An Long-term Follow-up Trial of Kidney Tx Patients Treated With Imlifidase or PE After an AMR: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for An Long-term Follow-up Trial of Kidney Tx Patients Treated With Imlifidase or PE After an AMR (NCT04711850), a registered phase not stated study. The primary outcome is Overall Graft Survival at Year 3.

2. Clinical Question

This is a follow-up question about outcomes observed after prior treatment, rather than a direct randomized test of imlifidase against PE. Because allocation to the earlier treatment groups is not stated and the registry cautions against treating the arms as comparable controls, differences between groups would not by themselves establish that the earlier treatment caused an outcome. The stated aim was to collect information on long-term outcomes, including graft and patient survival, kidney function, treatment of rebound donor specific antibodies (DSA), and anti-drug antibodies (ADAs).

3. Trial Design

This was a prospective, observational long-term follow-up study of kidney transplant recipients who had received imlifidase or plasma exchange for active or chronic active antibody-mediated rejection (AMR) in feeder Study 16-HMedIdeS-12. No treatment was given in the follow-up study. The two groups therefore refer to treatment received in the feeder study, not to treatments assigned as part of this follow-up.

The stated purpose was to collect data during an extended follow-up period of 3 years. Listed outcomes include graft survival, patient survival, kidney function measured using eGFR and S/P-creatinine, presumed or biopsy-proven AMR episodes, other presumed or biopsy-proven rejection episodes, and DSA levels. The primary outcome was overall graft survival at Year 3, measured as the number of participants with a functioning graft at that timepoint.

The registry lists enrollment of 18 and a status of TERMINATED. It gives a start date of 2021-01-20 and a primary completion date of 2023-03-30. The record specifically says that premature termination meant 7 patients in the imlifidase group and 6 patients in the PE group had no graft-survival data for the 3-year timepoint. The Year 3 outcome counts for those with data are not reported in the registry record.

Allocation to the earlier treatment groups is not stated. The registry cautions that this is not a randomized comparison and that the arms are not a like-for-like control comparison. The record does not report additional details about the feeder study’s allocation process, eligibility criteria, recruitment procedures, or analysis populations. Those details should not be inferred from the group labels or the follow-up design.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Due to the premature termination of the trial, 7 patients in the Imlifidase treatment group and 6 patients in the Plasma exchange treatment group had no graft survival data for the 3 year timepoint

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 Graft Survival at Year 3, measured over 3 years after start of AMR treatment in feeder study (16-HMedIdeS-12).

The primary endpoint is overall graft survival at Year 3, expressed as the number of participants with a functioning graft. The timeframe is 3 years after the start of AMR treatment in feeder Study 16-HMedIdeS-12. Graft survival is defined from that treatment start to graft loss. The registry defines graft loss as permanent return to dialysis for at least 6 weeks, re-transplantation, or nephrectomy.

This endpoint is used to describe whether the transplanted kidney remained functioning over the stated follow-up period. Counting participants with a functioning graft is a direct summary at the specified timepoint; it is not, by itself, a time-to-event comparison or an adjusted estimate of the effect of treatment. The registry record does not state a statistical method for handling the timing of graft loss or censoring.

Interpretation is constrained by the record’s statement that 7 participants in the imlifidase group and 6 in the PE group had no graft-survival data for the 3-year timepoint because of premature termination. The number with a functioning graft among those with available data is not reported in the registry record. Without those outcome counts and a clear account of how missing observations were handled, the endpoint cannot be used to quantify the observed Year 3 graft status or compare groups.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a prospective, observational follow-up study. Prospective follow-up generally means that outcomes are collected after the study begins according to a defined follow-up plan. Observational means that the follow-up study does not assign the treatment being evaluated. In this record, participants had received imlifidase or PE in feeder Study 16-HMedIdeS-12, and no treatment was given in the long-term follow-up. These features make the study useful for describing subsequent outcomes, but they do not create a randomized treatment comparison.

What does the primary endpoint count?

The primary endpoint is the number of participants with a functioning graft at Year 3. It is a count at a specified timepoint. The record defines graft survival as time from the start of AMR treatment in the feeder study to graft loss, and defines graft loss as permanent return to dialysis for at least 6 weeks, re-transplantation, or nephrectomy. A timepoint count and a full time-to-event analysis are not interchangeable. In general, time-to-event methods use both event timing and follow-up information, while a count at a fixed timepoint summarizes status at that time. The registry record does not report which statistical method, if any, was used to analyze time to graft loss.

Why does the observational design matter?

In a randomized comparison, allocation by chance is intended to make treatment groups comparable on average, including for measured and unmeasured characteristics. This record does not state how allocation to imlifidase or PE occurred in the feeder study, and warns that the arms are not a like-for-like control comparison. In general, differences in observational group outcomes may reflect differences in participant characteristics, clinical circumstances, or other factors, as well as any treatment differences. Statistical adjustment can sometimes address measured factors, but cannot automatically resolve unmeasured differences. The record does not report adjusted estimates or the variables that might have been used for adjustment.

How should missing outcomes be understood?

The registry attributes missing Year 3 graft-survival data for 7 imlifidase-group patients and 6 PE-group patients to premature termination. A missing outcome is not itself an event and does not identify the participant’s graft status. In general, missing data can affect interpretation when the probability of having an observed outcome is related to the outcome itself or to participant characteristics. Complete-case summaries describe only participants with observed data and can be unrepresentative if missingness is related to outcome. Other approaches make assumptions about the unobserved outcomes; those assumptions and any method for handling missing data are not reported in the registry record.

The registry gives no Year 3 graft counts, so it is not possible to assess the balance of observed outcomes across groups or to evaluate the consequences of missing data from the endpoint results. The reasons and timing of missingness beyond the statement about premature termination are not reported in the registry record. It also does not state whether other outcomes had missing observations or whether different outcome-specific populations were used.

What can the listed analyses establish?

The record lists 0 analyses. It therefore contains no reported statistical comparison to interpret for the outcomes described. There are no reported estimates of treatment-group differences, standard errors, confidence intervals, or p-values. In general, an estimate describes the direction and size of a measured contrast, while an interval estimate also expresses uncertainty under a statistical model. A p-value assesses compatibility between data and a specified null model, given the analysis assumptions; it does not measure clinical importance or prove a causal effect. None of these quantities can be inferred from the outcome names or from the study’s enrollment.

Multiple outcome measures are listed, including survival, kidney function, rejection episodes, and DSA levels. When several outcomes or comparisons are tested, the chance of finding at least one apparently notable result can increase. In general, a prespecified multiplicity strategy can control or describe that issue. The registry record does not report such a strategy, an analysis hierarchy beyond identifying the primary outcome, or whether any interim analyses were planned or conducted.

What do the planning assumptions mean?

The record describes a sample-size planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. For time-to-event outcomes, the planning illustration uses the total number of events; for other outcomes, it expresses participants per arm. These are planning illustrations, not observed power or evidence that the study achieved a particular level of power. The numerical illustrations and the effect fractions are not reported in the registry record. The trial’s own sample-size justification is not reported in the registry record.

In general, power calculations depend on assumptions about the outcome, the effect size to detect, the analysis method, and the data available. A calculation using an observed effect is especially dependent on that estimate and should not be read as proof that an analysis was adequately powered. Missing outcome data can also reduce the information available for analysis. Since the record does not provide the underlying endpoint results or a complete statistical plan, the planning assumptions cannot be used to infer the precision of an actual treatment comparison.

What role do dispersion and uncertainty measures play?

The primary endpoint is a count of participants, and no dispersion estimate is reported for it. More generally, measures of variability describe how spread out participant-level observations are, while confidence intervals describe uncertainty around an estimated quantity under a model. For count outcomes, the distribution may be more variable than a simple model assumes; in general, over-dispersion means that observed variability exceeds the model’s expected variability and can make standard errors too small if it is ignored. The registry record does not report a model, dispersion assessment, or uncertainty estimate for the primary endpoint.

Because no analyses are listed and no numerical graft-survival result is reported, the relevant statistical conclusion is limited: the registry describes what was intended to be measured, but does not present the result or its precision. This limitation is distinct from whether the study collected other clinical information, and it prevents an assessment of the statistical evidence for a group difference.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 10 outcome measures, including the Year 3 primary graft-survival endpoint and secondary outcomes involving earlier graft-survival timepoints, patient survival, kidney function, rejection episodes, and DSA levels. It does not report a multiplicity adjustment, a hierarchy for testing secondary outcomes, or whether outcomes were analyzed as confirmatory or descriptive. When many outcomes are examined, general statistical practice recognizes that the chance of at least one apparently unusual result can rise. The record does not provide enough analysis detail to determine how that concern was handled.

The record lists 0 analyses. It does not report outcome estimates, p-values, confidence intervals, adjusted comparisons, or an analysis plan. The intended analysis populations, including definitions of who was included in each outcome analysis, are not reported in the registry record. Nor are interim analyses, protocol deviations, or the treatment of participants who discontinued follow-up reported.

For the primary endpoint, the record states that premature termination left 7 participants in the imlifidase group and 6 participants in the PE group without graft-survival data at the 3-year timepoint. The Year 3 graft status for these participants is not reported. The record does not state how missing data were handled, whether any sensitivity analysis was conducted, or whether missingness affected other outcomes. In general, missing observations can complicate estimates when their absence is related to participant outcome or characteristics; the record does not describe the assumptions used to address this possibility.

Accordingly, the extent of missing information is clear for the primary timepoint, but its statistical handling and impact cannot be assessed from the registry record. The actual endpoint counts and any analysis results are not reported in the registry record.

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 0% reporting threshold.

The adverse-event summary lists 11 participants at risk in the imlifidase group and 7 in the PE group. In those groups, the registry records 0 participants with serious events and 0 with other events, and 0 deaths in each group. These are counts as recorded for the listed at-risk groups; they are not estimates of comparative safety.

A recorded count of zero means that no affected participants are listed in that summary. It does not establish that an event is impossible, or that none occurred outside the population, observation period, or definitions represented in the registry. The record does not report the adverse-event definitions, the duration of safety observation, or the criteria used to decide that a participant was at risk. The listed at-risk groups should therefore be kept distinct from the overall enrollment of 18.

The record lists no top serious-event terms. It does not provide event-level descriptions or comparative statistical analyses. In general, adverse-event counts are most informative when read alongside the number and characteristics of participants observed, the length of observation, event definitions, and completeness of follow-up. Those details are not reported in the registry record, so the counts should be interpreted narrowly as the posted summaries rather than as a complete account of safety during all study follow-up.

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

The record documents an observational effort to follow kidney transplant recipients after AMR treatment in a feeder study. It identifies a primary question about graft status at Year 3 and lists other outcomes relevant to longer-term follow-up, including patient survival, kidney function, rejection episodes, and DSA levels. The design can describe outcomes collected during follow-up, but the registry record does not report the Year 3 graft counts or analyses needed to quantify those outcomes.

The record also says that 7 patients in the imlifidase group and 6 in the PE group had no graft-survival data at Year 3 because the trial was terminated prematurely. This missingness limits what can be learned about the stated primary endpoint. Missing data do not indicate graft loss or a functioning graft, and the record does not report how the missing outcomes were handled.

The study should not be interpreted as a randomized comparison of imlifidase and PE. The registry does not state the allocation process and cautions that the arms are not a like-for-like control comparison. In general, an observed difference between groups in an observational follow-up could arise from factors beyond the earlier treatment. The registry record does not give adjusted estimates that could help address measured group differences, and adjustment alone would not resolve unmeasured confounding.

The adverse-event summary records zero affected participants and zero deaths in each listed group, with the stated at-risk counts. These counts do not establish a general absence of safety events beyond the scope of the registry summary. The observation period and event definitions are not reported in the registry record.

Thus, the record establishes the study’s purpose, its follow-up structure, the outcomes it lists, and an important limitation caused by premature termination. It does not establish a numerical level of Year 3 graft survival, a treatment effect, the precision of a group contrast, or a complete safety profile. Those conclusions require outcome results and analysis details that are not reported in the registry record.

13. Why This Trial Matters Statistically

Long-term follow-up is statistically distinct from measuring an outcome soon after treatment. Graft survival, patient survival, kidney function, rejection episodes, and antibody levels can describe different aspects of the course after AMR treatment. Following participants over time can therefore add information about outcomes beyond the initial treatment episode. The stated follow-up period in this record was 3 years, and graft survival at Year 3 was identified as the primary outcome.

The statistical value of follow-up depends not only on the outcome chosen but also on whether outcomes are observed and reported. The record’s statement that 7 patients in the imlifidase group and 6 in the PE group lacked Year 3 graft-survival data makes missingness especially relevant. Without the observed counts and an account of missing-data handling, readers cannot tell what the Year 3 endpoint showed or how much uncertainty surrounds it.

The record also illustrates why the design matters when interpreting comparisons. The groups are based on treatments received in a feeder study, and the registry cautions that they are not a like-for-like control comparison. An observational follow-up can describe what happened in the groups, but group contrasts alone do not identify the causal effect of earlier treatment. That distinction remains important even when the outcome is clinically meaningful.

Finally, registered outcomes and statistical results are not the same thing. This record lists 10 outcome measures but 0 analyses, and it does not report the primary endpoint values. The record is informative about the questions the study aimed to address and the limitations that affected follow-up, while leaving the numerical answers unavailable. This separation between study intent, data availability, and analyzed evidence is central to careful interpretation of clinical-trial registry records.

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 the absence of reported Year 3 graft-survival counts. The registry says that premature termination left 7 patients in the imlifidase group and 6 in the PE group without graft-survival data at that timepoint, but does not provide the graft status of those participants or the number with functioning grafts among those observed. The primary outcome therefore cannot be quantified from the registry record.

The design further limits causal interpretation. The follow-up was observational, no treatment was given during it, allocation to earlier treatment is not stated, and the record warns that the arms are not a like-for-like control comparison. The registry record does not report group characteristics or adjusted estimates that would clarify comparability. A difference, if one were reported, could not automatically be attributed to the earlier treatment.

The record lists 10 outcome measures but 0 analyses. Numerical results for the secondary outcomes are not reported in the registry record, and details of outcome-specific analysis populations, missing-data methods, multiplicity handling, and statistical models are not reported. The adverse-event summary has no event definitions or observation window reported in the registry record. These gaps limit both efficacy and safety interpretation.

The registry lists the study as TERMINATED, but does not report further detail about the circumstances of termination, the protocol’s original sample-size justification, or whether interim analyses were planned or conducted. These details should not be inferred. Overall, the record describes the study question and follow-up design, while leaving key outcome values and analysis details unavailable.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: An Long-term Follow-up Trial of Kidney Tx Patients Treated With Imlifidase or PE After an AMR — NCT04711850.
• Registry record last updated 2025-05-28; status last verified 2025-05.
• Results first posted 2025-05-11.
• 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

NCT04711850 is a prospective, observational long-term follow-up study of kidney transplant patients previously treated with imlifidase or PE for active or chronic active AMR in feeder Study 16-HMedIdeS-12. No treatment was given in the follow-up study. The sponsor is Hansa Biopharma AB. The registry lists enrollment of 18, a start date of 2021-01-20, a primary completion date of 2023-03-30, and status TERMINATED.

The primary outcome was the number of participants with a functioning graft at Year 3 after the start of AMR treatment in the feeder study. The registry reports that 7 imlifidase-group patients and 6 PE-group patients had no graft-survival data for the 3-year timepoint because of premature termination. The Year 3 outcome counts and statistical analyses are not reported in the registry record.

The registry lists 10 outcome measures and 0 analyses. It cautions that the earlier-treatment arms are not a like-for-like control comparison. The posted adverse-event summaries list zero affected participants and zero deaths in each group, with at-risk counts of 11 and 7.