Natalizumab High Titer Immunogenicity and Safety: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Natalizumab High Titer Immunogenicity and Safety (NCT00516893), a na phase 2 study. The primary outcome is Number of Participants With Anti-Natalizumab Antibody Negative, Transient Positive, and Persistent Positive Status.

2. Clinical Question

3. Trial Design

This was a Phase 2, multicenter, open-label, single-group study of natalizumab high titer, also identified as BG00002-E. The intervention was a biological product. The registry lists an enrollment of 113 and the condition as multiple sclerosis. The study began in 2006-10, had primary completion in 2007-10, and is listed as completed. The sponsor was Biogen.

Participants received natalizumab high titer 300 mg as an intravenous infusion over 60 minutes once every 4 weeks for up to 9 doses. The study had no masking, and allocation is recorded as not applicable. There was no randomized comparator arm, so the design describes outcomes observed in participants who received the study intervention rather than a between-group treatment contrast.

The primary objective was to evaluate the immunogenicity of natalizumab produced by a modified manufacturing process in participants with relapsing forms of multiple sclerosis. The secondary objective was to evaluate safety. The listed secondary outcomes include participants with adverse events, serious adverse events, and discontinuations due to adverse events; mean change from baseline in Expanded Disability Status Scale scores at Week 36; and annualized relapse rate. Numerical results for these secondary outcomes, apart from the adverse-event information described in the registry, are not reported in the registry record.

The primary antibody assessments were scheduled every 12 weeks from Week 0 (Baseline) to Week 36. The primary analysis population was narrower than everyone enrolled: participants had to receive at least one dose, have a negative baseline antibody result, and have at least one post-dose antibody assessment. The number meeting those criteria is not reported in the registry record.

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: Participants who received at least 1 dose of natalizumab, had a negative baseline antibody result, and had at least 1 antibody assessment after the first dose.

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 Anti-Natalizumab Antibody Negative, Transient Positive, and Persistent Positive Status, measured over Assessed every 12 weeks from Week 0 (Baseline) to Week 36.

The primary endpoint counts participants in three anti-natalizumab antibody categories: negative, transient positive, and persistent positive. It is an immunogenicity measure: it describes whether antibody was detected after treatment and whether positivity occurred at one or more assessments according to the registry’s definitions. Negative means no detectable antibody at any post-baseline visit. Transient positive means a positive result at only one post-baseline visit before the last visit. Persistent positive means positive results at two or more post-baseline visits at least 42 days apart, or a positive result at the last post-baseline visit.

Assessments were scheduled every 12 weeks from Week 0 (Baseline) to Week 36. Repeated assessment is relevant because antibody detection may differ across visits; a single positive result is not classified the same way as positivity meeting the persistent definition. These categories describe observed test status under the study’s rules. They do not, by themselves, establish the clinical consequences of antibody detection.

In general, a categorical endpoint can make a biological response easier to summarize than a sequence of individual test results, but its meaning depends on the stated thresholds and assessment schedule. Here, the registry gives the definitions and the eligible population, but does not report the number of participants in any category. The primary endpoint’s observed distribution and its precision therefore cannot be evaluated from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a single-group design estimate?

In general, a single-group study describes outcomes observed among people who receive an intervention. It can characterize the frequency or pattern of recorded outcomes in that study population. Without a separate comparison group, it does not directly estimate how outcomes would differ under another treatment or under no treatment. This distinction is especially important when an outcome could also be influenced by participants’ underlying condition, other care, or how long they are observed.

This study is listed as single-group, with allocation not applicable and no masking. The registry record therefore does not define a randomized treatment contrast. Its central primary-outcome question is descriptive: how participants who met the antibody assessment criteria were classified under the stated definitions. The record does not report a comparative estimate or an analysis adjusting for other factors.

How should the antibody categories be understood?

The endpoint is categorical rather than a continuous measurement. Each eligible participant is classified as negative, transient positive, or persistent positive using the post-baseline antibody assessments. The definitions distinguish a participant with no detectable antibody, one with a positive result at only one visit before the final visit, and one whose positive results meet the persistence rule or are positive at the last visit. The schedule was every 12 weeks from Week 0 (Baseline) to Week 36, while the persistent-positive definition also refers to assessments at least 42 days apart.

In general, categories simplify a sequence of repeated measurements, but they discard some detail about when results changed and how many visits were positive. The categories should be read using their prespecified definitions, not as a general measure of clinical response. The record does not report the category counts, so the distribution cannot be summarized or compared with any other estimate.

What would a confidence interval tell a reader?

In general, a confidence interval expresses the statistical uncertainty around an estimate. A narrower interval indicates greater precision under the assumptions of the method; a wider interval indicates less precision. It does not resolve limitations in study design, such as lack of a control group, nor does it account for biases that were not included in the model. The registry record does not report confidence intervals for the antibody categories or the listed secondary outcomes.

In general, a p-value summarizes how compatible data are with a specified statistical null model, given the model’s assumptions. It is not the probability that a hypothesis is true, and it does not measure clinical importance. No analysis records are listed in the registry, and no p-values or other inferential results are reported for the primary endpoint. A reader should not infer statistical significance or its absence from the lack of a reported test.

What do the planning assumptions mean?

The planning illustration assumptions describe a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect to detect defined as a stated fraction of the observed effect. The illustration’s stated output is participants per arm for 80% power or participants per arm for 90% power, except that time-to-event illustrations use total events. These are planning conventions, not outcomes observed in this single-group trial. Since the registry design has no two-arm randomized comparison, the illustration assumptions do not describe the study’s actual allocation or observed power.

In general, a sample-size illustration asks how much information a hypothetical future study might need under chosen assumptions. Its result depends on the assumed effect, variability, statistical test, and design. It is not evidence that a completed study had a particular probability of detecting an effect. The registry record does not report the trial’s own sample-size justification, so the planning illustration should not be read as the original protocol rationale.

Why can over-dispersion matter?

In general, over-dispersion occurs when outcome variability is greater than a statistical model expects. If a model assumes less variation than the data contain, standard errors may be too small and intervals or tests may appear more precise than warranted. Models for counts or rates can be especially sensitive to this issue. The registry record does not report a model for annualized relapse rate, its dispersion assumptions, or a fitted analysis, so no trial-specific conclusion about over-dispersion can be made.

More generally, an analysis should match the outcome and the study design. Binary or categorical results need clear denominators and handling of missing assessments; repeated measurements may require methods that account for within-participant dependence; rates require an appropriate time-at-risk definition. The record gives the primary endpoint definitions and the assessment schedule, but not the statistical procedures used to analyze them. The registry record does not report whether estimates were adjusted, how missing observations were handled, or whether sensitivity analyses were conducted.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures and identifies antibody status as the primary endpoint, with adverse events, EDSS change at Week 36, and annualized relapse rate among the secondary outcomes. Testing or estimating several outcomes can raise multiplicity concerns. In general, when multiple hypotheses are tested, the chance of at least one apparently notable result can increase unless the analysis plan addresses that issue. The registry record does not report a multiplicity adjustment, a hierarchy among secondary outcomes, or an inferential plan. It is therefore not possible to determine how multiplicity was handled.

The registry defines the primary antibody population as participants who received at least one dose, had a negative baseline antibody result, and had at least one assessment after the first dose. It does not report the number meeting those criteria, the number with missing antibody assessments, or how incomplete follow-up was handled. In general, missing outcome data can affect both the denominator and the estimated distribution, particularly when the reason for missingness is related to outcome status. No particular missing-data assumption or imputation method is reported in the registry record.

The registry record does not report analysis populations for the secondary outcomes or explain whether they used all enrolled participants, treated participants, or another defined group. It also does not report interim analyses, a statistical analysis plan, or sensitivity analyses. These details matter because analysis populations and missing-data methods determine which observations contribute to an estimate and how robust that estimate may be. Their absence limits interpretation; it does not establish that a particular method was or was not used outside the registry record.

11. Safety Results

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

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: abortion spontaneous (1.8%), bronchitis (1.8%), multiple sclerosis relapse (1.8%), abdominal pain (0.9%), chest pain (0.9%).

For the Natalizumab High Titer group, the registry records 112 participants at risk for the serious-event summary and 7 participants with serious adverse events. It also records 112 at risk for the other-adverse-event summary and 79 participants with other adverse events. These are counts of participants with events as categorized in the record, not counts of all event episodes. The registry’s serious-event terms and listed percentages are Abortion spontaneous (1.8%), Bronchitis (1.8%), Multiple sclerosis relapse (1.8%), Abdominal pain (0.9%), Chest pain (0.9%), and Chronic obstructive pulmonary disease (0.9%).

In general, an adverse-event count describes what was recorded during observation and does not by itself show that the intervention caused the event. A single-group study has no concurrent control group for contextualizing event frequencies. The registry record does not report event-level timing, duration, recurrence, or causal assessment in the available information. The death count is not reported in the registry record, and a numerical count of discontinuations due to adverse events is not reported in the registry record. The term-level percentages should be read as posted, without inferring unreported denominators or relationships among events.

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

The study was designed to assess immunogenicity and safety of natalizumab high titer in participants with relapsing forms of multiple sclerosis. Its primary endpoint uses defined antibody-status categories assessed from baseline through Week 36. The record also identifies several safety and clinical outcomes. This gives readers useful context about what the study set out to measure and how the antibody categories were defined.

However, the registry record does not report the primary endpoint counts. It therefore does not show the observed distribution of negative, transient positive, and persistent positive status, or the precision of any estimate. The listed enrollment of 113 should not be substituted for the primary endpoint denominator, because the primary population had additional eligibility criteria and its size is not reported in the registry record.

The safety information includes counts of participants with serious and other adverse events and selected term-level percentages. These observations describe events recorded in the study group. They do not establish that natalizumab high titer caused an event, nor do they provide a comparison with a different intervention. The secondary outcome list alone is not a result: numerical findings for EDSS change, annualized relapse rate, and discontinuations due to adverse events are not reported in the registry record.

In general, an observed result is most informative when its population, denominator, uncertainty, and analysis method are clear. Here, several of those elements are not reported for the primary endpoint. The single-group design also limits comparative interpretation regardless of the size of any observed frequency. No conclusion about comparative benefit or harm can be drawn from the registry information. The record supports understanding the study’s design and what it sought to measure, but not a quantitative conclusion about its primary immunogenicity result.

13. Why This Trial Matters Statistically

This trial matters statistically because it illustrates the difference between a study objective and a reportable result. The registry states a clear immunogenicity question and defines negative, transient positive, and persistent positive antibody status. But without the counts in those categories, readers cannot estimate the observed distribution or its precision. An endpoint definition is necessary for interpretation, but it is not a substitute for the outcome data.

The design also illustrates why a single-group study has a distinct inferential role. It can document antibody and safety observations under a specified regimen, but it does not supply a randomized comparison. A reader should not treat the recorded event frequencies as comparative risks or as proof of causation. The absence of masking is another design feature relevant to interpretation, though the registry record does not report an analysis addressing its potential effects.

Finally, the gap between the enrolled population and the defined primary-outcome population highlights the importance of denominators. Eligibility required a negative baseline result and at least one post-dose assessment, while the size of that analysis population is not reported in the registry record. Without a clear denominator and account of missing assessments, the precision and representativeness of the endpoint result cannot be assessed. These are general principles for reading immunogenicity studies, and they are particularly important when the registry record does not provide numerical primary results.

14. 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.

Several limitations are specific to this record. The primary endpoint’s category counts are not reported in the registry record, so the principal immunogenicity result cannot be quantified. The registry gives an enrollment of 113, but does not report how many participants met the primary population criteria or how many contributed antibody assessments at each visit. It also does not report missing-assessment counts or how incomplete follow-up was handled.

The design was single-group, open-label, and had no masking. There was no randomized comparator, so outcome frequencies cannot be interpreted as a treatment contrast. The record does not report an adjusted analysis that might address differences in participant characteristics or other influences on outcomes. The scheduled follow-up for the primary endpoint ended at Week 36, and the record does not provide a longer-term antibody-status result.

Safety reporting is also limited in the available registry information. Counts are given for participants with serious and other adverse events, and selected serious-event terms have percentages, but event timing, recurrence, causal attribution, and the death count are not reported in the registry record. Discontinuations due to adverse events are named as an outcome, but their numerical result is not reported. Numerical results for EDSS change and annualized relapse rate are likewise not reported.

The registry does not report the statistical analysis plan, sample-size justification, interim analyses, multiplicity procedures, or missing-data methods. These absences constrain assessment of the analysis and its precision. They do not establish that a method was not used outside the registry record; they mean that the method cannot be evaluated from the record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Natalizumab High Titer Immunogenicity and Safety — NCT00516893.
• Registry record last updated 2014-05-15; status last verified 2014-05.
• Results first posted 2009-08-13.
• 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.

18. Record Summary

This completed Phase 2 study evaluated natalizumab high titer (BG00002-E) in participants with relapsing forms of multiple sclerosis. It was a multicenter, open-label, single-group study with enrollment of 113, sponsored by Biogen. The described regimen was 300 mg by intravenous infusion over 60 minutes once every 4 weeks for up to 9 doses.

The primary endpoint classified eligible participants as antibody negative, transient positive, or persistent positive, with assessments every 12 weeks from Week 0 (Baseline) to Week 36. The registry record does not report the counts for these categories or the size of the primary analysis population. The record reports 7 participants with serious adverse events and 79 with other adverse events among 112 at risk in the Natalizumab High Titer group. Numerical results for the other listed secondary outcomes are not reported in the registry record. The design supports descriptive interpretation of recorded outcomes, not a randomized comparison.