This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Safety Study of Eteplirsen to Treat Early Stage Duchenne Muscular Dystrophy (NCT02420379), a non-randomized phase 2 study. The primary outcome is Number of Participants With Treatment Emergent Adverse Events (TEAEs), Serious TEAEs, and TEAEs Leading to Discontinuation.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02420379 |
| Phase | Phase 2 |
| Condition | Duchenne Muscular Dystrophy (DMD) |
| Allocation | Non-Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 33 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Sarepta Therapeutics, Inc. |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned patients with early-stage Duchenne muscular dystrophy (DMD). The eteplirsen group included patients amenable to exon 51 skipping, while the untreated control group included patients not amenable to exon 51 skipping. The registry record does not provide further eligibility details in the information summarized for this question.
Intervention
The intervention was eteplirsen. The arm description specifies weekly infusions of 30 mg/kg for approximately 20 patients. The study was open-label, so masking was not used.
Comparator
The comparator was an untreated group described as approximately 20 patients with DMD who were not amenable to exon 51 skipping. These participants were to be observed for 96 weeks. Because treatment allocation was non-randomized and exon 51 amenability differed between the groups, this is not a like-for-like control comparison.
Primary question
The primary outcome asks how many participants experienced treatment-emergent adverse events (TEAEs), serious TEAEs, and TEAEs leading to discontinuation, from baseline up to 100 weeks. The registry defines these outcomes as participant counts. The record also lists changes in dystrophin protein levels and immunohistochemistry intensity at Week 48 and 96 as secondary outcomes. The central statistical question is descriptive: what event counts were recorded in each group, and how much confidence can be placed in a comparison when the groups were not randomized and differed in exon 51 amenability?
3. Trial Design
This was a Phase 2, open-label, multi-center study with a parallel-group model and non-randomized allocation. Masking was none. The study is recorded as completed, with enrollment of 33. Its stated purpose was to assess the safety, tolerability, efficacy, and pharmacokinetics of eteplirsen in patients with early-stage DMD who were amenable to exon 51 skipping.
The eteplirsen arm description specifies weekly infusions of 30 mg/kg for approximately 20 patients. The control group was described as approximately 20 patients with DMD who were not amenable to exon 51 skipping and would be observed for 96 weeks. These are planned arm descriptions; the registry record’s posted safety denominators are 26 for eteplirsen and 7 for the untreated group. They should not be treated as evidence that the planned allocation was achieved.
The primary safety outcome covers baseline up to 100 weeks. Its definition includes events that developed or worsened during treatment, with the on-treatment period extending from the first dose to 28 days after the last dose, up to 100 weeks. The listed secondary outcomes assess change from baseline in dystrophin protein levels quantified by Western blot and dystrophin intensity by immunohistochemistry at Week 48 and 96.
Because allocation was not randomized, and the untreated group was not amenable to exon 51 skipping while the treated group was, differences between groups may reflect differences in participant characteristics as well as treatment exposure. The registry record does not report a statistical plan that would resolve this design limitation.
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: A total of 33 participants were enrolled in the study treatment.
Overall Study
| Stage | Eteplirsen 30 mg/kg | Control Group (Untreated) (Non-exon 51 Amenable Participants) |
|---|---|---|
| STARTED | 26 | 7 |
| COMPLETED | 25 | 3 |
| NOT COMPLETED | 1 | 4 |
Reasons for not completing this period:
| Reason | Eteplirsen 30 mg/kg | Control Group (Untreated) (Non-exon 51 Amenable Participants) |
|---|---|---|
| Withdrawal by Subject | 0 | 3 |
| Unable to complete due to schooling | 0 | 1 |
| Transitioned to commercial drug | 1 | 0 |
Analysis population for the primary outcome, as defined in the registry: Full set included all participants who were enrolled in the eteplirsen group and received at least 1 dose of eteplirsen as well as all participants who were enrolled in the untreated group and had at least 1 assessment post-enrollment assessment.
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: Full set included all participants who were enrolled in the eteplirsen group and received at least 1 dose of eteplirsen as well as all participants who were enrolled in the untreated group and had at least 1 assessment post-enrollment assessment.
| Characteristic | Unit | Eteplirsen 30 mg/kg | Control Group (Untreated) (Non-exon 51 Amenable Participants) | Total |
|---|---|---|---|---|
| Participants analysed | 26 | 7 | 33 | |
| Age, Continuous | years | 5.0 (SD 0.82) | 5.0 (SD 1.00) | 5.0 (SD 0.85) |
| Sex: Female, Male: Female | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Male | Participants | 26 | 7 | 33 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 5 | 0 | 5 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 21 | 7 | 28 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 2 | 1 | 3 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 1 | 0 | 1 |
| Race (NIH/OMB): White | Participants | 22 | 6 | 28 |
| Race (NIH/OMB): More than one race | Participants | 1 | 0 | 1 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | participants | 26 | 7 | 33 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants With Treatment Emergent Adverse Events (TEAEs), Serious TEAEs, and TEAEs Leading to Discontinuation, measured over Baseline up to 100 weeks.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint counts participants with treatment-emergent adverse events, serious treatment-emergent adverse events, and treatment-emergent adverse events leading to discontinuation. It is a participant-count outcome, rather than a measure of the total number of events or event severity on a continuous scale. The registry describes an adverse event as an untoward medical occurrence that need not be causally related to study drug.
A serious adverse event is defined by specified outcomes, including death, a life-threatening event, required or prolonged inpatient hospitalization, persistent or significant disability or incapacity, or congenital anomaly. A treatment-emergent event is one that was absent before treatment and developed during the on-treatment period, or one that worsened relative to the pre-treatment state. The stated period runs from first dose through 28 days after the last dose, up to 100 weeks.
Counting participants with events is useful for describing how many people in an observed group experienced an outcome. It does not, by itself, describe the number of repeated events per participant or establish that the study drug caused an event. The registry lists discontinuation due to TEAEs as part of the primary outcome, but the event counts for that component are not reported in the registry record. The posted safety figures distinguish serious events from other adverse events, and should be interpreted within their stated group denominators.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted safety counts describe events observed in the study groups; they do not establish a causal treatment effect. In the eteplirsen group, the record lists 26 of 26 participants with other adverse events and 4 of 26 with serious adverse events. In the untreated control group, it lists 5 of 7 with other adverse events and 0 of 7 with serious adverse events. Deaths are recorded as 0 in each group. These are descriptive counts from groups assembled without randomization.
The comparison is especially limited because the groups differed in exon 51 amenability: the eteplirsen group was amenable, whereas the untreated control group was not. The registry explicitly cautions that this is not a like-for-like control comparison. Non-random allocation means that the groups may differ for reasons other than study treatment. The raw event counts therefore cannot isolate the effect of eteplirsen from group differences, and they should not be read as a randomized estimate of comparative safety.
The denominators also differ: the posted safety figures are based on 26 participants in the eteplirsen group and 7 in the control group. In particular, zero serious events recorded in the smaller untreated group does not show that serious events cannot occur in that group. Rare or uncommon outcomes can be difficult to characterize with limited observations. No confidence intervals or formal comparative estimates are reported in the registry record, so the precision of a group difference is not quantified there.
The primary outcome includes TEAEs leading to discontinuation, but a separate count for that component is not reported in the registry record. The available group counts should not be used to infer a discontinuation count. Nor do the counts establish whether individual events were caused by treatment: the registry’s AE definition explicitly does not require a causal relationship.
Several serious-event terms are listed with a frequency of 3.8%: Foreign body, Coxsackie viral infection, Influenza, Rhinovirus infection, and Rhabdomyolysis. Those entries describe terms recorded in the registry; they do not constitute a complete account of event timing, severity beyond the serious classification, or causal attribution. The record does not provide enough detail to assess whether a participant experienced more than one term.
Overall, the posted figures support a descriptive account of reported adverse events within each group. They do not support a precise or unbiased causal comparison between eteplirsen and no treatment. The non-randomized design, different exon 51 amenability, limited control-group denominator, and missing comparative analysis all constrain interpretation.
9. Statistical Methods Explained
The primary outcome is binary at the participant level: a participant either had a specified event category recorded during the defined period or did not. The registry reports counts of participants with events. A count is directly useful for describing what was observed, but it does not by itself provide a complete comparison of underlying risk or uncertainty. Interpretation depends on the denominator, the outcome definition, the observation period, and how participants entered each group.
What does a participant count convey?
A participant count records people with at least one event in a category. It is not the same as an event count: one participant could experience more than one event, while the participant count would still represent that person once for the category. The registry record does not give a detailed event-by-event account or clarify whether serious-event terms overlap within participants. For that reason, the serious-event terms should not be added together to derive a total number of affected participants.
The posted data list 26 of 26 participants with other adverse events and 4 of 26 with serious adverse events in the eteplirsen group. For the untreated group, the corresponding entries are 5 of 7 and 0 of 7. These denominators indicate the participants represented in the posted safety figures; the arm descriptions’ approximate planned group sizes are not substitutes for those observed denominators. The denominators are essential context, particularly because the groups are unequal in size.
Why does the group comparison need caution?
In a randomized comparison, random allocation is intended to make groups comparable on average with respect to factors that could affect outcomes. This trial was non-randomized. The groups also differed by exon 51 amenability, with the treated group amenable and the untreated group not amenable. A difference in observed event counts could therefore reflect treatment, participant characteristics, or other differences between groups. The registry itself states that the arms are not a like-for-like control comparison. A statistical adjustment cannot be assumed to remove this limitation; the registry record does not report such an analysis.
Open-label conduct means masking was none. For outcomes based on adverse-event reporting, knowledge of treatment assignment can be relevant to how events are noticed, reported, or classified. This is a general methodological concern, not evidence that reporting differed in this study. The registry record does not report procedures that would allow a reader to assess that possibility.
How should uncertainty be understood?
A confidence interval is a general statistical tool for expressing the uncertainty around an estimated quantity. It gives a range of values compatible with the data under the method’s assumptions; it does not guarantee that the true value lies within that range. With small groups or infrequent outcomes, intervals can be wide, reflecting limited information. The registry record does not report confidence intervals or a formal comparative estimate for these safety counts, so their precision as comparisons is not quantified.
A p-value is another general tool, used in some analyses to assess how compatible data are with a specified null model. It is not a measure of clinical importance or the probability that a treatment works. No p-value for a comparison of these adverse-event counts is reported in the registry record. A reader should not infer one from the counts alone.
What do planning illustrations represent?
Any sample-size illustrations associated with the posted results are planning exercises based on the observed effect, not evidence of the trial’s original design or a measure of observed power. Their stated assumptions include a two-sided significance level of 0.05, equal allocation, and a normal approximation; the target effect is expressed as a fraction of the observed effect. Such calculations are hypothetical and do not correct for non-random allocation or the differing amenability of the two groups. The registry record does not report that these were the study’s own design assumptions.
For outcomes other than time-to-event outcomes, the planning illustrations are expressed as participants per arm for a stated power target. These are prospective planning quantities, not observed participant counts and not proof that the trial was adequately powered. The registry record does not report a sample-size justification or an original power calculation. The illustrations should therefore remain separate from interpretation of the observed safety data.
For this trial, the most defensible statistical reading is descriptive: identify the event categories, their participant counts and denominators, and the observation period, while keeping the design limitations visible. The available record does not support a randomized causal estimate or a quantified measure of uncertainty for the group comparison.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 8 outcome measures, including the primary safety outcome and secondary measures of change from baseline in dystrophin protein levels by Western blot and dystrophin intensity by immunohistochemistry at Week 48 and 96. It reports no analyses. A statistical plan for prioritizing outcomes, controlling multiplicity, or interpreting results across several outcomes is not reported in the registry record. Without such information, the record does not establish how multiple outcomes or measurement times were handled analytically.
The registry record does not report an approach to missing outcome data, reasons for missingness, or a sensitivity analysis. The primary outcome’s stated population includes participants enrolled in the eteplirsen group who received at least 1 dose, and participants in the untreated group with at least 1 post-enrollment assessment. This definition gives a rule for inclusion in the described population, but does not explain how missing assessments within that population were handled.
The safety figures have denominators of 26 for eteplirsen and 7 for the untreated group. Those figures should be read as the posted safety populations, not as proof that every outcome was observed at every planned time point. No additional analysis population or missing-data method is reported in the registry record. These gaps matter because the interpretation of observed counts depends on who was included and whether follow-up differed across participants.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Eteplirsen 30 mg/kg | 4 | 26 | 15.4% |
| Control Group (Untreated) (Non-exon 51 Amenable Participants) | 0 | 7 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Eteplirsen 30 mg/kg | 0 of 26 |
| Control Group (Untreated) (Non-exon 51 Amenable Participants) | 0 of 7 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Eteplirsen 30 mg/kg | 26 of 26 |
| Control Group (Untreated) (Non-exon 51 Amenable Participants) | 5 of 7 |
Most frequent serious adverse event terms
| Event term | Organ system | Eteplirsen 30 mg/kg | Control Group (Untreated) (Non-exon 51 Amenable Participants) |
|---|---|---|---|
| Foreign body | Injury, poisoning and procedural complications | 1 of 26 | 0 of 7 |
| Coxsackie viral infection | Infections and infestations | 1 of 26 | 0 of 7 |
| Influenza | Infections and infestations | 1 of 26 | 0 of 7 |
| Rhinovirus infection | Infections and infestations | 1 of 26 | 0 of 7 |
| Rhabdomyolysis | Musculoskeletal and connective tissue disorders | 1 of 26 | 0 of 7 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Eteplirsen 30 mg/kg | Control Group (Untreated) (Non-exon 51 Amenable Participants) |
|---|---|---|---|
| Cough | Respiratory, thoracic and mediastinal disorders | 23 of 26 | 3 of 7 |
| Nasopharyngitis | Infections and infestations | 16 of 26 | 2 of 7 |
| Rhinorrhoea | Respiratory, thoracic and mediastinal disorders | 13 of 26 | 0 of 7 |
| Vomiting | Gastrointestinal disorders | 11 of 26 | 2 of 7 |
| Rash | Skin and subcutaneous tissue disorders | 13 of 26 | 0 of 7 |
| Upper respiratory tract infection | Infections and infestations | 11 of 26 | 1 of 7 |
| Pyrexia | General disorders | 11 of 26 | 1 of 7 |
| Nasal congestion | Respiratory, thoracic and mediastinal disorders | 10 of 26 | 0 of 7 |
| Headache | Nervous system disorders | 10 of 26 | 0 of 7 |
| Ear infection | Infections and infestations | 8 of 26 | 1 of 7 |
Serious events with the highest arm-level rate: foreign body (3.8%), coxsackie viral infection (3.8%), influenza (3.8%), rhinovirus infection (3.8%), rhabdomyolysis (3.8%).
The serious adverse event figures are participant counts: 4 of 26 in the eteplirsen group and 0 of 7 in the untreated control group. The registry also records 0 deaths in each group. The other adverse-event counts are 26 of 26 for eteplirsen and 5 of 7 for the control group. These figures are descriptive and should be interpreted with their denominators.
The registry lists Foreign body, Coxsackie viral infection, Influenza, Rhinovirus infection, and Rhabdomyolysis, each at 3.8%, among the top serious-event terms. The percentages are reported as such; they should not be summed because the record does not establish whether terms occurred in separate participants. The event-term list does not provide details on timing or establish causality.
An adverse event need not be caused by study drug. A serious adverse event is classified by the specified outcomes in the registry definition, not simply by a judgment that the event was severe. Zero serious events recorded among the 7 untreated participants does not establish zero risk. The study’s non-randomized groups and different exon 51 amenability also make a direct treatment comparison inappropriate. Counts of TEAEs leading to discontinuation are not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The posted results describe adverse events observed among participants included in the safety figures. They show that other adverse events were recorded for 26 of 26 participants receiving eteplirsen and 5 of 7 participants in the untreated group. Serious adverse events were recorded for 4 of 26 and 0 of 7, respectively; deaths were recorded as 0 in each group. These findings are counts from a completed, open-label, non-randomized study.
They do not show that eteplirsen caused any particular event, because the registry defines an adverse event as not necessarily having a causal relationship with study drug. They do not establish that the groups had the same underlying likelihood of adverse events. Participants in the treated group were amenable to exon 51 skipping, while those in the untreated group were not, and treatment was not randomly assigned. The registry cautions that the groups are not a like-for-like control comparison.
The figures also do not provide a precise estimate of a treatment-related difference. The control denominator is limited, and the registry record does not report confidence intervals or a formal comparative analysis. A zero count in one group is an observation in that group, not evidence that the event cannot occur. The record also does not report a separate count for TEAEs leading to discontinuation, despite including that category in the primary outcome.
These safety counts do not answer whether dystrophin measures changed, even though such measures are listed as secondary outcomes. Results for those secondary outcomes are not included in the registry record for this record. More broadly, the posted data should be read as a descriptive safety account, not as proof of benefit, lack of benefit, or comparative safety.
13. Why This Trial Matters Statistically
This trial illustrates why the design of a comparison matters as much as the outcome counts. A parallel-group study may present treated and untreated groups side by side, but non-randomized allocation does not ensure that the groups are comparable. In this record, exon 51 amenability differs between the groups, and the registry specifically warns that they are not a like-for-like control comparison. That limitation remains important even when counts and denominators are clearly reported.
The study also illustrates the distinction between a participant with an event and the number of events. The primary outcome counts participants, while serious-event terms provide a separate descriptive listing. Those representations answer different questions and should not be combined without information about overlap or event-level details.
Safety findings are more informative when their definitions and observation periods are explicit. Here, the registry defines treatment-emergent events in relation to treatment exposure and specifies the period through 28 days after the last dose, up to 100 weeks. It also distinguishes serious events by their consequences. Such definitions help readers understand what a count represents, while not establishing that treatment caused an event.
Finally, the record shows why uncertainty and missing analysis details matter. Counts alone do not quantify precision, and the registry does not report comparative confidence intervals, a formal analysis, or a multiplicity approach. Planning illustrations based on the observed effect are not a substitute for the study’s own sample-size justification, which is not reported in the registry record. Together, these points encourage a disciplined interpretation: describe the observations, identify the limits of comparison, and avoid treating the data as a causal estimate.
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 principal limitation for interpreting the safety comparison is the non-randomized design. The treated and untreated groups also differ in exon 51 amenability, so the untreated group is not a like-for-like control. The registry explicitly flags this concern. As a result, observed differences in event counts cannot be attributed to treatment alone.
The posted safety denominators are 26 for the eteplirsen group and 7 for the control group. The smaller control denominator limits what can be learned about uncommon events, and a zero count in that group should not be interpreted as absence of risk. The record does not report confidence intervals or a formal between-group analysis to quantify uncertainty.
The study was open-label, with no masking. The record does not provide details that would allow an assessment of whether knowledge of group assignment affected adverse-event reporting or classification. It also does not report the separate count of TEAEs leading to discontinuation, although discontinuation is part of the primary outcome.
The registry lists secondary dystrophin outcomes and 8 outcome measures overall, but a multiplicity strategy is not reported. Missing-data methods, sensitivity analyses, and details of the treatment of incomplete assessments are also not reported in the registry record. A sample-size justification and the study’s original statistical plan are not reported. These omissions restrict assessment of the analysis and its precision, in addition to the limitations inherent in the group comparison.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Safety Study of Eteplirsen to Treat Early Stage Duchenne Muscular Dystrophy — NCT02420379.
- Registry record last updated 2021-01-25; status last verified 2020-12.
- Results first posted 2020-07-22.
- 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.
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18. Record Summary
NCT02420379 is a completed Phase 2, open-label, multi-center, parallel-group study of eteplirsen in early-stage DMD. Allocation was non-randomized and masking was none. Enrollment was 33. The eteplirsen arm description specifies weekly infusions of 30 mg/kg; the untreated group consisted of participants not amenable to exon 51 skipping and was to be observed for 96 weeks.
The primary outcome counts participants with treatment-emergent adverse events, serious TEAEs, and TEAEs leading to discontinuation, from baseline up to 100 weeks. Posted safety counts include 26 of 26 with other adverse events and 4 of 26 with serious adverse events in the eteplirsen group, compared with 5 of 7 and 0 of 7 in the untreated group. Deaths are recorded as 0 in each group. The record cautions that the arms are not a like-for-like control comparison. Comparative analyses, confidence intervals, multiplicity methods, and missing-data methods are not reported in the registry record.