Pharmacodynamic Biomarkers to Support Biosimilar Development: PCSK9 Inhibitors: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pharmacodynamic Biomarkers to Support Biosimilar Development: PCSK9 Inhibitors (NCT04189484), a randomized phase 1 study. The primary outcome is Baseline-adjusted Area Under Effect Curve (AUEC) for LDL-C for Evolocumab and Alirocumab.

2. Clinical Question

3. Trial Design

This was a randomized, double-masked, parallel-arm phase 1 study with a placebo control. The registry describes a single-dose design in healthy subjects, with four dose groups for each of the two active drugs and one placebo arm. The study was sponsored by the Food and Drug Administration (FDA), began on 2020-01-07, had a primary completion date of 2021-04-07, and is recorded as completed.

The evolocumab arms received 21 mg, 35 mg, 70 mg, or 140 mg subcutaneously. The alirocumab arms received 15 mg, 25 mg, 50 mg, or 100 mg subcutaneously. The placebo arm received a single subcutaneous dose. Planned enrollment was 72. The primary outcome records 7 or 8 participants in each arm, while the safety records list 8 participants at risk in every arm; the registry record does not explain these differences in counts.

The endpoint timeframe included measurements before dosing and after dosing at 24 hours, then on Days 2, 3, 4, 5, 7, 10, 14, 21, 28, 35, and 42 for all arms. Additional measurements were scheduled on Day 56 for the intermediate-high and high-dose groups of both drugs and placebo, and on Days 70 and 84 for the high-dose groups of both drugs and placebo. The registry record does not report the randomization procedure, masking procedures, or the allocation ratio.

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.

Only the first 6 of 9 groups are shown.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Analysis population includes all subjects who did not discontinue before the end of 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.

Only the first 6 of 10 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Baseline-adjusted Area Under Effect Curve (AUEC) for LDL-C for Evolocumab and Alirocumab, measured over Day -1 and 0h (pre-dose), 24h (post-dose); once on Day 2, 3, 4, 5, 7, 10, 14, 21, 28, 35, and 42 for all Arms. Additionally, once on Day 56 for Arms C, D, G, H, & I; and once on Day 70 and 84 for Arms D, H, & I..

The primary endpoint was baseline-adjusted area under the effect curve (AUEC) for low-density lipoprotein cholesterol (LDL-C), expressed in mg/dL*day. AUEC represents the baseline-subtracted area under the LDL-C concentration-time curve across the recorded follow-up measurements. It reflects the magnitude and duration of change over time rather than a single measurement at one visit.

For this endpoint, more negative AUEC values represent greater reductions in LDL-C exposure from baseline. The registry describes determining each subject’s maximum decrease from baseline LDL-C using all sampled timepoints. The recorded measurement schedule extended from pre-dose through follow-up, with additional later assessments for specified higher-dose arms and placebo.

This kind of pharmacodynamic measure is useful in a dose-ranging study because it captures a response over time and can contribute information about dose-response behavior. The study’s stated purpose was to assess pharmacokinetics and pharmacodynamics across dose ranges and inform operating characteristics for future clinical pharmacology pharmacodynamic similarity studies. The registry’s endpoint description says AUEC values were log-transformed and an ANCOVA model was used to calculate geometric means and 90% confidence intervals for treatment groups. Numerical confidence intervals and model-based group estimates are not reported in the registry record summarized for the primary endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a continuous measurement: baseline-adjusted LDL-C AUEC, expressed in mg/dL*day. The posted arm summaries give a mean, standard deviation, and number of subjects for each of the nine arms. A mean describes the central value of the observations in an arm. The standard deviation describes how spread out individual values are around that mean; it is not a confidence interval and does not by itself quantify the precision of a comparison between arms.

What does AUEC capture?

In general, an area-under-the-effect-curve measure combines information across repeated measurements over time. It can distinguish a response that is brief from one that is sustained, even when both involve changes at individual measurement times. In this trial, the endpoint was baseline-adjusted, and the registry defines more negative AUEC values as greater reductions in LDL-C exposure from baseline. The measurement schedule included pre-dose observations and repeated follow-up visits, with some later visits limited to specified arms.

The registry endpoint description also says the maximum decrease from baseline LDL-C was determined using all sampled timepoints. It states that AUEC values were log-transformed and that an ANCOVA model was used to calculate geometric means and 90% confidence intervals for each treatment group. The posted arm entries, however, are described as means and standard deviations. The numerical model estimates and confidence intervals are not reported in the registry record. Specific ANCOVA covariates, model diagnostics, and details of the transformation and back-transformation are not reported in the registry record.

How should variability and uncertainty be understood?

In general, a confidence interval describes a range of values compatible with an estimate under a specified statistical procedure and assumptions. It conveys uncertainty in an estimate; it is not a range containing a fixed proportion of individual participants’ measurements. The 90% confidence intervals mentioned in the endpoint description would relate to the model-based group estimates, but their endpoints are not reported in the registry record. The standard deviations posted for the arms describe observed within-arm spread and cannot substitute for those confidence intervals.

Arm sizes in the primary outcome entries range from 7 to 8 participants. With small arm-level samples, estimates can be sensitive to individual observations, and uncertainty may be substantial. This is a general statistical consideration, not a claim about a particular participant’s influence in this trial. The registry record does not provide individual-level data or additional precision measures that would allow that influence to be assessed.

What can be concluded without comparison tests?

Arm means allow descriptive reading of the recorded values. They do not, on their own, provide an adjusted estimate of a contrast between arms or quantify the uncertainty of that contrast. The registry record contains no analysis rows and no two-arm comparison estimates or p-values for this continuous endpoint. Consequently, the numerical arm summaries do not support a formal claim about statistical evidence for a dose difference, a drug difference, or a difference from placebo.

In general, an analysis comparing arms would need to define the contrast, its estimate, and an uncertainty measure, using the prespecified or otherwise documented model. The registry record does not report the planned contrasts or enough detail to reconstruct an adjusted analysis. Recalculating contrasts from arm summaries would not reproduce the described ANCOVA model and would require assumptions that are not documented in the registry record. No recalculated comparison is presented.

Why does dispersion matter?

In general, greater dispersion means individual measurements vary more widely around the group estimate. That variability affects the precision of estimated group means and comparisons. The posted standard deviations vary across dose groups, so a reader should not infer equal precision merely because arms have similar participant counts. The placebo standard deviation is also substantial relative to the spread in some active arms, but the registry record does not provide a formal comparison of variability.

For a continuous endpoint, mean and standard deviation are often informative descriptive summaries when their use and assumptions are appropriate. The endpoint description’s use of log-transformation and ANCOVA indicates that the stated model-based analysis involved more than a simple comparison of the posted means. The registry record does not report diagnostics, residual assumptions, handling of any values unsuitable for transformation, or sensitivity analyses. Those details matter when assessing whether model-based estimates are robust.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Arm A: Evolocumab Low Dose", "Arm B: Evolocumab Intermediate Low Dose", "Arm C: Evolocumab Intermediate High Dose", "Arm D: Evolocumab High Dose", "Arm E: Alirocumab Low Dose", "Arm F: Alirocumab Intermediate Low Dose")
n   <- c(7, 8, 8, 8, 8, 8)
m   <- c(-380, -754, -866, -1832, -580, -581)
sp  <- c(228, 573, 658, 806, 360, 319)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Arm A: Evolocumab Low Dose  7  -380.000  228.000  -590.865  -169.135
CARM  Arm B: Evolocumab Intermediate Low Dose  8  -754.000  573.000  -1233.040  -274.960
CARM  Arm C: Evolocumab Intermediate High Dose  8  -866.000  658.000  -1416.102  -315.898
CARM  Arm D: Evolocumab High Dose  8  -1832.000  806.000  -2505.833  -1158.167
CARM  Arm E: Alirocumab Low Dose  8  -580.000  360.000  -880.968  -279.032
CARM  Arm F: Alirocumab Intermediate Low Dose  8  -581.000  319.000  -847.691  -314.309

11. Multiplicity, Missing Data and Analysis Populations

The registry lists seven secondary outcomes, including ApoB measures, pharmacokinetic measures, and dose-response or pharmacodynamic model parameters. It does not report numerical results for those secondary outcomes in the record. The registry record also does not report a multiplicity strategy, such as a hierarchy of outcomes or an adjustment across multiple tests. Without that information, the control of false-positive findings across multiple outcomes or comparisons cannot be assessed.

The primary endpoint population is described as including subjects who did not discontinue before the end of the study. This is not described as an all-randomized population. The registry record does not report the reasons for discontinuation, the number of subjects who discontinued, or missing-data methods for the primary endpoint. It also does not describe how incomplete measurement schedules were handled or whether any imputation or sensitivity analyses were used.

The primary outcome entries list 7 or 8 subjects per arm, while the safety entries list 8 at risk in every arm. These counts pertain to different posted results, and the registry record does not explain the difference. They should not be treated as interchangeable denominators. No analysis rows are listed, and planned analyses or prespecified analysis populations beyond the primary endpoint population description are not reported in the registry record.

In general, missing outcome values and multiple analyses can affect interpretation because they influence which observations contribute to estimates and how much uncertainty is appropriate. The available registry information does not permit assessment of these issues beyond the stated analysis population and the posted arm counts.

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 non-serious adverse event terms

The safety records list 8 participants at risk in each arm. No serious adverse events were reported in any of the nine arms, and deaths were recorded as 0 in every arm. The listed number of participants with other adverse events was 5 in the evolocumab low-dose arm, 1 in the evolocumab intermediate-low arm, 5 in the evolocumab intermediate-high arm, and 3 in the evolocumab high-dose arm. For alirocumab, the corresponding counts were 4, 3, 1, and 5; the placebo count was 4.

These are arm-level counts, not estimates of comparative risk. The registry record does not report a statistical comparison of adverse events between arms, event severity details for the other adverse events, or a causal assessment for individual events. Zero recorded serious adverse events in these groups should be read as a description of the posted observations, not proof that serious events cannot occur. The safety denominators are the listed participants at risk; they are not the primary endpoint counts.

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

The posted results describe baseline-adjusted LDL-C AUEC values after single doses of evolocumab and alirocumab across four dose groups for each drug, alongside placebo. Under the registry’s definition, more negative values indicate greater reductions in LDL-C exposure from baseline. The arm-level means vary across dose groups, and the high-dose group for each drug has the most negative mean among that drug’s four groups.

Those descriptive patterns do not establish that one dose, drug, or active treatment differs statistically from another. The registry record does not report comparison estimates, p-values, or numerical confidence intervals for the posted arm results. It also does not report the numerical results for the listed secondary outcomes. The endpoint description identifies a model-based analysis, but the corresponding model estimates are not reported in the registry record.

The study’s stated purpose was to assess pharmacokinetics and pharmacodynamics across an appropriate dose range and inform operating characteristics for future clinical pharmacology pharmacodynamic similarity studies. The trial’s listed interventions are evolocumab, alirocumab, and placebo; no biosimilar intervention is listed. Therefore, the primary results do not directly answer whether a biosimilar is similar to a reference product.

The study involved healthy subjects and single-dose administration. The posted AUEC values are pharmacodynamic measurements, not clinical outcome results. They do not establish long-term response, effectiveness in a patient population, or comparative safety beyond the adverse-event counts recorded for this study. The registry record does not report a sample-size justification or other information that would support claims about the trial’s power to detect a particular difference.

14. Why This Trial Matters Statistically

Dose-ranging studies can contribute information about the shape and variability of a pharmacodynamic response over time. In this study, the primary endpoint uses repeated LDL-C measurements to create a baseline-adjusted AUEC, while the secondary outcomes include additional pharmacodynamic, pharmacokinetic, and model-parameter measures. This range of outcomes reflects the stated aim of supporting the design of future clinical pharmacology pharmacodynamic similarity studies.

For statistical planning, response magnitude and variability are both relevant. Means describe the observed arm-level response, while standard deviations show that individual measurements vary within arms. Differences in dispersion across groups can affect the precision of future estimates and the sample sizes required for planned comparisons. The posted summaries may therefore be informative as descriptive inputs, but they do not themselves establish the precision of a comparison or validate a future design.

In general, planning estimates depend on the target contrast, the analysis model, the significance level, desired power, allocation, and assumptions about variability. The registry record does not report the trial’s own sample-size justification or the details of a future similarity margin or comparison. The posted arm summaries should not be mistaken for an observed-power calculation or for proof that a later study will be adequately designed.

The trial also illustrates why the distinction between descriptive data and inferential comparisons matters. Arm-level means can show the values recorded at different doses, but without contrast estimates and uncertainty measures they do not establish statistical separation. A future study’s conclusions would depend on its prespecified estimand, comparison, analysis, and uncertainty—not only on these observed means.

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 primary outcome results are reported as arm-level means and standard deviations, but the registry record does not report the model-based geometric means or 90% confidence intervals described in the endpoint methods. No two-arm comparison estimates or p-values are listed, and no analysis rows are recorded. This limits formal interpretation of differences among doses, drugs, and placebo.

The endpoint description notes log transformation and ANCOVA, but the registry record does not report the covariates, diagnostic checks, assumptions, or sensitivity analyses. It also does not report how missing repeated measurements were handled. The stated primary endpoint population excludes subjects who discontinued before study end, but discontinuation counts and reasons are not reported.

The primary endpoint sample counts are 7 or 8 per arm, and the safety records list 8 at risk in each arm. The record does not explain the different counts. The small arm sizes also mean the summaries may be sensitive to individual observations; this is a general limitation of interpreting small groups, not a quantified finding about these data.

Finally, the study involved healthy subjects receiving single doses and had a pharmacodynamic and pharmacokinetic purpose. No biosimilar arm is listed, and numerical results for secondary outcomes are not reported in the record. These features constrain what can be inferred about product similarity, clinical outcomes, longer-term response, or safety beyond the posted event counts.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Pharmacodynamic Biomarkers to Support Biosimilar Development: PCSK9 Inhibitors — NCT04189484.
• Registry record last updated 2024-04-22; status last verified 2023-11.
• Results first posted 2024-04-22.
• 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

NCT04189484 is a completed phase 1 randomized, double-masked, parallel-arm, placebo-controlled study sponsored by the Food and Drug Administration (FDA). It enrolled healthy subjects and assessed single-dose evolocumab and alirocumab across four dose groups per drug, with a placebo arm. Planned enrollment was 72.

The primary outcome was baseline-adjusted LDL-C AUEC, measured in mg/dL*day. Posted arm-level means and standard deviations are available, but comparison estimates, p-values, and the numerical model-based confidence intervals described in the endpoint methods are not reported in the registry record. The record lists seven secondary outcomes but does not report their numerical results in the information. Safety records report no serious adverse events and no deaths in any arm.