Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of ISIS 443139 in Participants With Early Manifest Huntington's Disease: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of ISIS 443139 in Participants With Early Manifest Huntington's Disease (NCT02519036), a randomized phase 1, phase 2 study. The primary outcome is Number of Participants With Treatment-related Adverse Events (TEAEs).

2. Clinical Question

3. Trial Design

The registry describes a randomized, quadruple-masked, parallel-group study in Phase 1 and Phase 2. It was sponsored by Ionis Pharmaceuticals, Inc., and is listed as completed. The study began on 2015-08-06, with primary completion on 2017-11-08. The registry lists enrollment as 46. That enrollment figure should not be treated as the denominator for the primary outcome: the primary result uses the safety set, and the reported arm denominators vary.

The study compared placebo with five ISIS 443139 dose groups: 10 mg, 30 mg, 60 mg, 90 mg, and 120 mg. Each listed intervention was administered intrathecally on Study Days 1, 29, 57, and 85. The registry identifies the model as parallel, meaning participants were assigned to an arm rather than described as crossing between interventions. Randomization and quadruple masking are reported, but the identities of the masked roles and details of the randomization procedure are not reported in the registry record.

The stated purpose was to evaluate safety, tolerability, pharmacokinetics, and pharmacodynamics of multiple ascending doses in adults with early manifest Huntington's disease. The primary outcome was the number of participants with treatment-related adverse events, with a timeframe of up to approximately 28 weeks. The one listed secondary outcome concerns observed cerebrospinal fluid concentration for ISIS 443139. The registry reports eight outcome measures overall, while detailed results for only one secondary outcome are identified in the record. The trial's protocol-level allocation details, dose-escalation decision rules, and statistical analysis plan are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

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

Only the first 6 of 7 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Treatment-related Adverse Events (TEAEs), measured over Up to approximately 28 weeks.

The primary endpoint is the number of participants with treatment-emergent adverse events (TEAEs), reported in participants. Its timeframe is up to approximately 28 weeks. The registry describes an adverse event as an unfavorable or unintended sign, symptom, or disease temporally associated with the study or investigational drug, whether or not considered related to the drug. It defines a TEAE as an event that was present before the first dose and subsequently worsened, or an event that appeared after the first dose.

The endpoint is a participant count: each reported value represents participants meeting the endpoint definition, not the total number of separate events. A person can experience more than one adverse event, but this endpoint does not express that event burden. The distinction matters when reading the results: equal participant counts do not necessarily mean that the types, duration, severity, or number of events were equal.

Safety outcomes of this kind are relevant in an early-phase study evaluating escalating doses, since documenting adverse events is part of characterizing safety and tolerability. However, the endpoint's title refers to treatment-related events while the posted operational description focuses on whether an event emerged or worsened after dosing. The record does not give further detail about how treatment relatedness was judged for this endpoint. The count therefore should be interpreted according to the registry's stated definition rather than as proof that each event was caused by the study drug.

7. Results Posted in the Registry

• ISIS 443139 120 mg: 90.0% (9/10) versus 100.0% (12/12) on control; risk difference -10.0 percentage points (95% CI -28.6 to 8.6), risk ratio 0.90 (0.73–1.11); unadjusted two-proportion z-test p = 0.262.

8. Statistical Interpretation

9. Statistical Methods Explained

For a binary outcome such as whether a participant had at least one TEAE, the observed result in each arm can be expressed as a count of participants meeting the endpoint and the arm's safety-set denominator. These are the values reported for the primary endpoint. A participant-level outcome avoids counting the same participant multiple times when that person experiences several events, but it also does not describe the total number or pattern of events.

What does a risk difference describe?

A risk difference compares the proportion of participants meeting an outcome in one group with the corresponding proportion in another group. The registry reports the 120 mg group versus placebo, with a risk difference of -0.1. The negative sign indicates that the estimated outcome proportion in the 120 mg group was lower than the estimate in placebo for this comparison. This is an unadjusted comparison. It should not be confused with a risk ratio, which expresses a relative rather than an absolute contrast.

The registry also reports a risk ratio of 0.9 for that comparison. Risk differences and risk ratios use different scales, so their numerical values are not directly interchangeable. Neither measure by itself establishes that an intervention caused the observed difference. Interpretation also depends on uncertainty, study conduct, and the endpoint definition.

How should the p-value be read?

The reported unadjusted p-value is 0.262. In general, a p-value describes how unusual data at least as incompatible with a specified null model would be if that model and the test assumptions held. It is not the probability that the null hypothesis is true, and it does not measure the size or clinical importance of an effect. The registry record does not state the full testing procedure, its assumptions, or an analysis plan. The label unadjusted indicates that the reported value is not presented as adjusted for multiple comparisons.

Why does the confidence interval matter?

A confidence interval gives a range of effect estimates compatible with the data under the interval's method and assumptions. Here, the reported interval spans negative and positive values for the risk difference. That range includes the possibility of a lower event proportion in the 120 mg group and the possibility of a higher event proportion. It conveys substantial uncertainty around the point estimate. The bounds are not reproduced numerically because the posted bounds have more than three decimal places.

In general, sparse binary outcomes and small arm denominators can produce imprecise estimates. A count that differs by one participant may have a noticeable effect on an estimate when the group is small. General statistical explanation does not replace trial-specific information: the registry does not describe the method used to calculate the interval or whether it used an exact, normal-approximation, or other procedure.

What do the planning illustrations represent?

Planning illustrations based on an observed effect are not the trial's original design justification and are not observed power. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is defined as a stated fraction of the observed effect. For time-to-event outcomes, the illustration convention concerns total events; for other outcomes, it concerns participants per arm. These are general planning calculations, not evidence that the trial had a particular planned sample size or that it achieved a given power. The trial's own sample-size justification is not reported in the registry record.

The registry lists eight outcome measures and identifies one secondary outcome as posted. It reports no analyses count in the record. Those fields do not reveal whether all outcomes were assessed according to a prespecified hierarchy, how missing observations were handled, or whether additional comparisons were conducted. Those details are not reported in the registry record. The appropriate reading is limited to the outcome definitions and estimates actually posted, without assuming unreported modeling or adjustment procedures.

10. Confidence Intervals and Precision

The reported comparison of 120 mg with placebo has a risk difference of -0.1. Its confidence interval spans both negative and positive risk differences. In practical statistical terms, the interval includes estimates favoring a lower TEAE proportion in the 120 mg group as well as estimates favoring a higher proportion. The point estimate is therefore not precise enough, on its own, to settle the direction of the underlying difference.

A confidence interval communicates uncertainty about an estimated contrast, conditional on the method and assumptions used to construct it. It is not a range within which every participant's outcome lies, and it does not give the probability that the true effect is inside the particular interval. The registry record does not identify the calculation method or provide enough detail to evaluate its assumptions. The posted unadjusted p-value, 0.262, is consistent with the interval's failure to isolate one direction of difference, but the p-value and interval answer related rather than identical questions.

The arm denominators for the primary outcome are small, ranging from 3 participants in the 10 mg group to 12 in placebo. The 120 mg group has 10 participants in its denominator. With group sizes of this scale, the observed count can be an unstable guide to the underlying event proportion, and a limited number of outcomes can have a substantial influence on the estimate. The confidence interval is therefore important context for the observed counts.

Precision should not be confused with relevance. The endpoint is a safety measure, but the record does not establish how any estimated difference relates to the severity, timing, or clinical importance of individual events. Nor does the interval quantify uncertainty about unreported outcomes or longer-term follow-up. It applies to the reported comparison and endpoint, not to every dose, all safety questions, or disease-related outcomes.

11. Multiplicity, Missing Data and Analysis Populations

The registry identifies eight outcome measures, including the primary TEAE count and the secondary outcome of observed cerebrospinal fluid concentration for ISIS 443139. One secondary outcome is identified as posted. The record does not describe a prespecified hierarchy among outcomes, a family-wise error strategy, or other procedures for controlling multiplicity. It is therefore not possible to determine from the record how the broader set of outcomes was intended to affect interpretation of statistical tests.

The reported p-value for the 120 mg versus placebo comparison is explicitly unadjusted. It should be understood as the value for that comparison, not as an adjustment for the several dose groups or the multiple outcomes. The record does not report a testing plan for comparisons across all dose groups, and no inferential comparison is stated for each of the other dose groups. The absence of that information should not be filled by assuming that a particular adjustment was or was not planned.

The primary outcome population is defined as the safety set: participants who were randomized and received at least one dose. The arm-specific denominators are reported for this endpoint. The registry does not state how participants with incomplete follow-up, missing endpoint information, or withdrawal were handled, nor does it report an imputation method or sensitivity analysis. It is also not reported whether the posted endpoint counts use a particular rule for events occurring after discontinuation.

The record does not specify whether the analysis was intention-to-treat, per-protocol, or another analysis population for outcomes beyond the safety-set description. The detailed statistical analysis plan, including covariate adjustment and handling of repeated events, is not reported in the registry record. Consequently, interpretation should stay with the stated endpoint, safety population, arm counts, and reported unadjusted comparison rather than presuming methods that are not documented.

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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: post lumbar puncture syndrome (8.3%).

Serious adverse events are reported separately from the primary TEAE count. In the safety groups, the registry lists one participant with a serious adverse event in the placebo group and none in each ISIS 443139 dose group. It reports zero deaths in every listed group. These figures are participant counts, and they do not describe the full range of non-serious adverse events or their duration and severity.

The registry identifies post lumbar puncture syndrome as a serious adverse event term at 8.3%. The record does not give further context for this term in the information, such as the event's timing, outcome, or dose-group attribution. The percentage should therefore be read as the reported figure for that term rather than used to infer a rate within an individual dose arm.

Serious adverse event counts and the primary TEAE endpoint are not interchangeable. The primary endpoint counts participants meeting the TEAE definition, while the serious-event figures concern a subset classified as serious. A group can have many participants with TEAEs and few or no serious events. Conversely, a serious-event count alone does not capture the overall number or nature of adverse events. The registry figures are descriptive and do not establish that an event was caused by an intervention.

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

The results describe adverse-event experience in the study's safety set during follow-up of up to approximately 28 weeks. The primary endpoint counts participants with treatment-emergent adverse events, and the posted arm counts range from 3 of 3 in the 10 mg group to 12 of 12 in placebo, with 9 of 10 in the 120 mg group. These observations characterize the participants included in those arm-specific results; they are not precise estimates of what would occur in a broader population.

The reported comparison between 120 mg and placebo has an estimated risk difference of -0.1, with a confidence interval spanning both directions and an unadjusted p-value of 0.262. This does not establish a clear difference between those groups. It also does not establish equivalence or exclude differences that could matter. The record lacks a stated equivalence margin and does not report a design aimed at demonstrating equivalence.

These safety findings do not show whether ISIS 443139 improves, worsens, or has no effect on Huntington's disease symptoms or progression. The primary endpoint is not a measure of disease benefit. The listed secondary outcome on cerebrospinal fluid concentration does not, by itself, establish clinical benefit. The study's observations should not be generalized to populations or durations that are not described in the record.

Likewise, the posted counts do not determine causation. The endpoint definition describes the timing of treatment-emergent events, while the title uses the phrase treatment-related. Temporal association and a group-level count cannot prove that an individual event was caused by study drug. A complete interpretation would require detailed event descriptions, analysis methods, and context that are not reported in the registry record.

The result is best viewed as a limited, arm-level safety summary from a randomized early-phase study. It contributes descriptive information about the observed groups, but its uncertainty and the absence of a detailed statistical plan constrain stronger conclusions. No statement about overall benefit-risk or clinical use follows from these data alone.

14. Why This Trial Matters Statistically

This study is statistically informative because it illustrates the difference between an observed count and a precise estimate. The primary outcome counts participants with at least one qualifying event, and the groups have small denominators. A count can look straightforward while the uncertainty around a comparison remains wide enough to include effects in either direction. Reporting an interval alongside a point estimate helps make that uncertainty visible.

The multiple-dose structure also makes the scope of a comparison important. The registry reports several dose groups but gives a risk-difference estimate for 120 mg versus placebo. A result for that contrast does not automatically answer whether the other doses differ from placebo, whether there is a dose-response pattern, or how all outcomes should be considered together. Those questions require appropriate estimates and a transparent analysis plan, neither of which is fully documented in the record.

Another useful distinction is between a safety endpoint's label and its operational definition. The endpoint is titled treatment-related adverse events, but the description defines a TEAE using whether an event appeared or worsened after dosing. This illustrates why careful reading of the endpoint definition matters when interpreting an event count or making causal claims.

Finally, planning calculations based on the observed effect are illustrations rather than retrospective evidence of trial power. They depend on stated assumptions and do not substitute for a documented design rationale. Keeping those roles separate prevents an observed result from being mistaken for an original planning target or a guarantee of adequate precision.

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 endpoint results come from small arm-specific safety populations. The denominators range from 3 to 12 participants, limiting the precision and generalizability of the observed counts. The registry's overall enrollment figure of 46 is not the denominator used for the primary outcome, and the record does not provide an account reconciling enrollment with the arm-specific safety-set denominators.

The reported inferential comparison is limited to 120 mg versus placebo. Although the other dose groups have endpoint counts, the record does not post a risk-difference estimate and uncertainty interval for each of those contrasts. It is not possible to infer a dose-response relationship from the reported counts alone.

The endpoint description gives a treatment-emergent timing rule, but does not report detailed criteria for judging causality, severity grading, event duration, or adjudication. The serious adverse event summary likewise gives counts and a term, without detailed case narratives or arm attribution for the listed term. These omissions constrain interpretation of the clinical nature of the events.

The statistical analysis plan, sample-size justification, handling of missing outcome information, and multiplicity procedures are not reported in the registry record. Detailed results for the listed pharmacokinetic and pharmacodynamic evaluations are also not included in the registry record for this analysis. Follow-up beyond the stated primary-outcome timeframe and longer-term safety results are not reported. These limitations mean that the posted summaries cannot resolve all safety questions or support conclusions about disease outcomes.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of ISIS 443139 in Participants With Early Manifest Huntington's Disease — NCT02519036.
• Registry record last updated 2019-05-31; status last verified 2019-05.
• Results first posted 2019-05-31.
• 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

NCT02519036 is a completed randomized, quadruple-masked, parallel-group Phase 1/Phase 2 study sponsored by Ionis Pharmaceuticals, Inc. It evaluated intrathecal ISIS 443139 at 10 mg, 30 mg, 60 mg, 90 mg, and 120 mg, with placebo, in adults with early manifest Huntington's disease. The registry lists enrollment as 46 and the primary outcome timeframe as up to approximately 28 weeks.

The primary outcome was the number of participants with treatment-emergent adverse events in the safety set. The registry reports a risk difference of -0.1 for 120 mg compared with placebo, with an unadjusted p-value of 0.262 and a confidence interval spanning negative and positive risk differences. The record also lists observed cerebrospinal fluid concentration as a secondary outcome. A detailed statistical plan, missing-data approach, and multiplicity procedure are not reported in the registry record.