Open-label Extension for Phase 3 Clinical Trials of Simufilam: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Open-label Extension for Phase 3 Clinical Trials of Simufilam (NCT05575076), a na phase 3 study. The primary outcome is Number of Participants With Adverse Events.

2. Clinical Question

This is a safety and tolerability question, not a randomized comparison of simufilam with a control treatment. Because the study is open-label and single-group, its primary outcome describes events recorded among participants receiving simufilam; it cannot by itself establish how those events compare with what would have occurred without the study treatment.

The record describes the study as an extension for people who completed one of the parent Phase 3 trials. Its stated aim is to evaluate long-term safety and tolerability of simufilam 100 mg tablets. The primary endpoint is a participant count, rather than a measure of change in Alzheimer's disease symptoms or function. The registry record does not report an efficacy question or an efficacy outcome for this extension.

The study status is terminated. The registry record does not report the reason for termination, nor does the stated status alone explain whether or how termination affected follow-up or outcome collection. Those uncertainties matter when interpreting the safety counts: the posted figures describe what the registry records, but do not supply a full account of participants' time under observation or reasons for leaving follow-up.

3. Trial Design

The registry identifies this as a Phase 3, open-label, single-group extension study. Participants received simufilam 100 mg tablets twice daily. Masking is listed as none, and allocation is listed as not applicable. There is no concurrent control arm, so the design does not support a like-for-like treatment contrast within this study.

The extension was intended for participants who completed the RETHINK-ALZ or REFOCUS-ALZ Phase 3 trials. The stated purpose was to assess long-term safety and tolerability. The registry lists 1081 participants as enrolled. For the safety analysis, 1079 participants were included; the record explains that two enrolled participants did not receive study treatment and were excluded from that analysis set.

The study start date is 2022-11-07, and the primary completion date is 2025-01-31. Its status is terminated. The registry record does not report why it was terminated, whether termination altered the planned follow-up, or whether any interim review prompted the decision. The protocol's planned sample-size justification and detailed statistical analysis plan are not reported in the registry record.

The listed primary outcome is the number of participants with adverse events, with a timeframe of baseline to 52 weeks. The record lists one outcome measure and zero analyses. Consequently, the results should be read as descriptive safety reporting rather than as the output of a reported comparative statistical analysis. The record does not describe randomization, masking, or a control-group strategy because this is not a randomized controlled comparison.

In an extension study, observations occur after participants have entered the extension and received its treatment. Without a concurrent control group, changes in health status and event occurrence cannot be separated from background risks, disease course, prior treatment history, or other influences using this study alone. This is a general limitation of single-group designs, not a finding about the cause of any particular event in this 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.

Before assignment: This was an open-label extension study.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The number of subjects in the analysis (1079) differs by two subjects compared to the Participant Flow module (1081), because there are two subjects who were enrolled but did not receive study treatment and were not included in the 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.

Population: 1079 participants are in the safety analysis (with baseline characteristics).

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Adverse Events, measured over Baseline to 52 weeks.

The primary endpoint is the number of participants with adverse events during the baseline-to-52-week timeframe. Its stated purpose is to evaluate long-term safety and tolerability of simufilam 100 mg tablets in participants who completed one of the parent Phase 3 studies. The endpoint is a count of participants affected, not a count of all event episodes.

As a general statistical distinction, a participant-based endpoint records whether a participant experienced an event, while an event-based endpoint can count repeated episodes for the same participant. A participant count can therefore describe how many people were affected without showing how often events recurred, how long they lasted, or how severe every event was. The registry record does not provide those details for the primary endpoint.

A safety endpoint is used to describe events observed during treatment and follow-up. In this record, it does not measure whether simufilam improved Alzheimer's disease symptoms or changed disease progression. No efficacy endpoint is listed in the registry record. Nor does a single-group adverse-event count establish that treatment caused an event: without a concurrent comparator, the count cannot distinguish treatment-associated risk from background occurrence or other factors.

The endpoint's interpretation also depends on who was included and how completely events were observed. The record identifies a safety analysis set of 1079 participants and explains the difference from the enrollment count. It does not report details of missing outcome data, the event-collection procedures, or how incomplete follow-up was handled. Those omissions limit assessment of how fully the count captures events over the stated timeframe.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What kind of endpoint is this?

The primary outcome is a count of participants with adverse events. In statistical terms, that is a participant-level binary outcome: each participant either contributes to the count as having an event or does not, according to the event definition and observation period. The registry gives the outcome title, unit, and timeframe, but does not report a more detailed operational definition of an adverse event or how multiple events in one participant were handled for this endpoint.

General explanation: a participant-level count differs from counting every event episode. If one person experiences repeated episodes, a participant count still describes the person as affected rather than enumerating each episode. Event counts and participant counts answer different questions, so they should not be interchanged. The registry also reports serious-event terms and deaths, which provide additional safety descriptions but do not replace the stated primary endpoint.

What does a single-group design permit?

The study is single-group, open-label, and has no concurrent comparator. The observed count describes the safety experience recorded among participants treated with simufilam in the extension. It does not estimate a difference between treatment groups. General explanation: a randomized comparator can help distinguish outcome patterns associated with assigned treatments from background changes, though it does not remove every uncertainty. In this study, there is no randomized comparison within the extension to support that kind of contrast.

Because masking is listed as none, participants and study personnel were not masked to treatment assignment in this study. General explanation: knowledge of treatment can potentially influence how symptoms are noticed, reported, assessed, or recorded. The registry does not report specific steps used to address these possibilities, so their effect on the posted counts cannot be evaluated from the record.

How should the safety count be understood?

The registry reports 92 participants with serious adverse events in the safety analysis set and a separate count of 0 for other adverse events. These categories are presented as registry results; the record does not provide additional definitions or a narrative explaining the relationship between the categories. The serious-event terms are accompanied by reported percentages. No confidence intervals or statistical tests are reported for these safety results.

General explanation: a confidence interval expresses the uncertainty associated with an estimate, conditional on the statistical method and its assumptions. It is not a guarantee that the true value lies within the interval. Since the registry record does not report intervals for these counts or percentages, the precision of the estimates cannot be assessed from interval estimates in this record.

General explanation: when observations vary more than a simple statistical model assumes, standard errors and intervals from that model can be too narrow. This is often described as over-dispersion. It can matter for repeated event counts or clustered data, but the registry record does not report a model for repeated events or a dispersion estimate. The primary endpoint is a participant count, so there is no reported over-dispersion adjustment to interpret.

What do the analysis population and missing data imply?

The safety analysis includes 1079 participants, while enrollment is 1081. The registry attributes the difference to two enrolled participants who did not receive study treatment and were not included in the safety analysis set. This makes clear that the posted safety count is based on treated participants in that set, rather than the full enrollment count.

General explanation: analyses of safety outcomes can be affected by incomplete observation. If participants leave follow-up, an event may not be captured in the same way as for participants observed throughout the planned period. The registry record does not report the extent or handling of missing outcome data, reasons for discontinuation, or any imputation procedure. It is therefore not possible to assess from the record whether missingness could have affected the observed count.

What do the planning assumptions mean?

The registry's sample-size assumptions describe planning illustrations based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They are not the design of this extension, which is single-group, and they are not evidence of observed power. General explanation: a sample-size calculation describes the size a hypothetical study might need under stated assumptions; it does not show that a completed study had a particular probability of detecting an effect. The registry record does not report the protocol's sample-size justification or a comparative treatment effect for this primary safety endpoint.

These assumptions also do not turn a descriptive safety count into a treatment comparison. Any planning illustration based on a fraction of an observed effect depends on the effect estimate and modeling assumptions used. The record lists zero analyses and does not report the relevant comparative estimates for the primary endpoint. The planning assumptions should therefore not be interpreted as inferential results from this extension.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and zero analyses. It identifies the primary safety outcome as the number of participants with adverse events, but does not report a statistical analysis plan specifying hypothesis tests, confidence intervals, or adjustment for multiple comparisons. A multiplicity strategy is therefore not reported in the registry record.

General explanation: multiplicity arises when many outcomes, time points, subgroups, or statistical tests are examined. Testing many hypotheses can increase the chance of finding an apparently notable result by chance. Prespecified testing and suitable adjustment can help control that risk. Because the registry record does not report an inferential testing program, no multiplicity adjustment can be assessed from the posted results.

Missing-data methods are also not reported in the registry record. The record explains that the safety set excludes two enrolled participants who did not receive study treatment, but it does not describe whether outcome information was incomplete for participants in the safety set, how incomplete follow-up was handled, or whether any imputation was used. The distinction between exclusion before treatment and missing outcome information after treatment is important; the record explains the former but not the latter.

The record identifies the safety analysis population as 1079 participants. It does not report additional analysis populations, sensitivity analyses, subgroup analyses, or an approach for handling participants with differing follow-up. Those omissions limit assessment of how robust the safety summaries are to alternative analytic choices. The registry's reported event counts remain descriptive, but a reader cannot use this record to determine whether other analysis populations or missing-data assumptions would have changed them.

11. 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 5% reporting threshold.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: syncope (0.9%), pneumonia (0.6%), urinary tract infection (0.4%), atrial fibrillation (0.4%), covid-19 (0.3%).

The registry reports 92 participants with serious adverse events in the safety analysis set of 1079 participants and reports 9 deaths. The serious-event terms accompanied by the largest percentages are syncope (0.9%), pneumonia (0.6%), urinary tract infection (0.4%), atrial fibrillation (0.4%), COVID-19 (0.3%), and myocardial infarction (0.3%). The record also reports 0 participants with other adverse events.

These figures are descriptive safety summaries. The registry record does not provide enough detail to determine the timing, duration, recurrence, or cause of each event, or whether participants experienced more than one serious-event term. It also does not report further details about the deaths, including their causes or timing. The percentages should be understood as the values recorded alongside the serious-event terms, not as causal estimates.

General explanation: serious adverse events are important safety observations, but their occurrence during a study does not by itself establish that the study treatment caused them. A concurrent comparator and detailed clinical assessment can help address causal questions; this extension has no concurrent control group. The reported counts therefore describe events recorded in the study and do not establish how those counts compare with background risk.

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

The registry record documents a safety-focused, open-label extension in which participants received simufilam 100 mg twice daily. It reports a primary endpoint of participants with adverse events over baseline to 52 weeks, along with serious adverse event information and deaths. These data describe the events recorded for the safety analysis set and are relevant to understanding what the registry reports about safety monitoring.

The record does not establish that simufilam caused the reported events, nor does it establish that the treatment prevented or increased events compared with another option. There is no concurrent comparator group, no randomized contrast, and no reported inferential analysis of the primary endpoint. The extension therefore cannot by itself estimate a treatment effect relative to a control condition.

The record also does not report an efficacy outcome. The primary measure is a safety count, not a measure of Alzheimer's disease symptoms, function, or disease progression. The posted results should not be taken as evidence for or against clinical benefit.

Precision is another limitation. The registry reports event counts and percentages but no confidence intervals or hypothesis tests for these results. General explanation: uncertainty intervals can show how much sampling uncertainty surrounds an estimate, while tests address a prespecified statistical question. Without such results, the precision of the reported summaries cannot be judged using those tools.

The study is marked terminated, and the reason for termination is not reported in the registry record. The record also does not explain whether termination changed follow-up or the completeness of event collection. These unknowns do not erase the posted figures, but they constrain what can be concluded about the full safety experience over time. The sound interpretation is limited to the descriptive results, defined safety population, and timeframe recorded, while recognizing the absence of comparative and detailed follow-up information.

13. Why This Trial Matters Statistically

This study illustrates why design and endpoint type shape the questions that safety data can answer. A participant count with adverse events is an accessible description of the number of people affected, while serious-event terms and death counts add further safety information. But none of these summaries creates a controlled treatment comparison when the study has only one open-label group.

The registry also makes the analysis population distinction explicit: 1081 participants were enrolled, while the safety analysis set contains 1079 because two enrolled participants did not receive study treatment. Keeping those populations distinct is important when interpreting safety counts. It prevents readers from assuming that every enrolled participant was included in the safety analysis.

Statistically, the record is notable for the gap between descriptive reporting and inferential analysis. It lists one outcome measure and zero analyses. The record therefore gives event summaries but no reported uncertainty intervals, hypothesis tests, or model-based estimates. This illustrates that a numerical result does not necessarily answer a comparative or causal question.

The record's planning assumptions are also distinct from the design that was conducted. The assumptions describe a two-arm planning illustration, whereas the extension is single-group. General explanation: planning calculations depend on chosen assumptions and do not demonstrate observed power or substitute for an analysis of collected outcomes. They cannot supply the missing comparator for this study.

Finally, the terminated status and absent explanation underscore the role of follow-up context in safety interpretation. Event counts are most informative when their observation periods, missing data, event definitions, and analysis populations are clear. Some population information is reported, but other details are not reported in the registry record. Recognizing both the recorded evidence and its boundaries is central to sound statistical interpretation.

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 design has no concurrent comparator and is not randomized. As a result, observed event counts cannot be used as a direct estimate of how event occurrence differs from a control group. The open-label design also leaves potential for knowledge of treatment to influence event reporting or assessment; the registry record does not describe measures used to address this.

The registry reports a baseline-to-52-week timeframe for the primary endpoint, but does not give detailed information about individual follow-up duration, event ascertainment procedures, or repeated events. It reports 9 deaths without further details about cause or timing. The reason the study was terminated, and any effect termination had on follow-up or data collection, are not reported in the registry record.

The safety analysis set contains 1079 participants, with the record explaining that two enrolled participants did not receive study treatment and were excluded. The record does not report how missing outcome data among treated participants were handled, whether outcome information was incomplete, or whether sensitivity analyses were performed.

Although serious adverse event terms are reported with percentages, the record does not provide additional participant-level detail, uncertainty intervals, or comparative estimates. It does not report a statistical analysis plan, multiplicity procedures, or a sample-size justification for this extension. It lists zero analyses, so there are no reported inferential results for the primary endpoint. No efficacy outcome is reported, limiting the scope of conclusions to the posted safety descriptions.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Open-label Extension for Phase 3 Clinical Trials of Simufilam — NCT05575076.
• Registry record last updated 2025-05-23; status last verified 2025-02.
• Results first posted 2025-05-14.
• 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

The registry record describes NCT05575076, an open-label, single-group Phase 3 extension study of simufilam 100 mg tablets taken twice daily in participants with mild to moderate Alzheimer's disease who completed the RETHINK-ALZ or REFOCUS-ALZ Phase 3 trials. The study's stated purpose is to assess long-term safety and tolerability.

The primary outcome is the number of participants with adverse events from baseline to 52 weeks. The registry reports 1081 enrolled participants and a safety analysis set of 1079, explaining that two enrolled participants did not receive study treatment. It reports 92 participants with serious adverse events, 0 with other adverse events, and 9 deaths. The record lists one outcome measure and zero analyses.

The study started on 2022-11-07, has a primary completion date of 2025-01-31, and is marked terminated. The reason for termination is not reported in the registry record. With no concurrent control group and no reported inferential analysis, the posted results are descriptive safety information rather than a comparative treatment-effect estimate.