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 A Fabry Disease Gene Therapy Study (NCT04040049), a na phase 1, phase 2 study. The primary outcome is Frequency of Treatment-emergent Adverse Events (AEs).
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04040049 |
| Phase | Phase 1, Phase 2 |
| Condition | Fabry Disease, Lysosomal Storage Diseases |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 3 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Spur Therapeutics |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned adult male participants with classical Fabry disease. The brief summary describes a multinational study intended to assess FLT190 in up to 15 participants. The registry reports that 3 participants were treated; 8 remaining participants were withdrawn due to screening failure, including one withdrawn due to a protocol violation.
Intervention
FLT190 is described as a recombinant adeno-associated viral vector administered as a single intravenous infusion. The study used ascending doses across cohorts: 0.75 × 1012 vg/kg in Cohort 1 and 1.5 × 1012 vg/kg in Cohort 2. This was a gene therapy intervention, and the record describes one administration rather than a repeated dosing schedule.
Comparator
There was no randomized comparator. The registry describes a baseline-controlled, non-randomized, open-label, single-group study, while the two dose cohorts received different FLT190 doses. These cohorts are not a like-for-like control comparison. Details of any formal comparison with baseline are not reported in the registry record.
Primary question
The primary endpoint asks how many participants experienced treatment-emergent adverse events from screening to W38. It is a safety-focused count, not an efficacy endpoint. Although the record includes serious adverse-event information, it does not report a numerical result for the primary endpoint or an analysis of treatment benefit.
3. Trial Design
The trial is registered as a Phase 1/2 study of FLT190 in Fabry disease. Its official title describes a baseline-controlled, non-randomized, open-label, single-ascending-dose design. The allocation field is recorded as NA, the masking as none, and the model as single group. These features mean the study does not provide a randomized comparison between FLT190 and a control treatment. The dose cohorts are descriptions of exposure to different FLT190 doses, not independent control arms.
The intervention was FLT190, a recombinant adeno-associated viral vector administered by a single intravenous infusion. The record lists 0.75 × 1012 vg/kg for Cohort 1 and 1.5 × 1012 vg/kg for Cohort 2. The primary safety timeframe runs from screening to W38. The registry lists enrollment of 3, while the brief summary describes an intended study of up to 15 adult male participants. The primary outcome description states that 3 participants were treated and that 8 remaining participants were withdrawn due to screening failure; one of those screen failures was withdrawn due to a protocol violation.
The study started on 2019-07-08, its primary completion date is 2023-05-02, and its status is terminated. The reason for termination is not reported in the registry record. Further details about the protocol, cohort assignment procedures, dose-escalation decisions, and the operational meaning of baseline control are not reported in the registry record. These gaps limit how fully the design can be reconstructed from the registry alone.
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: Participants were to undergo screening assessments for up to 18 weeks prior to Day 1 (gene therapy infusion). Treatment-eligible participants reported to the infusion trial site on the day prior to receiving the gene therapy infusion (Day -1).
Overall Study
| Stage | 0.75 × 1012 Vector Genomes (vg)/kg FLT190 (Cohort 1) | 1.5 × 1012 vg/kg FLT190 (Cohort 2) |
|---|---|---|
| STARTED | 2 | 1 |
| COMPLETED | 2 | 1 |
| NOT COMPLETED | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: Three participants were treated, which included: 2 participants treated with 0.75 × 1012 vg/kg (Cohort 1) and 1 participant treated with 1.5 × 1012 vg/kg (Cohort 2). 8 remaining participants were withdrawn due to screening failure. One of the screen failures was withdrawn due to a protocol violation (screening phase was too long) and was subsequently re-screened under a new participant ID, becoming one of the 3 treated participants.
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.
| Characteristic | Unit | FLT190: 0.75 × 1012 vg/kg | FLT190-01: 1.5 × 1012 vg/kg | Total |
|---|---|---|---|---|
| Participants analysed | 2 | 1 | 3 | |
| Age, Continuous | years | 37 (29 to 45) | 46 (46 to 46) | 40 (29 to 46) |
| Sex: Female, Male: Female | Participants | 0 | 0 | 0 |
| Sex: Female, Male: Male | Participants | 2 | 1 | 3 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Asian | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): White | Participants | 2 | 1 | 3 |
| Race (NIH/OMB): More than one race | Participants | 0 | 0 | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: United Kingdom | Participants | 1 | 1 | 2 |
| Region of Enrollment: Germany | Participants | 1 | 0 | 1 |
6. Primary Endpoint
The registry lists the primary outcome as Frequency of Treatment-emergent Adverse Events (AEs), measured over From screening to W38.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is the frequency of treatment-emergent adverse events, expressed as the number of participants with an event. Its timeframe is from screening to W38, and its stated purpose is to investigate the safety of systemic administration of FLT190. This endpoint focuses on whether participants experienced events after entering the study’s observation period. It does not, by itself, establish that an event was caused by FLT190.
Counting participants with events is a straightforward way to describe how many people were affected, rather than how many separate event episodes occurred. That distinction matters because one participant may experience more than one event. The registry’s endpoint description does not give event-level definitions, grading rules, or a threshold for what qualified as an adverse event. Those details are not reported in the registry record.
Safety endpoints are used in early-phase studies to characterize observed harms and inform how exposure is monitored. This is a general explanation of the role of such endpoints, not a claim about a specific decision made in this trial. The posted record does not report a numerical result for the primary endpoint. Serious adverse-event information is listed separately, so it should not be treated as a complete numerical result for all treatment-emergent adverse events.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry identifies treatment-emergent adverse events as the primary endpoint, but does not report a numerical result for that endpoint. As a result, the primary safety outcome cannot be quantified from the registry record. The posted serious adverse-event information gives counts for the two dose cohorts: in the 0.75 × 1012 vg/kg cohort, 1 of 2 participants at risk was reported as affected; in the 1.5 × 1012 vg/kg cohort, 1 of 1 was reported as affected. These are very small cohorts, and the counts should be read as descriptions of the observed participants rather than as stable estimates of event frequency in a broader population.
The record also lists other adverse events and deaths by cohort. For other adverse events, 2 of 2 participants at risk were affected in the 0.75 × 1012 vg/kg cohort, and 1 of 1 in the 1.5 × 1012 vg/kg cohort. The death count is 0 in each cohort. These are posted counts, not evidence that event risk is equal across doses or that either dose caused or prevented an event. The cohorts are not randomized comparison groups, and their sizes do not support reliable between-dose conclusions.
Serious adverse-event terms listed in the record include Transaminase increase, Pyrexia, and Urinary Tract Infection, each reported as 100.0%, and Myocarditis, reported as 50.0%. Those percentages describe the registry’s reported serious-event terms, but the record does not provide enough detail to reconstruct their denominators, timing, recurrence, severity grades, or overlap among participants. A reported term is not, on its own, proof of a causal relationship to treatment.
No statistical analyses are listed in the registry record. There are no reported confidence intervals, formal hypothesis tests, adjusted estimates, or numerical primary-endpoint results. Consequently, the precision of the observed counts cannot be characterized using trial-specific interval estimates. In general, estimates from very small samples are highly uncertain: a small change in the observed count can substantially alter a proportion. This general statistical point reinforces why the posted counts should not be read as precise estimates of population-level risk.
The study’s non-randomized, open-label, single-group structure also limits causal interpretation. Without a randomized control group, differences between cohorts cannot be separated from differences in participant characteristics, follow-up, or other factors. The record describes the study as baseline-controlled, but details of the baseline measures and analyses are not reported in the registry record. The posted data therefore describe events observed in the treated participants; they do not establish comparative safety or efficacy.
9. Statistical Methods Explained
The endpoint is a count of participants who experienced treatment-emergent adverse events during the stated period from screening to W38. This is a binary outcome at the participant level: each participant either has at least one event recorded for the endpoint or does not. The count of participants with an event is different from a count of all event episodes. If a participant experiences multiple events, a participant-level count generally counts that person once for the endpoint, whereas an event-level summary may count each episode. The registry record does not report detailed counting rules or event definitions.
What does a participant count convey?
A count is a direct description of the observed sample. It can be useful for seeing how many people experienced an outcome, but the count alone does not show how precise a population estimate would be. In general, uncertainty around a proportion depends on both the observed proportion and the number of people observed. When the sample is very small, estimates can change substantially with a single participant’s outcome. Confidence intervals are a general way to express this uncertainty: they provide a range of values compatible with the data under stated assumptions. The registry record does not report confidence intervals for the primary endpoint.
The cohort-specific serious-event information is also presented as counts among participants at risk. Those denominators are small: the record lists 2 at risk in the 0.75 × 1012 vg/kg cohort and 1 at risk in the 1.5 × 1012 vg/kg cohort. The corresponding serious-event counts are 1 and 1. These quantities describe what was recorded in those cohorts. They do not supply a precise estimate for a wider population, and the cohort counts do not constitute a controlled dose comparison.
Why does the design affect interpretation?
Random allocation is one way to make groups more comparable, on average, with respect to measured and unmeasured characteristics. This is a general feature of trial design, not a claim that randomization guarantees balance in every study. This trial is recorded as non-randomized, open-label, and single-group, with allocation listed as NA. Participants and investigators were not masked according to the registry. That design can be appropriate for collecting early safety observations, but it offers limited protection against bias in comparisons and event reporting. The registry record does not report a formal statistical comparison between dose cohorts or with an external control group.
The title calls the study baseline-controlled. In general, a baseline-controlled design compares post-treatment measurements with measurements taken before treatment. Such a comparison can describe change over time, but without a control group it cannot distinguish treatment effects from natural variation, changes over time, or other influences. The particular baseline measures, analysis methods, and numerical baseline comparisons are not reported in the registry record. No conclusion about change from baseline can therefore be drawn from the available primary outcome information.
What can be inferred from the listed percentages?
The registry lists serious adverse-event terms with percentages: Transaminase increase, Pyrexia, and Urinary Tract Infection are each reported as 100.0%, while Myocarditis is reported as 50.0%. A percentage is a proportion expressed on a percentage scale, but interpreting it requires knowing its denominator and how events were grouped. The record does not provide sufficient detail to independently reconstruct those percentages or determine whether terms overlapped within participants. They should be read as registry-reported descriptions, not as comparative risks or estimates of treatment-attributable harm.
General statistical practice distinguishes descriptive summaries from inferential analyses. Descriptive summaries report what was observed; inferential methods quantify uncertainty or test a specified hypothesis under assumptions. The registry lists 0 analyses and does not report a formal statistical plan, hypothesis tests, model-based estimates, or confidence intervals. The reason for any absent analysis is not reported in the registry record. No significance claim or adjusted estimate can be derived from the posted counts alone.
How should planning illustrations be understood?
The record describes planning illustrations based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It states that the effect to detect is a stated fraction of the observed effect. In general, such calculations explore how a future study’s sample size might depend on an assumed effect and statistical design. They are not observed trial results, and they are not observed power. The record does not report the numerical effect estimate underlying the illustrations or the numerical planning results in the outcome analysis record.
More generally, power is a design-stage probability of detecting a specified effect under assumptions; it is not a measure of whether a completed study has shown an effect. Planning based on an observed effect can also be unstable when the original estimate comes from a very small sample. These general considerations are relevant to interpreting planning calculations, but they do not establish what sample size this trial required. The trial’s own sample-size justification is not reported in the registry record. No planning illustration can compensate for missing primary-endpoint results or create evidence of a treatment effect.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists one primary outcome measure and no analyses. It does not report a statistical analysis plan describing hypothesis tests, outcome hierarchies, or an approach to multiplicity. Multiplicity arises when multiple outcomes, time points, subgroups, or comparisons are tested; without an analysis plan, it is not possible to determine whether any adjustment was intended or needed for a particular inferential claim. The number and nature of any unreported analyses are not reported in the registry record.
The primary endpoint’s numerical result is not reported. Although the record lists serious and other adverse-event counts, these do not fill in the missing primary endpoint result. It is also not reported whether all treated participants completed observation through W38, how much follow-up was available for each participant, or how incomplete observations were handled. Reasons for missing endpoint data beyond the stated screening failures are not reported in the registry record. No missing-data method or analysis population definition is reported.
The record says that 3 participants were treated and that 8 remaining participants were withdrawn due to screening failure, including one withdrawn due to a protocol violation. This describes screening and treatment status, but does not establish which participants contributed to every posted outcome or whether all planned measurements were collected. The registry does not report an intention-to-treat population, a safety population definition, or a per-protocol population definition. Without those definitions and the endpoint results, the analysis denominator for the primary safety outcome cannot be established from the record.
In general, missing data can affect interpretation when the chance of an observation being absent is related to participants’ characteristics or outcomes. The record does not provide enough information to assess such a mechanism. No assumptions about why data may be absent or how they were handled should be made.
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 |
|---|---|---|---|
| FLT190: 0.75 × 1012 vg/kg | 1 | 2 | 50.0% |
| FLT190:1.5 × 1012 vg/kg | 1 | 1 | 100.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| FLT190: 0.75 × 1012 vg/kg | 0 of 2 |
| FLT190:1.5 × 1012 vg/kg | 0 of 1 |
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 |
|---|---|
| FLT190: 0.75 × 1012 vg/kg | 2 of 2 |
| FLT190:1.5 × 1012 vg/kg | 1 of 1 |
Most frequent serious adverse event terms
| Event term | Organ system | FLT190: 0.75 × 1012 vg/kg | FLT190:1.5 × 1012 vg/kg |
|---|---|---|---|
| Transaminase increase | Investigations | 1 of 2 | 1 of 1 |
| Myocarditis | Cardiac disorders | 1 of 2 | 0 of 1 |
| Pyrexia | General disorders | 0 of 2 | 1 of 1 |
| Urinary Tract Infection | Infections and infestations | 0 of 2 | 1 of 1 |
Most frequent non-serious adverse event terms
| Event term | Organ system | FLT190: 0.75 × 1012 vg/kg | FLT190:1.5 × 1012 vg/kg |
|---|---|---|---|
| Fatigue | General disorders | 2 of 2 | 0 of 1 |
| Transaminase increase | Investigations | 1 of 2 | 1 of 1 |
| Pain in lower extremity | Musculoskeletal and connective tissue disorders | 1 of 2 | 1 of 1 |
| Rhinitis | Infections and infestations | 1 of 2 | 1 of 1 |
| Corneal clouding | Eye disorders | 1 of 2 | 0 of 1 |
| Bloating | Gastrointestinal disorders | 1 of 2 | 0 of 1 |
| Nausea | Gastrointestinal disorders | 1 of 2 | 0 of 1 |
| Diarrhea | Gastrointestinal disorders | 1 of 2 | 0 of 1 |
| Abdominal pain | Gastrointestinal disorders | 1 of 2 | 0 of 1 |
| Heartburn | Gastrointestinal disorders | 1 of 2 | 0 of 1 |
Serious events with the highest arm-level rate: transaminase increase (100.0%), pyrexia (100.0%), urinary tract infection (100.0%), myocarditis (50.0%).
The serious adverse-event counts are reported by dose cohort. For FLT190 at 0.75 × 1012 vg/kg, 1 of 2 participants at risk was affected; for FLT190 at 1.5 × 1012 vg/kg, 1 of 1 was affected. The registry reports 0 deaths in each cohort. These figures describe observed participants, not a comparison with an untreated group. Since allocation was non-randomized and the cohorts are very small, the counts cannot establish that one dose is safer than the other or estimate population-level risk precisely.
The record separately reports that other adverse events affected 2 of 2 participants at risk in the 0.75 × 1012 vg/kg cohort and 1 of 1 in the 1.5 × 1012 vg/kg cohort. Serious-event terms include Transaminase increase, Pyrexia, and Urinary Tract Infection, each listed at 100.0%, and Myocarditis, listed at 50.0%. The registry does not report enough detail to establish the denominators behind each term percentage, whether participants experienced multiple terms, or the timing and severity of each event. The percentages should therefore be read as registry-reported summaries, not as proof of causation. The primary treatment-emergent adverse-event endpoint has no numerical result reported in the registry record.
12. What the Result Does, and Does Not, Mean
The posted record documents a small, open-label study of a single intravenous infusion of FLT190 in adults with classical Fabry disease. It reports that 3 participants were treated in two dose cohorts and provides cohort-level serious and other adverse-event counts. It also lists several serious adverse-event terms and reports 0 deaths in each cohort. These are observations from the participants represented in the record.
The record does not report a numerical result for the primary endpoint, which is the number of participants experiencing treatment-emergent adverse events from screening to W38. Nor does it report statistical analyses, confidence intervals, or a formal comparison between dose cohorts. The available counts therefore do not determine the frequency of the primary endpoint across the treated participants, and they do not provide a precise estimate of safety in a broader population.
The design also does not support a controlled causal conclusion. The trial was non-randomized, open-label, and recorded as single group; the different dose cohorts are not like-for-like randomized controls. The record’s baseline-controlled description does not come with reported baseline results or an analysis of change from baseline. Thus the posted information does not establish that FLT190 caused any listed event, nor does it establish whether the intervention altered disease outcomes.
These limitations do not make the observations meaningless. Descriptive event information can document what was recorded among participants exposed in a study. But the distinction between an observed event, an event judged related to treatment, and a population-level estimate is important. The registry record does not report the details needed to make those distinctions for every listed event. No conclusion about efficacy or comparative safety follows from the posted counts alone.
13. Why This Trial Matters Statistically
This trial illustrates how early-phase, single-group evidence can be informative in a descriptive sense while remaining limited for comparative inference. The registry records a gene therapy intervention, a single-infusion approach, and two ascending-dose cohorts. It also documents that only 3 participants were treated, despite a brief-summary plan describing a study of up to 15 adult male participants. The record states that 8 remaining participants were withdrawn due to screening failure, including one withdrawal due to a protocol violation. Those features are important context for reading any event counts.
Statistically, the central issue is not simply whether events were reported, but what the available denominators and design allow readers to infer. The serious adverse-event counts and listed terms provide descriptive information, while the absence of a primary-endpoint result, analyses, and uncertainty estimates prevents a fuller assessment of the endpoint. Small cohorts also mean that observed counts can be sensitive to the outcome of an individual participant. This is a general property of sparse data, not evidence for a particular unreported result.
The registry also highlights the distinction between dose cohorts and a control group. Different doses can be relevant to dose exploration, but non-randomized cohorts do not isolate the effect of dose. Without reported comparative methods and sufficient data, the counts cannot identify a dose-response relationship. The baseline-controlled label likewise cannot substitute for documented baseline measurements and analysis.
For clinical researchers and biostatisticians, the record underscores the value of clearly reporting endpoint definitions, analysis populations, follow-up completeness, and uncertainty alongside counts. Those details are not reported in the registry record. The study therefore offers a case in which design and reporting limits are central to the statistical interpretation, rather than features that can be resolved by re-reading the observed counts.
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 is the very small treated population: the registry reports 3 participants treated, distributed across the 0.75 × 1012 vg/kg and 1.5 × 1012 vg/kg cohorts. The serious-event denominators are correspondingly small. Counts from cohorts of this size are highly sensitive to individual observations and cannot provide precise estimates of event frequency for a wider population.
The study was non-randomized, open-label, and recorded as a single-group design. The dose cohorts are not randomized controls, so apparent differences between their event counts cannot be attributed to dose. The record calls the study baseline-controlled, but baseline measurements and comparative analyses are not reported in the registry record. There is no reported control group against which to interpret events or disease outcomes.
The primary endpoint result is not reported, and the registry lists no analyses. Definitions and grading criteria for adverse events, relatedness assessments, timing, recurrence, and event-level denominators are not reported in the registry record. Follow-up completeness, missing-data handling, and analysis-population definitions are also not reported. These omissions limit both the reconstruction of the outcome summaries and the assessment of their precision.
The record states that the study was terminated, but the reason for termination is not reported in the registry record. The relationship between termination and the screening failures or safety observations is not reported either. The intended enrollment of up to 15 participants and the reported treatment of 3 should not be treated as evidence about why the study ended. No efficacy result or conclusion about treatment benefit is reported in the posted information.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Fabry Disease Gene Therapy Study — NCT04040049.
- Registry record last updated 2026-09-03; status last verified 2026-08.
- Results first posted 2026-08-06.
- 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
NCT04040049 is a Phase 1/2 study of FLT190 in adult male participants with classical Fabry disease. The registry describes a non-randomized, open-label, baseline-controlled, single-ascending-dose design. FLT190 was administered as a single intravenous infusion, with cohorts listed at 0.75 × 1012 vg/kg and 1.5 × 1012 vg/kg. The primary endpoint is the frequency of treatment-emergent adverse events from screening to W38.
The registry reports 3 participants treated and states that 8 remaining participants were withdrawn due to screening failure, including one withdrawn due to a protocol violation. The trial is listed as terminated; the reason is not reported in the registry record. Serious and other adverse-event counts are listed by cohort, with 0 deaths in each cohort. The primary endpoint’s numerical result and statistical analyses are not reported in the registry record. The non-randomized design and small cohorts limit comparative and population-level interpretation.