A Study of Abemaciclib in Healthy Participants: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of Abemaciclib in Healthy Participants (NCT02672423), a randomized phase 1 study. The primary outcome is Pharmacokinetics (PK): Area Under the Concentration Versus Time Curve From Zero to Infinity (AUC[0-∞]).

2. Clinical Question

The study’s stated purpose was to measure how much abemaciclib entered the bloodstream and how long the body took to eliminate it after administration in different formulations. It also sought to evaluate the effect of a high-fat meal on tablet pharmacokinetics. Tolerability and side-effect information were collected as additional study aims.

These questions concern pharmacokinetics in healthy participants, not treatment of a medical condition. The registry explicitly describes the study as research and not intended to treat any condition. Its results therefore address measured drug exposure under the study conditions; they do not directly answer questions about clinical benefit or outcomes in patients.

3. Trial Design

NCT02672423 is a completed phase 1 study with randomized allocation, no masking, and a crossover model. The registry gives an enrollment of 127 and identifies healthy participants as the study population. Participants could enroll in only one of the three parts. The study began in 2016-02, and primary completion was recorded in 2016-10.

Parts A and C each used two periods. In Part A, participants received the reference formulation, three 50 mg capsules, and the test formulation, a 150 mg tablet, orally on Day 1 in each period. Part B used three periods and included the reference capsules, a 150 mg tablet, and three 50 mg tablets. Part C compared the 150 mg tablet taken with a high-fat meal and without a high-fat meal across two periods. The registry describes the fed and fasted conditions in both sequence orders.

The crossover structure means that participants received more than one study condition over time within their assigned part. The posted endpoint summaries are organized by formulation or condition and part. Their group counts should not be added to infer a count of unique participants: the registry reports crossover periods, and the endpoint and safety group counts are not identical in every part.

The brief study description says Parts A and C lasted about 44 days including follow-up, while Part B lasted about 60 days including follow-up. Screening could occur up to 28 days before the first dose. These durations and the reported schedule describe the study’s conduct; the registry record does not provide enough detail to reconstruct every operational or analysis procedure.

Randomization and crossover are relevant design features for comparing pharmacokinetic conditions, because measurements can be collected under multiple conditions in the same participant. However, the registry does not report the randomized sequence-generation method, masking procedures beyond “none,” or the statistical model used for any formal comparison.

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: A 2- and 3-period crossover study conducted in 3 parts, with Part A followed by Parts B and C. Participants received single oral doses of abemaciclib on 2 separate occasions in Parts A and C and on 3 separate occasions in Part B.There was a washout interval of at least 16 days between periods.

Only the first 6 of 10 groups are shown.

Period 1

Reasons for not completing this period:

Washout 1

Period 2

Reasons for not completing this period:

Washout 2

Analysis population for the primary outcome, as defined in the registry: All randomized participants who received at least one dose of study drug and had evaluable PK data.

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: All randomized participants who received at least one dose of study drug.

6. Primary Endpoint

The registry lists the primary outcome as Pharmacokinetics (PK): Area Under the Concentration Versus Time Curve From Zero to Infinity (AUC[0-∞]), measured over Parts A and C Periods 1 and 2; Part B Periods 1, 2, 3: Predose, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 24, 48, 96, 120,144,168 and 192 hours postdose.

The primary endpoint is pharmacokinetic area under the concentration-versus-time curve from zero to infinity, written as AUC[0-∞] and measured in nanograms*hour/milliliter (ng*hr/mL). It represents the area beneath a participant’s blood concentration curve over time, extended from dosing toward the full elimination period. As a general pharmacokinetic concept, AUC is used as a measure of overall systemic drug exposure: a larger AUC corresponds to greater integrated concentration over the measured time course, not necessarily to a particular clinical outcome.

The registry reports the endpoint as a geometric mean with geometric coefficient of variation. Concentration samples were scheduled at predose and at multiple postdose times extending to 192 hours. The listed schedule differs by study part and period as described in the endpoint timeframe.

The stated endpoint population is all randomized participants who received at least one dose of study drug and had evaluable pharmacokinetic data. This definition is narrower than enrollment: a participant must meet the dosing and evaluability criteria to contribute to the endpoint population. The registry does not explain how evaluability was determined or how incomplete concentration profiles were handled.

AUC is useful for comparing exposure across formulations or food conditions because it condenses the concentration-time profile into a single measure. The posted summaries describe exposure within each listed group. They do not include confidence intervals, formal comparison estimates, or p-values, so they do not establish the precision or statistical significance of differences between conditions.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The endpoint is summarized using geometric means and geometric coefficients of variation. These are commonly used for pharmacokinetic measurements, which are often positively skewed: values can extend farther upward than downward, and variability may increase with the measurement level. As a general statistical approach, taking logarithms can make such data more symmetric and can make relative comparisons easier to model. The registry reports geometric summaries, but the exact transformation and model used for any analysis are not reported in the registry record.

What does a geometric mean represent?

A geometric mean is formed from logged measurements and then expressed back on the original scale. In general, it describes a central value in multiplicative rather than additive terms. It can be more representative than an arithmetic mean when values vary proportionally or have a right-skewed distribution. Here, the reported geometric means summarize AUC within each listed condition; they are not treatment-effect estimates or evidence of a formal comparison by themselves.

How should geometric coefficient of variation be read?

The geometric coefficient of variation describes relative dispersion on a multiplicative scale. As a general concept, it conveys how variable observations are in relation to their central level, rather than measuring spread in the original units in the same way as a standard deviation. It is not a confidence interval, and it should not be read as the range containing a specified proportion of participants. The registry gives this measure for each posted AUC group, but does not provide confidence limits for the group means or contrasts.

Why is the crossover design important?

In a crossover study, participants receive different conditions in separate periods. A general advantage is that a participant can serve as their own comparison, helping account for stable differences between people. A valid analysis generally needs to account for the relationship between repeated measurements from the same participant. Depending on the design and assumptions, it may also need to consider period and sequence effects. The registry identifies a crossover model and reports the dosing periods, but does not state which model terms or assumptions were used in an analysis.

Because the posted results are marginal group summaries, they do not retain the within-participant pairing. An analyst cannot reconstruct the paired variability or a paired confidence interval from the group means and geometric coefficients of variation alone. Nor can the summaries establish whether period, sequence, or other design factors were included in a sponsor analysis. No such analysis results are posted in the registry record.

What would a confidence interval add?

As a general explanation, a confidence interval expresses uncertainty around an estimate under a specified statistical procedure. For a formulation or food-condition comparison, an interval around the relevant contrast would help show which effect sizes remain compatible with the data and model. It would be needed to judge the precision of a comparison. The registry does not report confidence intervals for the primary endpoint, and no comparison estimates are listed. The group-level geometric coefficients of variation cannot substitute for those intervals.

What do the planning illustrations mean?

Any sample-size planning illustration is distinct from an observed trial result. The stated planning assumptions use a two-sided significance level of 0.05, equal allocation, a normal approximation, and an effect defined as a stated fraction of the observed effect. Such illustrations are conditional calculations for planning, not observed power and not evidence that a particular comparison was statistically significant. For non-time-to-event outcomes, the stated convention is participants per arm; time-to-event illustrations use total events. No illustration should be read as the trial’s original sample-size justification, which is not reported in the registry record.

The registry does not report an inferential analysis for the primary endpoint. Therefore, statistical interpretation should remain anchored to the descriptive summaries and the limitations of the available group-level information. Formal conclusions about equivalence or a food effect would require a defined comparison, its estimate and uncertainty, and the analysis details behind it.

10. Multiplicity, Missing Data and Analysis Populations

The registry record does not report a statistical analysis plan, a multiplicity procedure, or formal primary-endpoint analyses. It lists zero analyses and no posted secondary outcomes. Accordingly, it is not possible to determine how the study’s several formulation and food-condition comparisons were prioritized or whether any adjustment for multiple comparisons was planned or used. The registry record does not report interim analyses or a sample-size justification.

Multiplicity matters in general when several hypotheses are tested: a collection of tests can increase the chance of at least one apparently unusual result even if no true differences exist. This general concern does not establish that the study used multiple testing or that any particular adjustment was appropriate. The record simply does not state how comparisons were handled inferentially.

The endpoint population is defined as randomized participants who received at least one dose and had evaluable pharmacokinetic data. However, the record does not describe the criteria for evaluability, the number of participants excluded from a particular endpoint summary, or the handling of missing concentration samples. It also does not report imputation methods, sensitivity analyses, or procedures for incomplete profiles.

In a crossover study, missing observations can affect the availability of within-participant comparisons. As a general point, the treatment of incomplete periods can influence which participants contribute to a contrast and how uncertainty is estimated. Without the analysis population by comparison and the missing-data methods, the effect of missingness cannot be assessed. The group counts alone do not reveal why counts differ across conditions.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports no serious adverse events in the listed safety groups: each group has zero serious events among participants at risk. This is a description of the posted counts, not proof that serious events are impossible or that the study can exclude a risk. The record does not list serious adverse event terms.

Other adverse events are reported separately from serious events. The listed counts are 7 and 6 in the two Part A groups; 21, 17, and 22 in the Part B groups; and 3 and 1 in the two Part C sequence groups. The corresponding participants-at-risk counts are 14 for each Part A group, 88, 87, and 88 for the Part B groups, and 24 for each Part C group. These are counts as posted for each group, not a basis for combining participants across crossover periods.

The registry displays deaths as null rather than giving a numeric count, so deaths are not reported in the registry record. The adverse-event summaries do not provide event severity detail, causal attribution, or a formal comparison between conditions. They should therefore be read as descriptive safety counts only, not as evidence of a comparative safety difference.

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

The posted endpoint results describe systemic abemaciclib exposure in healthy participants under the formulations and food conditions studied. The AUC values and geometric coefficients of variation allow a reader to see the reported central exposure and relative dispersion for each listed group. They do not, on their own, answer whether a tablet formulation is statistically equivalent to the capsule reference or quantify a formal food effect.

Equivalence is not established merely because two reported group means appear close. A formal equivalence assessment requires a prespecified criterion and an estimate with uncertainty evaluated against that criterion. The registry does not post those comparison results, confidence intervals, or an equivalence conclusion. Similarly, the Part C values are descriptive summaries for fed and fasted conditions; without the formal comparison and its uncertainty, their separation is not by itself a conclusive estimate of food effect.

The findings are limited to pharmacokinetic measurements and safety information collected in the study population. Healthy participants are not the same as patients receiving treatment for a medical condition. The registry says the study was for research purposes and was not intended to treat a condition. No clinical efficacy endpoint is reported, and the record does not show whether differences in AUC correspond to any clinical benefit or harm.

The record also does not establish how precise the posted group summaries are as estimates of the contrasts of interest. The geometric coefficients of variation indicate relative variability, but they are not uncertainty intervals around comparisons. With no posted inferential analyses, the results support a descriptive account of observed exposure and adverse-event counts, while leaving formal comparative conclusions unresolved.

13. Why This Trial Matters Statistically

This trial illustrates why design and summary statistics must be considered together. A crossover design can make within-participant comparisons possible, while the registry’s posted endpoint results are group-level geometric summaries. The summaries communicate exposure levels and relative variability, but do not preserve the paired information needed to assess a crossover contrast and its precision.

It also demonstrates the distinction between a pharmacokinetic endpoint and a clinical outcome. AUC is a useful measure of overall systemic exposure, but it is not itself a measure of how a person feels, functions, or experiences a clinical event. The study’s focus is the behavior of abemaciclib in healthy participants under different formulations and meal conditions.

The record shows why a descriptive result should not be mistaken for an inferential conclusion. Values can be compared visually or read side by side, but a formal claim requires a defined estimand, analysis method, and uncertainty assessment. Those comparison results are not posted in the registry. In particular, a bioequivalence question cannot be resolved from the central values alone.

Finally, the endpoint summaries and safety summaries use different group counts and purposes. Recognizing that distinction helps prevent accidental pooling or overinterpretation. Statistical reporting is most informative when it presents the relevant analysis population, comparison estimate, uncertainty, and handling of missing data alongside the design and endpoint definitions.

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 for statistical interpretation is that the registry posts descriptive AUC summaries but no formal analysis results. It provides no comparison estimates, confidence intervals, or p-values, and does not report whether the formulations met a bioequivalence criterion. The reader cannot assess the precision of a contrast or determine the conclusion of a sponsor analysis from these summaries alone.

The record identifies the design as crossover but does not provide the analysis model, sequence-generation details, or treatment of period effects. Group summaries do not retain the within-participant correlation that is important to a paired comparison. The criteria for evaluable pharmacokinetic data and the handling of missing samples or incomplete periods are also not reported in the registry record.

The posted AUC results come from three separate study parts with different conditions and period structures. They should not be treated as a single combined comparison. The record does not report a formal adjustment or a hierarchy for the several formulation and food-condition questions. It also does not provide a sample-size justification or statistical analysis plan.

Generalizability is limited by the study population: the participants were healthy, and the study was described as research rather than treatment of a medical condition. The safety information is presented as counts, without detailed event descriptions, attribution, or comparative analysis. Death counts are not reported in the registry record. These limitations leave the posted results useful as descriptive pharmacokinetic and safety information, but insufficient for broader clinical conclusions.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study of Abemaciclib in Healthy Participants — NCT02672423.
• Registry record last updated 2019-01-04; status last verified 2018-12.
• Results first posted 2018-08-03.
• 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

NCT02672423 is a completed randomized, unmasked, phase 1 crossover study of abemaciclib in healthy participants. It examined capsule and tablet formulations and the effect of a high-fat meal on tablet pharmacokinetics across three parts. The registry reports enrollment of 127 and identifies AUC[0-∞] as the primary endpoint, summarized using geometric means and geometric coefficients of variation.

Descriptive AUC results are posted for each listed formulation and condition. The record does not report formal analyses, confidence intervals, p-values, or an equivalence conclusion. It defines the endpoint population as randomized participants who received at least one dose and had evaluable pharmacokinetic data, but does not describe missing-data methods or the analysis model.

Safety summaries report zero serious adverse events in the listed groups and separate counts for other adverse events. Death counts are not reported in the registry record. Overall, the posted information describes exposure and event counts but does not establish inferential or clinical conclusions.