Safety and Efficacy of AbobotulinumtoxinA for the Treatment of Platysmal Bands: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety and Efficacy of AbobotulinumtoxinA for the Treatment of Platysmal Bands (NCT04080882), a randomized phase 2 study. The primary outcome is Responder Rate at Month 1 for a Single Dose of abobotulinumtoxinA Compared to Placebo.

2. Clinical Question

3. Trial Design

The registry record describes NCT04080882 as a randomized, double-blind, phase 2 study of abobotulinumtoxinA for platysmal bands. Its official title characterizes it as multicenter, dose-ranging, double-blind, and placebo-controlled. The record lists a sequential model and an enrollment of 80. The study began on 2019-09-25, had primary completion on 2019-12-30, and is marked completed.

The planned intervention list names placebo and three abobotulinumtoxinA doses, each described as being injected into platysma bands. However, the primary-outcome population note states that, due to a business decision, the study did not proceed to enroll dose 2 or dose 3. The posted primary comparison is consequently between placebo and Dose 1. It should not be interpreted as an observed comparison among all the dose groups named in the intervention list.

The primary outcome was the count of participants meeting the responder definition at Month 1 after treatment. The record gives 20 participants in the placebo group and 60 in the Dose 1 group for that outcome. It records 3 placebo responders and 36 Dose 1 responders. The registry record does not report the allocation procedure in further detail, such as how the randomization sequence was generated or concealed. It also does not report the exact masking procedures or which roles remained masked.

The title and design fields establish the randomized, double-blind, placebo-controlled framework, but do not supply a complete protocol or operational description. The original design rationale, planned enrollment by dose, and reasons beyond the stated business decision for not proceeding with the later doses are not reported in the registry record. The results therefore speak to the posted Dose 1 versus placebo comparison, with the design and reporting limitations described in the other statistical interpretations.

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: Due to business decision study did not proceed to enroll dose 2 or dose 3.

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: Due to business decision study did not proceed to enroll dose 2 or dose 3.

6. Primary Endpoint

The registry lists the primary outcome as Responder Rate at Month 1 for a Single Dose of abobotulinumtoxinA Compared to Placebo, measured over Month 1 after treatment.

The primary endpoint is the number of participants who met the responder definition at Month 1 after treatment. A responder was defined as a participant achieving grade 1 or 2 in platysmal band severity on the Investigator Live Assessment. The registry record labels the measure as a count of participants and gives the assessment time as Month 1 after treatment.

This binary responder definition turns an assessment into two categories for analysis: meeting the specified grade criterion or not meeting it. Reporting the count together with the group size allows the responder proportion to be understood within each group. For this endpoint, the registry record reports 36 responders among 60 participants in the Dose 1 group and 3 among 20 participants in the placebo group.

As a general statistical point, a prespecified binary endpoint can make a treatment comparison easier to interpret than a collection of ungrouped assessment scores, because the endpoint states in advance which outcomes count as responses. That convenience comes with a loss of detail: participants on opposite sides of the responder threshold may have assessments that are close, while participants on the same side may differ in severity. The registry record does not describe the full assessment scale, the rationale for choosing the grade threshold, or any additional endpoint details beyond the responder definition and timing. The endpoint therefore captures the particular categorical response recorded at Month 1, not every aspect of platysmal band severity, safety, durability, or response at other times.

7. Results Posted in the Registry

• AbobotulinumtoxinA Dose 1: 60.0% (36/60) versus 15.0% (3/20) on control; risk difference 45.0 percentage points (95% CI 25.0 to 65.0), risk ratio 4.00 (1.38–11.59); unadjusted two-proportion z-test p = <0.001.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is binary: each participant either meets the stated responder definition or does not. The definition is grade 1 or 2 on the Investigator Live Assessment at Month 1 after treatment. For a binary outcome, an analysis commonly begins by describing the number of participants with the event and the number assessed in each group. The registry gives 36 responders among 60 participants receiving Dose 1, and 3 among 20 receiving placebo. It also reports response proportions of 0.6 and 0.15, respectively.

The principal reported contrast is the risk difference, which subtracts one group's response proportion from the other group's response proportion. In this record, the reported risk difference is 0.45. In general, a risk difference is expressed on the same proportion scale as the outcome and describes an absolute contrast. It does not say how many participants would respond in a different population, and it is not interchangeable with a ratio measure. Its interpretation depends on the outcome definition, follow-up time, and groups being compared.

The registry also reports a risk ratio of 4.0 and an odds ratio of 8.5. These measures express contrasts differently from the risk difference. A risk ratio compares the response proportions directly, while an odds ratio compares the odds of response. As a general point, ratios can appear numerically larger or smaller than an absolute difference because they use different scales. The risk ratio and odds ratio are not substitutes for the group counts or for understanding how common the outcome was in each group. Their reported uncertainty ranges are wide, so point estimates should not be interpreted without considering that uncertainty.

The p-value is reported as unadjusted and < 0.001. In general, a p-value evaluates how unusual data at least as extreme as those observed would be under a specified statistical model. It does not measure the probability that the null hypothesis is true, nor does it communicate the precision or clinical importance of the estimated difference. The registry record does not identify the test used to obtain this p-value, the model details, or whether a different prespecified analysis was used by the sponsor. No adjusted p-value is reported.

The registry reports an interval for the risk difference. In general, an interval estimate conveys sampling uncertainty around an estimate, conditional on the method and assumptions used to calculate it. A narrower interval indicates greater precision on that measure's scale; a wider interval indicates less precision. The confidence level and calculation method are not reported in the registry record, so readers cannot verify the interval procedure or interpret its nominal coverage from this record alone. The interval remains useful as a reminder that the point estimate is not exact, but it should be read with that reporting gap in mind.

The trial is described as randomized and double-blind. Random allocation is intended, in general, to make treatment groups comparable on average at the time of assignment, including on characteristics that may not be measured. Masking is intended to reduce the influence of knowledge of assignment on care, assessment, or reporting. These design features can support a fair comparison, but the registry record does not report the sequence-generation method, allocation concealment, masking details, or whether masking was maintained. The design labels alone do not establish how successfully these protections were implemented.

The study title describes a dose-ranging design, and the interventions list includes three active doses plus placebo. The primary outcome note says that dose 2 and dose 3 were not enrolled because of a business decision. The reported primary comparison is therefore restricted to Dose 1 and placebo. The record does not provide results for un-enrolled doses or establish that the planned dose-ranging questions were answered. The sequential model is recorded, but details of the sequence or its consequences for the analysis are not reported.

Several elements needed to reproduce or fully appraise the statistical analysis are absent. The record does not describe the analysis population, the handling of participants with missing outcome assessments, whether the analysis followed assigned treatment, or any covariate adjustment. It does not identify a statistical analysis plan, the method for the interval estimate, or the test underlying the p-value. As a general principle, missing-outcome assumptions and analysis-population choices can affect both estimates and uncertainty. Since these details are not reported in the registry record, the posted outcome should be read as the recorded summary rather than as a fully reproducible analysis.

There is one posted outcome measure and no posted secondary outcomes. The record lists no analysis entries. This means the registry display does not offer a broader set of outcome comparisons with which to check consistency or evaluate other prespecified questions. It also means the available result cannot establish whether additional analyses were conducted outside the posted record. General concerns about multiplicity arise when many outcomes, time points, doses, or analyses are considered: repeated testing can increase the chance of a chance-positive finding if no suitable plan is used. The registry record does not report a multiplicity strategy, so no adjustment or absence of adjustment beyond the stated unadjusted p-value should be assumed.

10. Confidence Intervals and Precision

The reported risk difference is 0.45, with an interval estimate recorded in the registry. The lower and upper bounds are not repeated because the registry's displayed endpoints exceed the three-decimal-place limit for this explanation. The confidence level and interval calculation method are not reported in the registry record. Those details matter: an interval's interpretation depends on how it was constructed and the coverage level it was intended to have.

In general, a confidence interval communicates uncertainty around an estimate arising from sampling variation under a statistical method. It does not mean that all values inside the interval are equally likely, nor does it guarantee that the true value lies within that one computed interval. A wider interval indicates less precision than a narrower interval on the same scale. The uncertainty should be considered together with the point estimate and the counts, particularly because the placebo group contains 20 participants and 3 responders.

The registry also reports a risk ratio of 4.0 with interval bounds of 1.381 and 11.59, and an odds ratio of 8.5 with bounds of 2.244 and 32.19. These intervals span a substantial range of possible effect magnitudes on their respective scales. The ratio scales answer different questions from the absolute risk difference, so their intervals should not be directly compared numerically with the difference interval.

The interval estimates do not address every source of uncertainty. They cannot resolve questions about missing data, the exact analysis population, the interval method, or generalizability beyond the study. Those details are not reported in the registry record. The precision represented by the posted estimates is therefore conditional on the analysis and data as recorded, rather than a complete measure of uncertainty about the result in all settings.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size figures are planning illustrations based on the observed risk difference, not a report of the original trial's sample-size calculation. The figures are participants per arm, not total events. The planning assumptions listed in the registry record are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each scenario uses a stated fraction of the observed effect as the effect to detect. The trial's own original design assumptions are not reported in the registry record.

For planning for 100% of the observed effect, the illustration lists 17 participants per arm for 80% power and 23 participants per arm for 90% power. For planning for 75% of the observed effect, it lists 29 participants per arm for 80% power and 38 participants per arm for 90% power. For planning for 50% of the observed effect, it lists 59 participants per arm for 80% power and 79 participants per arm for 90% power. These are hypothetical planning scenarios, not observed group sizes or an alternative account of who took part.

In general, power is the chance that a study using a specified design and analysis would detect an effect of the chosen size at the chosen significance level, if that effect were present and the assumptions held. The 80% and 90% columns represent two planning targets: the latter aims for a greater chance of detecting the specified effect, and requires more participants in these illustrations. Smaller effects are harder to distinguish from random variation, so planning for a smaller fraction of the observed effect requires more participants per arm. These figures are not observed power.

The sample-size curve should be read as a visual aid to the same planning relationship: as the effect used for planning becomes smaller, the required group size increases under the listed assumptions. It does not show a separate trial result, and it does not reveal the sponsor's original calculation. Because the observed effect is used as the starting point, the illustrations depend on an estimate from this particular study and should not be treated as guaranteed requirements for another design or population.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.150; treatment proportion p₁ = 0.600; average p̄ = 0.375.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6847 = 1.3419.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6062 = 0.5102.
4. n = (1.3419 + 0.5102)² / (0.4500)² = 16.9, rounded up to 17 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.15                          # control proportion
p1 <- 0.6                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(4080882)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 17 (80% power), 23 (90% power)
 75% of observed effect: n per arm = 29 (80% power), 38 (90% power)
 50% of observed effect: n per arm = 59 (80% power), 79 (90% power)
power.prop.test: 16.9 
Simulated power at n = 17 per arm: 0.814 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry record lists one outcome measure, the Month 1 responder count, and no posted secondary outcomes. It also lists no analysis entries. This is a narrow posted results record; it does not describe a wider analysis plan or establish what analyses may have been conducted outside the registry. No multiplicity adjustment is reported. The reported p-value is explicitly unadjusted.

Multiplicity is a general statistical concern when several hypotheses are tested. Considering multiple outcomes, time points, doses, subgroups, or analysis choices can increase the chance that at least one result appears statistically notable by chance. A prespecified analysis plan and an appropriate strategy for the family of comparisons can help clarify how such results should be interpreted. The registry record does not report whether a multiplicity plan existed or how it would apply to the planned dose-ranging questions. Since dose 2 and dose 3 were not enrolled, the posted primary comparison concerns Dose 1 and placebo only; it cannot answer how other planned dose comparisons would have turned out.

Missing-data handling is not reported in the registry record. The outcome counts and group sizes are posted, but the record does not say whether any assigned participants lacked a Month 1 assessment, how such cases were handled, or whether the displayed analysis included all assigned participants. The analysis population is also not reported. It is therefore not possible from this record to determine whether the primary comparison followed assignment, used a different population, or applied a missing-outcome assumption.

The registry record does not report the statistical analysis plan, any covariate adjustment, or the test used for the unadjusted p-value. It also does not report an interim-analysis plan. These omissions should not be filled by assumptions. They limit the ability to assess whether the displayed estimate and uncertainty match a prespecified analysis and how sensitive the result could be to missing outcome information or analytic choices.

14. 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 non-serious adverse event terms

The posted safety counts distinguish serious adverse events, other adverse events, and deaths. For serious adverse events, the registry reports 0 affected participants among 20 at risk in the placebo group and 0 among 60 at risk in the Dose 1 group. For other adverse events, it reports 7 affected participants among 20 at risk in the placebo group and 14 among 60 at risk in the Dose 1 group. The deaths field is 0 for each group.

These are counts of participants with an event, not counts of event episodes or measures of event severity beyond the serious-versus-other classification. The registry lists no top serious adverse-event terms. The record does not provide further detail on event definitions, timing, duration, relatedness, or how adverse events were collected. The counts should therefore be read as the safety information posted for these groups, not as a complete safety profile.

Zero reported serious events in these groups does not establish that serious events cannot occur. As a general statistical point, when an event is uncommon, a limited amount of observation may leave substantial uncertainty about its frequency. The safety counts also do not establish causation. They describe events recorded in the registry by group; additional context would be needed to evaluate their nature and relationship to treatment.

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

The posted result describes a higher Month 1 responder proportion in the Dose 1 group than in the placebo group under the registry's specified definition. The registry reports 36 responders among 60 Dose 1 participants and 3 among 20 placebo participants, with response proportions of 0.6 and 0.15. The reported risk difference is 0.45, and the unadjusted p-value is < 0.001. These measures summarize the observed comparison; none alone conveys every dimension of uncertainty or relevance.

The result does not demonstrate that every participant responded, or that the same response would occur in other populations, settings, or time periods. The endpoint is a threshold-based assessment at Month 1. It does not describe how scores changed for each participant, how long any response lasted, or what occurred at later assessments. Those outcomes are not reported in the registry record.

The result also does not establish the effects of Dose 2 or Dose 3. Although the intervention list names those doses, the primary outcome note states that the study did not proceed to enroll them because of a business decision. Nor does the result resolve every possible safety question. The record contains posted counts for serious and other adverse events, but does not provide detailed event descriptions, timing, relatedness, or a broader safety account.

Statistical significance is not the same as certainty, importance, or applicability. The estimate has an interval, but the confidence level and method are not reported in the registry record. The analysis population, missing-data handling, statistical test, and multiplicity strategy are also not reported. These limitations mean the result should be understood as the posted randomized comparison, not as a complete account of all design and analysis decisions or as a claim about outcomes beyond those measured.

16. Why This Trial Matters Statistically

This trial is statistically informative because it reports a direct randomized comparison on a clearly defined binary endpoint, with both group counts and an absolute risk-difference estimate. The responder criterion makes the outcome interpretable as whether a participant reached a stated assessment threshold at Month 1. The record also reports a p-value and ratio measures, allowing readers to see several statistical descriptions of the same primary comparison.

At the same time, the record illustrates why an estimate should not be read in isolation. The interval estimate and reported ratio intervals convey uncertainty around the point estimates, and the placebo group includes 20 participants. The confidence level and method for the risk-difference interval are not reported, so even a posted interval leaves methodological questions. Likewise, the unadjusted p-value does not disclose the analysis test or account for any set of other planned comparisons.

The difference between the planned dose-ranging description and the posted comparison is important. The intervention list includes three doses, but the record says dose 2 and dose 3 were not enrolled. Consequently, the available primary results address Dose 1 versus placebo rather than dose response across the planned range. The business decision recorded in the outcome note narrows what can be learned from this study's posted results.

The planning illustrations also show how sample-size requirements depend on the effect chosen for planning and the desired power. They are based on the observed effect and specified assumptions, not the trial's original design calculation. Together, the endpoint definition, posted effect estimates, uncertainty, incomplete analysis details, and un-enrolled doses demonstrate the importance of separating what the data describe from what the record does not establish.

17. 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.

Several limitations are specific to this study record. The main one is that the planned dose-ranging comparison did not proceed across all listed doses: the primary outcome note says dose 2 and dose 3 were not enrolled because of a business decision. The posted primary results therefore concern Dose 1 versus placebo only, and do not provide an observed comparison for the other listed doses.

The primary outcome is a binary responder measure at Month 1, based on grade 1 or 2 in the Investigator Live Assessment. This summarizes whether a threshold was met but does not show the distribution of assessment grades or the amount of change within each category. The registry record does not report results at other time points, durability, or secondary outcomes. It lists no posted secondary outcomes.

The record gives group counts and an unadjusted p-value but does not report the test used, the confidence level or method for the risk-difference interval, the analysis population, or missing-data handling. It does not report the statistical analysis plan, multiplicity strategy, interim analyses, or detailed randomization and masking procedures. These gaps limit reproducibility and assessment of potential analytic or operational bias.

The safety report is also limited to summary counts. Serious adverse event counts and deaths are reported as zero in both groups, while other adverse event counts are posted, but descriptions, timing, duration, relatedness, and collection methods are not reported. Finally, the registry enrollment figure does not supply further demographic or clinical detail in the posted outcome description. Generalizability beyond the recorded study population cannot be evaluated from the available record alone.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Safety and Efficacy of AbobotulinumtoxinA for the Treatment of Platysmal Bands — NCT04080882.
• Registry record last updated 2022-08-26; status last verified 2021-01.
• Results first posted 2021-01-22.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

21. Record Summary

NCT04080882 is a completed randomized, double-blind phase 2 study of abobotulinumtoxinA for platysmal bands. The registry record lists an enrollment of 80 and identifies the primary outcome as the Month 1 responder count, using grade 1 or 2 on the Investigator Live Assessment as the responder definition.

The posted primary comparison is Dose 1 versus placebo. The registry reports 36 responders among 60 Dose 1 participants and 3 among 20 placebo participants, a risk difference of 0.45, and an unadjusted p-value of < 0.001. Dose 2 and dose 3 were not enrolled because of a business decision. The record reports no secondary outcomes and no analysis entries.

Serious adverse events and deaths are listed as 0 in each group; other adverse events are listed as 7 in the placebo group and 14 in the Dose 1 group. Important analysis details, including the analysis population, missing-data handling, interval method, and multiplicity strategy, are not reported in the registry record.