Atacicept in Subjects With Optic Neuritis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Atacicept in Subjects With Optic Neuritis (NCT00624468), a randomized phase 2 study. The primary outcome is Change From Baseline in Retinal Nerve Fiber Layer (RNFL) Thickness in the Affected Eye at Last Observed Value (LOV).

2. Clinical Question

The endpoint was intended to assess a structural measure using optical coherence tomography (OCT). The study description says the trial aimed to evaluate safety and tolerability and to explore a possible neuroprotective effect assessed by OCT. The statistical question is narrower than that broad aim: it concerns a particular change in retinal nerve fiber layer thickness, in the affected eye, at the last observed value.

The record does not report numerical results for the primary endpoint or an analysis comparing the treatment groups. It therefore does not establish the direction, size, or precision of any group difference. The registry record also does not report participant characteristics beyond the condition and population description, so the clinical question cannot be refined using information about baseline characteristics.

3. Trial Design

This was a Phase II, randomized, parallel-group, placebo-controlled study of atacicept in subjects with optic neuritis as a clinically isolated syndrome. The official title describes a multicenter study and a 36-week treatment course. The brief summary says study medication was given by subcutaneous injections. The registry lists 34 enrolled participants, with 17 at risk in each group during the double-blind period.

The registry identifies the masking as quadruple. The official title also calls the study double-blind. The record does not identify which roles were masked or explain the relationship between these descriptions. The placebo is described as matched to atacicept. Further details of the randomization procedure, including sequence generation and allocation concealment, are not reported in the registry record.

The study status is terminated. The record gives a start date of 2008-06 and a primary completion date of 2009-09, but the reason for termination is not reported in the registry record. No conclusion about why the study ended follows from the status alone.

The primary endpoint was change from baseline in retinal nerve fiber layer (RNFL) thickness in the affected eye at the last observed value (LOV), identified as Week 48. This endpoint timeframe differs from the 36-week treatment course stated in the official title. The registry record does not explain the timing or procedures connecting those timeframes. It also lists secondary outcomes covering RNFL thickness, macular thickness and volume, low-contrast letter acuity, and contrast sensitivity. The record does not provide numerical analyses for these outcomes.

Random allocation and a matched placebo establish the intended framework for a between-group comparison, but design labels do not reveal how the study was conducted in practice. Details such as the participant flow, adherence, actual duration of exposure, and reasons for missing observations are not reported in the registry record. The arm descriptions contain no additional details about treatment administration.

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.

Double-blind Period

Reasons for not completing this period:

Safety Follow-up (SFU) Period

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: ITT population included all randomized participants. Here, "n" signifies those participants who were evaluable for the specified category.

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.

Population: Intent-to-treat (ITT) population included all randomized participants.

6. Primary Endpoint

The registry lists the primary outcome as Change From Baseline in Retinal Nerve Fiber Layer (RNFL) Thickness in the Affected Eye at Last Observed Value (LOV), measured over Baseline, LOV (Week 48).

The primary endpoint is the change from baseline in RNFL thickness in the affected eye at the last observed value (LOV), specified as Week 48. Thickness is measured in micrometers. The registry describes OCT measurements in 12 sectors, each separated by 30 degrees, taken in triplicate for each eye; measurements are then averaged over the 12 sectors. The change is defined as the RNFL thickness at LOV minus the thickness at baseline.

RNFL thickness is a structural measure of the retina. The study description identifies OCT assessment as a way to explore a possible neuroprotective effect in optic neuritis. In general, a structural endpoint can provide a measurable way to track change in tissue over time, but its interpretation depends on how the measure relates to the clinical question and on the quality and completeness of the observations. The registry record does not report validation details or a threshold for interpreting a particular change as clinically meaningful.

The endpoint is summarized as a mean with standard deviation. In general, a mean describes the average observed change in a group, while the standard deviation describes variability among observations. A mean alone does not show the uncertainty in a treatment-group comparison. No numerical mean, standard deviation, confidence interval, or treatment comparison for this endpoint is reported in the registry record, so the size and precision of the observed changes cannot be assessed from the posted results.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The design labels describe how the trial was intended to compare groups, but they do not substitute for a reported analysis. Randomization assigns participants to groups using a chance-based process. In general, this can reduce systematic differences in baseline characteristics between groups, although balance is not guaranteed in a small trial. The registry identifies the study as randomized and parallel-group. Further information about sequence generation, allocation concealment, and the actual allocation process is not reported in the registry record.

What does the endpoint calculation represent?

The endpoint is a change score: RNFL thickness at LOV minus RNFL thickness at baseline. In general, a change score expresses how a measurement differs from its starting value. The registry specifies the affected eye and defines LOV as Week 48. It also describes OCT measurements across 12 sectors, taken in triplicate and averaged across sectors. The endpoint is reported as a continuous measure in micrometers, with the mean and standard deviation specified as summary statistics. The numerical group summaries and comparison are not reported in the registry record.

For a continuous outcome, an analysis may estimate a mean in each group and a contrast between groups. The contrast would communicate how far apart the group averages are on the endpoint scale. In general, an estimate should be read alongside its uncertainty and the analysis assumptions. The registry record does not report the specific model, adjustment variables, contrast method, confidence interval method, or inferential results used for the primary endpoint. These details should not be inferred from the endpoint’s designation as a mean.

What does masking add?

Masking is intended to limit the influence of knowledge about assigned treatment on participant experience, care, outcome assessment, or other processes. The registry lists quadruple masking, and the official title describes the study as double-blind. The roles covered by the masking terminology and the procedures for maintaining masking are not reported in the registry record. Therefore, the labels describe the recorded design but do not establish how masking was implemented or whether it remained intact.

How should the analysis population be understood?

The primary outcome description defines the ITT population as all randomized participants. It also states that “n” signifies participants evaluable for the specified category. In general, an ITT approach aims to analyze participants according to their randomized assignment, which preserves the comparison created by randomization. A reported evaluable count can be smaller than the number randomized when an outcome is unavailable or cannot be assessed, but the record does not give primary-endpoint evaluable counts or reasons for any unavailable measurements. The analysis population actually used for a numerical primary comparison is not reported in the registry record.

What uncertainty and planning assumptions are available?

No primary-endpoint estimate, confidence interval, or p value is reported. In general, uncertainty measures help distinguish a relatively precise estimate from one that remains compatible with a broad range of effects. They do not replace consideration of clinical relevance, study conduct, and missing data.

The registry’s sample-size assumptions describe a planning illustration based on the observed effect, not the trial’s own design. The stated assumptions are a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. In general, such sample-size calculations are planning illustrations, not observed power and not evidence that an effect was present. No specific sample-size illustration values are included in the registry record summarized for this analysis.

What can be concluded from the available methods record?

The endpoint definition and high-level design are available, but the detailed statistical analysis plan is not reported in the registry record. Information about model choice, covariate adjustment, handling of repeated measurements, missing-data procedures, sensitivity analyses, and interim analyses is not reported in the registry record. Consequently, the stated methods do not permit independent reconstruction of the primary comparison or assessment of its statistical assumptions.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 10 outcome measures. Secondary outcomes include RNFL thickness, macular thickness at two stated distances around the fovea, macular volume, low-contrast letter acuity, and contrast sensitivity. Several outcomes are assessed at more than one time point. Considering multiple outcomes or time points can create multiple opportunities to find a result that appears notable by chance. In general, a prespecified analysis hierarchy or multiplicity adjustment can help clarify how such results should be interpreted. The strategy for handling multiplicity is not reported in the registry record.

The primary endpoint is identified, but there is no reported numerical analysis for it. No analysis entries are recorded. The registry record does not report whether other outcomes were analyzed, which time points were prioritized, or whether analyses were adjusted for baseline values or other variables. The existence of listed outcomes alone does not establish which comparisons were prespecified or how they were interpreted.

The record defines the ITT population as all randomized participants and notes that “n” represents participants evaluable for a specified category. It does not report the number evaluable for the primary endpoint, the amount or pattern of missing outcome data, reasons for missing observations, or methods for addressing missingness. In general, missingness can affect the interpretation of an estimated change if the availability of measurements is related to participant characteristics or outcomes. No particular missing-data mechanism or method can be inferred.

The endpoint is defined at LOV, identified as Week 48, while the official title describes a 36-week treatment course. The record does not explain how the last observed measurement was selected or how participants without a Week 48 measurement were handled. These omissions limit assessment of both the outcome definition in practice and the analysis population.

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: myelitis (7.7%), pyrexia (7.7%), blister (7.7%), bacterial pyelonephritis (7.1%), multiple sclerosis (7.1%).

The registry reports serious adverse events separately for the double-blind and SFU periods. The abbreviation SFU is not explained in the registry record. During the double-blind period, serious adverse events affected 0 of 17 participants in the placebo group and 0 of 17 in the atacicept group. During the SFU period, the corresponding counts were 1 of 13 for placebo and 2 of 14 for atacicept. The record does not report deaths in these entries.

For other adverse events, the registry lists 14 of 17 participants in the placebo group and 16 of 17 in the atacicept group during the double-blind period. During the SFU period, it lists 6 of 13 for placebo and 10 of 14 for atacicept. These are participant counts recorded for the specified periods; they do not indicate event severity, duration, relatedness to treatment, or whether a participant experienced more than one event. Further details about how these events were collected and classified are not reported in the registry record.

The record lists serious-event terms with percentages: Myelitis, Pyrexia, and Blister at 7.7% each; Bacterial pyelonephritis, Multiple sclerosis, and Myelitis transverse at 7.1% each. The registry does not provide enough context in these entries to infer the treatment relationship or compare risks across groups for each term. In general, adverse-event counts should be interpreted alongside exposure, definitions, duration of observation, and participant-level details. These figures alone do not establish a causal safety difference between the groups.

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

The record documents a randomized, placebo-controlled Phase II study of atacicept in participants with optic neuritis as a clinically isolated syndrome. It describes an OCT-based primary endpoint: change from baseline in RNFL thickness in the affected eye at LOV, identified as Week 48. It also records selected adverse-event counts and a set of secondary outcome measures.

Those design and endpoint details explain what the study set out to examine; they do not answer whether the groups differed. Numerical primary outcome results, a treatment-group estimate, and an uncertainty measure are not reported in the registry record. The posted information therefore does not show whether RNFL thickness increased or decreased on average, whether changes differed between groups, or how precisely any difference was estimated. No conclusion about efficacy or lack of efficacy follows from the absence of these results.

The listed adverse-event counts describe events recorded during specified study periods. They do not, on their own, establish that an event was caused by treatment or that one group had a different safety profile. The registry does not report the reason for termination, the detailed analysis plan, or the missing-data procedures. These gaps further limit interpretation of both outcome and safety information.

In general, a clinical trial result is interpreted by considering the estimated effect, its uncertainty, study conduct, outcome completeness, and clinical context. A registry design description is useful for understanding the intended comparison, while a complete interpretation also requires reported analyses and enough information to assess how they were performed. In this record, the design and measurement definitions are more fully described than the numerical evidence needed to answer the primary comparative question.

13. Why This Trial Matters Statistically

This trial raises statistical issues that are important when evaluating small randomized studies with structural outcomes. The record reports 34 enrolled participants and describes a continuous OCT-based primary endpoint. Continuous measurements can preserve information across a range of observed values, but a useful treatment comparison still requires group summaries, an estimated contrast, and an indication of uncertainty. Those primary numerical results are not reported in the registry record.

The endpoint is defined using a change from baseline and an LOV measurement identified as Week 48. The official title describes a 36-week treatment course. The difference between the treatment-course duration and endpoint timeframe makes clear reporting of measurement schedules and participant follow-up especially relevant; those details are not reported in the registry record. The endpoint’s measurement protocol is described, but the record does not explain how measurements unavailable at the specified time were handled.

The record also lists multiple secondary outcomes and repeated time points. In general, a broad set of outcomes can help characterize different aspects of a study, but it makes prespecification and transparent handling of multiple comparisons important. The multiplicity strategy is not reported in the registry record, and no outcome analysis entries are recorded.

Finally, the ITT population definition appears alongside an evaluability-based description of “n.” This distinction matters because the randomized population and the number with an evaluable measurement need not be identical. Without endpoint-specific counts and a missing-data account, readers cannot assess whether all randomized participants contributed to the primary endpoint analysis. Together, these features illustrate why transparent reporting of estimates, uncertainty, populations, and analysis decisions is essential to interpreting clinical trial evidence.

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.

The most consequential limitation for interpretation is that the registry record does not report a numerical primary endpoint analysis. There is no reported mean change by group, between-group estimate, confidence interval, or p value. As a result, the primary comparative question cannot be answered from the posted results, and the direction or precision of any effect cannot be assessed.

The study is marked terminated, but the reason for termination is not reported in the registry record. The record does not state whether the planned enrollment was achieved, give participant flow through the study, or explain the number evaluable for the primary endpoint. It also does not report reasons for missing measurements or methods for handling them. These omissions prevent assessment of how complete the endpoint data were.

The primary endpoint is identified as LOV at Week 48, while the official title describes a 36-week treatment course. The registry record does not explain the relationship between those timeframes, the timing of measurements, or how LOV was selected for participants with differing observation histories. Although the OCT measurement procedure is described, additional information about quality control and measurement reproducibility is not reported in the registry record.

The record lists multiple secondary outcomes, including repeated time points, but does not report a multiplicity strategy or detailed analysis plan. It also does not report baseline participant characteristics, the reasons for termination, or the roles covered by quadruple masking. The SFU abbreviation is not defined. These limitations do not show that a particular design or analysis problem occurred; they identify information not reported in the registry record that would be needed for a fuller assessment.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Atacicept in Subjects With Optic Neuritis — NCT00624468.
• Registry record last updated 2016-02-17; status last verified 2016-01.
• Results first posted 2016-02-17.
• 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

NCT00624468 is a randomized, parallel-group, placebo-controlled Phase II study of atacicept in participants with optic neuritis as a clinically isolated syndrome. The official title describes a multicenter study and a 36-week treatment course; the brief summary describes subcutaneous injections. The registry lists 34 enrolled participants and a terminated status.

The primary endpoint is change from baseline in RNFL thickness in the affected eye at LOV, identified as Week 48, measured using OCT. The record describes the measurement procedure and identifies an ITT population, but numerical primary endpoint analyses are not reported. It lists secondary outcomes involving retinal structure and visual measures, along with adverse-event counts for the double-blind and SFU periods. The reason for termination, detailed statistical analysis methods, and missing-data procedures are not reported in the registry record.