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 Gene Therapy Study in Severe Hemophilia A Patients With Antibodies Against AAV5 (NCT03520712), a na phase 1, phase 2 study. The primary outcome is Number of Participants With Treatment Emergent Adverse Events.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03520712 |
| Phase | Phase 1, Phase 2 |
| Condition | Hemophilia A, Gene Therapy, Clotting Disorders |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 3 |
| Arms in the primary outcome | n/a |
| Lead sponsor | BioMarin Pharmaceutical |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns people with severe hemophilia A, residual factor VIII levels of 1 IU/dL or less, and pre-existing antibodies against AAV5. The registry describes an enrollment of 3. Age, sex, and other eligibility details are not reported in the registry record.
Intervention
Participants received valoctocogene roxaparvovec, described as an AAV-based gene therapy vector. The listed open-label arm specifies a single administration of BMN270 at a dose of 6E13 vg/kg. The study was intended to assess safety, tolerability, and efficacy in this population.
Comparator
There is no concurrent comparison group. The study is identified as single-group, with allocation recorded as not applicable and masking recorded as none. Consequently, the registry record does not support a like-for-like comparison with an untreated group or another therapy.
Primary question
The primary endpoint asks how many participants experienced treatment-emergent adverse events, defined as events that newly appeared or worsened in severity after investigational product administration began. The endpoint timeframe is up to 5 years post-infusion. Secondary outcomes include factor VIII activity, factor VIII use and infusion rates, and bleeding episodes requiring exogenous factor VIII therapy.
Statistically, the primary question is descriptive: what adverse-event experience was recorded in this treated group? Without a comparator, the study cannot estimate a treatment-versus-control contrast from its design. The registry record does not report a statistical hypothesis or an inferential analysis for the primary endpoint.
3. Trial Design
NCT03520712 is a Phase 1/2, open-label, single-group study sponsored by BioMarin Pharmaceutical. Its stated intervention is valoctocogene roxaparvovec, an AAV-based gene therapy vector. The arm description specifies a single administration of BMN270 at 6E13 vg/kg. The registry lists an enrollment of 3 and identifies the study as terminated. The recorded start date is 2018-04-24, and the primary completion date is 2024-08-07.
The study has no like-for-like control arm: allocation is listed as not applicable, masking as none, and the model as single-group. Thus, the design can describe outcomes observed after administration, but does not itself separate treatment-associated changes from the course participants might have experienced without treatment. Open-label conduct also means participants and study personnel were not masked according to the registry record.
The primary endpoint is a count of participants with treatment-emergent adverse events over a timeframe of up to 5 years post-infusion. The safety analysis population is described as the intention-to-treat population, defined in the record as all participants who received the BMN270 infusion. Secondary outcomes cover factor VIII activity at Week 26, factor VIII utilization and infusion rate from Week 5 onward, and reduction in bleeding episodes requiring exogenous factor VIII therapy.
The registry record does not report the reason for termination, the recruitment history, or whether the planned enrollment was reached. It also does not report a protocol-based sample-size justification or details of any interim analyses. Those omissions limit conclusions about how the observed enrollment relates to the original study plans.
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: 10 participants were planned to be enrolled. 3 participants met all eligibility criteria \& were enrolled in study. There were 26 screen failures.
Overall Study
| Stage | BMN 270 6E13 vg/kg |
|---|---|
| STARTED | 3 |
| COMPLETED | 1 |
| NOT COMPLETED | 2 |
Reasons for not completing this period:
| Reason | BMN 270 6E13 vg/kg |
|---|---|
| Early termination of the study by Sponsor | 2 |
Analysis population for the primary outcome, as defined in the registry: The safety analysis was based on the ITT population. The intention-to-treat (ITT) population was comprised of all participants who have received the BMN 270 infusion.
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: The intention-to-treat (ITT) population was comprised of all participants who have received the BMN 270 infusion.
| Characteristic | Unit | BMN 270 6E13 vg/kg |
|---|---|---|
| Participants analysed | 3 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 3 |
| Age, Categorical: >=65 years | Participants | 0 |
| Sex: Female, Male: Female | Participants | 0 |
| Sex: Female, Male: Male | Participants | 3 |
| Race/Ethnicity, Customized: White Non-Hispanic | Participants | 2 |
| Race/Ethnicity, Customized: Black or African American | Participants | 1 |
| Region of Enrollment: United Kingdom | participants | 1 |
| Region of Enrollment: South Africa | participants | 2 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants With Treatment Emergent Adverse Events, measured over Up to 5 years post-infusion..
| 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 (TEAEs). The registry defines a TEAE as an adverse event that newly appeared or worsened in severity after initiation of investigational product administration. The endpoint is measured over a timeframe of up to 5 years post-infusion, and the safety analysis is described as based on the intention-to-treat population: all participants who received the BMN270 infusion.
A participant count is a direct way to describe how many people in the analyzed group had at least one event meeting the endpoint definition. It is useful for summarizing observed safety experience, while retaining a clear connection to people rather than to a total number of event episodes. A count alone, however, does not describe the number of separate events, their duration, their severity, or whether they were judged related to treatment. Those details are not part of the endpoint definition stated in the registry record.
The posted adverse-event breakdown separately reports participants affected by serious and other adverse events. These categories should be read according to their labels, not treated as interchangeable measures. The registry record does not report an inferential analysis, a confidence interval, or a comparative effect estimate for the primary endpoint.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary endpoint is a safety count in a single-group study, not a comparison of treatment strategies. The registry reports an enrollment of 3 and describes the safety analysis population as participants who received the infusion. In the adverse-event breakdown, the BMN 270 6E13 vg/kg group lists 3 participants at risk for serious adverse events, with 1 affected; it also lists 3 at risk for other adverse events, with 3 affected. The death count is 0. These are descriptive counts from the posted record.
The reported serious adverse-event term is Hypersensitivity, listed at 33.3%. The registry record does not provide further detail in the listed term about timing, duration, clinical course, or attribution. The percentage should be interpreted as a description of the registry’s reported serious-event entry, not as a comparative risk estimate. No control group is available to estimate how the event frequency might differ under another condition.
Because the observed group is small, the counts have limited ability to characterize the range of possible safety experiences in a broader population. General statistical principle: estimates based on few observations are typically imprecise, and a single participant’s outcome can meaningfully affect the descriptive picture. No confidence interval is reported in the registry record, so readers cannot use a posted interval to assess the statistical uncertainty around these counts.
The record also lists secondary outcomes concerning factor VIII activity, factor VIII use and infusion, and bleeding episodes requiring exogenous factor VIII. Their names describe what was intended to be measured, but results for those outcomes are not reported in the registry record. The available adverse-event counts therefore cannot answer the efficacy questions listed among the secondary outcomes.
The study is marked terminated, but the reason is not reported in the registry record. Termination alone does not identify whether the cause was safety, recruitment, administrative, or another matter. The record does not report a comparator, a prespecified analysis plan, or inferential analyses. As a result, the posted results support a concise account of what was observed in this group, not a causal conclusion or a precise estimate for other patients.
9. Statistical Methods Explained
What does a participant count convey?
The primary endpoint uses a count of participants who experienced at least one qualifying treatment-emergent adverse event. This is a participant-level summary: it answers how many people met the endpoint definition rather than how many separate event episodes occurred. One person may experience more than one event, but the participant count does not distinguish repeated events from a single event. The registry record does not report a separate event-total measure for the primary endpoint.
General statistical explanation: a count is easy to interpret as an observed description, but its meaning depends on the group and event definition. Counts do not by themselves provide a measure of precision, and they do not establish that an event was caused by the intervention. The registry’s definition includes events that newly appeared or worsened after administration began; the definition alone does not establish causal attribution.
Why does the design matter for interpretation?
The study is single-group and open-label, with no concurrent comparator. A single-group result can describe outcomes recorded among participants who received the intervention. It cannot directly estimate the difference between outcomes under intervention and outcomes under a concurrent alternative. Changes in outcomes over time can also reflect factors other than the intervention. General statistical explanation: a comparator helps provide a reference for interpreting observed outcomes, but the registry record lists no such reference group for this study.
Open-label conduct means that treatment assignment was not masked, and in this single-group study there was no alternate assignment to conceal. Awareness of treatment can affect how symptoms are reported, assessed, or recorded. This is a general design consideration, not evidence that any particular reported event was misclassified in this trial.
How should uncertainty be considered?
A confidence interval is a statistical range intended to express uncertainty around an estimate under specified assumptions. General statistical explanation: narrow intervals indicate greater precision, while wide intervals indicate less precision. The registry record does not report a confidence interval or an inferential analysis for the primary count. The enrollment of 3 and the listed adverse-event counts therefore give a limited descriptive view, without a reported interval that quantifies uncertainty.
When groups are small, estimates can be sensitive to the outcome of an individual participant. This does not invalidate the observed counts; it means the counts should not be treated as precise estimates of what would occur in a larger or different population. No extrapolation to a population rate is reported in the registry record.
What do the serious-event entries distinguish?
The adverse-event breakdown separates serious adverse events from other adverse events. The serious-event figures list 3 at risk and 1 affected; the other-event figures list 3 at risk and 3 affected. The death count is 0, and Hypersensitivity is listed as the top serious term at 33.3%. These entries describe different labels and should not be collapsed into a single interpretation. The record does not provide event-level narratives or additional information about timing and attribution.
General statistical explanation: event severity categories are not measures of treatment effect. A serious-event count describes events meeting a seriousness classification, while an overall adverse-event count can include events that are not classified as serious. Neither count alone establishes causation or compares risks across treatments.
What do planning illustrations mean?
Any sample-size planning illustrations associated with the posted results are hypothetical calculations based on an observed effect and stated planning assumptions. They are not observed outcomes, and they are not a report of the study’s original design justification. The registry record does not report that justification. A planned sample size also should not be read as observed power: power is a design property under specified assumptions, whereas a post hoc calculation based on observed results does not establish that the trial was adequately powered.
General statistical explanation: planning calculations depend on assumptions about the effect to detect, allocation, significance level, and statistical model. Different assumptions can lead to different planning requirements. The registry record does not report a statistical analysis plan for the primary endpoint, so no unreported model or inferential procedure should be presumed.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists several secondary outcomes, including factor VIII activity at Week 26, factor VIII utilization and infusion rate from Week 5 onward, and reduction in bleeding episodes requiring exogenous factor VIII. When a study assesses multiple outcomes, multiplicity is a general statistical concern: repeated hypothesis tests can increase the chance of at least one apparently notable result arising by chance. Possible approaches include prioritizing an endpoint or adjusting inference across tests, but the appropriate approach depends on the planned analysis.
A multiplicity procedure or hierarchy for these outcomes is not reported in the registry record. The record also lists no inferential analyses. Therefore, no adjustment method, testing sequence, or confirmatory status for the secondary outcomes can be inferred from the listed outcome names.
The registry record does not report how missing outcome data were handled, whether any participants had incomplete follow-up, or how missing measurements were incorporated into analyses. These details matter because an analysis may depend on which participants contribute data and how unavailable observations are treated. The stated safety population is the intention-to-treat population, defined as all participants who received the BMN270 infusion; this definition does not itself explain how missing safety information was handled.
The reason for termination and any effects on follow-up or outcome collection are not reported in the registry record. No interim-analysis plan or stopping rule is reported. Without those details, the completeness and analysis of follow-up cannot be assessed beyond the information explicitly recorded.
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 |
|---|---|---|---|
| BMN 270 6E13 vg/kg | 1 | 3 | 33.3% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| BMN 270 6E13 vg/kg | 0 of 3 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| BMN 270 6E13 vg/kg | 3 of 3 |
Most frequent serious adverse event terms
| Event term | Organ system | BMN 270 6E13 vg/kg |
|---|---|---|
| Hypersensitivity | Immune system disorders | 1 of 3 |
Most frequent non-serious adverse event terms
| Event term | Organ system | BMN 270 6E13 vg/kg |
|---|---|---|
| Alanine aminotransferase increased | Investigations | 2 of 3 |
| Arthralgia | Musculoskeletal and connective tissue disorders | 1 of 3 |
| Hypersensitivity | Immune system disorders | 1 of 3 |
| Animal scratch | Injury, poisoning and procedural complications | 1 of 3 |
| Face injury | Injury, poisoning and procedural complications | 1 of 3 |
| Onychomycosis | Infections and infestations | 1 of 3 |
| Tendon disorder | Musculoskeletal and connective tissue disorders | 1 of 3 |
| Covid-19 | Infections and infestations | 1 of 3 |
| Conjunctivitis viral | Infections and infestations | 1 of 3 |
| Limb injury | Injury, poisoning and procedural complications | 1 of 3 |
Serious events with the highest arm-level rate: hypersensitivity (33.3%).
The serious adverse-event entry lists 3 participants at risk and 1 affected in the BMN 270 6E13 vg/kg group. The other adverse-event entry lists 3 at risk and 3 affected. The death count is 0. These are counts in separate categories; they should not be added together, because the registry does not describe whether participants can appear in both categories.
Hypersensitivity is listed as the top serious adverse-event term at 33.3%. This is a reported term and percentage, not a comparison against another group. The registry record does not report further event-level details, such as timing, duration, or attribution, in the registry record for this analysis. The percentage should not be used to infer a broader risk rate or a treatment effect.
General statistical explanation: safety counts are most informative when the event definitions, observation period, analyzed population, and completeness of follow-up are clear. The record defines treatment-emergent events by their appearance or worsening after administration begins and gives a timeframe of up to 5 years post-infusion. It does not report a confidence interval or comparative safety analysis.
12. What the Result Does, and Does Not, Mean
The posted results describe adverse events recorded in a small, single-group study of valoctocogene roxaparvovec in people with severe hemophilia A and pre-existing antibodies against AAV5. They report the primary endpoint as a count of participants with treatment-emergent adverse events, and the safety breakdown separately reports serious and other adverse events. These findings are descriptive of the participants represented in the registry record.
The results do not establish what would have happened to the same participants without the intervention, because the design has no concurrent comparator. They also do not establish that an event was caused by the intervention. The registry’s temporal definition of a treatment-emergent event identifies when an event appeared or worsened relative to administration, but temporal association alone is not causal proof.
The record does not report results for the listed secondary outcomes on factor VIII activity, factor VIII use, infusion rate, or bleeding episodes. It therefore does not provide a basis in these posted results for drawing conclusions about those outcomes. The absence of reported results in the registry record should not be treated as evidence that a particular outcome did or did not occur.
The small enrollment limits precision and makes the descriptive results difficult to generalize beyond this study group. No confidence interval or inferential analysis is reported. The study is marked terminated, but the reason is not reported in the registry record; the status alone does not explain why it ended or what implications that had for data collection.
In short, the record documents a limited safety description for the treated group, including serious-event and other-event counts. It does not provide a controlled treatment comparison, a causal estimate, or reported efficacy results for the secondary endpoints.
13. Why This Trial Matters Statistically
This study is statistically notable because it addresses a population defined not only by severe hemophilia A but also by pre-existing antibodies against AAV5. The registry describes a Phase 1/2, open-label, single-group study of a single administration of valoctocogene roxaparvovec. The statistical interpretation must therefore remain closely tied to the observed group and the safety outcomes recorded.
In small early-phase studies, a participant-level safety count can be useful for recording observed events and identifying areas that may merit further description. At the same time, small enrollment limits precision and does not support strong generalization. Reporting the event definition, observation period, analysis population, and event categories helps readers understand what the count represents. The record supplies those basic endpoint and population descriptions, while leaving some analysis details unreported.
The single-group design also highlights the distinction between describing outcomes and estimating comparative effects. Without a concurrent control group, the observed safety entries cannot show how outcomes compare with an alternative. This is an important interpretive boundary even when the endpoint itself is clearly defined.
The registry lists secondary outcomes that could describe factor VIII activity, treatment use, and bleeding-related measures, but their results are not reported in the registry record. Their presence in the outcome list should not be mistaken for evidence about those outcomes. Likewise, the terminated status is part of the record, but the reason is not reported. Together, these features make careful separation of recorded details from unanswered questions especially important.
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 immediate limitation is the enrollment of 3 in a single-group study. The posted counts describe a limited set of observations and offer little precision for characterizing safety beyond the analyzed group. The registry record reports no confidence interval or inferential analysis for the primary endpoint.
There is no concurrent comparator, and the study is open-label. Consequently, the record cannot provide a controlled estimate of how outcomes differ from an alternative, and outcomes may be subject to general limitations associated with unmasked assessment. This does not show that a particular event was affected by those design features; it defines what the design can support.
The record lists secondary outcome measures but does not report their results. It also does not report a statistical analysis plan, multiplicity handling, missing-data methods, interim analyses, or the reason for termination. These omissions leave uncertainty about analysis decisions, completeness of follow-up, and the context for the study’s status.
The primary endpoint is a count of participants with treatment-emergent adverse events. It does not, by itself, describe event frequency per participant, duration, severity beyond the separate serious-event category, or causal attribution. Further event-level detail is not reported in the registry record. The reported 33.3% for Hypersensitivity should therefore be read as a registry entry, not as a comparative or broadly generalizable risk estimate.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Gene Therapy Study in Severe Hemophilia A Patients With Antibodies Against AAV5 — NCT03520712.
- Registry record last updated 2025-08-22; status last verified 2025-08.
- Results first posted 2025-08-22.
- 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
NCT03520712 is a Phase 1/2, open-label, single-group study sponsored by BioMarin Pharmaceutical. It evaluates valoctocogene roxaparvovec in severe hemophilia A with residual factor VIII levels of 1 IU/dL or less and pre-existing antibodies against AAV5. The arm description specifies a single BMN270 administration at 6E13 vg/kg. Enrollment is listed as 3; the study status is terminated.
The primary endpoint counts participants with treatment-emergent adverse events up to 5 years post-infusion. The safety population is defined as participants who received the infusion. The adverse-event breakdown reports serious and other event counts, a death count of 0, and Hypersensitivity at 33.3% as the top serious term.
The record does not report inferential analyses or results for the listed secondary outcomes. It also does not report the reason for termination, missing-data methods, multiplicity handling, or the study’s statistical analysis plan.