Long Term Follow-Up Study of Human Immunodeficiency Virus Type 1 (HIV-1) Positive Patients Who Have Received OZ1 Gene Therapy as Part of a Clinical Trial: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Long Term Follow-Up Study of Human Immunodeficiency Virus Type 1 (HIV-1) Positive Patients Who Have Received OZ1 Gene Therapy as Part of a Clinical Trial (NCT01177059), a na phase 2 study. The primary outcome is Percentage of Participants With Clonal Expansion of Cells With a Predominant OZ1 Insertion Site.

2. Clinical Question

The clinical question concerns long-term follow-up after participants with HIV-1 received gene therapy in an earlier phase 2 trial. The study aimed to monitor potential ill effects and record whether participants developed clonal expansion involving cells with a predominant OZ1 insertion site. It is an observational follow-up study, not a randomized comparison of treatments.

The follow-up schedule called for visits twice yearly until 5 years from initial infusion had elapsed, followed by yearly visits until withdrawal or study completion. That schedule provides the context for the safety surveillance, but it does not establish that every participant completed the same duration of observation. Individual follow-up duration and the handling of missed visits are not reported in the registry record.

3. Trial Design

NCT01177059 is a completed, phase 2, single-group observational follow-up study sponsored by Janssen-Cilag Pty Ltd. The registry lists enrollment as 68 and the condition as HIV-1. The study started on 2004-12-06, and primary completion was recorded as 2017-11-30. Its purpose was long-term follow-up of patients who had received an anti-HIV-1 ribozyme gene therapy product, OZ1, in an earlier phase 2 trial.

The follow-up protocol was designed to monitor and record potential ill effects from the gene therapy product and provide long-term safety information. The planned contact schedule was twice-yearly visits until 5 years from the initial infusion had elapsed, then yearly visits until withdrawal or study completion. The primary endpoint timeframe is described as approximately up to 15 years. These are protocol-level descriptions; the registry record does not report each participant’s actual observation time or visit completion.

The study is classified as observational, with allocation listed as not applicable, masking listed as none, and a single-group model. Thus, the record describes follow-up after prior treatment rather than assignment to study treatments. No concurrent control group is described, and the design does not support a like-for-like treatment comparison. Although the intervention listing names OZ1 transduced cells, the follow-up’s central activity was monitoring people previously infused in the earlier study.

The primary endpoint population is defined as a per-protocol population drawn from the safety population, including participants who received OZ1 or Moloney murine leukemia virus based retroviral vector, LNL6, transduced final cell product in the original OTH/OZ1-INT-1 study. This definition matters when interpreting the endpoint: the registry’s study description focuses on OZ1 recipients, while the stated primary analysis population also refers to participants who received LNL6 product. The numerical primary endpoint result and the number contributing to that endpoint are not reported in the registry record.

Completion status indicates that the registry lists the study as completed. It does not, by itself, show that all planned visits occurred or that all outcomes were available. Details of retention, protocol deviations, and the final analysis set are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: Participants who completed original study (OTH/OZ1-INT-1 \[NCT00074997\]) were enrolled in this long term follow-up (LTFU) study. After unblinding of original study, participants in placebo group were withdrawn from LTFU study, except first participant who received Moloney murine leukemia virus based retroviral vector (LNL6) transduced CD34+ cells.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Per protocol (PP) population set included all participants in the safety population who received OZ1 or Moloney murine leukemia virus based retroviral vector (LNL6) transduced final cell product in the original OTH/OZ1-INT-1 study.

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 baseline (safety) population included all participants who were enrolled in the original OTH/OZ1-INT-1 study and continued participation in the long term follow-up OZ1-HV1-202/OZ1HIV2001 study.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants With Clonal Expansion of Cells With a Predominant OZ1 Insertion Site, measured over Approximately up to 15 years.

The primary endpoint is the percentage of participants with clonal expansion of cells with a predominant OZ1 insertion site. It is a binary percentage outcome: for each participant, the endpoint concerns whether the specified clonal expansion was identified, and the reported summary would express the proportion meeting that definition. The registry record does not give the observed percentage or a confidence interval.

The record defines a predominant integration site as one with a density of at least 50% of the total signal detected by polymerase chain reaction, when the percentage of cells marked by vector was greater than 1% of the test cell population. These thresholds specify how the registry describes the endpoint; they do not reveal how many participants met it. Nor does the record provide assay-level details such as the number of samples tested per participant, the timing of samples, or how results below detection were handled.

Monitoring for clonal expansion is relevant to long-term safety surveillance after gene transfer because it tracks whether cells carrying a particular integration site become prominent in the measured signal. As a general statistical point, a predefined endpoint gives a consistent rule for classifying observations, but the meaning of a percentage still depends on the population measured, the observation period, and completeness of follow-up. Those details determine how directly the reported percentage represents the cohort under surveillance.

The endpoint is not itself a measure of overall clinical benefit or harm. It is a specific laboratory-based safety outcome. The registry record does not report the numerical result, its precision, or a comparison with an untreated or concurrently treated group.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Interpretation starts with the study’s design. NCT01177059 is classified as an observational, single-group follow-up study, and allocation is listed as not applicable. Participants had received gene therapy in an earlier phase 2 trial; the purpose of this registry study was continued follow-up. This structure differs from a randomized trial designed to assign participants to concurrent treatment groups. As a general statistical principle, without a comparable control group, observed events can be described in the followed cohort, but a treatment-attributable difference cannot be estimated directly from the follow-up alone.

What does a percentage endpoint represent?

The primary outcome is a percentage of participants meeting a defined laboratory criterion. A percentage summarizes how often a specified event or classification was observed in an analysis population. Its denominator is the number of participants who were actually assessed and included under the analysis rules, not necessarily the enrollment figure. The registry defines the primary population as a per-protocol set drawn from the safety population and including recipients of OZ1 or LNL6 transduced final cell product in the original study. The endpoint denominator and observed percentage are not reported in the registry record, so neither can be reconstructed from the enrollment figure.

The endpoint’s classification rule uses an integration-site density threshold of at least 50% of the total PCR signal, conditional on the percentage of vector-marked cells being greater than 1% of the test cell population. As a general measurement principle, a threshold makes an outcome operationally defined, but a classification near a cutoff may depend on assay variability and sample handling. The registry record does not describe assay reproducibility, repeated testing, or procedures for borderline or unavailable measurements. It is therefore not possible to assess those features from this record.

Why does the follow-up period matter?

Long-term outcomes depend on how long participants remain under observation and whether follow-up is complete. The protocol describes visits twice yearly until 5 years from initial infusion had elapsed and yearly thereafter until withdrawal or study completion. The primary endpoint timeframe is approximately up to 15 years. In a general time-to-event setting, participants may contribute different amounts of observation when follow-up ends at different times. A simple percentage can be difficult to interpret if observation opportunities differ, particularly when some participants have shorter follow-up. The registry does not report individual observation times or a time-to-event analysis for this endpoint, so the method used to account for unequal follow-up is not reported in the registry record.

A confidence interval, as a general concept, expresses uncertainty around an estimated quantity under a statistical model. It helps distinguish a relatively precise estimate from one that remains compatible with a wider range of values. No confidence interval or numerical estimate for the primary outcome is reported in the registry record. Thus, the precision of that outcome cannot be assessed from the posted information. The absence of an interval is not equivalent to a finding of no uncertainty.

What can safety counts establish?

Safety counts describe how many participants or events were recorded under the registry’s categories. The serious-event entries list 68 at risk and 7 affected, while the other-event entries list 68 at risk and 1 affected; deaths are listed as 0. The registry also lists six serious-event terms at 1.5% each. These figures should be read as descriptive entries, not as a comparison between treatments. The record does not describe attribution to OZ1, event onset, duration, recurrence, or severity beyond the serious-event category. As a general principle, an adverse event occurring during follow-up is not automatically evidence that the intervention caused it.

Over-dispersion is a general statistical issue that arises when observed variation exceeds what a simple model assumes. For a binary outcome, dependence among observations or unmodeled differences in risk can make a basic model’s uncertainty estimates too narrow. This study’s registry record does not describe a model for the primary endpoint, repeated-measure handling, or any adjustment for participant-level clustering. Over-dispersion therefore cannot be evaluated as a feature of the reported analysis; it is a general consideration rather than a documented method used in this study.

How should planning illustrations be understood?

Sample-size planning illustrations use assumptions about the effect to detect, significance level, allocation, and statistical approximation. The assumptions associated with the illustrations specify a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and effects defined as stated fractions of an observed effect. They are explicitly planning illustrations based on an observed effect, not the trial’s own design. They do not establish that the study was powered as planned, and they are not observed power. The record does not report a sample-size justification for the follow-up protocol. The planning calculations should not be interpreted as evidence about the primary endpoint’s result or as a description of the study’s actual single-group design.

Finally, the registry lists three outcome measures and no analyses. It does not describe the statistical model, hypothesis tests, confidence-interval method, interim analyses, or a prespecified statistical plan. These omissions limit the ability to evaluate how outcome data were analyzed and how uncertainty was quantified. They do not justify filling in methods from customary practice: the method used is not reported in the registry record.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Anti-HIV-1 Ribozyme (OZ1) Transduced Cells")
n      <- c(37)
events <- c(0)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Anti-HIV-1 Ribozyme (OZ1) Transduced Cells  37  0  0.0  0.0  9.5  0.0  9.4  0.1  9.3

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists three outcome measures and no analyses. It does not report a multiplicity plan describing whether one outcome was designated as the sole confirmatory endpoint, how other outcomes were treated, or whether any adjustment was planned for multiple comparisons. A multiplicity adjustment is a general statistical approach to controlling the chance of false-positive findings when several hypotheses are tested. Without a reported testing plan and analysis results, there is no basis to determine whether multiplicity was relevant to the reported conclusions or how it was handled.

Missing-data procedures are also not reported in the registry record. The follow-up schedule called for twice-yearly visits until 5 years from initial infusion and yearly visits thereafter until withdrawal or study completion, but the record does not state how missed visits, unavailable assay results, withdrawal, or incomplete follow-up were handled. It also does not give the number of participants contributing to the primary endpoint. Enrollment of 68 is not necessarily the same as the primary analysis denominator.

The primary population is described as the per-protocol population within the safety population, including recipients of OZ1 or LNL6 transduced final cell product in the original study. The registry record does not explain exclusions, deviations, or the specific rules for inclusion in this set. This makes it difficult to determine how closely the analyzed population, if analyzed, would correspond to all enrolled participants.

No interim analyses, statistical analysis plan, or method for handling missing outcomes is reported in the registry record. These gaps do not prove that such procedures were absent; they mean the record does not document them. The posted information therefore does not permit a full assessment of selective reporting, missingness, or analysis-population sensitivity.

12. 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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: rib fracture (1.5%), basal cell carcinoma (1.5%), hodgkin's disease (1.5%), kaposi's sarcoma (1.5%), papillary thyroid cancer (1.5%).

The registry’s safety entries for the OZ1 transduced-cell group list 68 participants at risk for serious adverse events and 7 affected. For other adverse events, the record lists 68 at risk and 1 affected. Deaths are listed as 0. These are descriptive safety figures in the registry; they are not a comparison against a control group.

The serious-event terms listed are Rib Fracture, Basal Cell Carcinoma, Hodgkin's Disease, Kaposi's Sarcoma, Papillary Thyroid Cancer, and Skin Cancer. Each is reported at 1.5%. The registry record does not provide further details about the timing, duration, recurrence, or clinical circumstances of these terms. It also does not report whether the events were judged related to the gene therapy product. Their appearance in a safety listing should not be interpreted as establishing causation.

As a general statistical distinction, the number of affected participants and the number of individual events are not necessarily interchangeable: one participant can experience more than one event. The record does not provide event-level counts that would clarify this distinction for these entries. The listed at-risk figures describe the safety fields, but they do not establish that all participants had equal follow-up duration. The follow-up schedule was long term, and actual observation time by participant is not reported in the registry record.

These entries therefore offer a limited descriptive view of recorded safety outcomes. They do not, on their own, measure comparative risk or establish whether any event was caused by OZ1.

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

The registry record describes a long-term observational safety follow-up of people who had received OZ1 gene therapy in an earlier phase 2 trial. It gives the primary endpoint definition, the intended follow-up schedule, and selected safety counts. It does not report a numerical result for the primary endpoint, so the frequency of clonal expansion under the stated definition cannot be determined from the record.

The endpoint is specific: it concerns clonal expansion of cells with a predominant OZ1 insertion site, defined using PCR signal density and vector-marked-cell thresholds. It is not a general summary of all safety outcomes, and it is not a direct measure of overall health or treatment benefit. The registry’s safety entries provide additional descriptions, including serious and other adverse-event counts, but do not establish whether events were caused by the gene therapy.

The design also sets limits on interpretation. This was a single-group observational follow-up with no concurrent randomized comparator described. Any recorded outcome would describe the followed participants, not the difference between assigned treatments. Because individual follow-up duration, the primary endpoint denominator, and missing-data handling are not reported, the completeness and precision of long-term outcome estimates cannot be assessed from the registry record.

The planned surveillance period extended to approximately up to 15 years, with visits scheduled twice yearly until 5 years from initial infusion had elapsed and yearly thereafter until withdrawal or study completion. This indicates the intended scope of monitoring, not that every participant was observed for the full period. Completion status does not resolve that distinction.

Accordingly, the record supports understanding what the study set out to monitor and how its primary endpoint was defined. It does not support a numerical conclusion about that endpoint, a causal claim about the intervention, or a comparative claim against another treatment. Those conclusions would require results and analysis details that are not reported in the registry record.

14. Why This Trial Matters Statistically

This study is statistically notable because it addresses follow-up after a gene therapy intervention over an extended period. Long-term surveillance raises questions that differ from those in a short-term efficacy comparison: how outcomes are defined, how long participants are observed, how incomplete follow-up is handled, and whether safety events can be attributed to the intervention. The registry describes the intended schedule and a specific clonal-expansion endpoint, making those issues visible even though it does not report the endpoint result.

The primary outcome definition illustrates how laboratory measurements become a participant-level classification. A predominant integration site is defined through a threshold based on PCR signal and the percentage of vector-marked cells. Clear operational criteria can support consistent classification, but interpretation also depends on assay procedures, repeat testing, and missing measurements. Those details are not reported in the registry record.

The single-group observational design is another important statistical feature. It can describe recorded outcomes among people followed after prior treatment, but it does not provide a randomized concurrent comparison. This distinction prevents descriptive safety counts from being mistaken for a treatment effect. It also makes clear why the adverse-event figures and primary endpoint should be read as cohort observations rather than evidence of comparative risk.

Finally, the record demonstrates the difference between a study’s planned surveillance and its reported evidence. A long intended observation horizon does not by itself show that each participant completed that follow-up, and a completed study status does not supply a missing endpoint estimate. Reporting the analysis denominator, individual follow-up, uncertainty intervals, and missing-data approach would help readers assess how representative and precise any estimate is. Those details are not reported in the registry record, so statistical interpretation remains constrained.

15. 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 central limitation is that the registry record does not report the numerical primary endpoint result. It therefore provides no estimate of the percentage meeting the clonal-expansion definition and no measure of its precision. The definition is detailed, but the result and endpoint denominator are not.

The study is single group and observational, with allocation listed as not applicable. No concurrent comparator is described. As a result, the record cannot support a randomized comparison or distinguish outcomes associated with the prior gene therapy from other explanations. The safety entries are descriptive and do not include an attribution assessment.

The primary population includes participants who received OZ1 or LNL6 transduced final cell product in the original study. The enrollment figure is 68, but the number included in the primary endpoint analysis is not reported. The record does not explain the inclusion and exclusion rules in more detail or report how many participants completed the planned follow-up.

Although visits were planned twice yearly until 5 years from initial infusion and yearly thereafter until withdrawal or study completion, actual follow-up duration by participant is not reported. Nor are missing-data procedures, assay handling for unavailable results, or any time-to-event method documented. These omissions limit assessment of how incomplete or unequal observation may affect the endpoint.

The record lists three outcome measures and no analyses. It does not report a statistical analysis plan, inferential methods, confidence intervals, interim analyses, or multiplicity procedures. The serious-event terms and counts likewise lack event-level context, timing, and stated attribution. These are limitations of what the registry record documents; they should not be taken to prove that the underlying study did not collect or analyze such information.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Long Term Follow-Up Study of Human Immunodeficiency Virus Type 1 (HIV-1) Positive Patients Who Have Received OZ1 Gene Therapy as Part of a Clinical Trial — NCT01177059.
• Registry record last updated 2018-12-12; status last verified 2018-11.
• Results first posted 2018-12-12.
• 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.

19. Record Summary

NCT01177059 is a completed phase 2 observational study of long-term follow-up after prior OZ1 gene therapy in participants with HIV-1. It is listed as a single-group study with allocation not applicable and no masking. Enrollment is 68; the study started on 2004-12-06, and primary completion was 2017-11-30.

The protocol describes safety monitoring, visits twice yearly until 5 years from initial infusion and yearly thereafter until withdrawal or study completion. The primary endpoint is the percentage of participants with clonal expansion of cells with a predominant OZ1 insertion site, with a timeframe of approximately up to 15 years. The record does not report its numerical result or analysis denominator.

Safety entries list 7 affected among 68 at risk for serious adverse events, 1 affected among 68 at risk for other adverse events, and 0 deaths. The primary analysis population is described as the per-protocol population within the safety population who received OZ1 or LNL6 transduced final cell product in the original study. The registry lists three outcome measures and no analyses; missing-data and statistical-analysis methods are not reported in the registry record.