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Diabetes Phase 3 Continuous Endpoint NCT03136484

Efficacy and Safety of Semaglutide Versus Canagliflozin as add-on to Metformin in Subjects With Type 2 Diabetes: Complete Statistical Analysis

This analysis concerns a phase 3 randomized comparison of semaglutide and canagliflozin, each added to metformin, in people with type 2 diabetes. The registered primary outcome is change in HbA1c from week 0 to week 52, but numerical comparative results are not reported in the registry record.

Trial start: 2017-03-15  ·  Enrollment: 788  ·  Sponsor: Novo Nordisk A/S
Scope of this record

This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.

1. Trial at a Glance

This page covers the registry results for Efficacy and Safety of Semaglutide Versus Canagliflozin as add-on to Metformin in Subjects With Type 2 Diabetes (NCT03136484), a randomized phase 3 study. The primary outcome is Change in HbA1c.

788
Enrollment
Phase 3
n/a
Arms
In the primary outcome
n/a
Effect
No re-analysis shown
n/a
95% CI
See limitations
FeatureRegistry value
ClinicalTrials.gov identifierNCT03136484
PhasePhase 3
ConditionDiabetes, Diabetes Mellitus, Type 2
AllocationRandomized
Design modelParallel
MaskingDouble
Enrollment788
Arms in the primary outcomen/a
Lead sponsorNovo Nordisk A/S
Results postedYes

2. Clinical Question

Population

The trial concerns subjects with type 2 diabetes receiving background metformin. The registry describes conduct across Africa, Asia, Europe, North America and South America. It records enrollment of 788 and defines the full analysis set as all randomized participants; the number analyzed refers to participants with available data.

Intervention

The experimental regimen was once-weekly subcutaneous semaglutide at 1.0 mg, with a canagliflozin placebo. The comparison is therefore between the active semaglutide regimen and the active canagliflozin regimen, rather than between either drug and no treatment.

Comparator

The comparator regimen was once-daily oral canagliflozin at 300 mg, with a semaglutide placebo. The record lists placebo interventions for both drugs, consistent with the two regimens being masked within the trial.

Primary question

The primary outcome asks how HbA1c changed from week 0 to week 52 in each randomized group. The intended comparison is the glycaemic-control outcome for semaglutide added to metformin versus canagliflozin added to metformin. Numerical arm-level changes and a between-group estimate are not reported in the registry record, so the magnitude and precision of that comparison cannot be assessed from the recorded information.

Statistically, this is a comparison of two active add-on regimens in a parallel-group randomized trial. The question is not whether either regimen differs from metformin alone, because the registry describes metformin as background treatment in both arms and does not list a metformin-only group. The record names change in HbA1c as the primary outcome and also lists measures such as body weight, fat mass, fasting plasma glucose, self-measured glucose profiles and cholesterol outcomes as secondary outcomes. Those additional outcomes do not substitute for the missing numerical primary comparison.

3. Trial Design

The registry describes a phase 3, randomized, double-masked, parallel-group trial. Its title identifies the comparison as semaglutide versus canagliflozin added to metformin in subjects with type 2 diabetes. Enrollment is recorded as 788. The trial status is completed; the recorded start date is 2017-03-15 and the primary completion date is 2018-10-16.

The two arm descriptions pair each active drug with a placebo for the other drug: semaglutide with canagliflozin placebo, and canagliflozin with semaglutide placebo. The brief summary specifies once-weekly subcutaneous semaglutide at 1.0 mg and once-daily oral canagliflozin at 300 mg. Both regimens are described against background metformin. The record calls the trial double-masked but does not report the masking procedures in further detail.

The primary outcome is change in HbA1c from week 0 to week 52. Its description distinguishes an on-treatment without rescue medication observation period from an in-trial observation period. The former begins at first dose and ends at the earlier of last dose plus 7 days or first initiation of rescue medication. The latter begins at randomization and continues through the period after rescue medication or premature trial-product discontinuation, if either occurs, until last contact, withdrawal of consent or death, whichever comes first.

The registry lists 61 outcome measures and 2 analyses. It also lists secondary outcomes covering body weight, total fat mass, fasting plasma glucose, self-measured plasma glucose profiles and fasting cholesterol measures. The registry record does not report the randomization method, allocation concealment procedures, detailed masking procedures, or the statistical analysis plan.

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: Study design: Body composition (sub-study) was measured using dual x-ray absorptiometry (DXA) scans in a planned subset of randomised participants.

Overall Study

StageSemaglutide + Canagliflozin PlaceboCanagliflozin + Semaglutide Placebo
STARTED394394
Exposed392394
COMPLETED367372
NOT COMPLETED2722

Reasons for not completing this period:

ReasonSemaglutide + Canagliflozin PlaceboCanagliflozin + Semaglutide Placebo
Withdrawal by Subject1914
Lost to Follow-up78
Death10

Analysis population for the primary outcome, as defined in the registry: Full analysis set comprised of all randomised participants. "Number analyzed"=participants with available data.

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.

CharacteristicUnitSemaglutide + Canagliflozin PlaceboCanagliflozin + Semaglutide PlaceboTotal
Participants analysed394394788
Age, ContinuousYears55.7 (SD 11.1)57.5 (SD 10.7)56.6 (SD 10.9)
Sex: Female, Male: FemaleParticipants171193364
Sex: Female, Male: MaleParticipants223201424
Ethnicity (NIH/OMB): Hispanic or LatinoParticipants156137293
Ethnicity (NIH/OMB): Not Hispanic or LatinoParticipants238257495
Ethnicity (NIH/OMB): Unknown or Not ReportedParticipants000
Race/Ethnicity, Customized: Race : American Indian or Alaska nativeParticipants134
Race/Ethnicity, Customized: Race : AsianParticipants6263125
Race/Ethnicity, Customized: Race : Black or African AmericanParticipants283058
Race/Ethnicity, Customized: Race : Native Hawaiian or Other Pacific IslanderParticipants000
Race/Ethnicity, Customized: Race : WhiteParticipants297290587
Race/Ethnicity, Customized: Race : OtherParticipants6713
Race/Ethnicity, Customized: Race : Not ApplicableParticipants011
HbA1cPercentage (%) of HbA1c8.3 (SD 1.0)8.2 (SD 1.0)8.3 (SD 1.0)

6. Primary Endpoint

The registry lists the primary outcome as Change in HbA1c, measured over Week 0, week 52.

ElementRegistry entry
Result typeMean
Measure of spreadStandard Deviation
UnitPercentage (%) of HbA1c
Endpoint classificationContinuous Endpoint

The primary endpoint is change in HbA1c, expressed as a percentage of HbA1c, from week 0 to week 52. The registry expands HbA1c as glycosylated haemoglobin and identifies the endpoint as a mean with standard deviation as its dispersion measure. It is framed as a measure of glycaemic control, matching the stated aim of comparing the two add-on regimens on that outcome.

Change is useful for a treatment comparison because it describes how the measured outcome differs from baseline to the specified follow-up, rather than reporting only a value at one time. In general, comparing group-level changes can address whether the observed trajectories differ, while an estimate of the between-group difference and its uncertainty is needed to judge how precisely the comparison is known. Neither arm-level mean changes nor a numerical between-group estimate is reported in the registry record, so the magnitude of the primary outcome cannot be interpreted from the record available.

The endpoint description specifies two observation periods. The on-treatment period excludes observations after rescue medication begins and is tied to exposure to the trial product. The in-trial period includes observations after rescue medication or premature discontinuation, if these occur, and follows participants until the defined end of observation. These periods represent different ways of handling post-randomization events; they should not be treated as interchangeable estimands.

7. Why No Re-analysis Is Shown

Reported as posted, not recalculated. Primary outcome has several categories or time points; not reduced to one comparison. A result is recalculated only when the posted data support a clean two-arm comparison, so no result is shown beyond what the sponsor posted.

8. Statistical Interpretation

Clinical Biostats interpretation

The registry identifies a clinically focused comparison: change in HbA1c between a semaglutide regimen and a canagliflozin regimen, each used with metformin. It provides the endpoint definition, timeframe, analysis population description and observation-period rules. It does not report the numerical outcome summaries needed to quantify the primary comparison. In particular, arm-specific mean changes, standard deviations, the between-group estimate and its confidence interval are not reported in the registry record.

As a result, no conclusion about the direction, size or precision of the primary outcome difference can be drawn from these recorded details. A trial title, design and endpoint establish what was intended to be compared; they do not establish what the results were. The absence of numerical results in the record is also not evidence that the two regimens had equal outcomes. It leaves the comparative effect undetermined from this information.

The two observation periods matter to interpretation. An on-treatment analysis focuses on measurements during a defined period tied to treatment exposure and excludes observations after rescue medication begins. An in-trial analysis retains follow-up after rescue medication or premature discontinuation, if either occurs. In general, these analyses answer different questions because they handle events after randomization differently. Without numerical results for each analysis and an explanation of how the analyses were interpreted, the record does not establish whether conclusions were consistent across observation periods.

The registry states that the full analysis set comprised all randomized participants, while the number analyzed means participants with available data. That wording distinguishes the intended analysis population from the participants contributing outcome data. It does not disclose how much outcome data were missing, how missing observations were handled, or whether the available-data counts differed between arms. Those details affect how confidently estimates can be interpreted, but they are not reported in the registry record.

The record includes safety counts, but those counts do not fill the gap in the primary efficacy results. Serious adverse events affected 18 participants in the semaglutide arm and 21 in the canagliflozin arm; the recorded numbers at risk were 392 and 394, respectively. The record also lists other adverse-event counts and deaths. Counts alone do not establish causation or a comparative safety effect, especially without definitions, follow-up detail and uncertainty estimates. They describe recorded events within this trial, not a complete assessment of comparative benefit and harm.

Overall, the registry record permits a description of the trial question, structure and endpoint rules. It does not permit a quantitative reading of the primary treatment comparison or a determination of its statistical significance. Any more specific claim about the efficacy result would require numerical outcome information that is not reported in the registry record.

9. Statistical Methods Explained

The registry describes the design as randomized, double-masked and parallel-group. In general, random allocation is intended to reduce systematic differences between groups at the start of a trial, while masking is intended to limit the influence of treatment knowledge on participants, clinicians or outcome assessment. A parallel-group design assigns participants to a regimen that is compared with another regimen over the course of the trial. These design labels describe the broad structure; the registry record does not report the detailed procedures used to generate or conceal allocation or to maintain masking.

What does a mean change represent?

The registered primary measure is a mean change in HbA1c from week 0 to week 52. A mean is a summary of the observed values in a group. Standard deviation describes how dispersed individual values are around that group mean; it is not the same as the uncertainty in the estimated mean or in the treatment contrast. The record names standard deviation as the dispersion measure but does not report the numerical means or standard deviations for the primary outcome.

For a treatment comparison, the central quantity is usually the difference between the groups’ mean changes. A confidence interval, when reported, describes a range of values compatible with the data and the analysis assumptions, and indicates the estimate’s precision. A narrow interval indicates greater precision than a wide interval. A confidence interval does not itself prove that a treatment effect is important, nor does a significance test describe the full range of plausible effects. No numerical treatment contrast, confidence interval or primary-outcome p-value is reported in the registry record, so none can be interpreted for this trial from these registry entries.

Why distinguish observation periods?

The endpoint description defines an on-treatment without rescue medication period and an in-trial period. The on-treatment period starts at first dose and ends at the earlier of last dose plus 7 days or rescue medication initiation. The in-trial period begins at randomization and can include follow-up after rescue medication or premature trial-product discontinuation, if these occur, until the stated end condition. These rules determine which observations contribute to an analysis.

In general, excluding measurements after rescue medication answers a different question from retaining follow-up after such events. The former describes outcomes during a treatment-exposure period under the stated rule; the latter describes outcomes during the trial follow-up despite those events. Neither analysis is automatically preferable in every setting. Their interpretation depends on the scientific question and the analysis plan. The registry record does not report why these particular approaches were selected or how results from the periods were combined or prioritized.

What do the planning assumptions mean?

The planning illustration is described as using the observed effect, a two-sided significance level of 0.05, equal allocation between the two arms and a normal approximation. It considers effects set as a stated fraction of the observed effect. These are planning assumptions, not observed trial outcomes. In general, a sample-size calculation estimates how much information a future study might need under specified assumptions. Its output depends on the assumed effect and variability, the chosen significance level, desired power and design. If the assumed effect is smaller, more information is generally required to distinguish it from no difference at a fixed design criterion.

The illustration must not be interpreted as observed power for this completed trial. Observed power is not a substitute for reporting the estimate and its uncertainty. Nor does a planning calculation establish that the original trial was designed using those assumptions: the registry record describes the illustration as based on the observed effect and does not report the trial’s own sample-size justification. Numerical planning counts are not reported in the registry record.

Why does variability matter?

In general, outcome variability affects the precision of a mean difference. When individual measurements vary considerably, a group mean is less precise for a given amount of information. Standard deviation is one way to describe that variability for a continuous outcome. It should be considered alongside the estimated treatment difference and its confidence interval, rather than treated as evidence of a treatment effect by itself. The registry names standard deviation as the dispersion measure but supplies no numerical primary-outcome values with which to assess variability.

Normal approximations can be useful for planning or inference under stated conditions. Their suitability depends on the outcome distribution and analysis design. The record states that the planning illustration uses a normal approximation; it does not report diagnostic checks or details of the statistical model used for the trial’s primary analysis. No further model assumptions should be inferred from the planning description.

What can be read from the safety counts?

The adverse-event record distinguishes serious adverse events from other adverse events and records deaths separately. These are event summaries, not estimates of the primary HbA1c effect. In general, event counts should be interpreted with the population at risk, event definitions, observation period and uncertainty in mind. A difference in raw counts does not by itself show that treatment caused an event or that one regimen has a different underlying risk. The registry does not report inferential comparisons for the listed safety counts.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 61 outcome measures and 2 analyses, with change in HbA1c identified as the primary outcome and several secondary outcomes named. The secondary measures include body weight, total fat mass, fasting plasma glucose, self-measured plasma glucose summaries and fasting cholesterol measures. When many outcomes or analyses are examined, the chance of at least one apparently notable result can increase. In general, a prespecified hierarchy or multiplicity adjustment can help control how results are interpreted across multiple comparisons.

The statistical plan for multiplicity is not reported in the registry record. It is therefore not possible to determine whether the listed outcomes were tested in a hierarchy, whether any adjustment was used, or which comparisons were intended to support confirmatory conclusions. The record also does not provide numerical estimates or p-values for the primary and secondary outcomes, so the potential impact of multiple testing cannot be assessed from the recorded information.

The primary outcome description specifies an on-treatment without rescue medication period and an in-trial period. These differing observation rules create distinct analysis contexts. The record does not report a multiplicity strategy for interpreting results across the periods or indicate a primary analysis hierarchy between them. The stated fact that the record lists 2 analyses does not by itself explain their relationship or priority.

The full analysis set is described as all randomized participants, and the number analyzed is defined as participants with available data. This does not establish that every randomized participant had an observed week 52 outcome. The amount and pattern of missing data, reasons for missingness, imputation methods, sensitivity analyses and any handling of incomplete follow-up are not reported in the registry record. In general, missing-data assumptions can influence estimates when outcome availability is related to participant characteristics or outcomes. The record does not provide enough information to assess those assumptions.

11. Safety Results

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

ArmParticipants with serious adverse eventsParticipants at riskPercentage
Semaglutide + Canagliflozin Placebo183924.6%
Canagliflozin + Semaglutide Placebo213945.3%
Participants with at least one serious adverse event
Serious adverse events by armSemaglutide + Canagliflozin P…4.6%Canagliflozin + Semaglutide P…5.3%% of participants with at least one serious adverse event

Deaths

ArmDeaths (participants affected of at risk)
Semaglutide + Canagliflozin Placebo1 of 392
Canagliflozin + Semaglutide Placebo0 of 394

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

ArmParticipants affected of at risk
Semaglutide + Canagliflozin Placebo185 of 392
Canagliflozin + Semaglutide Placebo120 of 394

Most frequent serious adverse event terms

Event termOrgan systemSemaglutide + Canagliflozin PlaceboCanagliflozin + Semaglutide Placebo
CholelithiasisHepatobiliary disorders0 of 3923 of 394
Urinary tract infectionInfections and infestations3 of 3920 of 394
NephrolithiasisRenal and urinary disorders2 of 3920 of 394
Non-cardiac chest painGeneral disorders1 of 3921 of 394
PneumoniaInfections and infestations1 of 3921 of 394
PyrexiaGeneral disorders0 of 3922 of 394
Abdominal pain upperGastrointestinal disorders1 of 3920 of 394
Airway complication of anaesthesiaInjury, poisoning and procedural complications1 of 3920 of 394
Angina unstableCardiac disorders0 of 3921 of 394
Ankle fractureInjury, poisoning and procedural complications0 of 3921 of 394

Most frequent non-serious adverse event terms

Event termOrgan systemSemaglutide + Canagliflozin PlaceboCanagliflozin + Semaglutide Placebo
NauseaGastrointestinal disorders89 of 39226 of 394
DiarrhoeaGastrointestinal disorders59 of 39237 of 394
VomitingGastrointestinal disorders50 of 3929 of 394
HeadacheNervous system disorders26 of 39227 of 394
NasopharyngitisInfections and infestations23 of 39226 of 394
ConstipationGastrointestinal disorders20 of 39223 of 394
Back painMusculoskeletal and connective tissue disorders11 of 39221 of 394
Decreased appetiteMetabolism and nutrition disorders26 of 3926 of 394
DyspepsiaGastrointestinal disorders22 of 3928 of 394

Serious events with the highest arm-level rate: urinary tract infection (0.8%), cholelithiasis (0.8%), nephrolithiasis (0.5%), pyrexia (0.5%), abdominal pain upper (0.3%).

Do not overextend the safety comparison. Serious-adverse-event counts are safety observations, not efficacy outcomes, and should not be combined with the primary result into a single benefit-risk number.

The registry separates serious adverse events from other adverse events and reports deaths separately. For serious adverse events, the number at risk is 392 in the semaglutide plus canagliflozin-placebo group and 394 in the canagliflozin plus semaglutide-placebo group; the recorded number affected is 18 and 21, respectively. For other adverse events, the numbers at risk are 392 and 394, and the numbers affected are 185 and 120, respectively. The record reports 1 death in the semaglutide group and 0 in the canagliflozin group.

These are counts, not adjusted estimates of comparative risk. They do not indicate whether an event was caused by treatment, and the registry record does not report inferential comparisons for them. Serious adverse-event terms listed include urinary tract infection and cholelithiasis at 0.8% each, nephrolithiasis and pyrexia at 0.5% each, and upper abdominal pain and an airway complication of anaesthesia at 0.3% each. The percentages are registry-listed terms; the record does not provide enough detail to infer event severity beyond the serious-event classification or to establish causality.

In general, safety counts require context about definitions, duration of observation, follow-up completeness and uncertainty. They should not be read as proof that either regimen is safer or less safe. The registry record does not report a detailed safety analysis plan or the methods used to compare event rates.

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

The record establishes that a randomized, double-masked, parallel-group phase 3 trial compared semaglutide and canagliflozin as add-on treatments to metformin in subjects with type 2 diabetes. It defines change in HbA1c from week 0 to week 52 as the primary outcome and describes two observation periods. Those details clarify the trial question and how observations were classified.

They do not establish the primary result. The numerical arm-level changes, between-group estimate, confidence interval and p-value are not reported in the registry record. Consequently, the record does not show whether the groups differed, how large any difference was, or how precisely it was estimated. Missing result information should not be mistaken for evidence of no difference, nor can the trial’s title or design be used to infer the direction of an outcome.

The trial’s secondary outcome list indicates additional domains that were measured, but their numerical results are not reported. Without outcome estimates and a stated multiplicity plan, it is not possible to judge their magnitude or how they relate to the primary outcome. The existence of many listed outcomes also does not mean that each was a confirmatory test.

The safety counts describe events recorded in the two groups, including serious events, other events and deaths. Counts are useful for describing what was recorded, but do not alone establish treatment causation or comparative safety. The registry record does not provide confidence intervals or inferential comparisons for these counts.

In general, a trial result is best understood through its estimated effect, uncertainty, analysis population and handling of missing data, alongside the design and outcome definitions. Those numerical and methodological details are incomplete in the registry record. Accordingly, these registry entries support a description of the study’s structure and its registered question, not a conclusion about the comparative clinical effect of the regimens.

13. Why This Trial Matters Statistically

This trial is statistically notable as a randomized head-to-head comparison of two active regimens added to metformin. The parallel-group design addresses a direct comparison between the semaglutide and canagliflozin strategies rather than comparing either strategy with no active add-on treatment. The double-masked description and placebo pairing are relevant design features because they indicate an effort to compare the regimens under masking, although the procedures are not detailed in the registry record.

The endpoint definition also matters. Change in HbA1c is specified from week 0 to week 52, and the registry distinguishes an on-treatment period without rescue medication from an in-trial period that may include follow-up after rescue medication or discontinuation. These analysis choices can lead to different interpretations because they treat post-randomization events differently. Reporting both clearly, with estimates and uncertainty, would help readers understand how the comparison depends on the chosen observation period.

The record’s distinction between the full analysis set and participants with available data highlights a further statistical issue: the randomized population and the group contributing observed outcome data need not be identical. Without missing-data details, readers cannot determine how incomplete follow-up was handled or how robust the results might be to alternative assumptions.

The registered outcome list is extensive, and the record lists multiple analyses. In general, clear prespecification and multiplicity handling are important when several outcomes and analysis choices are examined. The record does not report those details. Most importantly, numerical primary results are not reported, so the statistical importance of the design cannot be translated into a quantitative treatment comparison from this record alone.

14. Limitations

The principal limitation for interpreting this trial from the registry record is the absence of numerical primary-outcome results. Although the endpoint, unit, timeframe and dispersion measure are identified, arm-specific mean changes, standard deviations and a between-group estimate are not reported in the registry record. Confidence intervals and p-values for the primary comparison are also not reported, preventing assessment of effect magnitude and precision.

The record describes the full analysis set as all randomized participants and says the number analyzed means participants with available data. It does not report arm-specific numbers analyzed for HbA1c, missing-data amounts, reasons for missingness, imputation procedures or sensitivity analyses. It is therefore not possible to evaluate whether outcome availability could affect the comparison.

The primary outcome description includes an on-treatment without rescue medication period and an in-trial period. The registry record does not explain the relative priority of these analyses or provide a numerical comparison for each. It also does not report the statistical analysis plan, the model used for the primary outcome, the randomization and allocation-concealment procedures, or detailed masking methods.

The registry lists 61 outcome measures and 2 analyses, but does not report a multiplicity strategy or a hierarchy for interpreting secondary outcomes. Safety information is presented as counts and selected terms, without inferential comparisons or detailed methods for assessing event rates. These limitations concern what can be concluded from the registry record; they do not establish that the trial itself lacked analyses or procedures that are simply not reported in the record.

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18. Record Summary

NCT03136484 is a completed phase 3 randomized, double-masked, parallel-group trial of semaglutide versus canagliflozin added to metformin in subjects with type 2 diabetes. The registry records enrollment of 788, a start date of 2017-03-15 and a primary completion date of 2018-10-16. Its primary outcome is mean change in HbA1c from week 0 to week 52, with standard deviation named as the dispersion measure.

The endpoint description distinguishes an on-treatment without rescue medication period from an in-trial period. The record lists secondary outcomes involving weight, fat mass, glucose and cholesterol measures. It also reports serious and other adverse-event counts and deaths. Numerical comparative results for the primary HbA1c outcome, the detailed statistical plan, multiplicity handling and missing-data methods are not reported in the registry record. The recorded design and endpoint define the intended comparison, but the recorded information does not quantify its primary result.

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