Pharmacokinetics of Intravenous Difelikefalin in Chinese Adult Subjects on Haemodialysis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pharmacokinetics of Intravenous Difelikefalin in Chinese Adult Subjects on Haemodialysis (NCT05885763), a na phase 1 study. The primary outcome is Evaluation of the PK Profile of Difelikefalin - Cmax - Dose 1.

2. Clinical Question

The clinical question is therefore descriptive: what pharmacokinetic profile and safety experience were observed during a short course of intravenous difelikefalin in adult Chinese subjects receiving haemodialysis? This design can characterize measurements made in the treated group, but it cannot estimate a treatment difference against an untreated or active-control group. Because the study is open-label, participants and investigators were not masked to treatment assignment; in a single-arm study there is no competing assignment to conceal.

The record describes a repeated dosing schedule and a one-week safety follow-up after the treatment period. It does not report the dose amount, the detailed timing of blood collection, or the numerical endpoint results. Without those details and results, the primary question can be identified, but its answer cannot be reconstructed from the registry record. The available safety counts describe events reported in the study group and should not be read as a controlled estimate of risk.

3. Trial Design

The registry describes a Phase 1, single-arm, open-label study, with allocation listed as not applicable. Its stated purpose is to evaluate pharmacokinetics, safety, and tolerability of intravenous difelikefalin in adult Chinese subjects on haemodialysis. The study is marked completed, with a registry enrollment of 30.

According to the brief description, difelikefalin was given as intravenous bolus injections on a repeated schedule of 3 times weekly. The treatment period lasted one week, followed by a safety follow-up period of one week. The record identifies one treatment arm, described as a one-week, single-arm, open-label treatment phase. The specific dose, the timing of individual administrations, and the follow-up procedures are not reported in the registry record.

The study began on 2023-06-26, and primary completion is recorded as 2023-10-09. These are registry dates and do not by themselves describe the timing of each participant’s treatment or assessments. The record does not give further details about recruitment, eligibility, discontinuations, or the number of participants contributing data to each outcome.

A single-group design is suited to describing measurements made among people who receive the study treatment. It does not create a concurrent control group, so observed changes cannot be separated from other influences through a between-group comparison. The open-label design also means treatment masking is absent. A randomized comparison is not reported and would not be a like-for-like interpretation of this study’s design. The registry lists 14 outcome measures and 0 analyses. Details of the protocol’s statistical plan, sample-size justification, and analysis populations 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.

Overall 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.

6. Primary Endpoint

The registry lists the primary outcome as Evaluation of the PK Profile of Difelikefalin - Cmax - Dose 1, measured over 1 week.

The primary endpoint is titled “Evaluation of the PK Profile of Difelikefalin - Cmax - Dose 1.” Cmax means the maximum, or peak, observed plasma concentration. The stated unit is ng/mL, the summary measure is a geometric mean, and the stated measure of dispersion is the geometric coefficient of variation. The timeframe is one week.

In general, Cmax is used to describe the peak concentration observed after a dose. It is one aspect of pharmacokinetics, which concerns how drug concentrations change in the body over time. A peak concentration can help characterize the concentration profile, but it does not by itself describe the full profile or establish a clinical benefit. Its interpretation depends on details such as the dose and the timing of sample collection; those details are not reported in the registry record.

In general, a geometric mean is a summary appropriate for measurements analyzed on a multiplicative scale, while a geometric coefficient of variation describes relative dispersion around that summary. Neither the endpoint value nor its geometric coefficient of variation is reported in the registry record. The endpoint description names Dose 1, but the record does not provide the numerical Cmax estimate or enough sampling detail to assess how precisely it was measured.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Pharmacokinetic studies characterize drug concentration measurements over time. The primary endpoint in this record is Cmax, the maximum observed plasma concentration after Dose 1. The endpoint is summarized using a geometric mean, with geometric coefficient of variation as the dispersion measure. These choices describe how the endpoint was intended to be summarized, but the registry record does not report the calculated result or the detailed analysis methods.

What does a geometric mean describe?

In general, a geometric mean summarizes positive measurements by working on a logarithmic scale and transforming the result back to the original scale. It can be useful when values vary multiplicatively or have a right-skewed distribution. It is not interchangeable with an arithmetic mean: the two summarize data differently. The registry’s choice of a geometric mean signals the intended summary scale, but the underlying observations and numerical summary are not reported in the registry record.

How should the geometric coefficient of variation be read?

In general, a coefficient of variation expresses dispersion relative to the scale of a measurement rather than in the measurement’s original units. A geometric coefficient of variation is used with summaries on a geometric scale. It gives information about variability among measurements, not a confidence interval for the geometric mean and not a measure of treatment benefit. No value for this dispersion measure is reported in the registry record, so the amount of observed variability cannot be assessed.

What does Cmax capture, and what does it leave out?

Cmax captures the peak concentration observed in the sampling process. In general, its value can depend on the dose and on when samples are collected relative to administration. A concentration-time profile contains more information than a peak alone; Cmax does not describe all aspects of exposure or the duration of concentrations. The registry record does not report the dose amount, the sampling schedule, or other numerical pharmacokinetic results. It is therefore not possible to assess whether the recorded sampling would capture the peak fully, or to compare Cmax with other exposure measures.

Why does the study design matter?

A single-arm study observes one group receiving the study intervention. It can describe outcomes within that group, but it does not provide a concurrent control distribution. In general, randomization helps make comparison groups similar in expectation, while masking can limit some sources of assessment or behavior bias. Neither creates a comparator when the design has only one group. Here, allocation is listed as not applicable, masking is none, and the model is single group. The record therefore does not support interpreting the results as a randomized treatment contrast.

The study is open-label, meaning treatment assignment is not masked. For a laboratory concentration measurement, the endpoint may be less subjective than some clinical outcomes, but lack of masking does not remove potential influences on treatment delivery, sample collection, or other study procedures. The registry record does not describe safeguards or operational procedures, so their role cannot be assessed.

What can a planning illustration tell the reader?

In general, a sample-size planning illustration estimates how many participants might be needed under specified assumptions to detect a target effect. Such a calculation is not an analysis of what happened in the completed study and is not observed power. The planning assumptions described for this record include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the target effect is expressed as a stated fraction of the observed effect. These are planning assumptions, not a description of this single-arm study’s design. They do not provide evidence of a treatment effect or replace the study’s primary endpoint result. Numerical planning outputs are not reported in the registry record.

For a count outcome, the variance may be greater than a simple model assumes; this is called over-dispersion. In general, accounting for over-dispersion can affect uncertainty estimates and planning calculations. The registry record does not identify a count-based primary analysis or report an over-dispersion adjustment. No inference about such a method should be made from the safety counts alone.

More broadly, a statistical result is most informative when it gives the estimate, its uncertainty, the analysis population, and the method used to obtain it. The record provides the primary endpoint definition and the design description, but does not report the estimate, confidence interval, participant count contributing to the endpoint, or statistical model. The intended summary can be explained, but its numerical result and reproducibility cannot be evaluated from the information in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 14 outcome measures and 0 analyses. It identifies the primary endpoint as Cmax after Dose 1, but does not report a complete statistical plan explaining how the primary and other outcomes were analyzed. Procedures for controlling multiplicity are not reported in the registry record.

In general, multiplicity arises when several outcomes, time points, or comparisons are examined. The more opportunities there are to identify an apparently notable result, the more important it is to know whether outcomes were prespecified and whether an adjustment or hierarchy was used. The count of outcome measures alone does not establish that all were tested together or that any particular adjustment was needed. The relevant analysis details are not reported in the registry record.

Missing-data methods, reasons for missing measurements, and the completeness of endpoint data are not reported in the registry record. The analysis populations are also not reported. Therefore, the registry enrollment of 30 cannot be assumed to equal the number contributing to the primary endpoint or to each safety outcome. The record does not describe exclusions, withdrawals, or how observations unavailable at a scheduled assessment were handled.

These omissions limit assessment of selection and uncertainty. In general, if data are missing, the method used to address them can affect the estimate and its precision; the impact depends on why data are missing and how the analysis is conducted. Without the analysis population and missing-data approach, readers cannot determine whether the reported summaries, if available, would represent all enrolled participants or a subset. The registry does not report enough information to judge these issues.

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.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: abscess limb (3.3%), syncope (3.3%).

For the one-week, single-arm, open-label treatment phase, the registry reports 30 at risk for serious adverse events and 2 affected. It reports 30 at risk for other adverse events and 11 affected. The number of deaths is 0. The serious terms listed are Abscess limb and Syncope, each with a reported frequency of 3.3%.

These are descriptive safety figures for the study group, not comparisons with an untreated group or another treatment. The record distinguishes serious adverse events from other adverse events, but does not provide full event-level details, timing, relatedness, or the number of events per affected participant. The listed percentages should be read as recorded, not as evidence of causation or as a controlled risk estimate.

The safety group is named for the treatment phase. Although the brief description also notes a safety follow-up period of one week, the outcome timeframe and completeness of follow-up for these specific counts are not reported in the registry record. The figures should not be extended beyond the reporting group or period described.

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

The record establishes that this was a completed Phase 1, single-arm, open-label study intended to characterize the pharmacokinetics, safety, and tolerability of repeated intravenous difelikefalin in adult Chinese subjects on haemodialysis. It specifies a primary pharmacokinetic endpoint: Cmax after Dose 1, summarized as a geometric mean with geometric coefficient of variation. The registry also reports safety counts for the treatment phase.

It does not establish the numerical Cmax observed, the variability of that measurement, or the precision of any pharmacokinetic estimate. The primary endpoint’s result is not reported in the registry record. There is no reported confidence interval or other uncertainty measure for that endpoint. The study’s stated purpose and endpoint definition are not substitutes for the missing numerical result.

Because the study has no comparator group, it cannot estimate a difference between difelikefalin and a control condition. A single-group result, even when fully reported, would describe observations among participants who received the intervention under the study conditions. It would not by itself show what would have occurred without treatment or under another regimen. The design also does not establish comparative safety.

The safety entries indicate that serious and other adverse events were recorded, and that the death count was 0 in the reported group. Those counts do not demonstrate that an event was caused by treatment, nor do they rule out risks not observed or not captured in this study. The record lacks details needed to assess the context, timing, and completeness of the safety observations.

In general, statistical interpretation depends on the estimate, its uncertainty, the analysis methods, and the population included. Those details are not reported for the primary endpoint. The most defensible reading is therefore limited: the registry describes the study’s design and intended pharmacokinetic measure and records selected safety counts, but it does not supply a numerical primary result or a controlled treatment comparison.

13. Why This Trial Matters Statistically

This study raises a useful statistical distinction between describing a pharmacokinetic profile and estimating a comparative treatment effect. Cmax is a concentration endpoint intended to characterize a peak after dosing. A single-arm design can summarize such measurements in the treated group, but it cannot provide a concurrent contrast with a control group. Keeping those questions separate prevents a descriptive result from being interpreted as comparative evidence.

The endpoint’s geometric summary is also relevant to how readers understand reported concentration data. In general, geometric summaries and geometric measures of dispersion are suited to multiplicative patterns and relative variability. Knowing which summary was planned helps readers interpret a result if it is available. Here, the numerical estimate and dispersion are not reported in the registry record, so the intended scale is clear while the observed value and its precision are not.

The record further illustrates why design and reporting details matter together. A completed status and an enrollment count do not identify the number of observations used for each outcome. Without an analysis population, missing-data approach, and statistical plan, readers cannot fully evaluate the path from measurements to a result. The 14 outcome measures make it particularly important to know how outcomes were prioritized and how multiplicity was addressed, although those procedures are not reported.

Finally, safety counts need a distinct interpretation from efficacy or pharmacokinetic estimates. They describe events recorded in the study group, but do not create a controlled comparison or establish causation. For biostatisticians and clinical researchers, the central lesson is to separate the endpoint’s definition, the design’s inferential reach, and the information actually reported. Each answers a different question.

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 primary endpoint is defined, but its numerical result is not reported in the registry record. The geometric coefficient of variation and any confidence interval or other uncertainty measure are also not reported. This prevents assessment of the observed Cmax, the variability of concentrations, and the precision of the primary estimate.

The study has one open-label treatment group and no comparator. Its design therefore cannot distinguish treatment-associated observations from changes or influences that would also occur without treatment or under another regimen. A controlled treatment difference cannot be inferred from this record. The dose amount is not reported, limiting interpretation of the concentration endpoint in relation to dosing.

The timing and frequency of pharmacokinetic sampling are not reported. Those details matter for interpreting a maximum observed concentration, because the measured peak depends in part on when samples are taken. The record also does not report other numerical pharmacokinetic results that might provide context for Cmax.

Although the registry enrollment is 30, participant counts contributing to the primary endpoint and other outcomes are not reported. Analysis populations, withdrawals, missing-data handling, and outcome-specific completeness are not reported. The statistical analysis plan, sample-size justification, and multiplicity procedures are also not reported in the registry record.

The safety figures are descriptive and limited by the lack of event-level detail. The record does not report timing, treatment relatedness, full follow-up completeness, or contextual information for the listed events. The reported safety counts should not be treated as comparative risks or as proof of causation. These limitations restrict what can be concluded from the registry record, even though the study is marked completed.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Pharmacokinetics of Intravenous Difelikefalin in Chinese Adult Subjects on Haemodialysis — NCT05885763.
• Registry record last updated 2025-02-14; status last verified 2025-02.
• Results first posted 2025-02-14.
• 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 record describes NCT05885763, a completed Phase 1, single-arm, open-label study of intravenous difelikefalin in adult Chinese subjects on haemodialysis. Enrollment is 30. The treatment period is one week, with repeated bolus injections scheduled 3 times weekly, followed by a safety follow-up period of one week. The specific dose amount is not reported in the registry record.

The primary endpoint is Cmax after Dose 1, expressed as a geometric mean with geometric coefficient of variation, in ng/mL, over a timeframe of one week. Its numerical result and analysis details are not reported. The registry lists 14 outcome measures and 0 analyses.

For the treatment phase, the record reports 2 affected by serious adverse events, 11 affected by other adverse events, and 0 deaths. Abscess limb and Syncope are each listed among the serious terms at 3.3%. With no comparator group, these safety figures are descriptive rather than comparative.