Investigation of the Safety and Feasibility of AAV1/SERCA2a Gene Transfer in Patients With Chronic Heart Failure: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Investigation of the Safety and Feasibility of AAV1/SERCA2a Gene Transfer in Patients With Chronic Heart Failure (NCT00534703), a randomized phase 2 study. The primary outcome is Overall Safety and Feasibility of Administering AAV1/SERCA2a to LVAD Patients.

2. Clinical Question

The clinical question combines an early safety assessment with feasibility: whether the intervention could be administered and evaluated in this LVAD population, and what safety events were recorded. The record identifies a randomized, parallel-group study and lists AAV1/SERCA2a and placebo as the interventions. It does not give enough outcome data to estimate a comparative effect or to determine how the planned NAb+ and NAb- comparisons were carried out.

Several secondary outcomes concern biological or cardiac measurements, including myocardial detection of the viral vector genome by qPCR, left ventricular ejection fraction, SERCA2a and other protein levels, and isolated-myocyte function. These outcomes describe proposed measurements, not reported findings. The registry lists 5 secondary outcomes, but does not provide analysis results for them.

3. Trial Design

The registry classifies the study as Phase 2, randomized, quadruple-masked, and parallel-group. It lists AAV1/SERCA2a and placebo as the two interventions. The AAV1/SERCA2a arm is described as SERCA gene therapy, while placebo is described as saline solution. The record does not report the method of random sequence generation, allocation concealment, or which roles were masked.

The intended study population was patients with chronic heart failure who had received a left ventricular assist device. The stated aim was to evaluate safety and feasibility of administering AAV1-CMV-SERCA2a in that setting. The primary outcome was defined over 6 months and was to include death, major adverse cardiovascular events, and out-of-range laboratory values. Its description refers to comparisons of both AAV1/SERCA2a-treated cohorts, NAb+ and NAb-, with placebo. The record does not report how participants were assigned to those cohorts or provide separate cohort-level outcome data.

Enrollment was 5, and the registry states that the trial was terminated early. The recorded start was 2014-07 and primary completion was 2015-09; the study status is terminated. The registry explicitly connects early termination and the small enrollment with the inability to perform full statistical analysis of primary and secondary outcomes. Instead, results were presented descriptively.

The record does not report a target enrollment, a rationale for the planned sample size, detailed eligibility criteria, treatment dose, administration procedures, or follow-up procedures beyond the primary outcome timeframe. It also does not report the reasons for termination. These absences limit assessment of how closely conduct matched the original design and how broadly findings might apply. The design labels establish the broad structure of the study, but do not reveal operational details needed to assess randomization or masking in practice.

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.

Overall Study

Analysis population for the primary outcome, as defined in the registry: The trial was terminated early with only 5 subjects enrolled. As a result full statistical analysis for both primary and secondary outcomes was impossible and results have been presented taking a descriptive approach instead

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.

6. Primary Endpoint

The registry lists the primary outcome as Overall Safety and Feasibility of Administering AAV1/SERCA2a to LVAD Patients, measured over 6 months.

The primary endpoint is titled overall safety and feasibility of administering AAV1/SERCA2a to LVAD patients. It is measured as a count of participants, with a timeframe of 6 months. The registry defines safety through the incidence of death, major adverse cardiovascular events, and out-of-range laboratory values. The endpoint description says both AAV1/SERCA2a-treated cohorts, NAb+ and NAb-, would be compared with placebo.

A combined safety endpoint can capture different kinds of potential harm within a defined observation period. General explanation: describing the number of participants affected can make clear how many people experienced an event, while specifying the event categories defines what is being counted. The interpretation still depends on knowing how each event was defined, collected, and attributed. Those detailed operational definitions are not reported in the registry record.

The endpoint title also includes feasibility, but the registry does not give a separate numerical feasibility measure. It does not report a primary-outcome estimate, a confidence interval, or an inferential test. The record says early termination and enrollment of only 5 subjects made full statistical analysis impossible, and that the results were presented descriptively. Thus, the stated endpoint identifies the intended assessment; it does not furnish a comparative estimate of safety or feasibility.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry provides limited information about statistical methods. It identifies the primary endpoint as a count of participants, describes early termination and a descriptive approach, and records no outcome analyses. It does not report a detailed statistical analysis plan, an inferential method for the primary endpoint, an adjustment strategy, or the handling of missing observations. The methods below explain general statistical concepts relevant to reading such a record; they are not claims about methods actually used in this trial.

What does a count endpoint represent?

The primary outcome is expressed as participants experiencing specified safety events. A participant count is a descriptive quantity: it records how many people met an endpoint definition. For a comparative analysis, the count needs to be interpreted alongside the number of participants assessed in each group and the rules defining eligibility for the endpoint. The record gives some group sizes for adverse-event reporting, but no primary-outcome values that can be analyzed. It also does not state whether the primary endpoint was treated as a composite, whether participants could meet more than one component, or how repeated events were handled.

General explanation: binary outcomes distinguish whether an event occurred for a participant. A comparison may be expressed in different ways, such as a difference between group event proportions or a relative measure, but each requires clearly defined data and assumptions. No such comparative estimate is reported for this primary endpoint. No new comparison should be reconstructed from the sparse counts because those counts are not reported as the primary endpoint and the endpoint's full coding rules are unavailable.

Why does a confidence interval matter?

General explanation: a confidence interval describes the range of effect estimates reasonably compatible with the data and the statistical method, under its assumptions. It conveys precision as well as direction and magnitude. A narrow interval generally indicates greater precision than a wide interval, while an interval spanning effects in different directions can leave the interpretation uncertain. The registry record does not report a confidence interval for the primary endpoint. With no reported estimate and no interval, the uncertainty around a treatment comparison cannot be quantified from this record.

Small groups commonly yield imprecise estimates, especially when outcomes are uncommon. General explanation: each observed event can have substantial influence when few participants are assessed, and estimates may be unstable. This is relevant to interpreting the adverse-event counts in a study with enrollment of 5, but it does not justify calculating or inferring a comparative effect. Unequal group sizes also mean that raw counts alone do not provide a fair comparison. Even when denominators are stated, estimates based on very small groups remain highly uncertain.

What does randomization contribute?

General explanation: random assignment aims to make treatment groups comparable, on average, with respect to measured and unmeasured factors. That benefit depends on how randomization was implemented and on preserving the assigned groups in analysis. The record labels the study randomized, but does not report sequence generation, allocation concealment, or a participant flow account. It is therefore possible to describe the design classification, but not to assess these implementation details. Randomization also cannot overcome the severe limits on precision created by the recorded enrollment.

The registry also labels the study quadruple-masked. General explanation: masking can reduce the influence of expectations on care, outcome assessment, or reporting, depending on who is masked and how. The record does not identify the masked roles or report whether masking was maintained. The label should therefore not be expanded into a claim about specific staff, participants, or assessors.

What does descriptive analysis tell the reader?

General explanation: descriptive statistics present observed data without using a statistical test to claim that a group difference is unlikely to be due to chance. Counts can be useful for documenting events and identifying what was recorded. They do not, by themselves, establish a causal relationship or show that groups differ reliably. The registry says a descriptive approach was used because early termination and enrollment of only 5 subjects made full statistical analysis impossible. This is consistent with treating the posted event counts as observations rather than confirmatory evidence.

A p-value, if reported, would address compatibility between data and a specified statistical model under a null hypothesis; it would not measure the probability that a treatment is effective or the probability that a result is true. No p-value or inferential test for the primary comparison is reported. Nor does the record report an adjusted analysis or a model for the planned NAb+ and NAb- comparisons. There is no basis for assuming that an unreported model or adjustment was performed.

How should planning illustrations be understood?

The registry describes sample-size assumptions used for planning illustrations: a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and effects set as stated fractions of the observed effect. For time-to-event illustrations, the stated output is the total number of events; for other outcomes, it is participants per arm. These are planning illustrations computed from the observed effect, not the study's own design.

General explanation: a sample-size calculation asks how much information a future study might need under stated assumptions, including a target effect and a chosen statistical threshold. Its output is not evidence that an earlier study had a particular chance of detecting an effect. In particular, an observed-effect-based illustration can be sensitive to an unstable observed estimate. The record does not report a sample-size justification for this trial, and the planning illustrations must not be described as observed power.

The registry does not report the underlying observed primary effect needed to interpret such illustrations as a direct result of this trial. It also does not report a complete statistical plan, prespecified decision rules, or the details required to reproduce an analysis. Accordingly, statistical interpretation should remain close to the descriptive information and explicit limitations in the record.

10. Multiplicity, Missing Data and Analysis Populations

The record lists 5 secondary outcomes in addition to the primary safety and feasibility outcome. These include viral-vector genome detection in myocardium, left ventricular function, SERCA2a and other protein levels, and isolated-myocyte function. No secondary analyses are reported. The record does not describe a prespecified hierarchy of outcomes, a strategy for controlling multiplicity, or whether any outcome was intended to be exploratory.

General explanation: when researchers examine multiple outcomes or multiple comparisons, the chance of finding an apparently notable result by chance can increase. Procedures for multiplicity can help control that risk, but the appropriate approach depends on the study's aims and analysis plan. Since the registry does not report such a plan or inferential results, it is not possible to determine whether multiplicity was addressed.

Missing-data procedures are also not reported. The registry notes that values were missing or not estimable for a two-arm comparison of the binary endpoint, but does not explain which observations were unavailable, why they were unavailable, or how missingness was handled. It gives no imputation method, sensitivity analysis, or outcome-specific completeness information. The reason for termination is not reported.

The record does not identify the analysis population, such as whether analyses were intended to follow assigned groups or include only participants meeting particular criteria. It does not give a participant flow account, treatment adherence information, or details of withdrawals. These omissions prevent assessment of exclusions and of how the enrolled participants contributed to each outcome. In view of early termination and the descriptive presentation, these missing details further restrict both comparison and reproducibility.

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

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: lvad alarm (25.0%), worsening heart failure (25.0%), heart transplantation (25.0%), death (25.0%).

The registry reports serious adverse events for 2 participants in the AAV1/SERCA2A group, with 4 participants at risk, and for 0 participants in the placebo group, with 1 participant at risk. Other adverse events were reported for 4 participants in the AAV1/SERCA2A group, with 4 at risk, and for 1 participant in the placebo group, with 1 at risk. The record also reports 1 death in the AAV1/SERCA2A group and 0 in placebo.

These figures are descriptive counts from groups of very different size. They do not provide a precise comparative estimate, and they cannot establish whether the intervention caused an event. The registry does not report detailed event definitions, adjudication procedures, timing for each event, or whether multiple event categories could apply to a participant. It is therefore important not to treat the counts as if they were a complete causal assessment.

The serious-event terms listed are LVAD Alarm, Worsening heart failure, Heart transplantation, and Death, each reported as 25.0%. The record does not explain the denominator or the calculation behind these values. They should be read as reported term summaries, not as comparable group-specific risks. In such a small, prematurely terminated study, the counts can describe what was recorded but cannot support a stable estimate of relative safety.

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

This record documents an early-phase study designed to examine the safety and feasibility of AAV1/SERCA2a administration in patients with chronic heart failure who had received an LVAD. It gives the broad randomized, quadruple-masked, parallel-group design, identifies placebo as the comparator, and specifies a 6-month primary outcome timeframe. It also reports some adverse-event counts and lists planned secondary measures.

What the record does not provide is a statistically analyzable comparison of the primary endpoint. The registry explicitly states that early termination after enrollment of 5 subjects made full analysis of primary and secondary outcomes impossible. No primary effect estimate, confidence interval, or p-value is reported. The descriptive counts cannot establish a treatment effect, determine whether group differences are meaningful, or show that an event was caused by treatment.

The listed secondary outcome areas do not constitute findings. Without measurement values and analysis results, the record cannot establish whether myocardial viral-vector genomes were detected, whether cardiac function changed, or whether protein or myocyte measures differed. The outcome descriptions show what the study planned to assess, not what those assessments found.

Nor does the registry establish the reasons for early termination, the completeness of follow-up, or the generalizability of observations to other patients. Statistical planning illustrations, if consulted, describe hypothetical planning under stated assumptions rather than observed power or confirmatory evidence from this trial. The appropriate interpretation is narrow: the record offers limited descriptive safety information from a small trial and does not support a precise comparative conclusion about safety or feasibility.

13. Why This Trial Matters Statistically

This trial illustrates a recurring statistical distinction between a study's question and the evidence its completed record can answer. The stated question was comparative: safety and feasibility of AAV1/SERCA2a relative to placebo, including comparisons of NAb+ and NAb- treated cohorts with placebo. Yet early termination and enrollment of 5 subjects prevented full statistical analysis, according to the registry. A prespecified or clinically relevant question does not guarantee that the observed data will be sufficient to estimate an answer precisely.

It also shows why event counts require context. Serious and other adverse-event counts are important descriptive information, but the group sizes are markedly unequal and small. A reader cannot turn those counts into a dependable treatment comparison without outcome definitions, a suitable analysis, and uncertainty estimates. Terms summarized as percentages likewise need a clear denominator and method before they can be interpreted as risks.

The study is also a useful reminder that planned outcomes and observed results are different kinds of information. The secondary outcome list describes biological and functional measurements that were of interest. In the absence of reported analyses, it does not establish results for those measures. The registry's explanation of descriptive reporting is therefore central to interpreting the record.

Finally, planning illustrations should not be mistaken for evidence about the trial's ability to find an effect. They depend on assumptions and are presented separately from a trial's actual design and observed analysis. This distinction matters when a study is too small or incomplete for confirmatory analysis: prospective planning can inform future research, but it cannot replace missing comparative evidence in the existing record.

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 main limitation is early termination after enrollment of 5 subjects, which the registry identifies as the reason full statistical analysis of primary and secondary outcomes was impossible. The resulting descriptive presentation leaves no reported primary comparison or uncertainty interval. The record does not give the reason for termination, so its implications for recruitment, conduct, or follow-up cannot be assessed.

Group sizes were highly unequal: the registry lists 4 participants in the AAV1/SERCA2A arm and 1 in placebo. Such limited information makes event counts especially unstable and reduces the usefulness of between-group comparisons. The record does not provide a separate outcome summary for the NAb+ and NAb- cohorts, despite naming both in the primary-outcome description.

Several details needed to evaluate the data are not reported in the registry record: participant flow, baseline characteristics, missing-data handling, analysis populations, endpoint coding rules, and the statistical analysis plan. It is not possible to assess comparability of groups at baseline, completeness of outcome collection, or whether the reported event categories were applied consistently. The record does not describe who was masked or how randomization was implemented.

The safety reporting is limited by the absence of detailed event definitions and denominator explanations for the listed serious-event terms. The registry does not report enough information to determine whether events overlapped or how event timing was handled. Secondary outcomes are listed, but results and analysis estimates are not reported. Together, these limitations mean the record supports only a cautious descriptive reading and cannot support broad conclusions about comparative safety, feasibility, or biological effects.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Investigation of the Safety and Feasibility of AAV1/SERCA2a Gene Transfer in Patients With Chronic Heart Failure — NCT00534703.
• Registry record last updated 2023-02-08; status last verified 2023-01.
• Results first posted 2020-02-25.
• 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 describes a Phase 2 randomized, quadruple-masked, parallel-group study of AAV1/SERCA2a versus placebo in patients with chronic heart failure who had received an LVAD. The primary outcome concerned overall safety and feasibility over 6 months, with safety defined by death, major adverse cardiovascular events, and out-of-range laboratory values.

The study was terminated early after enrollment of 5 subjects. The registry states that full statistical analysis was impossible and that results were presented descriptively. It reports adverse-event counts but no analyzable primary comparison, and it lists 5 secondary outcomes without reporting their analyses. The record therefore documents the trial's design and limited observations, but does not provide a precise comparative estimate of safety or feasibility.