Mechanism of Action of Ocrelizumab in Multiple Sclerosis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Mechanism of Action of Ocrelizumab in Multiple Sclerosis (NCT03344094), a registered phase not stated study. The primary outcome is Number of Participants With Complete Depletion of B Cells.

2. Clinical Question

3. Trial Design

The registry describes a study of the mechanism of action of ocrelizumab in multiple sclerosis. It lists University of Chicago as the sponsor, reports enrollment of 30, and marks the study as completed. The recorded start date is 2018-02-23 and the primary completion date is 2019-04-10. These dates describe the registry record; they do not, by themselves, provide information about the timing of individual assessments.

Four groups are described: MS-ocrelizumab treated, MS untreated, healthy control, and MS interferon-treated. The untreated MS and healthy control groups are described as age- and sex-matched. The interferon-treated group consists of people with MS receiving ongoing interferon-beta therapy. The treated group is described as receiving ocrelizumab 600 mg IV over 5 hours, twice a year, with a loading dose of 300 mg 2 weeks apart x 2 at the start.

The record says allocation was not stated and explicitly warns that this is not a randomized comparison and that the arms are not a like-for-like control comparison. It identifies only the ocrelizumab-treated MS group as analyzed for B-cell depletion; the other groups were not analyzed for that endpoint. Thus, the listed groups do not amount to a reported comparative treatment-effect analysis for the primary endpoint.

The primary outcome timeframe is 1 year. The record does not report the recruitment process, eligibility criteria, allocation procedure, masking, participant flow, or a detailed schedule of assessments. A protocol or statistical analysis plan is not reported in the registry record. The study's stated focus is mechanistic: measuring B-cell depletion, rather than reporting a randomized efficacy comparison.

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.

Before assignment: not needed

Overall Study

Analysis population for the primary outcome, as defined in the registry: The MS-ocrelizumab treated group was analyzed for depletion of B cells, whereas MS-untreated, healthy controls and MS interferon-treated groups were not analyzed for depletion of B cells.

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 Participants With Complete Depletion of B Cells, measured over 1 year.

The primary endpoint is the number of participants with complete depletion of B cells. The registry says this was assessed through lymphocyte surface-marker stains before and after ocrelizumab therapy, using flow cytometry on mononuclear cells stained with antibodies to B cells. Its timeframe is 1 year. The endpoint is expressed as a participant count, so it is a binary classification at the participant level: a participant either meets the stated complete-depletion criterion or does not.

As a general statistical concept, a mechanistic endpoint can describe whether a treatment is associated with a biological change in a target system. It is different from a clinical endpoint that directly describes symptoms, functioning, or other health outcomes. Complete depletion is relevant to the study's stated mechanism question because the record frames ocrelizumab as a B-cell-depleting therapy. The endpoint alone, however, does not describe the size of any clinical benefit or harm.

The registry's narrative also refers to comparing changes in the percentage of each cell subset before and after treatment. It does not give an operational threshold for what qualifies as complete depletion, nor does it report the observed participant count for this endpoint. Those definitions and the result are not reported in the registry record. The endpoint should therefore be interpreted as the planned measure described in the record, not as a result that can be reconstructed from the other information posted.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a participant-count endpoint: the number of participants with complete B-cell depletion. It also states that changes in the percentage of each cell subset before and after treatment would be compared using paired t tests and ANOVA. These are not necessarily the same statistical outcome. A count of participants meeting a complete-depletion criterion is categorical, while a percentage change in a cell subset is a numerical measurement. The record does not explain how the two descriptions connect analytically.

What does a paired t test address?

As a general statistical concept, a paired t test compares measurements that are linked within the same units, such as measurements from the same participant before and after an intervention. Pairing accounts for the fact that two observations from one person are related, rather than treating them as independent observations. The analysis typically concerns the average within-person change. Its interpretation depends on how the measurements are defined, whether the pairing is complete, and whether the assumptions used for the test are suitable for the data.

The registry mentions paired t tests for changes in percentages of cell subsets, but it does not report the actual measurements, the number of complete pairs, the estimated changes, or test results. It also does not describe how incomplete pairs or missing measurements were handled. Although the endpoint title refers to complete depletion, the record does not say that a paired t test was used to analyze that participant count.

What does ANOVA address?

As a general statistical concept, analysis of variance (ANOVA) is used to compare means across groups or conditions under a specified model. The exact interpretation depends on the model structure, including which groups or repeated measurements are included and how dependence among measurements is handled. The registry names ANOVA but does not specify the model, factors, contrasts, assumptions, or whether the analysis was actually carried out. It also does not report an ANOVA estimate or test result.

Because the record says the non-ocrelizumab groups were not analyzed for B-cell depletion, the listed control groups should not be assumed to have been included in an ANOVA of the primary depletion endpoint. Whether they contributed to another analysis of cell-subset percentages is not reported in the registry record.

How should a participant count be interpreted?

As a general concept, a participant count records how many people meet a defined event criterion. Interpreting such a count usually requires knowing the population evaluated, the event definition, the assessment window, and how missing or unevaluable observations were treated. A count without those details may be difficult to interpret as a frequency or compare across groups. Here, the registry provides a 1-year timeframe and identifies the ocrelizumab-treated MS group as the endpoint population, but it does not report the primary count or the threshold defining complete depletion.

The record reports 1 outcome measure and 1 analysis, but it does not provide a detailed analysis plan. It does not report whether the primary endpoint was analyzed with a confidence interval or a hypothesis test, what significance level was used for the endpoint, or whether any adjustment was planned for multiple tests. The paired t test and ANOVA language describes comparisons of percentage changes; it does not supply enough detail to reconstruct the statistical analysis.

What can a confidence interval contribute?

As a general statistical concept, a confidence interval expresses the precision of an estimate under the assumptions of a statistical method. A narrow interval indicates greater precision than a wide interval for the same type of estimate; an interval is not a guarantee that the true value lies inside it. The registry record does not report a confidence interval for the complete-depletion count or for a change in cell-subset percentages. Precision therefore cannot be evaluated from the posted primary results.

What are the planning illustrations?

As a general concept, sample-size planning uses assumptions about an effect, variability, allocation, significance level, and desired power to illustrate the size of a future study. The registry's planning assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a stated fraction of the observed effect. These are planning assumptions, not evidence that the completed study had a particular power. The record does not report a sample-size justification for the trial's own design, and any planning illustration should not be interpreted as observed power or as a result of the trial.

The registry does not report the planned or completed handling of interim analyses, deviations from the analysis plan, model diagnostics, or sensitivity analyses. These omissions limit reproducibility and prevent a detailed appraisal of whether the stated methods were appropriate for the data actually collected.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("MS-ocrelizumab Treated")
n      <- c(15)
events <- c(15)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  MS-ocrelizumab Treated  15  15  100.0  78.2  100.0  79.6  100.0  79.4  99.8

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 1 outcome measure and 1 analysis, but its narrative refers to changes in the percentage of each cell subset and names both paired t tests and ANOVA. The number and hierarchy of the cell subsets or statistical comparisons are not described. No multiplicity adjustment or testing hierarchy is reported in the registry record. Without that information, it is not possible to assess how the risk of false-positive findings across multiple comparisons was addressed.

Missing-data methods are not reported. The record does not state how participants without a follow-up measurement, incomplete paired measurements, or samples that could not be evaluated were handled. It also does not report the number of participants contributing data to the primary endpoint analysis. Enrollment is reported as 30, but the number analyzed for the primary endpoint is not reported in the registry record.

The analysis population is described more specifically than the missing-data approach: the MS-ocrelizumab treated group was analyzed for B-cell depletion, while the MS-untreated, healthy control, and MS interferon-treated groups were not. The record does not state whether all treated participants were included in that analysis, whether exclusions occurred, or how the analysis population was defined beyond the group label.

Allocation is not stated, and the registry says the groups are not a like-for-like control comparison. It does not report a prespecified statistical analysis plan, an interim analysis plan, or whether analyses were changed after data collection. These details are not reported in the registry record, so the completeness and prespecification of the analyses cannot be assessed.

12. 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 0% reporting threshold.

The registry reports zero serious adverse events for the MS-ocrelizumab treated group, with 15 at risk. It reports zero serious adverse events for the MS untreated group, with 5 at risk; for the healthy control group, with 5 at risk; and for the MS interferon-treated group, with 5 at risk. The record also reports zero other adverse events and zero deaths in each group.

These figures are counts as posted, not estimates from a comparative safety analysis. The registry does not report confidence intervals, a formal comparison among groups, the adverse-event collection procedures, or the duration of safety follow-up for these outcomes. It also does not list serious adverse-event terms. A count of zero means no events were recorded in the relevant field; it does not establish that no such event could occur or that the groups have identical safety profiles.

The groups should not be treated as randomized safety comparators: the registry says allocation was not stated and the arms are not a like-for-like comparison. The posted counts therefore describe the registry entries for each group, rather than a causal estimate of the effect of ocrelizumab on adverse events.

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

This record identifies a mechanistic question: whether complete B-cell depletion was observed among MS participants treated with ocrelizumab over a timeframe of 1 year. It describes flow cytometry and cell-surface marker staining as the measurement approach. However, the primary endpoint count is not reported in the registry record. The posted results therefore do not establish how many participants had complete depletion or how precise any estimate would be.

The record also does not report the numerical results of the described paired t tests or ANOVA. There is no posted estimate of change in cell-subset percentages, no confidence interval, and no p-value. The statistical evidence for the planned cell measurements cannot be assessed from the information in the record.

The study includes untreated MS participants, healthy controls, and MS participants receiving interferon-beta, but the record says those groups were not analyzed for the primary depletion endpoint. It also states that the study was not randomized and that the arms are not a like-for-like control comparison. These groups should not be interpreted as supporting a randomized causal comparison of ocrelizumab against an alternative.

The adverse-event entries report zero serious events, zero other events, and zero deaths in each listed group. These counts are descriptive. Without further information on event ascertainment, follow-up, and comparative analyses, they cannot establish that an event is impossible or quantify a treatment-related difference.

As a general distinction, evidence about a biological mechanism is not the same as evidence about a clinical outcome. Even a clearly measured biological change would not, by itself, answer questions about symptoms, disability, or overall clinical benefit. The registry record does not report those outcomes as results. No medical conclusion about treatment should be drawn from the missing primary result or the descriptive safety counts.

14. Why This Trial Matters Statistically

This study is statistically notable for the distinction between a mechanistic endpoint and a clinical outcome. Its stated primary measure is the number of participants with complete B-cell depletion, assessed through laboratory methods. Such a measure can address a biological question, but it is not interchangeable with an outcome describing how participants feel or function. Clear separation of these endpoint types helps readers avoid interpreting a laboratory measure as a clinical treatment effect.

The record also illustrates why design details matter when groups are listed. Untreated MS participants, healthy controls, and participants receiving interferon-beta appear in the registry, but the primary depletion analysis was limited to the ocrelizumab-treated MS group. The registry further states that allocation was not stated and the arms are not a like-for-like comparison. Group labels alone do not make a valid comparative analysis.

Another statistical issue is alignment between the outcome and the method description. The outcome is framed as a participant count with complete depletion, while the narrative mentions paired t tests and ANOVA for changes in cell-subset percentages. Those methods may address different data summaries. Reporting the endpoint definition, analysis population, model, estimate, and uncertainty would allow readers to understand how the analysis answers the stated question.

Finally, the absence of the primary result and inferential statistics limits what can be learned from this registry record. The posted adverse-event counts are descriptive and do not substitute for the missing mechanistic result. The record is therefore useful for identifying the study's question, groups, and intended measurement approach, while also showing the importance of complete outcome reporting.

15. 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 limitation for interpreting this study is that the registry record does not report the result for its stated primary endpoint. It gives no count of participants with complete B-cell depletion, no estimate of uncertainty, and no operational definition or threshold for complete depletion. The outcome is therefore not interpretable as a reported finding from this record.

The endpoint description and analysis description are not fully aligned. The primary endpoint is a participant count, while the narrative describes comparing changes in percentages of cell subsets using paired t tests and ANOVA. The record does not specify how these analyses relate, which estimates were primary, or what statistical model was used. Actual test results are not reported.

Only the ocrelizumab-treated MS group was analyzed for depletion. The other listed groups were not analyzed for this endpoint, and the record cautions that the arms are not a like-for-like control comparison. Allocation is not stated. Accordingly, the record does not support a randomized comparison of the primary endpoint across groups.

The registry does not report the number analyzed for the endpoint, missing-data handling, exclusions, detailed participant flow, or the definition of the analysis population beyond the group description. It also does not report a detailed statistical analysis plan, multiplicity procedures, or whether the stated analyses were prespecified. These omissions limit assessment of both bias and reproducibility.

Safety information is limited to posted event counts. The record does not provide event terms, ascertainment methods, confidence intervals, or comparative analyses. These limitations are specific to the information available in this registry record and should not be resolved by assumptions about the study protocol or its conduct.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Mechanism of Action of Ocrelizumab in Multiple Sclerosis — NCT03344094.
• Registry record last updated 2025-02-21; status last verified 2024-05.
• Results first posted 2025-02-21.
• 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.

19. Record Summary

NCT03344094 is a completed study titled “Mechanism of Action of Ocrelizumab in Multiple Sclerosis,” sponsored by the University of Chicago. The registry reports enrollment of 30, a start date of 2018-02-23, and a primary completion date of 2019-04-10.

The primary endpoint is the number of participants with complete B-cell depletion over a timeframe of 1 year. The record describes measurement using flow cytometry and marker antibodies, and says changes in cell-subset percentages would be compared using paired t tests and ANOVA. It identifies the MS-ocrelizumab treated group as the population analyzed for depletion; the other listed groups were not analyzed for that endpoint.

The registry does not report the primary endpoint result or inferential results. It reports zero serious adverse events, zero other adverse events, and zero deaths in each listed group. Allocation is not stated, and the record cautions that the arms are not a like-for-like control comparison.