Safety, Tolerability, and Pharmacokinetics of Multiple Rising Doses of TAK-137 in Adults With Attention-Deficit/Hyperactivity Disorder.: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety, Tolerability, and Pharmacokinetics of Multiple Rising Doses of TAK-137 in Adults With Attention-Deficit/Hyperactivity Disorder. (NCT02163915), a randomized phase 1 study. The primary outcome is Percentage of Participants Who Experience at Least One Treatment Emergent Adverse Event (TEAE).

2. Clinical Question

3. Trial Design

This was a phase 1 randomized, double-blind, placebo-controlled study with quadruple masking and a parallel-group model. Its stated purpose was to characterize the safety and tolerability of multiple oral doses of TAK-137 in adults with ADHD. Takeda is listed as the sponsor. The registry record lists the study as terminated; a reason for termination is not reported in the registry record.

The listed dose cohorts were TAK-137 0.5 mg, 2 mg, 5 mg, and 10 mg, each taken once daily on Days 1-7. A fifth TAK-137 cohort was also described, with its dose to be determined from data collected in Cohorts 1-3. Placebo-matching tablets were listed for Cohorts 1-5. The posted primary outcome groups include placebo and the first four TAK-137 doses; a result for the fifth cohort is not reported in the registry record.

The registry record lists a study start of 2014-06 and primary completion of 2014-11. Enrollment is listed as 47. The primary outcome used the safety analysis set, defined as participants who received at least one dose of study drug. This safety outcome was assessed from Day 1 up to Day 14, a period that includes the dosing days and extends beyond them. The registry record does not report the reason for termination, cohort-specific allocation procedures, or details of how participants were assigned within cohorts.

Randomization and masking describe safeguards intended to reduce selection and assessment biases, but they do not remove the uncertainty created by small cohort sizes. The parallel design means the reported groups are separate treatment groups rather than repeated treatment periods for each participant. Details such as the allocation ratio and any procedures used to maintain masking 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 historical diagnosis of attention-deficit/hyperactivity disorder (ADHD) were enrolled in one of the five cohorts to receive TAK-137 (0.5 milligram \[mg\], 2 mg, 5 mg, 10 mg, or matching placebo) once daily for up to 7 days.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Safety analysis set was defined as all participants who received at least one 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: Safety analysis set was defined as all participants who received at least one dose of study drug.

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants Who Experience at Least One Treatment Emergent Adverse Event (TEAE), measured over Day 1 up to Day 14.

The primary endpoint is the percentage of participants who experienced at least one treatment-emergent adverse event (TEAE) from Day 1 up to Day 14. The registry defines an adverse event as an unfavorable or unintended medical occurrence in a participant who received a drug. It may be a sign, symptom, disease, or clinically significant laboratory finding, and it does not have to be considered related to treatment. A TEAE is defined by timing: its onset occurs after the participant receives study drug.

This endpoint is used to describe the occurrence of adverse events during the stated observation period. Counting participants with at least one event gives a participant-level summary: a participant is counted as having an event whether they had one qualifying event or more than one. It therefore does not describe the total number of events, their duration, severity, or relationship to treatment. Those details are not conveyed by the primary percentage alone.

For a phase 1 study whose stated purpose is to characterize safety and tolerability, this kind of measure can describe how often participants experienced an event after dosing. Its interpretation depends on the population analyzed, the event definition, the observation window, and the size of each group. The posted percentages address occurrence in the safety analysis set; they do not establish that TAK-137 caused the reported events. Causal attribution and fuller clinical descriptions are not reported in the primary endpoint results.

7. Results Posted in the Registry

• Cohort 2: TAK-137 2 mg: 0.0% (0/10) versus 50.0% (5/10) on control; risk difference -50.0 percentage points (95% CI -81.0 to -19.0); unadjusted two-proportion z-test p = 0.010.
• Cohort 4: TAK-137 10 mg: 20.0% (2/10) versus 50.0% (5/10) on control; risk difference -30.0 percentage points (95% CI -69.7 to 9.7), risk ratio 0.40 (0.10–1.60); unadjusted two-proportion z-test p = 0.160.

8. Statistical Interpretation

9. Statistical Methods Explained

The posted outcome is a binary participant-level measure: each participant either experienced at least one TEAE during the stated period or did not. The registry expresses this outcome as a percentage of participants. In general, a percentage is calculated from the number of participants meeting the endpoint and the number evaluated in the group. The posted group sizes and percentages allow readers to see the scale of the evidence, but small groups mean that each participant’s outcome can noticeably affect the percentage.

What does a risk difference describe?

In general, a risk difference subtracts the event proportion in a reference group from the event proportion in another group. A negative estimate means the observed proportion was lower in the named treatment group than in the reference group, while a positive estimate means it was higher. It is an absolute contrast, expressed on the probability scale. For the 2 mg cohort, the reported risk difference is -0.5; for the 10 mg cohort, it is -0.3. These are registry-reported estimates, not additional calculations. A risk difference can be clinically easier to interpret than a relative measure because it describes an absolute change in event probability, but it remains uncertain when based on small groups.

What do risk ratios and odds ratios add?

In general, a risk ratio compares the event probability in one group with the event probability in another. An odds ratio compares the odds rather than the probabilities. Both are relative measures, and their numerical meaning differs from an absolute risk difference. The registry reports a risk ratio of 0.4 and an odds ratio of 0.25 for the 10 mg comparison, each with an interval. Because their intervals include the no-difference reference value of 1, those estimates are not precise enough to rule out no relative difference on the basis of the posted interval. Relative measures can also be difficult to interpret when event counts are sparse, so the group event counts and absolute contrast are important context.

How should the p-values be read?

In general, a p-value measures how incompatible the observed data are with a specified null model, under the assumptions of the statistical test. It is not the probability that the null hypothesis is true, and it does not quantify the probability that the finding will replicate. The registry reports unadjusted p-values of 0.01 for the 2 mg comparison and 0.16 for the 10 mg comparison. “Unadjusted” means the reported value is not presented as corrected for multiple comparisons. The test details and any pre-specified multiplicity strategy are not reported in the registry record.

These p-values should be considered alongside the estimates, intervals, group sizes, and the number of dose groups examined. A small p-value does not make an estimate precise or establish causality; a larger p-value does not demonstrate equivalence. With small group sizes, sparse event counts can make statistical procedures sensitive to their assumptions. The methods used to calculate the reported intervals and p-values are not reported in the registry record, so the exact analysis cannot be independently characterized from the registry summary alone.

Why do the event counts matter?

The posted primary outcome percentages correspond to 5 of 10.0 participants for placebo, 5 of 8.0 for 0.5 mg, 0 of 10.0 for 2 mg, 6 of 9.0 for 5 mg, and 2 of 10.0 for 10 mg. These counts make clear that the percentage differences rest on few participants. One person’s outcome can shift a group percentage substantially when the denominator is small. The pattern across the cohorts is not a simple progression with dose, and no dose-trend analysis is reported in the registry record.

In general, statistical uncertainty tends to be greater with fewer observations, especially when the event is uncommon or absent in a group. Standard methods that rely on large-sample approximations may be less reliable with sparse counts. Alternative approaches can be considered in such settings, but the registry does not identify the methods used for the comparisons. No recalculated estimates are presented because the registry comparisons are the posted analyses and there is no reported discrepancy to resolve.

What do the planning figures mean?

The registry includes a planning illustration for the 10 mg comparison, based on the observed effect and stated assumptions: a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. In general, such illustrations estimate the participants per arm that might be needed to detect an effect under those assumptions. The listed scenarios are planning for 100%, 75%, and 50% of the observed effect. For 80% power, the corresponding figures are 39, 73, and 170 participants per arm; for 90% power, they are 52, 97, and 227 participants per arm.

These are planning illustrations, not observed power and not a statement of the trial’s original sample-size justification. They use the observed effect as a starting point, and the assumed effect size strongly influences the resulting figures. The rationale for the original enrollment and any prospective sample-size calculation are not reported in the registry record. The illustration is available only for the 10 mg contrast in the posted results.

10. Confidence Intervals and Precision

The reported intervals communicate uncertainty around the comparison estimates. In general, a confidence interval is a range produced by a statistical procedure that, under its assumptions, reflects the precision of an estimate. A wider interval indicates less precision than a narrower interval on the same scale. An interval is not a guarantee that the true effect lies within its bounds, nor does it show the range of individual participant outcomes.

For the 2 mg comparison, the risk difference is -0.5 and the reported interval extends from -0.810 to -0.190. This interval is entirely below zero, the reference value for no absolute difference. The point estimate is a large absolute contrast, but the interval remains broad, reflecting uncertainty around its magnitude. The observed event counts were 0 of 10.0 in the 2 mg group and 5 of 10.0 in placebo.

For the 10 mg comparison, the risk difference is -0.3, with an interval from -0.697 to 0.097. Since that range crosses zero, the posted interval includes no absolute difference as well as differences in either direction. The reported risk-ratio interval, from 0.1 to 1.599, and odds-ratio interval, from 0.034 to 1.819, each include 1, their reference value for no relative difference. These ranges are wide in relation to their estimates, so the relative effects are imprecisely determined.

There are no intervals posted for the individual cohort percentages in the primary outcome listing. The methods for calculating the comparison intervals are not reported in the registry record. With group sizes of 8.0 to 10.0 and few events, small changes in observed counts could materially alter estimates. The intervals therefore warrant more weight than a simple comparison of point estimates, while still being understood as conditional on the analysis method and assumptions.

Precision is not the same as importance. An estimate can be large but imprecise, and a precise estimate would still require interpretation in light of the endpoint, population, and study design. These results describe a short observation period and a small phase 1 study; they do not establish how estimates would behave in a larger or different population.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists comparisons for the 2 mg and 10 mg cohorts against placebo, while the primary outcome also reports values for the 0.5 mg and 5 mg cohorts. The registry record lists 0 analyses and does not report a detailed statistical analysis plan or a multiplicity adjustment. The two posted p-values are explicitly unadjusted. When several doses or outcomes are examined, the chance of observing an apparently unusual result can increase across the collection of comparisons. In general, multiplicity procedures are used to control or describe that issue, but no such procedure is reported. The unadjusted results should therefore be treated as exploratory evidence rather than as a complete family-wise assessment.

The registry lists 10 outcome measures and four posted secondary outcomes related to TAK-137 pharmacokinetics: maximum observed plasma concentration, maximum observed plasma concentration at steady state, time to reach maximum concentration, and area under the plasma concentration-time curve over the dosing interval. Numerical results for those measures are not included in the registry record for this analysis; their values are not reported in the registry record. The registry record also does not report how multiplicity across safety and pharmacokinetic outcomes was handled.

The safety analysis set is defined as all participants who received at least one dose of study drug. This definition identifies the population used for the primary safety measure, but the registry record does not report how missing outcome observations were handled, whether any participants lacked endpoint data, or whether sensitivity analyses were conducted. It also does not report a separate intention-to-treat analysis population or details of exclusions from the safety set. The posted group sizes identify the denominators for the outcome groups, but do not explain the disposition of all enrolled participants.

In general, missingness matters because a percentage among participants with outcome data may not represent everyone assigned to a group if outcome availability is related to treatment or events. No assumptions about missing outcomes can be made from the registry record. Likewise, the available information does not establish whether the analyses were specified before the results were observed. These gaps limit assessment of selective reporting and the robustness of the comparisons.

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 0% reporting threshold.

Most frequent non-serious adverse event terms

The serious adverse event summary reports zero affected participants in the placebo group and in each of the four listed TAK-137 dose groups. The corresponding numbers at risk are 10, 8, 10, 9, and 10. The registry also lists no serious adverse event terms in its serious-event summary. These figures concern serious adverse events specifically; they should not be confused with the primary TEAE endpoint, which includes adverse events that are not classified as serious.

Zero reported serious events in these small groups means no affected participants are recorded in the listed groups during the registry’s serious-event reporting. It does not prove that serious events cannot occur, or that the groups are equivalent in serious-event risk. Rare events can be missed in small studies, and a short observation period may provide limited opportunity to observe events. The serious-event reporting timeframe is not separately stated in the registry information.

Death counts are not reported in the registry record. This should not be rephrased as confirmation that there were no deaths. The summary also does not provide narrative descriptions, severity grades for non-serious events, or investigator judgments about causality. The primary TEAE percentages offer a broader count of participants with at least one event, while the serious-event figures provide a narrower category. Neither summary alone gives a complete account of the clinical character or cause of reported events.

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

The results describe the proportion of participants in small treatment cohorts who experienced at least one TEAE from Day 1 up to Day 14. The observed percentages ranged from 0.0% in the 2 mg group to 66.7% in the 5 mg group, with 50.0% in placebo, 62.5% in the 0.5 mg group, and 20.0% in the 10 mg group. This variation is descriptive and does not form a steadily ordered pattern across the tested doses.

The posted 2 mg comparison has a negative risk difference and an interval entirely below zero, while the 10 mg comparison has an interval that crosses zero. These estimates summarize the observed comparisons with placebo, but the small group sizes make the effect sizes uncertain. The registry does not report comparisons for every dose cohort, and the unadjusted p-values do not account for any multiplicity. The record also does not report the reasons for study termination, a detailed analysis plan, or missing-data methods.

The findings do not establish that TAK-137 caused or prevented the adverse events. A TEAE is defined by its onset after study drug is received, not by a judgment that the drug caused it. The endpoint does not describe the number of events per participant, their severity, or their clinical significance. The zero serious adverse event counts do not establish the absence of risk, particularly given the small groups and the limited observation window.

The study’s stated objective was safety and tolerability characterization, not a test of ADHD symptom benefit. The registry record does not report a clinical efficacy endpoint in the registry record used for this analysis. These data therefore cannot answer whether TAK-137 improves ADHD symptoms, nor can they establish longer-term safety. They are best read as early, short-term safety observations in the enrolled study groups, with substantial uncertainty and incomplete reporting on several analytic details.

In general, a phase 1 result can inform subsequent questions about tolerability and pharmacokinetics, but it is not by itself a basis for broad conclusions about all adults with ADHD. Differences between these small cohorts could reflect the limited amount of information available, as well as genuine differences; the registry results do not distinguish between those possibilities.

14. Why This Trial Matters Statistically

This study illustrates how a simple binary safety endpoint can look different across several small dose cohorts. Reporting both percentages and group sizes helps readers recognize that each percentage rests on a limited number of participants. The 0.0% result in the 2 mg group and 66.7% result in the 5 mg group may appear striking when considered alone, but the underlying group sizes are 10.0 and 9.0. In small groups, individual outcomes have substantial influence on the displayed proportions.

The comparisons also show why absolute and relative measures should be read together with their uncertainty. The risk differences express absolute contrasts, while the reported risk ratio and odds ratio describe relative contrasts for the 10 mg comparison. Their intervals communicate that the estimates are not highly precise. A point estimate is not a complete result: its interval, event counts, comparator, and analysis context all matter.

The registry record also demonstrates the distinction between outcome reporting and a full analysis plan. The posted results include unadjusted p-values and comparison estimates, but the multiplicity strategy, missing-data approach, and interval calculation methods are not reported. Without those details, readers should be cautious about treating a single p-value as conclusive, especially when multiple dose groups and outcomes are listed.

Finally, the planning illustration based on the 10 mg observed effect shows how sample-size requirements depend on the effect size assumed for future planning. It is not the study’s observed power and does not reveal the original sample-size rationale. Keeping planning assumptions separate from observed results is important: a calculation based on an observed contrast does not make that contrast more certain. The statistical value of this record lies in the concrete description of early outcomes and in the questions it leaves open for better-reported, larger studies.

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.
• Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.

The principal limitation is the small size of the reported dose groups: the outcome denominators range from 8.0 to 10.0. Consequently, the percentages are sensitive to the outcome of a small number of participants, and the estimates have limited precision. The comparison intervals reinforce this uncertainty, particularly for the 10 mg group, where the risk-difference interval crosses zero.

The primary endpoint captures whether a participant had at least one TEAE, not the number of events, their duration, severity, or causal relationship to study drug. The registry’s definition explicitly allows events that are not considered related to treatment. A more detailed breakdown of event types and investigator assessments is not reported in the registry record. The serious-event summary is also sparse, and death counts are not reported in the registry record.

Only comparisons for the 2 mg and 10 mg cohorts are posted. There is no reported formal comparison for the 0.5 mg or 5 mg groups, and no dose-response analysis is reported in the registry record. The absence of a smooth pattern in the descriptive percentages should not be treated as proof that dose has no relationship with events. Conversely, an apparent difference in one cohort should not be treated as a reliable dose effect without appropriate analysis and replication.

Further limitations include the lack of reported methods for handling missing outcome data, details of the statistical tests and interval calculations, and a documented multiplicity strategy. The registry record does not explain why the study was terminated or provide the original sample-size rationale. The fifth cohort’s dose was to be determined from earlier cohort data, but its outcome is not included in the posted primary results. The short primary outcome timeframe, Day 1 up to Day 14, also restricts interpretation to the period described; longer-term outcomes are not established by these data.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Safety, Tolerability, and Pharmacokinetics of Multiple Rising Doses of TAK-137 in Adults With Attention-Deficit/Hyperactivity Disorder. — NCT02163915.
• Registry record last updated 2016-07-11; status last verified 2016-06.
• Results first posted 2016-07-11.
• 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.

19. Record Summary

NCT02163915 is a phase 1 randomized, double-blind, placebo-controlled study of multiple rising oral doses of TAK-137 in adults with ADHD. It used quadruple masking and a parallel-group model, and Takeda is listed as sponsor. The registry lists enrollment as 47, a study start of 2014-06, primary completion of 2014-11, and status as terminated. A reason for termination is not reported in the registry record.

The primary endpoint was the percentage of participants with at least one TEAE from Day 1 up to Day 14 in the safety analysis set. Posted percentages were 50.0% for placebo, 62.5% for TAK-137 0.5 mg, 0.0% for 2 mg, 66.7% for 5 mg, and 20.0% for 10 mg. Comparisons with placebo are reported for 2 mg and 10 mg. The groups are small, and several details about analysis methods, multiplicity, and missing data are not reported in the registry record.

The results provide short-term descriptive safety information. They do not establish causality, longer-term safety, or clinical benefit for ADHD.