Perindopril Amlodipine for the Treatment of Hypertension: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Perindopril Amlodipine for the Treatment of Hypertension (NCT01556997), a randomized phase 3 study. The primary outcome is Change From Baseline to End of Treatment in the Mean Seated Trough Cuff Diastolic Blood Pressure (DBP)..

2. Clinical Question

This question is about measured change over the treatment period and the statistical evidence for differences between groups. It is not, by itself, a complete account of longer-term blood pressure control, outcomes beyond the posted measures, or the balance of benefits and harms. Those topics are not reported in the registry record.

3. Trial Design

The registry identifies this as a Phase 3, randomized, double-blind, parallel-group study. Its official title describes a multicenter study of a fixed-dose combination of perindopril arginine plus amlodipine besylate compared with perindopril erbumine and amlodipine besylate in people with essential hypertension. The record lists enrollment of 837. It marks the study as completed.

The listed groups were XOMA 985, amlodipine besylate, and perindopril erbumine. XOMA 985 is described as the fixed-dose combination; the other two are the separate comparator drugs. The posted primary-outcome group sizes are 271.0, 275.0, and 274.0, respectively. These endpoint-specific counts need not be read as the total enrollment; the record does not explain the difference between enrollment and these analysis counts.

The record gives the study start as 2012-02 and primary completion as 2013-02. The primary outcome is mean seated trough cuff diastolic blood pressure change from baseline to end of treatment, measured from Day 0 to Day 42. A secondary outcome is the corresponding change in mean seated trough cuff systolic blood pressure over the same period.

Although randomization and double masking are recorded, the registry record does not report the method used to generate or conceal allocation, the details of masking, or the planned sample-size justification. It also does not describe treatment adherence, participant flow, or how missing endpoint measurements were handled. These omissions limit what can be inferred about implementation and analysis beyond the information explicitly recorded.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The Analysis Population for the Primary Outcome (Change from baseline to end of treatment in the mean seated trough cuff diastolic blood pressure (DBP)) consists of the Intent-to-treat population for the study

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.

6. Primary Endpoint

The registry lists the primary outcome as Change From Baseline to End of Treatment in the Mean Seated Trough Cuff Diastolic Blood Pressure (DBP)., measured over Day 0 to Day 42.

The primary endpoint is change from baseline to end of treatment in mean seated trough cuff diastolic blood pressure, measured in mmHg. The timeframe is Day 0 to Day 42. “Change” expresses the endpoint as a difference from each participant’s baseline measurement rather than as an end-of-treatment value alone. The posted results summarize these changes as group means with standard deviations.

Diastolic blood pressure is the lower of the two values in a blood pressure reading. A seated trough cuff measurement refers to a measurement taken while seated at the trough point specified by the study; the registry record does not provide further measurement procedures or timing details. The record identifies the analysis population for this endpoint as the intent-to-treat population, but does not describe how participants with missing measurements were treated in that analysis.

In general, using change from baseline can describe how measurements shifted during the study while accounting for where participants began. The comparison of group changes is relevant to the randomized question because the groups were assigned to different study regimens. However, the posted summary statistics do not provide individual participant data, baseline distributions, or adjusted group estimates. The registry reports an ANCOVA analysis, but its adjustment variables and estimate are not specified. Those details are not reported in the registry record.

7. Results Posted in the Registry

• Amlodipine Besylate (AMLb): mean -13.20 versus -15.70 on control; difference 2.50 (95% CI 1.10 to 3.90), standardized effect d = 0.30; z-test p = <0.001.
• Perindopril Erbumine (PERe): mean -9.50 versus -15.70 on control; difference 6.20 (95% CI 4.76 to 7.64), standardized effect d = 0.72; 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.

Change From Baseline to End of Treatment in the Mean Seated Trough Cuff Systolic Blood Pressure (SBP).

• 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 deviations.
• Result:
  • Amlodipine Besylate (AMLb): mean -19.60 versus -23.40 on control; difference 3.80 (95% CI 1.32 to 6.28), standardized effect d = 0.26; z-test p = 0.003.
  • Perindopril Erbumine (PERe): mean -13.40 versus -23.40 on control; difference 10.00 (95% CI 7.60 to 12.40), standardized effect d = 0.70; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Amlodipine Besylate (AMLb) 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 higher for Perindopril Erbumine (PERe) than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The registry posts one secondary endpoint: change from baseline to end of treatment in mean seated trough cuff systolic blood pressure, measured from Day 0 to Day 42. Its overall direction is consistent with the primary endpoint summaries: the XOMA 985 group has a more negative mean change than either comparator group. The recalculated pairwise estimates likewise follow the same direction as the primary endpoint comparisons. This broad consistency is descriptive; it does not establish that the two endpoints provide independent confirmation.

The secondary endpoint is related to the primary question because both assess change in seated trough cuff blood pressure over the same period, but they measure different components of blood pressure. A pattern in one endpoint cannot be substituted for the other, and agreement in direction does not remove uncertainty about measurement, analysis choices, or missing observations. The registry record does not provide a detailed endpoint hierarchy or explain how secondary outcomes were used in the study’s formal conclusions.

The recalculated secondary comparisons are unadjusted. When multiple outcomes or comparisons are examined, interpreting each p-value as if it were the only test can overstate the strength of evidence. A multiplicity procedure can control or otherwise address this issue, but whether such a procedure was planned or applied is not reported in the registry record. The sponsor’s posted ANCOVA p-value is not enough to establish the multiplicity treatment of the secondary endpoint.

For these reasons, the secondary result is best read as supportive descriptive context rather than as a separate, definitive test. The direction across endpoints can be noted, while conclusions about confirmatory status, prespecification, and adjusted inference remain limited by the information in the registry record.

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

• Change From Baseline to End of Treatment in the Mean Seated Trough Cuff Systolic Blood Pressure (SBP).

9. Statistical Interpretation

10. Statistical Methods Explained

The registry identifies the primary analysis as an ANCOVA and reports a p-value of 0.025 for the three-group analysis. ANCOVA, or analysis of covariance, is a method for comparing a continuous outcome across groups while accounting for one or more covariates. In general, an ANCOVA can adjust for baseline measurements or other specified variables, potentially improving precision when the adjustment is appropriate. The registry record does not identify which covariates were included, how the model was specified, or the adjusted group estimates. No more detailed reconstruction of that analysis is possible from the record.

What does a group mean describe?

The primary endpoint is continuous, and the posted statistic is the mean change in blood pressure. A mean summarizes the center of the observed group values. It does not describe every participant’s response, the distribution’s shape, or whether individual values were clustered tightly around the mean. The standard deviation describes the spread of individual changes around that group mean. It is not the standard error of the mean and is not itself a confidence interval.

The endpoint counts are 271.0 for XOMA 985, 275.0 for amlodipine besylate, and 274.0 for perindopril erbumine. The record identifies the primary analysis population as intent-to-treat, but does not state how the analysis population was operationalized, whether all randomized participants contributed an endpoint, or how missing values were handled. The fact that an analysis population is named does not answer those questions.

How should the pairwise recalculations be understood?

The pairwise estimates are unadjusted recalculations from the posted group means, standard deviations, and sample sizes. For each comparator, the mean difference is oriented as the comparator mean change minus the XOMA 985 mean change. This makes a positive difference correspond to the more negative mean change in the XOMA 985 group. The estimates are not adjusted for baseline or other covariates, and they are not the ANCOVA estimates reported by the sponsor.

In general, a standard error expresses how much an estimate would be expected to vary across repeated samples under the calculation’s assumptions. A confidence interval uses that uncertainty to give a range of values reasonably compatible with the data and method. A p-value measures how unusual data at least as inconsistent with a specified null hypothesis would be if that null hypothesis and the model assumptions held. It is not the probability that the null hypothesis is true, nor does it measure the size or practical importance of an effect.

The recalculated pairwise p-values are unadjusted. When several comparisons are considered, the chance of at least one false-positive result can increase if each is assessed independently at the same threshold. The registry record does not report whether or how the sponsor adjusted for multiple comparisons. Therefore, the recalculated pairwise p-values should be read as descriptive inferential results under their stated unadjusted approach, not as a full account of the sponsor’s multiplicity strategy.

Why can the reported and recalculated analyses differ?

An ANCOVA and an unadjusted comparison of summary means can yield different estimates or p-values because they may use different information and assumptions. An adjusted analysis can account for covariates, while a summary-statistic recalculation cannot reproduce participant-level adjustment. Model specification, the analysis population, handling of missing data, and any multiplicity procedure may also matter. These are general reasons analyses can differ; the registry record does not identify which, if any, explain the difference in this trial.

The sponsor’s reported result is an overall ANCOVA p-value for the groups. It does not give the ANCOVA’s estimate or confidence interval, nor does it identify which group contrasts were assessed within that analysis. The recalculated confidence intervals concern pairwise unadjusted mean differences. They answer a narrower question and should not be substituted for a missing adjusted estimate.

What does over-dispersion mean in general?

For count outcomes, over-dispersion means that observed variability exceeds what a simple count model assumes; an inappropriate model can then understate uncertainty. The primary endpoint is a continuous blood pressure change, not a count outcome, and the registry record does not report a count model for it. The general concept is relevant when evaluating methods for other outcome types, but it is not a reported feature of this primary analysis.

Overall, the available methods information supports a cautious reading: the registry identifies randomization, masking, the endpoint, the analysis population label, and an ANCOVA result, while leaving several key model and missing-data details unspecified. The pairwise calculations offer a transparent unadjusted view of the posted summaries, with different inferential status from the sponsor’s analysis.

11. Confidence Intervals and Precision

The unadjusted recalculated 95% confidence interval for the mean difference between XOMA 985 and amlodipine besylate is 1.098 to 3.902 mmHg. For XOMA 985 compared with perindopril erbumine, the corresponding interval is 4.76 to 7.64 mmHg. These intervals are for pairwise mean differences calculated from the posted summary statistics; they are not confidence intervals from the sponsor’s ANCOVA.

In general, a confidence interval describes a range of values compatible with the observed data under a specified statistical method. Its width reflects statistical precision: narrower intervals indicate less sampling uncertainty under that method, while wider intervals indicate more. An interval does not account automatically for every uncertainty, such as unreported analysis choices, missing data, measurement procedures, or selection of outcomes.

Both recalculated intervals lie above zero, consistent with the positive orientation of the calculated differences: comparator mean change minus XOMA 985 mean change. The posted group means show more negative changes for XOMA 985. This does not mean every participant had a larger decrease, and an interval for a group mean difference does not describe individual outcomes.

The sponsor-reported ANCOVA has p = 0.025, but the registry record gives no corresponding estimate or confidence interval. Consequently, the precision of the sponsor’s adjusted estimate cannot be assessed from the record. The recalculated intervals should be interpreted as precision measures for the unadjusted comparisons only. They do not resolve the discrepancy between the overall reported analysis and the pairwise recalculations, or establish the precision of any adjusted pairwise contrast.

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 sample-size figures are planning illustrations, not the trial’s documented original design calculation. For the continuous blood pressure comparisons, the listed figures are participants per arm, not total events. The registry record does not report the assumptions used for the original sample-size justification, so the illustrations should not be taken as evidence of what the investigators planned before the study.

The stated illustration 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 specified as a fraction of the observed effect. The displayed rows therefore represent planning for 100%, 75%, and 50% of the observed effect. For the primary comparison with amlodipine besylate, the figures for 100% of the observed effect are 176 participants per arm for 80% power and 235 participants per arm for 90% power. At 50% of the observed effect, the corresponding figures are 702 and 939 participants per arm. The comparison with perindopril erbumine has its own set of figures, because its observed effect differs.

In general, power is the probability that a planned study will detect an effect of a specified size under the assumptions of its statistical model and decision rule, if that effect is present. The 80% power column gives the planned participants per arm for an 80% probability under those assumptions; the 90% column gives the participants per arm for a 90% probability. Smaller effects are harder to distinguish from random variation, so detecting them at the same power generally requires more participants. The illustrations are not observed power: they do not measure how likely this completed study was to detect its results after the data were collected.

The figures depend on the observed effects and stated planning assumptions. They do not incorporate undocumented features of the trial’s original design or prove that a particular sample size would be adequate under different assumptions.

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 = 2.500; pooled standard deviation σ = 8.355.
2. n = 2 × (1.96 + 0.842)² × 8.355² / 2.500² = 175.3, rounded up to 176 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 <- 2.5                      # observed difference in means
sigma <- 8.3548535779404                     # 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(1556997)
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 = 176 (80% power), 235 (90% power)
 75% of observed effect: n per arm = 312 (80% power), 418 (90% power)
 50% of observed effect: n per arm = 702 (80% power), 939 (90% power)
power.t.test: 176.3 
Simulated power at n = 176 per arm: 0.793 (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’s sponsor-reported primary analysis is an ANCOVA across the three groups, with p = 0.025. No adjusted estimate, confidence interval, or group-specific contrast is included in the record. The reported result therefore indicates the p-value recorded for that overall analysis, but does not reveal the magnitude or precision of its adjusted comparisons.

The pairwise comparisons in the posted statistical summaries are recalculated, unadjusted differences based on group means, standard deviations, and sample sizes. Their estimates and p-values do not reproduce the sponsor’s ANCOVA. Because the registry flags a discrepancy between the sponsor-reported analysis and the recalculations, the sponsor’s own analysis takes precedence. The recalculated results remain useful for describing the posted group summaries, but they should not be presented as the sponsor’s adjusted estimates or as a correction to the reported analysis.

The record does not explain the discrepancy. It does not specify the ANCOVA covariates, analysis details, or the reason its reported result differs from the unadjusted pairwise calculations. A firm explanation would require information not reported in the registry record. The overall ANCOVA p-value also should not be treated as if it posted pairwise adjusted results that the record does not contain.

15. Multiplicity, Missing Data and Analysis Populations

The registry record does not describe a multiplicity plan. It does not say whether the primary analysis was the sole confirmatory test, whether the two comparator contrasts were handled as a family, or whether the secondary endpoint was included in a testing hierarchy. It also does not report a correction or other procedure for multiple comparisons. Because the posted pairwise recalculations are unadjusted, their p-values should not be interpreted as multiplicity-adjusted evidence.

In general, multiplicity arises when several hypotheses, endpoints, or comparisons are examined. If each test is considered separately at a chosen threshold, the chance of at least one false-positive finding across the collection can be greater than for a single test. Statistical plans may address this in different ways, depending on the goals and structure of the study. No particular approach can be attributed to this trial from the available registry information.

The registry identifies the primary analysis population as the intent-to-treat population, but the record does not explain whether every randomized participant was included in the primary endpoint analysis or how missing measurements were handled. It does not report the number of participants with missing outcomes, reasons for missingness, imputation procedures, or sensitivity analyses. Those details matter because estimates can be affected if observed measurements do not represent the outcomes that would have been recorded for participants with missing data.

The posted endpoint group sizes do not by themselves resolve the missing-data question. The record gives enrollment of 837 and primary-outcome counts of 271.0, 275.0, and 274.0, but does not provide a participant-flow account linking those figures. It would be inappropriate to infer why the counts differ or to assume that missingness had no effect.

The registry also does not report the ANCOVA covariates, model diagnostics, assumptions, or handling of protocol deviations. These omissions prevent a detailed appraisal of the adjusted analysis. They do not establish that the procedures were inadequate; they mean the record does not contain the information needed to evaluate them. A careful interpretation therefore distinguishes the recorded overall ANCOVA result from the unadjusted recalculations and avoids attributing unreported methods to the study.

16. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 1% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: lip swelling (0.4%), renal failure acute (0.4%), hypotension (0.4%), pulmonary embolism (0.4%), osteoarthritis (0.4%).

The registry lists serious adverse events for 279 participants at risk in the XOMA 985 group, 280 in the amlodipine besylate group, and 278 in the perindopril erbumine group. The corresponding numbers reported as affected are 1, 3, and 2. These are group-level counts from the adverse-event record; they are not rates recalculated for comparison. The record also lists other adverse events, with 75, 68, and 53 participants affected in the same group order.

The serious-event terms listed include Lip Swelling, Renal Failure Acute, Hypotension, Pulmonary Embolism, Osteoarthritis, and Gastrointestinal Hemorrhage, each reported as 0.4%. The record does not attribute these terms to a specific group in the listed summary. It also does not give a death count; deaths are not reported in the registry record. That absence should not be read as evidence that no deaths occurred.

These counts do not establish comparative safety by themselves. The registry record does not provide event timing, duration, severity beyond the serious classification, exposure-adjusted rates, or enough detail to assess whether events were considered related to treatment. Small differences in counts should not be treated as evidence of a difference in risk without an appropriate analysis and fuller context.

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

The results describe mean changes in seated trough cuff blood pressure during Day 0 to Day 42 among the recorded study groups. For the primary endpoint, the posted mean changes are negative in all groups, with a more negative mean in the XOMA 985 group than in either comparator group. The unadjusted recalculated pairwise differences and intervals quantify those contrasts under a simple summary-statistic approach. The sponsor’s own reported primary analysis is an overall ANCOVA with p = 0.025, and its analysis takes precedence over the unadjusted recalculations.

These findings do not mean that every participant experienced the group-average change, or that the group summaries describe individual responses. They do not establish what happened beyond the recorded treatment period, because longer-term results are not reported in the registry record. Nor do they provide a complete account of outcomes outside the posted blood pressure measures.

The results also do not establish a complete benefit-harm comparison. The registry contains selected adverse-event counts and terms, but lacks the detail needed to assess event timing, attribution, and comparative risk fully. Its missing-data procedures, covariate adjustments, multiplicity approach, and original sample-size assumptions are not reported. These gaps constrain how precisely the analyses can be evaluated.

Randomization and double masking are recorded, which are important features of the study design. However, the registry entries do not allow a full assessment of how those procedures were implemented or how all analysis decisions were made. The most defensible reading is therefore limited to the recorded study design, posted endpoint summaries, the sponsor-reported overall analysis, and the clearly distinguished unadjusted recalculations. Neither the statistical results nor the adverse-event counts should be extended beyond what they measure and report.

18. Why This Trial Matters Statistically

This study illustrates why a registry result can contain more than one statistical view of the same endpoint. The posted group means and standard deviations support transparent unadjusted recalculations, while the registry also records an ANCOVA result from the sponsor. These methods answer related but not identical questions. Keeping the analyses distinct prevents a calculated pairwise contrast from being mistaken for an adjusted estimate that the registry does not report.

It also shows why an overall p-value is not a substitute for effect estimates and confidence intervals. The ANCOVA p-value records a result for the three-group analysis, but without its estimate and interval the size and precision of the adjusted effect cannot be read from the record. Conversely, the unadjusted pairwise intervals give estimates and precision for their own calculation, but do not supply the missing adjusted contrasts.

Sample-size illustrations are another important distinction. Planning figures based on observed effects can help readers understand how required sample size changes when a target effect is smaller, but they do not document the trial’s original design assumptions and are not observed power. The registry record does not report the original sample-size justification, so retrospective illustrations must remain separate from claims about the study’s planning.

Finally, the record demonstrates the importance of transparent reporting about multiplicity, missing data, analysis populations, and safety outcomes. Without those details, readers can describe the reported statistics but cannot fully assess all sources of analytical uncertainty. Clear separation of what is reported, recalculated, and unreported is central to a sound statistical 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.

Several trial-specific limitations follow from the scope of the registry record. It does not report the ANCOVA estimate, confidence interval, covariates, or pairwise adjusted contrasts. The overall p-value therefore cannot show the size or precision of the sponsor’s adjusted comparisons. The reason for the discrepancy between that analysis and the unadjusted recalculations is not reported in the registry record.

The record names the intent-to-treat population for the primary endpoint but does not explain how it was defined in practice, how missing endpoint values were handled, or how participant counts relate to the enrollment figure. It provides no participant-flow description or sensitivity analysis. Thus, the consequences of missing observations cannot be evaluated from these results alone.

The registry does not describe how randomization or masking was implemented, nor does it report adherence, treatment exposure, or protocol deviations. It also does not give the original sample-size justification, a detailed analysis plan, or a multiplicity procedure. The recalculated comparisons are unadjusted and should be distinguished from the sponsor’s ANCOVA.

For safety, the record gives counts of affected participants and selected serious-event terms but not detailed timing, duration, attribution, or exposure-adjusted analyses. Death counts are not reported in the registry record. The study’s posted blood pressure time frame ends at Day 42, so longer-term outcomes are not available in this record. These are reporting limitations; they do not establish that the study itself did not collect or analyze information beyond what is recorded.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Perindopril Amlodipine for the Treatment of Hypertension — NCT01556997.
• Registry record last updated 2015-09-28; status last verified 2015-08.
• Results first posted 2015-08-25.
• 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 record describes NCT01556997, a completed Phase 3, randomized, double-blind, parallel-group study of XOMA 985, a fixed-dose perindopril arginine/amlodipine besylate combination, compared with amlodipine besylate and perindopril erbumine in essential hypertension. Enrollment is listed as 837.

The primary endpoint is change in mean seated trough cuff diastolic blood pressure from baseline to end of treatment, over Day 0 to Day 42. A secondary endpoint measures the corresponding change in systolic blood pressure. The sponsor-reported primary analysis is an ANCOVA across the three groups with p = 0.025. Recalculated pairwise comparisons are unadjusted and are not substitutes for that reported analysis; the sponsor’s own analysis takes precedence.

The registry does not report several details needed for fuller appraisal, including the ANCOVA estimates and covariates, missing-data handling, multiplicity procedures, original sample-size assumptions, and detailed safety context. The posted results should be interpreted within those limits.