The Evaluation of Bococizumab (PF-04950615; RN316) in Reducing the Occurrence of Major Cardiovascular Events in High Risk Subjects: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Evaluation of Bococizumab (PF-04950615; RN316) in Reducing the Occurrence of Major Cardiovascular Events in High Risk Subjects (NCT01975389), a randomized phase 3 study. The primary outcome is Event Rate Per 100 Participant-years for First Occurrence of Major Cardiovascular (CV) Event.

2. Clinical Question

3. Trial Design

This was a Phase 3, randomized, quadruple-masked, parallel-group, placebo-controlled study sponsored by Pfizer. The registry lists enrollment of 10564 participants. The study began on 2013-10-29, and primary completion was recorded as 2017-04-03. Its status is terminated. The registry record does not report why the study was terminated, so the status alone does not establish the reason or its relationship to the results.

Participants were assigned to bococizumab or placebo. The bococizumab regimen was 150 mg by subcutaneous injection every 2 weeks; placebo was also administered subcutaneously every 2 weeks. The study concerned high-risk participants with cardiovascular disease receiving background lipid-lowering therapy and meeting the listed cholesterol criteria: LDL-C at least 100 mg/dL (2.6 mmol/L) or non-HDL-C at least 130 mg/dL (3.4 mmol/L).

The registry describes the primary outcome population as a full analysis set comprising randomized participants, with exclusions for individuals who attempted randomization more than once into a bococizumab cardiovascular outcomes trial or attempted randomization in more than one cardiovascular outcomes trial. It also identifies an exclusion involving participants at study Site 3027, but the description ends before the criterion is complete. The complete site-related rule is therefore not reported in the registry record.

The primary outcome follow-up was from baseline to the first adjudicated and confirmed major cardiovascular event, with a maximum duration of up to 3.4 years. The registry describes adjudication by an Adjudication Committee. Details of the randomization sequence, allocation concealment, visit schedule, adherence procedures, and the sponsor’s original sample-size rationale 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: The trial was terminated prematurely on November 1, 2016, due to the emerging clinical profile and the evolving treatment and market landscape for lipid-lowering agents.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: FAS: all participants who were randomized, excluding who attempted to be randomized more than once into a bococizumab CV outcomes trial (B1481022/B1481038) or attempted to be randomized in more than 1 CV outcomes trial and all participants enrolled at study Site 3027 where a quality-related event was identified.

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: Full analysis set (FAS): all participants who were randomized, excluding who attempted to be randomized more than once into a bococizumab cardiovascular (CV) outcomes trial (B1481022/B1481038) or attempted to be randomized in more than 1 CV outcomes trial and all participants enrolled at study Site 3027 where a quality-related event was identified.

6. Primary Endpoint

The registry lists the primary outcome as Event Rate Per 100 Participant-years for First Occurrence of Major Cardiovascular (CV) Event, measured over From baseline until the date of first adjudicated and confirmed occurrence of major CV event (maximum duration: up to 3.4 years).

The primary endpoint is an event rate for the first occurrence of a major cardiovascular event, expressed as events per 100 participant-years. Its composite includes cardiovascular death, non-fatal myocardial infarction, non-fatal stroke, and hospitalization for unstable angina needing urgent revascularization. Cardiovascular death includes the listed categories of sudden cardiac death, fatal myocardial infarction, death due to heart failure, death due to stroke, and death due to other cardiovascular causes. Events were to be adjudicated and confirmed.

An event rate uses the number of events in relation to the amount of participant follow-up time at risk. This allows the outcome to be expressed with exposure time in the denominator, rather than as a simple proportion of participants with an event. The registry’s outcome description says the rate was calculated as events per 100 participant-years at risk. The outcome timeframe runs from baseline through the first qualifying event, with follow-up lasting up to 3.4 years.

General statistical context: a composite outcome can capture several clinically important event types in one endpoint, but it combines outcomes that may differ in severity and frequency. The overall rate does not, by itself, show which component contributed most to the observed result. Component-specific event rates are among the listed secondary outcomes, but they do not replace the primary composite endpoint.

7. Results Posted in the Registry

• Bococizumab (PF-04950615): 3.33 versus 4.19 (Events per 100 participant-years) on control; rate ratio 0.79 (95% CI 0.65–0.97, derived from the posted confidence limits); p ≈ 0.025.

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.

Event Rate Per 100 Participant-years for First Occurrence of Composite Endpoint of Cardiovascular (CV) Death, Non-fatal Myocardial Infraction (MI) or Non-fatal Stroke

• Endpoint type: Event rate: events per unit of follow-up, compared as a rate ratio.
• Test: Poisson rate ratio, with the standard error taken from the posted confidence limits.
• Result:
  • Bococizumab (PF-04950615): 2.67 versus 3.58 (Events per 100 participant-years) on control; rate ratio 0.75 (95% CI 0.60–0.93, derived from the posted confidence limits); p ≈ 0.009.
• Interpretation:
  • The 95% confidence interval excludes no difference (a ratio of 1), so the event rate is statistically lower for Bococizumab (PF-04950615) than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Event Rate Per 100 Participant-years for First Occurrence of Composite Endpoint of All-cause Death, Non-fatal Myocardial Infraction (MI), Non-fatal Stroke or Hospitalization for Unstable Angina Needing Urgent Revascularization

• Endpoint type: Event rate: events per unit of follow-up, compared as a rate ratio.
• Test: Poisson rate ratio, with the standard error taken from the posted confidence limits.
• Result:
  • Bococizumab (PF-04950615): 3.76 versus 4.59 (Events per 100 participant-years) on control; rate ratio 0.82 (95% CI 0.68–0.99, derived from the posted confidence limits); p ≈ 0.040.
• Interpretation:
  • The 95% confidence interval excludes no difference (a ratio of 1), so the event rate is statistically lower for Bococizumab (PF-04950615) than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Event Rate Per 100 Participant-years for First Occurrence of Composite Endpoint of All-cause Death, Non-fatal Myocardial Infarction (MI) or Non-fatal Stroke

• Endpoint type: Event rate: events per unit of follow-up, compared as a rate ratio.
• Test: Poisson rate ratio, with the standard error taken from the posted confidence limits.
• Result:
  • Bococizumab (PF-04950615): 3.09 versus 3.97 (Events per 100 participant-years) on control; rate ratio 0.78 (95% CI 0.63–0.96, derived from the posted confidence limits); p ≈ 0.018.
• Interpretation:
  • The 95% confidence interval excludes no difference (a ratio of 1), so the event rate is statistically lower for Bococizumab (PF-04950615) than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The posted secondary outcomes cover several related cardiovascular composites and individual event categories. Across the secondary composites for which comparisons are included, the estimated rates and reported comparisons generally point in the same direction as the primary result. This broad alignment offers context for the primary composite, but it does not make every secondary outcome an independent confirmation.

Secondary outcomes use different combinations of events. Some add all-cause death or change which events are included, while others focus on a particular event type. Those changes affect what each estimate means. A difference in an alternative composite cannot be assumed to describe the same event experience as the primary composite, and the overall pattern does not reveal which component accounts for the primary result.

The registry lists 26 posted secondary outcomes. The reported analyses include unadjusted comparisons, and the record does not report a multiplicity correction or a prespecified hierarchy for interpreting the secondary tests. General statistical context: when many outcomes are tested, the chance of at least one apparently notable finding can increase if each test is treated as though it were the only test. Without a reported multiplicity strategy, secondary p-values carry less weight than a single prespecified primary analysis and should be interpreted cautiously.

The secondary findings are best read as supportive descriptions of related outcomes, not as a basis for claims that exceed the primary endpoint or the posted analysis. The registry does not report enough detail to determine which secondary findings were confirmatory, how they were prioritized, or whether all planned secondary outcomes were posted.

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

• Event Rate Per 100 Participant-years for First Occurrence of Composite Endpoint of Cardiovascular (CV) Death, Non-fatal Myocardial Infraction (MI) or Non-fatal Stroke
• Event Rate Per 100 Participant-years for First Occurrence of Composite Endpoint of All-cause Death, Non-fatal Myocardial Infraction (MI), Non-fatal Stroke or Hospitalization for Unstable Angina Needing Urgent Revascularization
• Event Rate Per 100 Participant-years for First Occurrence of Composite Endpoint of All-cause Death, Non-fatal Myocardial Infarction (MI) or Non-fatal Stroke
• Event Rate Per 100 Participant-years for First Occurrence of Hospitalization for Unstable Angina Needing Urgent Revascularization
• Event Rate Per 100 Participant-years for First Occurrence of Composite Endpoint of Cardiovascular (CV) Death, Non-fatal Myocardial Infarction (MI), Non-fatal Stroke or Hospitalization for Unstable Angina
• Event Rate Per 100 Participant-years for Cardiovascular (CV) Death
• Event Rate Per 100 Participant-years for First Occurrence of Any Myocardial Infarction (Fatal or Non-fatal)
• Event Rate Per 100 Participant-years for Fatal Myocardial Infarction (MI)

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is a rate, not simply the percentage of participants who experienced an event. The registry defines the measure as events per 100 participant-years at risk. Participant-years represent accumulated follow-up time across participants while they remain at risk of the event. A rate therefore incorporates both the number of events and the time during which events could be observed. The posted rate estimates are 4.19 for placebo and 3.33 for bococizumab, in events per 100 participant-years.

What does the rate ratio express?

The unadjusted re-calculation compares the two posted rates as a rate ratio. Its estimate is 0.795, with a 95% confidence interval from 0.650 to 0.971. General statistical context: a ratio of one represents equal rates, while a ratio below one represents a lower estimated rate in the numerator group relative to the reference group. The rate ratio summarizes the relative comparison; it does not give the absolute rate in either arm, so the arm-specific rates remain important for interpretation.

The re-calculation is based on posted summary statistics and is not a substitute for the sponsor’s own analysis. It is described as unadjusted because it does not incorporate covariate adjustment or other model features beyond the stated summary-based comparison. The registry also reports the sponsor’s log-rank analysis as a hazard ratio. That time-to-event analysis yields a hazard ratio of 0.79, with a 95% confidence interval from 0.65 to 0.97. A hazard ratio compares event hazards over follow-up under its modeling framework; a rate ratio compares event rates per exposure time. Similar numerical estimates do not make the measures identical.

Why use participant-time?

General statistical context: exposure-time rates can be useful when participants contribute different amounts of follow-up, because the denominator reflects time at risk rather than treating every participant as observed for the same duration. This approach still depends on how events and time at risk are defined. The registry specifies that the primary event is the first adjudicated and confirmed major cardiovascular event and gives a maximum follow-up duration of up to 3.4 years. It does not provide enough detail in the posted record to reconstruct individual follow-up, censoring, or the handling of all possible incomplete observations.

What does the log-rank analysis add?

The sponsor’s reported analysis uses the log-rank method and presents a hazard ratio with a 95% confidence interval. General statistical context: the log-rank method compares time-to-event experience while accounting for event timing and censoring under the analysis conventions used. The registry does not report the full model specification, assumptions checks, censoring rules, or whether the hazard ratio came from a particular adjusted model. Those details should not be inferred from the method label alone.

The registry describes the primary outcome as adjudicated by an Adjudication Committee. Adjudication is intended to apply endpoint definitions to reported events, but the record does not describe the committee’s procedures, its blinding, or how disagreements were resolved. The registry states that the primary endpoint population was a full analysis set of randomized participants, subject to specified exclusions. The Site 3027 exclusion text is incomplete, so the full population definition cannot be reproduced from the record.

The primary analysis has an unadjusted recalculated p-value of 0.025. General statistical context: a p-value describes how incompatible the observed data are with a specified null model, assuming that model and the analysis conditions are appropriate. 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 sponsor’s reported p-value is also described as below the 0.05 planning threshold, but the registry’s analysis details are not sufficient to infer whether that threshold was the formal primary testing rule.

Poisson-based calculations are used for the posted rate-ratio re-calculation. General statistical context: a simple Poisson model is commonly used for event counts over exposure time, but it assumes a particular relationship between the mean and variability of the counts. Over-dispersion means that the observed variability exceeds what a basic Poisson model expects; if present and not accommodated, uncertainty can be understated. The registry does not report a diagnostic assessment for over-dispersion or a model adjustment for it. The reported confidence interval should therefore be read as the interval from the stated recalculation method, not as proof that every modeling assumption was satisfied.

The registry record does not report the sponsor’s original statistical analysis plan, any interim analyses, the multiplicity strategy, missing-data procedures, or the original sample-size justification. These are not details that can be recovered from the outcome values alone. They are relevant to understanding how the primary and secondary hypotheses were specified and how the reported uncertainty should be interpreted.

11. Confidence Intervals and Precision

The primary arm-specific event-rate estimates are 4.19 events per 100 participant-years for placebo, with a 95% confidence interval from 3.66 to 4.78, and 3.33 for bococizumab, with a 95% confidence interval from 2.86 to 3.86. The re-calculated rate ratio is 0.795, with a 95% confidence interval from 0.650 to 0.971. The sponsor’s hazard ratio is 0.79, with a 95% confidence interval from 0.65 to 0.97.

General statistical context: a confidence interval gives a range of values compatible with the observed data under the analysis method and its assumptions. A narrower interval indicates greater statistical precision than a wider interval, but an interval does not account for every possible source of bias or uncertainty. It is not a guarantee that the true effect lies inside the interval in any particular analysis.

For the rate ratio, the interval is entirely below one, while remaining broad enough to include values closer to no relative difference as well as more pronounced relative differences. The interval should be considered together with the arm-specific rates and the endpoint definition. It does not identify which component of the composite drove the result, and it does not describe the certainty of effects on unmeasured outcomes.

The sponsor’s hazard-ratio interval and the recalculated rate-ratio interval are similar in scale, but they arise from different statistical summaries. Their similarity does not establish that the underlying estimands or assumptions are identical. The registry does not provide the complete sponsor model specification or diagnostics needed to assess every assumption behind either interval. Precision is therefore best understood as conditional on the reported analyses and the information available in the registry record.

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 figures are illustrations based on the observed effect, not the trial’s original design calculation. For this event-rate outcome, the figures are participants per arm. The stated assumptions are 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 the stated fraction of the observed effect. For time-to-event planning displays, the convention is a total number of events using the Schoenfeld approach; other planning displays give participants per arm.

The 80% power column gives the illustrative number of participants per arm for a design intended to have an 80% chance of detecting the specified effect under those assumptions, if that effect and the planning model were correct. The 90% power column applies the same idea to a design intended to have a 90% chance. These are design-planning quantities, not descriptions of how likely the trial’s observed result was to be correct.

The rows use the observed effect and smaller fractions of it. The planning figures rise as the effect to detect becomes smaller: a design generally needs more participants to distinguish a smaller effect from no difference, all else held constant. The sample-size illustrations are not observed power. They do not establish what the trial’s actual power was, because that would require the original design assumptions and other trial-specific information. The registry record does not report the original sample-size justification.

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, λ₀ and λ₁ are event rates per patient-year, and T is follow-up per participant in years. This assumes Poisson counts and equal follow-up.

Worked calculation for this trial

1. Control rate λ₀ = 0.0419; treatment rate λ₁ = 0.0333 events per patient-year; follow-up T = 3.40 years.
2. n = (1.96 + 0.842)² × (1/0.0419 + 1/0.0333) / (3.40 × [ln(0.795)]²) = 2,357.5, rounded up to 2,358 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
lambda0 <- 0.0419                      # control rate, events per patient-year
lambda1 <- 0.0333                      # treatment rate
tt      <- 3.4                       # follow-up per participant, years
n_per_arm <- function(power, frac = 1) {
  l1 <- lambda0 * (lambda1 / lambda0)^frac   # smaller effect = fraction of the observed log rate ratio
  ceiling(round((z_a + qnorm(power))^2 * (1 / lambda0 + 1 / l1) / (tt * log(l1 / lambda0)^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 = ",")))

# Simulation 1: Poisson counts. Simulation 2: over-dispersed counts (variance = 1.5 x mean), analysed with the matching variance.
set.seed(1975389)
n    <- n_per_arm(0.80)
reps <- 20000
m0 <- lambda0 * n * tt; m1 <- lambda1 * n * tt
x0 <- rpois(reps, m0); x1 <- rpois(reps, m1)
z  <- log(x1 / x0) / sqrt(1 / x0 + 1 / x1)
cat(sprintf("Simulated power, Poisson counts, n = %s per arm: %.3f\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE)))
phi <- 1.5
y0 <- rnbinom(reps, mu = m0, size = m0 / (phi - 1)); y1 <- rnbinom(reps, mu = m1, size = m1 / (phi - 1))
z2 <- log(y1 / y0) / sqrt(phi * (1 / y0 + 1 / y1))
cat(sprintf("Simulated power, over-dispersed counts (phi = 1.5), same n: %.3f\n", mean(abs(z2) > z_a, na.rm = TRUE)))

Output from running the code

100% of observed effect: n per arm = 2,358 (80% power), 3,157 (90% power)
 75% of observed effect: n per arm = 4,061 (80% power), 5,437 (90% power)
 50% of observed effect: n per arm = 8,860 (80% power), 11,862 (90% power)
Simulated power, Poisson counts, n = 2,358 per arm: 0.801
Simulated power, over-dispersed counts (phi = 1.5), same n: 0.625

The first simulation draws Poisson counts and should land close to the target power. The second allows extra variability (variance 1.5 times the mean, a purely illustrative value), which lowers the power at the same sample size, so rate trials usually need more participants than the Poisson formula suggests.

14. Analyses Reported by the Sponsor

The registry’s sponsor-reported primary analysis is a log-rank comparison with a hazard ratio of 0.79 and a 95% confidence interval from 0.65 to 0.97. The sponsor-reported p-value was below 0.05. Separately, the summary-based re-calculation compares the posted event rates and gives a rate ratio of 0.795, with a 95% confidence interval from 0.650 to 0.971 and an unadjusted p-value of 0.025.

These estimates are close numerically, but they are not identical measures: the sponsor reports a hazard ratio from a time-to-event analysis, while the re-calculation is an unadjusted rate ratio from posted summary rates. Differences in method and estimand mean that a numerical comparison should not be treated as a replication of the sponsor’s analysis. The registry does not provide enough detail to reconstruct the sponsor’s complete model or testing procedure.

The discrepancy indicator is false, so the record does not flag a discrepancy between the sponsor’s result and the recalculation. The sponsor’s analysis remains the registry’s own reported analysis; the recalculation is a supplementary summary-statistic comparison, not a replacement for it.

15. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary outcome, multiple secondary outcomes, and reported comparisons, but it does not report a multiplicity adjustment, a gatekeeping procedure, or a hierarchy governing the interpretation of tests. It also does not state whether the reported p-values were intended as confirmatory or exploratory for the secondary outcomes. Without that information, the family of hypotheses and the intended control of false-positive risk cannot be established from the record.

The primary outcome population is described as a full analysis set of randomized participants with exclusions for repeat randomization and an exclusion involving Site 3027. The site-related text is incomplete, so the complete analysis population rule is not reported in the registry record. The numbers at risk listed with the safety outcomes are not interchangeable with the primary endpoint population definition.

Missing-data methods are not reported in the registry record. The primary endpoint is defined around the first adjudicated and confirmed event, and the timeframe extends from baseline to that event, up to 3.4 years. However, the record does not give the detailed censoring rules, treatment of participants lost to follow-up, handling of missing endpoint information, or sensitivity analyses for incomplete data. These details matter because time-to-event and exposure-time analyses depend on how follow-up ends for participants without a recorded event.

The registry also does not report whether interim analyses were conducted, whether any stopping boundaries were used, or whether the statistical analysis plan changed. The study status is terminated, but the reason for termination is not reported in the registry record. Termination by itself does not establish an interim decision, a safety rationale, or a particular efficacy conclusion. The original sample-size justification and complete sponsor analysis plan are likewise not reported, limiting assessment of the planned testing framework.

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 2% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: angina unstable (1.8%), angina pectoris (1.7%), myocardial infarction (1.0%), non-cardiac chest pain (0.9%), acute myocardial infarction (0.8%).

The safety results list serious adverse events among 5279 participants at risk in the placebo group and 5276 in the bococizumab group. Serious adverse events were reported for 994 participants in the placebo group and 934 in the bococizumab group. Other adverse events were reported for 2128 and 2453 participants, respectively. Deaths were recorded for 61 participants in the placebo group and 54 in the bococizumab group.

These are registry counts, with the stated at-risk denominators; they are not the primary cardiovascular event-rate estimates and should not be read as a direct benefit-risk comparison. The registry also lists serious adverse event terms and percentages, including unstable angina at 1.8%, angina pectoris at 1.7%, myocardial infarction at 1.0%, non-cardiac chest pain at 0.9%, acute myocardial infarction at 0.8%, and pneumonia at 0.7%. The listed percentages are not assigned to a specific treatment group in the posted summary.

General statistical context: adverse-event counts do not, on their own, establish that an event was caused by the assigned treatment. Interpretation also depends on definitions, exposure time, event ascertainment, and the completeness of follow-up. The registry record does not provide enough detail in these summaries to resolve those issues.

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

The posted results show a lower estimated primary event rate in the bococizumab group than in the placebo group during the stated follow-up period. The recalculated rate ratio is 0.795, with a 95% confidence interval from 0.650 to 0.971. The sponsor’s log-rank analysis reports a hazard ratio of 0.79, with a 95% confidence interval from 0.65 to 0.97. Both summaries describe the comparison of the assigned groups for the registry-defined endpoint, under their respective methods.

These findings do not establish the result for every cardiovascular outcome, every component of the composite, or every participant group. A composite event rate does not show how much each component contributed, and the posted primary comparison is not a complete account of safety. The adverse event summaries are separate descriptive counts and should not be treated as proof of causation.

General statistical context: statistical evidence is not the same as clinical importance, and a confidence interval does not remove uncertainty about study conduct, analysis choices, or applicability. The registry does not report the complete analysis plan, missing-data procedures, multiplicity approach, or original sample-size rationale. The study is marked terminated, but the reason is not reported in the registry record. Those gaps mean the results should be described within their documented endpoint, population, and analysis context rather than extended to claims not evaluated by the posted data.

No conclusion about treatment decisions follows from this statistical summary. It describes the estimates, uncertainty, and limits of the registry results without substituting for clinical judgment or a complete assessment of the evidence.

18. Why This Trial Matters Statistically

This trial is statistically informative because it places a clearly defined cardiovascular composite at the center of a randomized, placebo-controlled comparison and reports both exposure-time event rates and a sponsor-reported time-to-event analysis. Those two forms of summary make it possible to distinguish the arm-specific event experience from a relative comparison, while also showing that different analytical methods can produce estimates that are related but not identical.

The result also illustrates why precision and analysis populations matter. The primary rate ratio has a confidence interval that remains below one, but the interpretation is still conditional on the endpoint definition, the method used to calculate uncertainty, and the completeness of follow-up. The registry’s incomplete population description and absence of detailed missing-data and censoring methods limit a full appraisal of those conditions.

The breadth of secondary outcomes makes multiplicity especially relevant. Related composites can help characterize whether the primary pattern is consistent across outcome definitions, but many unadjusted comparisons should not be treated as a series of independent confirmations. The registry does not report how the secondary testing family was controlled or prioritized.

Finally, the sample-size illustrations demonstrate the distinction between planning and observed results. They show how assumed effect size and desired power affect participant requirements, but they are not the original design rationale and do not tell readers the trial’s observed power. Together, these features make the record useful for learning how to read event-rate outcomes, confidence intervals, alternative estimands, and incomplete reporting without overstating what the results establish.

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.
• Rate comparisons use a Poisson approximation unless the sponsor posted confidence limits; real event counts are often over-dispersed.

Several limitations are specific to the available record. The study is marked terminated, but the reason for termination is not reported in the registry record. The dates of study start and primary completion are listed, but the record does not explain how termination related to follow-up, conduct, or analysis. No reason should be inferred from the status label alone.

The primary outcome population description is incomplete. It identifies exclusions for repeat randomization and an exclusion involving study Site 3027, but the site criterion is cut off. This prevents a complete account of which randomized participants contributed to the primary analysis. The record also does not give detailed censoring rules, missing-data procedures, or sensitivity analyses for incomplete follow-up.

The sponsor’s log-rank result is reported, but the full model specification, assumptions checks, and analysis plan are not. The summary-based rate-ratio calculation is unadjusted and uses a Poisson approach; the record does not report an assessment of over-dispersion or an adjustment for it. The two estimates therefore should be read as related analyses, not as interchangeable measures.

The multiplicity strategy, interim-analysis history, original sample-size justification, and any changes to the statistical analysis plan are not reported in the registry record. Secondary findings consequently have less clearly documented inferential status. Safety summaries provide counts and listed terms, but the brief record does not supply enough detail to assess causality, exposure-adjusted risks, or the full context of adverse event ascertainment.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: The Evaluation of Bococizumab (PF-04950615; RN316) in Reducing the Occurrence of Major Cardiovascular Events in High Risk Subjects — NCT01975389.
• Registry record last updated 2019-05-01; status last verified 2019-04.
• Results first posted 2018-06-12.
• 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

The registry describes a Phase 3 randomized, quadruple-masked, parallel-group study of bococizumab versus placebo in high-risk participants with cardiovascular disease receiving background lipid-lowering therapy. Enrollment was 10564, and the study status is terminated.

The primary outcome was the event rate per 100 participant-years for a first adjudicated major cardiovascular event, followed from baseline for up to 3.4 years. The posted rates were 4.19 for placebo and 3.33 for bococizumab. The sponsor reported a log-rank hazard ratio of 0.79 with a 95% confidence interval from 0.65 to 0.97; the unadjusted rate-ratio re-calculation was 0.795 with a 95% confidence interval from 0.650 to 0.971.

The registry does not report the reason for termination, the full original analysis plan, multiplicity procedures, missing-data methods, or the original sample-size justification. The primary result should therefore be interpreted alongside the stated endpoint and analysis methods, and with these reporting limitations in mind.