TAK-648 Multiple-Rising Dose Study in Healthy Japanese Participants and Non-Japanese Participants With Type 2 Diabetes Mellitus: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for TAK-648 Multiple-Rising Dose Study in Healthy Japanese Participants and Non-Japanese Participants With Type 2 Diabetes Mellitus (NCT02430870), a randomized phase 1 study. The primary outcome is Percentage of Participants Who Have at Least 1 Treatment-Emergent Adverse Event (TEAE) for Part 1.

2. Clinical Question

The central statistical question is descriptive: how often did at least one TEAE occur in the Part 1 TAK-648 and placebo groups during the stated observation period? The registry reports percentages for each group, together with the group sizes used for this result. It does not report a statistical comparison between the groups for this endpoint. Therefore, the posted values can be read as separate group summaries, not as an estimated treatment effect with a formal uncertainty interval or hypothesis test.

The study also included healthy Japanese participants in Part 2 and evaluated pharmacokinetic outcomes, including maximum plasma concentration and measures of area under the concentration-time curve. Those features address different questions from the Part 1 primary safety endpoint. The record does not report a primary Part 2 result in the registry record described for this analysis.

3. Trial Design

This was a phase 1, randomized, double-blind, placebo-controlled, parallel-group study of escalating multiple oral doses of TAK-648. The registry records quadruple masking. It describes the study as taking place at two centers and as including healthy participants and participants with type 2 diabetes mellitus. The enrollment was 48. The study status is completed; the recorded start is 2015-04 and primary completion is 2015-09.

The trial was organized into two parts with different populations and dose schedules. Part 1 involved participants with type 2 diabetes mellitus on a stable dose of metformin. The TAK-648 cohorts received 0.35 mg or 0.80 mg. Each Part 1 schedule included a single dose on Day 1, no study drug on Days 2 to 3, and once-daily administration from Day 4 through Day 17. The Part 1 placebo cohort followed the corresponding schedule.

Part 2 involved healthy participants of Japanese descent. Its TAK-648 cohorts covered doses of 0.05 mg, 0.15 mg, 0.35 mg, and 0.80 mg. The schedule described a single dose on Day 1, no drug administration on Days 2 to 3, and once-daily dosing from Day 4 through Day 10. A placebo cohort was also described for Part 2. These Part 2 cohorts are distinct from the Part 1 population and should not be combined with the Part 1 primary endpoint when interpreting the reported TEAE percentages.

Random allocation and masking describe how the study was organized, but the registry record does not report the allocation sequence method, concealment procedures, or which roles were included in the quadruple masking. It also does not report a statistical analysis plan or sample-size justification. The posted primary endpoint is a safety summary for Part 1, rather than a reported efficacy comparison. The record includes pharmacokinetic outcomes as secondary outcomes, but the corresponding numerical results 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 with a diagnosis of Type 2 Diabetes Mellitus (T2DM) were enrolled in 1 of 3 treatment groups: placebo, 0.35 mg or 0.80 mg TAK-648 in Part 1. Healthy Japanese volunteers were enrolled in 1 of 5 treatment groups: placebo, 0.05 mg, 0.15 mg, 0.35 mg or 0.80 mg TAK-648 in Part 2.

Only the first 6 of 8 groups are shown.

Part 1

Part 2

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Safety Analysis Set included of all participants who were enrolled and received at least 1 dose of study drug.

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: Randomized Set included all randomized participants.

Only the first 6 of 9 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants Who Have at Least 1 Treatment-Emergent Adverse Event (TEAE) for Part 1, measured over Up to Day 34.

The primary endpoint is the percentage of participants who had at least one treatment-emergent adverse event in Part 1, assessed up to Day 34. The registry defines an adverse event as an untoward medical occurrence in a participant administered a drug; a causal relationship to treatment is not required. A TEAE is an adverse event with onset after study drug is received. Thus, the endpoint records occurrence after treatment begins, not the investigator’s judgment that TAK-648 caused the event.

This endpoint is used to describe the frequency of participants experiencing any qualifying event during the observation period. Counting participants with at least one event gives a participant-level summary: a participant with multiple events still contributes to the endpoint as someone who experienced at least one. The measure does not convey how many events each affected participant had, how severe they were, or whether they led to treatment changes. Those questions require other reported outcomes and definitions.

For Part 1, the registry posts 83.3% for the 0.35 mg cohort, 33.3% for the 0.80 mg cohort, and 100.0% for placebo. The corresponding group sizes are 6, 6, and 4 participants. These percentages are descriptive and should be read with their small group sizes in mind. No confidence intervals or formal between-group test for this primary endpoint are reported in the registry record.

TEAE incidence is useful in a phase 1 study focused on safety and tolerability, but it is not a complete summary of safety. It does not distinguish types of events, duration, intensity, relatedness, or clinical importance. The registry separately reports serious adverse-event counts, which are considered in the safety discussion. A percentage with at least one TEAE should therefore be interpreted as one specific safety measure, not as a stand-alone assessment of the overall safety profile.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods can help distinguish a descriptive result from a comparative estimate. In this trial, the primary Part 1 outcome is a binary participant-level measure: each person either had at least one TEAE during the stated period or did not. The registry reports the percentage for each group and the group size. It does not report a confidence interval, a p-value, or a formal comparison for this primary outcome.

What does a percentage describe?

In general, a percentage with an event summarizes the share of a group whose participants meet a specified event definition. Here, the definition is at least one TEAE with onset after receiving study drug, assessed up to Day 34. A participant’s multiple events do not turn the endpoint into a count of all events; the endpoint is whether the participant had one or more. The posted values are 83.3% for TAK-648 0.35 mg, 33.3% for TAK-648 0.80 mg, and 100.0% for placebo. The associated group sizes are 6, 6, and 4.

Percentages make groups easy to describe on a common scale, but they do not remove the influence of small groups. With few participants, the status of an individual can have a substantial effect on a group percentage. This is a general feature of proportions in small samples, not evidence about which treatment is preferable. Confidence intervals are commonly used to express the uncertainty around an estimated proportion or difference. Such intervals are not reported for this endpoint in the registry record, so its precision cannot be read from an interval estimate.

Why is a group difference not the same as a treatment effect?

In general, a treatment-effect estimate compares outcomes between treatment groups and is interpreted with its uncertainty and the study’s design in view. The posted Part 1 percentages permit a descriptive look across groups, but the registry does not report an inferential comparison for the primary endpoint. The record indicates that comparative values were missing or not estimable for a two-arm comparison. Therefore, a numerical contrast, confidence interval, or significance test should not be reconstructed from the percentages as if it were the sponsor’s analysis. The discrepancy flag is false, but that does not create a reported treatment-effect analysis.

Randomization can support a fair comparison by assigning participants to study groups in a way intended to reduce systematic differences. Masking can reduce some influences on treatment delivery or outcome assessment. Those are general design principles. The registry records randomized allocation, quadruple masking, and a parallel model, but does not describe the detailed implementation of allocation or masking. It also does not report a statistical model for the primary endpoint. No particular adjustment, continuity correction, or exact test can therefore be attributed to the sponsor.

How should the planning assumptions be read?

General sample-size planning asks how many participants per arm would be needed to detect a specified effect under chosen assumptions. The registry’s planning illustration is described as using the observed effect, a stated fraction of that effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. These assumptions define a planning exercise; they are not a report of the trial’s original design justification and do not represent observed power. The registry record does not report the trial’s own sample-size justification. No planning result should be read as an observed trial finding.

The registry notes that planning illustrations for time-to-event outcomes use a total number of events, while other illustrations use participants per arm. That distinction is general: event-driven designs depend on the number of observed events, whereas many other calculations are expressed in participants. Neither type of planning quantity is an outcome observed in this trial. The results discussed for the primary endpoint are observed participant-level TEAE percentages, not planned sample sizes.

What do the secondary outcomes contribute?

The registry lists pharmacokinetic outcomes including Cmax, Tmax, AUClast, and AUC∞ for Parts 1 and 2. In general, Cmax refers to the maximum plasma concentration, Tmax to the time to that maximum, and area-under-the-curve measures summarize concentration over time according to their stated intervals. These outcomes describe drug exposure rather than the binary TEAE endpoint. Their numerical results and the methods used to analyze them are not reported in the registry record. The record lists 10 posted secondary outcomes and 18 outcome measures overall, but does not describe a multiplicity procedure or a full analysis plan.

Over-dispersion is a general issue for some count outcomes when observed variability exceeds what a simple probability model assumes. It is not the core issue for this primary endpoint, which is reported as a participant percentage rather than an event count per person. If repeated event counts or other outcomes were analyzed, model choice would depend on their distributions and the analysis plan; those details are not reported. The appropriate reading is therefore limited to the posted summaries and the distinctions the registry itself defines.

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("Part 1 Cohort 1: TAK-648 0.35 mg", "Part 1 Cohort 2: TAK-648 0.80 mg", "Part 1: Placebo Cohort 1-2")
n      <- c(6, 6, 4)
events <- c(5, 2, 4)
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  Part 1 Cohort 1: TAK-648 0.35 mg  6  5  83.3  35.9  99.6  43.6  97.0  42.1  96.3
ARM  Part 1 Cohort 2: TAK-648 0.80 mg  6  2  33.3  4.3  77.7  9.7  70.0  9.9  71.0
ARM  Part 1: Placebo Cohort 1-2  4  4  100.0  39.8  100.0  51.0  100.0  47.8  99.5

11. Multiplicity, Missing Data and Analysis Populations

The registry record identifies one primary endpoint in the results: the percentage of Part 1 participants with at least one TEAE up to Day 34. It also lists secondary outcomes, including pharmacokinetic measures for Parts 1 and 2, and reports 10 posted secondary outcomes and 18 outcome measures overall. However, the registry record does not report how multiplicity across endpoints, doses, or analyses was handled. Without a stated procedure, the reader cannot determine whether any adjustment was planned or applied to control the chance of false-positive findings across multiple statistical tests.

For the primary TEAE endpoint, the record posts group percentages and group sizes but no confidence intervals or formal comparison. It does not report a method for handling missing endpoint data, withdrawals, or participants with incomplete observation. The Safety Analysis Set is defined as participants who were enrolled and received at least one dose of study drug. The endpoint description does not give additional rules for event coding, follow-up after discontinuation, or the treatment of incomplete records.

The record lists no analyses for this endpoint in the registry record described. That is different from evidence that no analysis was performed; it means the registry record does not report an analysis result. The comparative calculation is marked as unavailable or not estimable for a two-arm binary-percentage comparison. Consequently, no reported inferential comparison can be used to resolve the descriptive differences among the group percentages.

Missing-data methods and multiplicity procedures can materially affect interpretation, particularly when many outcomes or groups are considered. In general, a complete-case description, an imputation approach, and a model-based analysis may answer somewhat different questions when observations are incomplete. These are general methodological considerations; the registry record does not identify which approach, if any, was used. The result should therefore be interpreted as the posted group-level summary, with the analysis population definition and reporting gaps kept in view.

12. 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 serious adverse-event listing reports zero participants affected in each listed cohort. For Part 1, the at-risk counts are 6 for TAK-648 0.35 mg, 6 for TAK-648 0.80 mg, and 4 for placebo; the corresponding serious-event affected counts are 0, 0, and 0. For Part 2, the at-risk counts are 6 in each TAK-648 cohort and 8 in placebo, and the serious-event affected counts are 0 in each listed cohort.

These are counts of participants with serious adverse events, not counts of all adverse events. They should not be confused with the primary TEAE percentages, which include any qualifying treatment-emergent adverse event and do not require seriousness or a causal link to treatment. Zero affected participants in a small study does not establish that serious events cannot occur or precisely characterize their likelihood in a broader population. Death counts are not reported in the registry record.

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

The result does mean that the registry reports different observed percentages of participants with at least one TEAE across the Part 1 groups during follow-up up to Day 34. The posted values are 83.3% for TAK-648 0.35 mg, 33.3% for TAK-648 0.80 mg, and 100.0% for placebo. The associated group sizes are 6, 6, and 4. These are descriptive results for this trial’s defined population, dosing schedules, and endpoint.

The result does not establish that TAK-648 caused or prevented any particular event. The registry’s definition of TEAE is based on timing after study drug, and does not require a causal relationship. The percentages do not tell which events occurred, how severe or persistent they were, how many events participants experienced, or whether events were judged related to treatment. The separate serious adverse-event listing reports no participants affected in the listed groups, but it does not replace the broader TEAE summary.

The posted percentages also do not demonstrate a statistically reliable difference between TAK-648 and placebo. The record does not report a formal comparison, confidence intervals, or p-values for the primary endpoint, and it indicates that a two-arm comparison was not estimable from the posted values. The numerical ordering of the percentages should not be treated as proof of a dose-response pattern. Small group sizes also mean that the observed percentages provide limited precision.

Nor does this endpoint establish efficacy. It is a safety measure in a phase 1 study, while the listed secondary outcomes concern pharmacokinetics. The registry record does not report numerical pharmacokinetic results in the registry record described, and the primary result is not a measure of diabetes control or another clinical benefit. Conclusions should remain confined to the participant-level TEAE summaries and other explicitly reported safety counts.

Finally, the result does not establish what would happen in populations, settings, schedules, or durations beyond those recorded. Part 1 involved participants with type 2 diabetes mellitus on stable metformin and a specified dosing schedule; Part 2 involved healthy participants of Japanese descent and a different schedule. The posted figures should not be generalized across those populations or to other treatment contexts without additional evidence.

14. Why This Trial Matters Statistically

This trial illustrates a common statistical distinction in early clinical research: a clear descriptive endpoint can be available even when a formal comparative result is not. The Part 1 primary outcome is defined at the participant level and reported as a percentage with at least one TEAE. That makes the result straightforward to describe, while leaving important questions about comparative precision unanswered because confidence intervals and a formal test are not reported.

The study also demonstrates why a denominator matters when reading percentages. The posted group sizes are 6, 6, and 4 for the primary Part 1 result. In general, percentages based on small groups can change noticeably with the outcome status of a participant. Reporting the group sizes alongside the percentages helps readers understand the scale of the evidence without mistaking a percentage for a precise population estimate.

Another statistical issue is separation of populations and questions. Part 1 concerns participants with type 2 diabetes mellitus on stable metformin, while Part 2 concerns healthy Japanese participants. Dose levels and dosing periods also differ between the parts. Combining the parts to create a larger-looking summary would obscure the distinct populations and would not match the Part 1 primary endpoint as registered.

Finally, the record shows that safety, tolerability, and pharmacokinetics were central study objectives, but the reported primary value addresses only one safety dimension. TEAE incidence is not a complete account of adverse-event type, severity, or causality, and pharmacokinetic outcomes answer a separate exposure question. The record’s missing inferential details and unreported numerical secondary results are relevant statistical context, not evidence that the unreported analyses had any particular outcome.

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 principal limitation for interpretation is the limited size of the Part 1 groups: the registry reports 6 participants in each TAK-648 cohort and 4 in placebo for the primary endpoint. These group sizes make the posted percentages descriptive and constrain how precisely they can represent event incidence beyond the participants observed. The registry record does not provide confidence intervals to express that uncertainty.

The record does not report a formal statistical comparison for the primary endpoint, a p-value, or a comparative effect estimate. It also does not provide the analysis method, missing-data rules, or a detailed statistical analysis plan. Therefore, the apparent differences among the percentages cannot be interpreted as statistically established treatment effects, and no independent treatment-effect calculation is presented.

The endpoint itself has a limited scope. It counts participants with at least one TEAE up to Day 34, without conveying event number, type, severity, duration, or causal assessment. Serious adverse events are reported separately, with no participants listed as affected in the cohorts, but death counts are not reported in the registry record. The absence of a reported serious event in these groups does not settle broader safety questions.

Generalizability is also limited by the distinct study parts and populations. Part 1 involved participants with type 2 diabetes mellitus on stable metformin and its own dosing schedule; Part 2 involved healthy Japanese participants and a different schedule. The trial is phase 1, and the registry record does not establish how these findings apply outside the study populations and conditions recorded. The record also does not report numerical results for the listed pharmacokinetic outcomes or the trial’s sample-size justification, so those aspects cannot add further context to the primary result.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: TAK-648 Multiple-Rising Dose Study in Healthy Japanese Participants and Non-Japanese Participants With Type 2 Diabetes Mellitus — NCT02430870.
• Registry record last updated 2016-08-31; status last verified 2016-07.
• Results first posted 2016-08-31.
• 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

NCT02430870 is a completed phase 1, randomized, double-blind, placebo-controlled, parallel-group study of multiple oral TAK-648 doses. The registry records quadruple masking, two centers, enrollment of 48, a start in 2015-04, and primary completion in 2015-09. Part 1 involved participants with type 2 diabetes mellitus on stable metformin; Part 2 involved healthy participants of Japanese descent.

The Part 1 primary endpoint was the percentage with at least one TEAE up to Day 34. The posted values were 83.3% for TAK-648 0.35 mg, 33.3% for TAK-648 0.80 mg, and 100.0% for placebo, with group sizes of 6, 6, and 4. No formal comparison or confidence interval is reported. Serious adverse-event affected counts are zero in each listed cohort; death counts are not reported in the registry record. The registry lists pharmacokinetic secondary outcomes, but their numerical results and the detailed analysis plan are not reported in the registry record.