifies the condition as rheumatoid arthritis and Sandoz as the sponsor. The study began in 2015-07, with primary completion in 2016-07.

Participants had active rheumatoid arthritis and previous treatment with Rituxan® or MabThera®. The randomized groups were GP2013, described as a proposed biosimilar rituximab, and originator rituximab, identified as Rituxan® or MabThera®. Both treatment courses used two intravenous infusions two weeks apart, on Day 1 and Day 14. Each description specifies 1000 mg of active molecule per infusion, diluted in 0.9% NaCl solution.

Randomization assigns participants to treatment groups by chance; in general, this can reduce systematic differences between groups at the start of a trial. Double masking means the registry classifies the study as double-blind, although the specific masked parties are not reported in the registry record. A parallel-group design means participants are assigned to a group and the comparison is between groups, rather than a crossover between treatments.

The study’s stated objective focused on potential safety risks of transitioning from US-licensed Rituxan® or EU-approved MabThera® to GP2013 compared with continuous originator treatment. It addressed general safety and immunogenicity. The registry record does not report the allocation ratio, the number of participants assigned to each group as a design target, or further operational details about multicenter conduct.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Safety Analysis Set

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Number of Patients Experiencing Anaphylactic Reactions, measured over Within 24 hours of each study drug infusion: on Day 1 and Day 14.

The primary endpoint counts participants who experienced anaphylactic reactions within 24 hours of each study-drug infusion, on Day 1 and Day 14. The registry identifies the outcome as a count of participants in the Safety Analysis Set. It reports 0 of 53 participants in the GP2013 group and 1 of 54 in the Rituxan® / MabThera® group.

The registry says the reactions were identified using 2006 NIAID/FAAN criteria. For participants without a history of infusion-related reactions during previous rituximab treatment, the definition required signs or symptoms in at least 2 of 4 organ systems: skin or mucosal tissue, respiratory organs, blood-pressure drop or associated symptoms, and gastrointestinal organs. The listed blood-pressure criterion includes systolic pressure <90 mmHg or a variance from baseline >30%. For participants with a history of infusion-related reactions, the same criteria applied; a rapid drop in systolic blood pressure meeting the stated threshold also counted even without involvement of other organ systems.

In general, a defined safety endpoint helps make event identification consistent across treatment groups. The endpoint is relevant to the stated safety objective because it captures a specified acute reaction after infusion. It does not, by itself, describe other safety outcomes or immunogenicity.

7. Results Posted in the Registry

• Rituxan® / MabThera®: 1.9% (1/54) versus 0.0% (0/53) on control; risk difference 1.9 percentage points (95% CI -1.7 to 5.4); unadjusted two-proportion z-test p = 0.320.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary at the participant level: a participant either met the anaphylactic-reaction definition within the specified observation window or did not. The registry presents counts of participants with the event in each group. In general, binary outcomes can be summarized using event proportions and compared using a difference in risks. A risk difference expresses the absolute separation between the event proportions in the groups; unlike a relative measure, it remains in the original probability scale.

The unadjusted recalculation gives a risk difference of 0.018, with the comparison ordered as originator rituximab relative to GP2013. Its 95% confidence interval is -0.017 to 0.054, and its p-value is 0.32. The calculation uses the posted group counts and is unadjusted. It is not the same as a model-based or covariate-adjusted analysis unless the registry explicitly says so; no adjusted method is reported in the registry record.

General explanation: an unadjusted comparison uses the group summaries without accounting for other participant characteristics. Randomization can make groups comparable on average, but an unadjusted result still reflects the observed group data and does not show whether additional adjustment was prespecified or performed. The registry record does not report covariates used in an adjusted model, nor does it report a statistical method for the sponsor analysis.

A confidence interval describes a range of values compatible with the data under the method’s assumptions. The 95% interval for the recalculated risk difference includes zero, so the data do not clearly distinguish a positive difference from a negative one at conventional significance levels. The interval’s width also matters: it communicates uncertainty, not just whether a threshold is crossed. General explanation: a confidence interval is not a guarantee that the true effect lies within its endpoints, and it does not assign a probability to the effect after observing the data.

The reported p-value of 0.32 is associated with the unadjusted comparison. General explanation: a p-value describes how unusual data at least as incompatible with a specified null hypothesis would be if that null and the model assumptions held. It is not the probability that the null is true, nor a measure of clinical importance. The registry does not report the exact test used for the recalculation or the sponsor analysis, so the p-value should be understood as the result of the posted unadjusted recalculation rather than as a fully specified protocol analysis.

The sponsor’s reported result uses the label Difference (%) and gives -1.9, with a 95% confidence interval from -20.6 to 16.9. The method is not reported. The unadjusted recalculation instead reports a risk difference of 0.018 in the direction of originator relative to GP2013. The signs are consistent with reversing the comparison order, but the estimates and interval limits are not numerically the same representation. The registry does not give sufficient methodological detail to determine whether the analyses differ only by ordering or also by method, rounding, or another feature. The sponsor’s result should therefore be retained as its own reported analysis, while the recalculation should be identified as unadjusted.

Multiplicity concerns the interpretation of multiple statistical tests or endpoints. The registry lists four outcome measures and six analyses, but the multiplicity strategy is not reported in the registry record. It is not possible to determine whether the primary outcome was tested within a formal hierarchy, whether p-values were adjusted, or how secondary outcomes were intended to affect interpretation. General explanation: when many outcomes or comparisons are examined, the chance of at least one apparently notable result can increase unless the analysis plan accounts for that multiplicity.

Missing-data methods are also not reported in the registry record. The record identifies the Safety Analysis Set for the primary outcome but does not define inclusion rules, describe exclusions, or explain how unavailable assessments were handled. The stated group denominators are 53 and 54. No inference about participants who may have lacked an assessment should be made beyond what the record reports.

Planning calculations based on an observed effect are illustrations, not observed trial results and not evidence of achieved power. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation, with the effect to detect defined as a fraction of the observed effect. The registry does not report the trial’s own sample-size justification or design assumptions. General explanation: planning estimates depend on their assumptions and should not be confused with the actual enrollment or with a retrospective claim that the trial had a particular probability of detecting an effect.

The primary endpoint uses a prespecified clinical definition in the registry record, including the 2006 NIAID/FAAN criteria and a 24-hour window after each infusion. Consistent event definitions support comparability, but the record does not report adjudication procedures, assessor training, or whether events were independently reviewed. No interim analysis plan or stopping rule is reported in the registry record.

10. Confidence Intervals and Precision

The unadjusted risk difference is 0.018, with a 95% confidence interval from -0.017 to 0.054. This interval is the main guide to the precision of the recalculated comparison. It includes zero and spans values below and above zero, so the observed data are compatible with different directions of the risk difference. The interval does not support a precise estimate of the direction or size of the group difference.

The event counts are 0 of 53 in the GP2013 group and 1 of 54 in the originator group. With so few events, the estimate is inherently sensitive to individual outcomes. General explanation: sparse binary data tend to produce substantial uncertainty because the observed proportions can shift noticeably when the event count changes by a small amount. A confidence interval makes that uncertainty visible rather than treating the point estimate as exact.

The registry also reports the sponsor’s Difference (%) as -1.9, with a 95% confidence interval from -20.6 to 16.9. This interval includes zero as well. The sponsor method is not reported, and the registry does not establish that its estimand and calculation match the unadjusted risk difference. The two intervals should therefore be interpreted according to their respective reported analyses, not combined or substituted for one another.

Precision is distinct from statistical significance. General explanation: a result can fail to reach a conventional significance threshold because the estimate is close to zero, because the data are imprecise, or both. Here, the very small number of primary events and the interval spanning both signs make uncertainty central to interpretation. The interval does not establish equivalence, because no equivalence margin is reported.

11. Analyses Reported by the Sponsor

The sponsor’s posted analysis reports a Difference (%) of -1.9, with a 95% confidence interval from -20.6 to 16.9. The registry does not report the statistical method used for that analysis, and no p-value is given for it. The sponsor estimate is therefore best read as the result reported by the registry, with its stated scale and interval.

The unadjusted recalculation from the posted participant counts gives a risk difference of 0.018 for originator rituximab relative to GP2013, with a 95% confidence interval from -0.017 to 0.054 and p = 0.32. This is a simple comparison of the posted group summaries. The ordering is opposite to a comparison expressed as GP2013 relative to originator, which can reverse the sign of a difference. However, the registry does not provide enough information to establish that the sponsor’s analysis differs only by ordering or uses the same calculation and scale.

Both reported confidence intervals include zero, but their numerical scales and limits are not the same. In the absence of a reported sponsor method or further analysis details, the sponsor result and the unadjusted recalculation should remain distinct. The registry does not mark a discrepancy between these results.

12. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures and six analyses. It does not report a multiplicity plan, a hierarchy of outcomes, or any adjustment to significance levels or confidence intervals for multiple testing. It is therefore not possible to tell whether the primary endpoint was the only confirmatory analysis or whether the other listed analyses were intended as supportive or exploratory.

General explanation: multiplicity matters because repeated testing can increase the chance of observing a result that appears statistically notable by chance. A prespecified strategy can clarify which findings are confirmatory and how uncertainty should be interpreted across outcomes. Without that strategy in the registry record, the primary endpoint result should be interpreted on its own reported terms, without assuming that multiplicity was or was not addressed.

The primary outcome population is named as the Safety Analysis Set, but its definition and membership rules are not reported in the registry record. The group denominators are 53 for GP2013 and 54 for Rituxan® / MabThera®. The record does not describe exclusions from that set, whether all randomized participants were included, or how missing or unevaluable outcome assessments were handled.

General explanation: missing outcome data can affect a comparison if participants without assessments differ from those with observed data, particularly if missingness is related to treatment or outcome. The record does not provide enough information to assess that possibility. It also does not report sensitivity analyses for missing outcomes or an imputation method.

The statistical analysis plan, interim analyses, sample-size justification, and stopping rules are not reported in the registry record. No assumption should be made about whether interim monitoring occurred or how enrollment was determined. Planning illustrations based on the observed effect are not evidence of the trial’s original design rationale or of achieved power.

13. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 2% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: atrial fibrillation (1.9%), cardiopulmonary failure (1.9%), hiatus hernia (1.9%), contusion (1.9%), humerus fracture (1.9%).

The registry reports serious adverse events affecting 0 of 53 participants in the GP2013 group and 3 of 54 in the Rituxan® / MabThera® group. It reports other adverse events affecting 19 of 53 and 21 of 54 participants, respectively. The registry also lists 0 deaths in the GP2013 group and 1 in the originator group.

These counts describe the posted safety categories; they are not the primary endpoint, which counts participants with anaphylactic reactions within 24 hours of infusion. The record does not provide a causal assessment for the serious adverse events or death, so these counts should not be interpreted as establishing that a study drug caused an event. Nor do the categories explain event timing, duration, recurrence, or severity beyond the serious classification.

The listed serious-event terms each have a reported frequency of 1.9%: atrial fibrillation, cardiopulmonary failure, hiatus hernia, contusion, humerus fracture, and pelvic fracture. The registry record does not provide additional case-level details in these results. Safety counts can help describe what was recorded during the study, but the group totals alone do not establish comparative risk, especially when event counts are small.

14. What the Result Does, and Does Not, Mean

The registry results show that the primary endpoint occurred in 0 of 53 participants assigned to GP2013 and 1 of 54 assigned to originator rituximab. The unadjusted risk difference is 0.018 for originator relative to GP2013, with a 95% confidence interval from -0.017 to 0.054 and p = 0.32. These are descriptions of the observed data and an unadjusted comparison, not proof that the groups have the same risk.

The confidence interval includes values on either side of zero. General explanation: this means the observed data do not precisely determine which group had the higher event risk, and the point estimate should not be treated as exact. The registry does not report an equivalence or non-inferiority margin, so the results cannot establish equivalence or non-inferiority on the basis of the primary endpoint.

The endpoint is narrowly defined: anaphylactic reactions within 24 hours of each infusion, using the stated criteria. It does not summarize all adverse events, all possible safety concerns, or immunogenicity. The registry lists additional safety counts, but those are different outcomes and cannot be substituted for the primary endpoint.

The study’s randomized, double-blind, parallel-group design provides a controlled framework for comparing the assigned treatments. Still, key interpretive details—including the statistical plan, missing-data handling, sponsor analysis method, and definition of the Safety Analysis Set—are not reported in the registry record. The primary outcome results should be read with those limitations in mind.

Nothing in these results alone establishes a general treatment effect beyond the measured endpoint and study population. The record concerns people with active rheumatoid arthritis previously treated with Rituxan® or MabThera® and compares transition to GP2013 with continued originator treatment. It does not justify extending the findings to other populations, outcomes, treatment schedules, or settings not described in the registry record.

15. Why This Trial Matters Statistically

This trial raises a statistical question that is difficult to answer precisely when the primary safety outcome is rare: how much can the observed data distinguish between the risks in two randomized groups? The posted counts are 0 of 53 for GP2013 and 1 of 54 for originator rituximab. The recalculated risk difference has a 95% confidence interval from -0.017 to 0.054, emphasizing the uncertainty surrounding the point estimate.

General explanation: when events are uncommon, even a randomized comparison may be imprecise unless the amount of information is sufficient for the outcome of interest. Randomization supports a fair comparison in principle, but it cannot guarantee that a small number of observed events will settle the size or direction of a difference. Confidence intervals are essential because they show a range of effects compatible with the data.

The record also illustrates why analysis labels and comparison direction matter. The sponsor reports a Difference (%) of -1.9, while the unadjusted recalculation reports a risk difference of 0.018 in the opposite group ordering. Because the sponsor method is not reported, the estimates should not be merged or treated as identical. Transparent reporting of the estimand, method, and direction helps readers understand whether analyses are directly comparable.

Finally, a safety objective can include outcomes beyond a single primary endpoint. The registry’s serious and other adverse-event counts provide additional descriptive information, but they do not resolve the uncertainty around anaphylactic reactions or establish causality. The distinction between a narrowly defined primary outcome, broader safety summaries, and the uncertainty of each comparison is central to responsible interpretation.

16. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The primary endpoint has very few observed events: 0 in the GP2013 group and 1 in the originator group. As a result, the unadjusted risk difference is uncertain, and the confidence interval includes zero and values in both directions. This limits how precisely the group comparison can be characterized.

The registry identifies a Safety Analysis Set but does not define it. It does not report how many participants were randomized to each group, how many were included in each analysis population, or whether any outcome assessments were missing. Missing-data handling and sensitivity analyses are not reported in the registry record.

The sponsor’s analysis is reported as a Difference (%) with a confidence interval, but its statistical method is not reported. The registry does not provide enough detail to establish whether that result and the unadjusted recalculation use the same estimand, method, or analysis population. The sponsor result and recalculation should consequently be read separately.

The registry lists multiple outcomes and analyses but does not report a multiplicity strategy, analysis hierarchy, interim analysis plan, or stopping rules. It also does not report the trial’s sample-size justification. The available planning assumptions describe illustrations based on an observed effect, not the original design rationale.

The record gives the endpoint definition and observation window but does not describe event adjudication, assessment procedures, or the specific parties who were masked. Serious adverse-event counts are provided without case-level detail or causal attribution. These limits constrain interpretation of both the primary endpoint and the broader safety summaries.

17. Related Tutorials

18. Related Statistical Calculators

19. Sources

• ClinicalTrials.gov: GP2013 Treatment in Patients With Active Rheumatoid Arthritis, Previously Treated With Rituxan® or MabThera® — NCT02514772.
• Registry record last updated 2017-12-28; status last verified 2017-11.
• Results first posted 2017-12-28.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

20. Record Summary

NCT02514772 is a completed Phase 3 randomized, double-blind, controlled, parallel-group, multicenter study sponsored by Sandoz. It enrolled 107 participants with active rheumatoid arthritis who had previously received Rituxan® or MabThera®. The comparison was transition to GP2013 versus continued originator rituximab, with both groups scheduled for infusions on Day 1 and Day 14.

The primary outcome counted anaphylactic reactions within 24 hours of each infusion in the Safety Analysis Set. The registry reports 0 of 53 participants with an event in the GP2013 group and 1 of 54 in the originator group. The unadjusted recalculation reports a risk difference of 0.018, with a 95% confidence interval from -0.017 to 0.054 and p = 0.32. The sponsor separately reports a Difference (%) of -1.9, with a 95% confidence interval from -20.6 to 16.9.

The registry does not report the sponsor method, missing-data approach, multiplicity plan, or sample-size justification. The low number of primary events and the uncertainty around the comparison are important when interpreting the posted results.