An Efficacy and Safety Study of Fremanezumab in Adults With Migraine: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for An Efficacy and Safety Study of Fremanezumab in Adults With Migraine (NCT03308968), a randomized phase 3 study. The primary outcome is DB Period: Change From Baseline in Monthly Average Number of Migraine Days During the 12-Week Period After the First Dose of Fremanezumab.

2. Clinical Question

The primary endpoint is a difference in change from baseline, expressed in days per month. A negative change represents fewer migraine days after treatment than at baseline. The registry reports separate comparisons of quarterly and monthly fremanezumab with placebo; it does not describe a direct statistical comparison between the two active schedules.

The clinical question is limited to the participants and period covered by the primary analysis. It concerns adults with chronic or episodic migraine and inadequate response to prior preventive treatment, not all people with migraine or all preventive-treatment settings. The blinded comparison covers up to Week 12. Although the study continued into an open-label period up to Week 24, that extension does not provide the same randomized placebo comparison described for the primary endpoint.

3. Trial Design

This was a Phase 3, randomized, quadruple-masked, parallel-group, placebo-controlled study. The registry lists enrollment of 838 participants and a completed status. The study start date was 2017-10-13, and primary completion was 2018-10-02. The sponsor was Teva Branded Pharmaceutical Products R&D, Inc.

Participants with chronic migraine and participants with episodic migraine were assigned within their subgroup in a 1:1:1 ratio to 2 active-treatment groups or placebo. The double-blind period involved monthly injections for 3 months, through up to Week 12. The primary comparison is based on this blinded period. The study then included an open-label extension lasting 3 months, up to Week 24, in which all participants received fremanezumab.

The treatment groups were placebo, fremanezumab quarterly, and fremanezumab monthly. In the quarterly schedule, the double-blind regimen began with fremanezumab on Day 0 and placebo injections on Days 28 and 56. The monthly schedule used fremanezumab injections over the double-blind period. The registry also describes placebo injections during the blinded period. The detailed arm descriptions are truncated in the registry record, so any additional regimen details are not reported in the registry record.

The primary analysis population was not simply everyone enrolled. It was the double-blind modified intention-to-treat set: participants who received at least 1 dose of study drug and had at least 10 days of postbaseline efficacy assessment for the primary endpoint. The registry lists 278 participants in the placebo primary analysis, 276 in the quarterly group, and 283 in the monthly group. Safety denominators differ from those primary analysis counts, and should be read as the relevant risk groups for the posted safety results.

The registry record does not report the original sample-size justification or the assumptions used in planning the trial. Those should not be inferred from the planning illustrations calculated from the observed results.

4. Participant Flow and Accounting

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

Before assignment: A total of 838 participants were randomized in a 1:1:1 ratio to placebo, fremanezumab quarterly, or fremanezumab monthly treatment groups.

Double-Blind Period (12 Weeks)

Reasons for not completing this period:

Open-Label Period (12 Weeks)

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: DB mITT analysis set included participants who received at least 1 dose of study drug and had at least 10 days of postbaseline efficacy assessment on the primary endpoint.

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: ITT analysis set included all randomized participants.

6. Primary Endpoint

The registry lists the primary outcome as DB Period: Change From Baseline in Monthly Average Number of Migraine Days During the 12-Week Period After the First Dose of Fremanezumab, measured over Baseline (Day -28 to Day -1), up to Week 12.

The primary endpoint was change from baseline in monthly average number of migraine days during the 12-week period after the first dose. The registry defines a migraine day as a calendar day with at least 4 consecutive hours of a headache meeting migraine criteria, at least 4 consecutive hours meeting criteria for probable migraine, or a headache of any duration treated with migraine-specific medication such as triptans or ergot compounds.

The baseline period was Day -28 to Day -1, and the outcome period extended up to Week 12. Monthly averages were normalized to a 28-day equivalent using the number of days on which the efficacy measure occurred and the number of days with e-diary assessments during the relevant period. Change was calculated as the post-baseline value minus the baseline value. This makes the outcome a change in migraine days per standardized month rather than a simple count over a period of variable diary completion.

A continuous change measure retains information about the size of the change for each participant, rather than reducing the endpoint to whether a participant crossed a response threshold. It can therefore describe average change across the analysis group. The endpoint is relevant to the study’s stated aim of evaluating prophylactic treatment, but its interpretation depends on the registry’s migraine-day definition, diary assessments, analysis population, and 12-week blinded timeframe.

The registry reports least-squares means and their standard errors for the primary endpoint. The least-squares means are model-based estimates from the sponsor’s analysis; the registry identifies ANCOVA for the between-group analyses. Details of the covariates and missing-data handling are not reported in the registry record.

7. Results Posted in the Registry

• Fremanezumab Quarterly: mean -3.70 versus -0.60 on control; difference -3.10 (95% CI -4.04 to -2.16), standardized effect d = -0.55; z-test p = <0.001.
• Fremanezumab Monthly: mean -4.10 versus -0.60 on control; difference -3.50 (95% CI -4.44 to -2.56), standardized effect d = -0.61; z-test p = <0.001.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

DB Period: Percentage of Participants Reaching at Least 50 Percent (%) Reduction From Baseline in Monthly Average Number of Migraine Days During the 12-Week Period After the First Dose of Fremanezumab

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Fremanezumab Quarterly: 34.1% (94/276) versus 9.0% (25/278) on control; risk difference 25.1 percentage points (95% CI 18.5 to 31.6), risk ratio 3.79 (2.52–5.70); unadjusted two-proportion z-test p = <0.001.
  • Fremanezumab Monthly: 33.9% (96/283) versus 9.0% (25/278) on control; risk difference 24.9 percentage points (95% CI 18.5 to 31.4), risk ratio 3.77 (2.51–5.67); unadjusted two-proportion z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for Fremanezumab Quarterly than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically higher for Fremanezumab Monthly than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

DB Period: Change From Baseline in Monthly Average Number of Headache Days of at Least Moderate Severity During the 12-Week Period After the First Dose of Fremanezumab

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard errors.
• Result:
  • Fremanezumab Quarterly: mean -3.90 versus -0.60 on control; difference -3.30 (95% CI -4.23 to -2.37), standardized effect d = -0.59; z-test p = <0.001.
  • Fremanezumab Monthly: mean -4.20 versus -0.60 on control; difference -3.60 (95% CI -4.53 to -2.67), standardized effect d = -0.64; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Fremanezumab Quarterly than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Fremanezumab Monthly than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

DB Period: Change From Baseline in Monthly Average Number of Migraine Days During the 4-Week Period After the First Dose of Fremanezumab

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard errors.
• Result:
  • Fremanezumab Quarterly: mean -4.10 versus -0.60 on control; difference -3.50 (95% CI -4.47 to -2.53), standardized effect d = -0.60; z-test p = <0.001.
  • Fremanezumab Monthly: mean -4.10 versus -0.60 on control; difference -3.50 (95% CI -4.47 to -2.53), standardized effect d = -0.60; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Fremanezumab Quarterly than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Fremanezumab Monthly than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The posted secondary outcomes generally point in the same direction as the primary endpoint. The active-treatment groups have higher percentages reaching the stated migraine-day reduction threshold, and their reported changes in headache days of at least moderate severity and migraine days over the shorter assessment period are more negative than the placebo results. This provides outcome-level context for the primary 12-week comparison without changing what the primary endpoint measures.

These outcomes cover different aspects and time windows: a responder threshold, headache days of at least moderate severity over the 12-week period, and migraine-day change over a shorter period. Agreement in direction can make the overall pattern easier to interpret, but the endpoints are related rather than wholly independent. They draw on migraine and headache diary outcomes in the same trial population and should not be counted as separate replications.

The registry lists 22 secondary outcomes, while the posted results include results for a subset. The registry does not report sponsor analyses for the three secondary outcomes described in the posted results. The unadjusted recalculations are not substitutes for a prespecified sponsor analysis, and their p-values should not be read as multiplicity-adjusted evidence.

When many outcomes are evaluated, the chance of obtaining an apparently unusual result by chance can increase if testing is not controlled. In general, multiplicity procedures or a prespecified testing hierarchy can address that concern, but the registry record does not report whether such procedures were used for these secondary endpoints. For this reason, unadjusted secondary findings carry less inferential weight than a primary endpoint analysis with a defined role in the trial. They are best treated as supportive descriptive evidence, not as independent proof or as a basis for claims beyond the endpoints and periods assessed.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• DB Period: Percentage of Participants Reaching at Least 50 Percent (%) Reduction From Baseline in Monthly Average Number of Migraine Days During the 12-Week Period After the First Dose of Fremanezumab
• DB Period: Change From Baseline in Monthly Average Number of Headache Days of at Least Moderate Severity During the 12-Week Period After the First Dose of Fremanezumab
• DB Period: Change From Baseline in Monthly Average Number of Migraine Days During the 4-Week Period After the First Dose of Fremanezumab
• DB Period: Percentage of Participants Reaching at Least 50% Reduction From Baseline in Monthly Average Number of Migraine Days During the 4-Week Period After the First Dose of Fremanezumab
• DB Period: Change From Baseline in Monthly Average Number of Days of Use of Any Acute Headache Medications During the 12-Week Period After the First Dose of Fremanezumab
• DB Period: Change From Baseline in Monthly Average Number of Headache Days of at Least Moderate Severity During the 4-Week Period After the First Dose of Fremanezumab
• DB Period: Number of Participants With Adverse Events (AEs) and Who Did Not Complete the Study Due to AEs
• OL Period: Number of Participants With AEs and Who Did Not Complete the Study Due to AEs

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous: it records change in monthly average migraine days rather than a yes-or-no event. The registry reports least-squares means for the treatment groups and identifies ANCOVA as the method for the sponsor’s primary comparisons. The results are expressed in days/month, with a negative change indicating a reduction from baseline.

What does ANCOVA contribute?

In general, analysis of covariance (ANCOVA) estimates group differences while accounting for specified covariates. Covariate adjustment can improve precision or account for baseline differences, depending on the model and data. The registry identifies ANCOVA and reports least-squares mean differences, but it does not list the covariates, model specification, or other implementation details. Those details should not be assumed.

A least-squares mean is a model-based group estimate, rather than necessarily the raw arithmetic mean. The sponsor’s posted between-group estimates are differences between these adjusted means. The registry gives a standard error for each arm’s least-squares mean and 95% confidence intervals for the sponsor’s differences. A standard error describes the estimated sampling uncertainty of a statistic; it is not the same quantity as the variability of individual participant outcomes.

How do the recalculations differ?

The recalculated comparisons are simple, unadjusted comparisons derived from the posted group summary statistics. They use the reported least-squares means and standard errors to form approximate pooled standard deviations and then calculate a two-group mean difference, confidence interval, and p-value. Because the group-level standard deviations are inferred approximately from standard errors, these recalculations are not a reconstruction of the sponsor’s ANCOVA. They do not reproduce adjustment for covariates or other model details that are not reported in the registry record.

The recalculated estimates match the sponsor’s reported mean differences at the displayed precision. Their confidence intervals are not identical to the sponsor’s intervals because the methods differ. The registry record does not indicate a discrepancy, so the recalculations serve as a transparent unadjusted check, while the sponsor’s ANCOVA remains the registry’s reported analysis.

What do the p-values mean?

In general, a p-value describes how compatible the observed data are with a specified null hypothesis under the assumptions of the analysis. It is not the probability that the null hypothesis is true, and it does not measure the size or practical importance of an estimated difference. The sponsor reports p < 0.001 for each primary comparison. The unadjusted recalculations report p < 0.001. The posted p-values should be read alongside the estimated differences and confidence intervals, not as stand-alone summaries.

The registry lists 2 reported primary analyses, each comparing an active group with placebo. It does not state whether or how the primary comparisons were adjusted for multiplicity. Although the study had a primary endpoint and multiple secondary outcomes, the exact testing sequence or family-wise error procedure is not reported in the registry record. General statistical practice recognizes that repeated testing can increase the chance of at least one false-positive result if no suitable adjustment or prespecified hierarchy is used. The trial’s approach cannot be inferred from that general principle.

How is the endpoint constructed?

The endpoint uses e-diary assessments and a 28-day-equivalent monthly average. In general, this type of normalization allows observations over periods with different numbers of assessment days to be expressed on a common monthly scale. The definition of a migraine day is clinical and operational: it includes specified headache duration and symptom criteria, probable migraine, or a headache treated with migraine-specific medication. A different endpoint definition could count days differently, so the operational definition matters when interpreting the outcome.

The stated primary analysis population is a modified intention-to-treat group: participants had to receive at least 1 dose and have at least 10 days of postbaseline efficacy assessment on the primary endpoint. This definition establishes who contributed to the primary analysis as described in the registry. How participants with less diary information were otherwise handled, and how missing values were treated within the analysis, are not reported in the registry record.

What can planning calculations establish?

Planning illustrations based on the observed effect can show how participant requirements vary when a future study aims to detect a specified fraction of that effect under stated assumptions. They do not explain the original trial’s design. The trial’s own sample-size justification and original assumptions are not reported in the registry record. The planning illustrations are not observed power and should not be interpreted as evidence that this completed trial had a particular probability of detecting an effect.

11. Confidence Intervals and Precision

A confidence interval gives a range of values compatible with the observed estimate under the analysis method and its assumptions. In general, narrower intervals indicate greater statistical precision, while wider intervals indicate greater uncertainty about the size of the estimated effect. They do not describe the range of individual participant responses.

For the sponsor’s ANCOVA, the estimated quarterly-versus-placebo difference was -3.1 days/month, with a 95% confidence interval from -3.84 to -2.42. The monthly-versus-placebo difference was -3.5 days/month, with a 95% confidence interval from -4.19 to -2.78. The intervals lie on the negative side of zero, consistent with the negative estimated differences under the model used for the reported analysis. The reported p-value for each comparison was p < 0.001.

The unadjusted recalculations give 95% confidence intervals of -4.042 to -2.158 for the quarterly comparison and -4.442 to -2.558 for the monthly comparison. These intervals are based on approximate, unadjusted calculations from the posted summary statistics. Their limits differ from the sponsor’s ANCOVA intervals because the calculations do not reproduce the sponsor’s adjusted model. The registry does not flag a discrepancy, and the sponsor’s reported analysis remains the primary model-based result.

Confidence intervals convey uncertainty in an average group difference, not certainty about the result in every participant or every setting. They also do not address missing-data assumptions, endpoint measurement limitations, multiplicity, or generalizability beyond the study population. Those issues require information beyond the interval itself. The registry does not report the covariates or missing-data methods needed to evaluate all assumptions behind the sponsor’s confidence intervals.

12. 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 planning illustrations express requirements as participants per arm for comparisons between two groups. They do not give total events: the outcome is continuous, and the stated sample-size assumption specifies participants per arm. The trial’s original design assumptions and sample-size justification are not reported in the registry record.

The illustrations use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to a stated fraction of the observed effect: 100%, 75%, or 50%. These are planning scenarios based on the observed result, not the assumptions that necessarily guided the original trial.

In plain terms, the 80% power column gives the estimated number of participants per arm under those assumptions for a design with an 80% chance of detecting the specified effect if that effect were present. The 90% power column gives the corresponding estimate for a design targeting a 90% chance. These are prospective design concepts, not probabilities assigned to the already completed trial. The figures are calculated separately for each comparison and endpoint.

As the target effect becomes smaller, more participants are generally needed to distinguish it from random variation at the same power and significance level. That pattern is visible when comparing planning for 100%, 75%, and 50% of the observed effect. The resulting figures are illustrative and depend on the stated assumptions; different variability, allocation, or analysis choices could produce different requirements.

These figures are not observed power. Observed power calculations based on an estimated effect do not provide a useful substitute for reading the effect estimate and its confidence interval. The planning values are better read as sensitivity illustrations: they show how a hypothetical future design’s participant requirement changes when the target effect is smaller or the desired power is higher.

13. 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, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -3.100; pooled standard deviation σ = 5.659.
2. n = 2 × (1.96 + 0.842)² × 5.659² / -3.100² = 52.3, rounded up to 53 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
delta <- -3.1                      # observed difference in means
sigma <- 5.65876478046046                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^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 (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(3308968)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 53 (80% power), 71 (90% power)
 75% of observed effect: n per arm = 93 (80% power), 125 (90% power)
 50% of observed effect: n per arm = 210 (80% power), 281 (90% power)
power.t.test: 53.3 
Simulated power at n = 53 per arm: 0.799 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-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.

14. Analyses Reported by the Sponsor

The registry reports the sponsor’s primary comparisons as ANCOVA estimates of least-squares mean differences. Quarterly fremanezumab versus placebo was estimated at -3.1 days/month, with a 95% confidence interval of -3.84 to -2.42 and p < 0.001. Monthly fremanezumab versus placebo was estimated at -3.5 days/month, with a 95% confidence interval of -4.19 to -2.78 and p < 0.001.

The recalculated comparisons are simple unadjusted calculations from the posted summary statistics. They give the same displayed mean differences, with different confidence interval limits and p-value thresholds. They are useful as a check on the scale and direction of the reported differences, but they do not replicate the ANCOVA because they do not incorporate the sponsor’s model adjustment. The registry record does not identify a discrepancy between the recalculations and the reported analysis.

For interpretation, the sponsor’s own ANCOVA results are the primary reported results. Recalculated estimates should be labeled and understood as unadjusted approximations, not as a competing adjusted analysis or a correction to the sponsor’s result. The registry does not provide the ANCOVA covariates or full model specification, so the reason for any difference in interval width cannot be determined from the record alone.

15. Multiplicity, Missing Data and Analysis Populations

The registry identifies a primary endpoint and multiple secondary outcomes, but does not report a multiplicity adjustment, testing hierarchy, or other procedure for controlling the interpretation of repeated statistical tests. It is therefore not possible to determine from the registry record whether the reported secondary comparisons were part of a prespecified inferential sequence or how any family-wise error was handled. In general, examining many outcomes can increase the chance of a nominally significant result occurring by chance when no suitable control is used. That general issue does not establish which procedure this trial used.

The registry specifies the primary endpoint analysis population: participants had to receive at least 1 dose and have at least 10 days of postbaseline efficacy assessment on the endpoint. That modified intention-to-treat definition is important because it is narrower than the full enrollment group. The record does not report how participants who did not meet those criteria were handled in other analyses.

Missing-data methods are not reported in the registry record. In particular, the record does not state the approach to incomplete e-diary observations, missing endpoint values, or sensitivity analyses for missingness. Since the primary outcome is based on diary assessments and normalized to a 28-day equivalent, the amount and pattern of missing diary information could matter to estimation. The effect cannot be assessed without the analysis details.

The registry reports ANCOVA for the sponsor’s primary comparisons but does not identify its covariates or full model specification. Interim analyses and their role, if any, are not reported in the registry record. The trial’s original sample-size justification and design assumptions are also not reported. These absences limit assessment of how the analysis plan was set and how robust the reported inference is to alternative choices, but they do not establish that a particular procedure was omitted.

16. 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: nephrolithiasis (0.7%), dysmenorrhoea (0.4%), menorrhagia (0.4%), uterine leiomyoma (0.4%), vulval cancer (0.4%).

The registry reports participants with serious adverse events separately from participants with other adverse events. In the safety risk groups, serious adverse events affected 13 of 277 participants in the placebo group, 10 of 276 in the quarterly fremanezumab group, and 11 of 285 in the monthly fremanezumab group. The corresponding counts for participants with other adverse events were 88 of 277, 90 of 276, and 81 of 285. The registry reports 0 deaths in each group.

These are counts of participants affected, not a comparison adjusted for differences in follow-up or other factors. The registry lists nephrolithiasis at 0.7%, and dysmenorrhoea, menorrhagia, uterine leiomyoma, vulval cancer, and metrorrhagia at 0.4% each among the top serious adverse event terms. The record does not identify a treatment-group attribution for those term percentages in the information, so they should not be assigned to a particular arm.

Safety counts should be interpreted in the context of the trial’s duration, population, and collection methods. They do not by themselves establish whether an event was caused by treatment, and they do not provide a complete comparison of all potential harms. The registry record does not report additional details needed to make that assessment.

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

The posted primary results show reductions from baseline in monthly average migraine days in all three groups during the blinded period. The sponsor’s ANCOVA estimated a larger reduction relative to placebo for each fremanezumab schedule, with negative between-group differences and confidence intervals that remain below zero. These are average estimates for the defined modified intention-to-treat analysis population, not predictions for an individual participant.

The findings apply to adults with chronic or episodic migraine who had inadequate responses to 2 to 4 classes of prior preventive treatments, as studied over the 12-week double-blind period. They do not automatically extend to people with different treatment histories, other populations, or longer-term comparisons. The open-label extension included fremanezumab for all participants and therefore is not the same randomized comparison with placebo.

The results do not establish that the monthly and quarterly schedules differ from one another. Each was compared with placebo, and the registry does not report a direct comparison of the active schedules. Nor do the group averages show how variable individual responses were or how many participants experienced particular changes beyond the posted responder endpoint.

The primary result also does not settle the interpretation of safety, missing data, or multiple secondary outcomes. The registry reports adverse event counts, but those counts alone do not establish causation or provide a complete benefit-harm assessment. Missing-data methods and multiplicity procedures are not reported in the registry record, so these aspects cannot be fully evaluated from the posted information.

Statistical estimates describe uncertainty under the assumptions of the chosen analysis. They are not medical advice and do not determine what treatment is appropriate for any individual. Their meaning is bounded by the trial’s eligibility criteria, endpoint definition, analysis population, measurement period, and reporting detail.

18. Why This Trial Matters Statistically

This study illustrates why the analysis population and endpoint definition matter as much as the headline treatment contrast. The primary result is based on participants who received at least 1 dose and had at least 10 days of postbaseline assessment, rather than everyone enrolled. Its migraine-day outcome is constructed from diary information using explicit headache criteria and converted to a 28-day equivalent. Those choices define the quantity being estimated.

It also demonstrates the distinction between an adjusted sponsor analysis and a simple recalculation. The sponsor’s ANCOVA reports model-based least-squares mean differences. The recalculations use posted summary statistics and provide an unadjusted approximation. Estimates can align at the displayed precision while confidence intervals differ because the calculations do not use identical methods. Keeping those results distinct helps prevent a summary-statistic check from being mistaken for a reproduction of the trial analysis.

Precision and statistical significance are related but not interchangeable. The estimated differences and their confidence intervals describe both direction and uncertainty in the group contrasts; the p-values address compatibility with a null hypothesis under a model. None alone captures clinical importance, variation among participants, or the adequacy of the analysis assumptions.

Finally, the study’s multiple secondary outcomes make transparent reporting of multiplicity and missing-data methods important. The registry provides a primary analysis definition and identifies ANCOVA, but it does not report several details needed to fully assess the analysis plan. Recognizing what the record establishes—and what remains unreported—is part of responsible interpretation.

19. 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 registry does not report the covariates or complete specification for the sponsor’s ANCOVA. The recalculated confidence intervals rely on approximate standard deviations inferred from standard errors and do not reproduce that adjusted analysis. Comparisons between sponsor and recalculated intervals should therefore account for their different methods.

The primary endpoint depends on e-diary assessments, and monthly averages are normalized to a 28-day equivalent. The registry does not report the amount or pattern of missing diary data, the method used to handle missing values, or sensitivity analyses. That limits assessment of how incomplete assessment could affect the estimates.

The primary analysis uses a modified intention-to-treat definition requiring at least 1 dose and at least 10 days of postbaseline efficacy assessment. The record does not describe how participants excluded from that analysis were handled, or provide enough information to assess the consequences of this inclusion rule.

The study includes chronic and episodic migraine subgroups and randomized treatment within subgroup, but the primary results described are overall arm comparisons. Subgroup-specific primary estimates are not reported in the registry record in the registry record. The registry also does not report a direct active-schedule comparison, so relative performance between monthly and quarterly treatment cannot be inferred from the separate placebo comparisons.

The 12-week blinded comparison does not establish comparative outcomes in the subsequent open-label period, where everyone received fremanezumab. Multiplicity procedures for the numerous secondary outcomes, interim analyses, and the original sample-size justification are not reported in the registry record. These limitations concern the scope and evaluability of the reported evidence; they do not establish that any particular analysis was improperly conducted.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: An Efficacy and Safety Study of Fremanezumab in Adults With Migraine — NCT03308968.
• Registry record last updated 2021-11-09; status last verified 2021-11.
• Results first posted 2019-10-09.
• 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.

23. Record Summary

NCT03308968 is a completed Phase 3 randomized, quadruple-masked, parallel-group, placebo-controlled study of fremanezumab in adults with chronic or episodic migraine and inadequate response to 2 to 4 classes of prior preventive treatments. The registry lists enrollment of 838 and a 12-week double-blind period followed by a 3-month open-label extension.

The primary endpoint was change from baseline in monthly average migraine days through Week 12. The sponsor reported ANCOVA comparisons of quarterly and monthly fremanezumab with placebo, with estimated differences of -3.1 and -3.5 days/month, respectively. Both sponsor-reported 95% confidence intervals were below zero, and each reported p < 0.001.

Secondary outcome results generally had directions consistent with the primary result, but multiplicity and missing-data methods are not reported in the registry record. Safety results include serious adverse event, other adverse event, and death counts by group. These findings describe the posted trial results and do not establish individual outcomes or longer-term comparative effects.