A Trial to Learn How Well REGN7508 Works for Preventing Blood Clots After a Knee Replacement in Adult Participants: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Trial to Learn How Well REGN7508 Works for Preventing Blood Clots After a Knee Replacement in Adult Participants (NCT06454630), a randomized phase 2 study. The primary outcome is Percentage of Participants With Confirmed, Adjudicated Venous Thromboembolism (VTE).

2. Clinical Question

The clinical question is framed around an early postoperative period and a composite outcome. That choice captures both venous clots detected through scheduled imaging and clinically apparent events. It also means that an event contributing to the endpoint need not have caused symptoms: asymptomatic deep vein thrombosis detected by venography was included. The posted outcome is a percentage of participants with an event, rather than a time-to-event measure. The registry record does not report further detail about how the components were weighted or how adjudication was conducted.

3. Trial Design

This was a phase 2, multicenter, randomized, open-label, active-control study of REGN7508 compared with enoxaparin after elective unilateral total knee arthroplasty. Randomized allocation and a parallel-group model were reported, and masking was listed as none. The registry record lists enrollment of 179 and the study status as completed. The listed start date is 2024-06-27, and the primary completion date is 2024-11-19.

The primary outcome was assessed through day 12. The registry reports endpoint results for 113 participants in the REGN7508 arm and 58 in the enoxaparin arm. These are the endpoint-specific population counts, not the overall enrollment figure. The modified intention-to-treat definition required randomization plus an evaluable venogram, a confirmed venous thromboembolism, or both. The record does not provide further details about participant flow from enrollment to this analysis population.

The active comparator gives the study a direct treatment-group contrast, while randomization is intended in general to support a fair comparison of assigned groups. Open-label allocation means participants and study personnel were not masked, according to the registry entry. The primary outcome was adjudicated, but the registry record does not report who performed adjudication or whether adjudicators were masked. The original sample-size rationale, allocation ratio planned in the protocol, and any planned interim analyses are not reported in the registry record.

The study also collected safety, pharmacokinetic, immunogenicity, and laboratory outcomes. These included adverse events, serum concentrations of REGN7508, antibodies against REGN7508, and changes in activated partial thromboplastin time and prothrombin time. The registry lists these as additional research outcomes; their presence does not by itself establish how they were prioritized or incorporated into the statistical 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: Of 201 participants screened, 179 participants met eligibility criteria and were randomized. All 179 randomized participants received study intervention.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Modified Intention to Treat Population (mITT): Randomized participants that had either an evaluable venogram, a confirmed episode of venous thromboembolism, or both.

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: Safety Analysis Set (SAF): All randomized participants who received any study drug; it is based on the treatment received (as treated).

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Participants With Confirmed, Adjudicated Venous Thromboembolism (VTE), measured over Through day 12.

The primary endpoint is the percentage of participants with confirmed, adjudicated venous thromboembolism through day 12. It is a composite: an event could be asymptomatic deep vein thrombosis found by unilateral venography of the operated leg, confirmed symptomatic deep vein thrombosis of either leg, or confirmed fatal or nonfatal pulmonary embolism. Unexplained death for which pulmonary embolism could not be ruled out was also included.

A composite endpoint can capture more than one clinically relevant manifestation of a condition and can increase the number of observed events available for comparison. Its interpretation depends on its components: a difference in the overall composite does not establish that every component followed the same pattern. Here, the reported primary percentage therefore describes participants meeting at least one specified component, not a single uniform event type.

Venography-based detection means the endpoint includes events that might not have produced symptoms, alongside symptomatic deep vein thrombosis and pulmonary embolism. This broad definition can be useful when a trial aims to assess clot occurrence systematically after surgery. It also makes the timing and ascertainment process important to interpretation. The registry specifies the period and component definitions, but details such as adjudication procedures and handling of unevaluable venograms are not reported in the registry record.

7. Results Posted in the Registry

• Enoxaparin: 17.2% (10/58) versus 7.1% (8/113) on control; risk difference 10.2 percentage points (95% CI -0.6 to 21.0), risk ratio 2.44 (1.02–5.84); unadjusted two-proportion z-test p = 0.040.

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.

Percentage of Participants With Major VTE

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Enoxaparin: 1.7% (1/58) versus 0.0% (0/113) on control; risk difference 1.7 percentage points (95% CI -1.6 to 5.1); unadjusted two-proportion z-test p = 0.162.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Enoxaparin and the control. The interval gives the range of effects that remain compatible with the data.

Percentage of Participants With Deep Venous Thrombosis (DVT)

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Enoxaparin: 17.2% (10/58) versus 7.1% (8/113) on control; risk difference 10.2 percentage points (95% CI -0.6 to 21.0), risk ratio 2.44 (1.02–5.84); unadjusted two-proportion z-test p = 0.040.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Enoxaparin and the control. The interval gives the range of effects that remain compatible with the data.

The additional outcomes cover several domains: other venous thromboembolism measures, bleeding and adverse events, drug concentration, laboratory changes, and antibodies against REGN7508. The registry reports results for some clinical outcomes, including major venous thromboembolism and deep vein thrombosis. The listed measures broaden the account of the trial beyond the primary composite, but they do not all address the same question or use the same type of measurement.

Overall, the secondary outcomes provide context rather than an independent confirmation of the primary result. They include components or related manifestations of venous thromboembolism, as well as safety and biological measures. In general, consistency across outcomes can be informative, but component results may not match a composite exactly because the composite combines different event types. The registry does not report enough detail to establish a hierarchy among secondary outcomes or to determine how they were intended to support interpretation of the primary endpoint.

Unadjusted secondary results carry less inferential weight when multiple outcomes are examined without a reported multiplicity strategy. In general, testing many outcomes increases the chance that some results appear notable through random variation alone. The registry record does not report whether secondary comparisons were adjusted, whether they were prespecified as confirmatory or exploratory, or how missing secondary measurements were handled. They should therefore be read as descriptive and supportive evidence, not as a collection of separate definitive tests.

Only the registry-listed outcomes and results can be assessed from this record. It does not provide a complete analysis plan, detailed participant-level outcome data, or enough inferential information for all additional measures to judge their precision consistently. The overall pattern must be interpreted with those limits in mind and alongside the primary analysis, rather than by treating each secondary outcome as an independent conclusion.

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

• Number of Participants With Major Bleeding and Clinically Relevant Non-major (CRNM) Bleeding
• Percentage of Participants With at Least One Treatment Emergent Adverse Event (TEAE)
• Percentage of Participants With Major VTE
• Percentage of Participants With Deep Venous Thrombosis (DVT)
• Concentrations of Total REGN7508 in Serum
• Fold Change From Baseline in Activated Partial Thromboplastin Time (aPTT)
• Fold Change From Baseline in Prothrombin Time (PT)
• Number of Participants With Anti-REGN7508 Antibodies by Status

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is binary at the participant level: a participant either met the composite venous thromboembolism definition through day 12 or did not. For a binary outcome, the event percentage gives the observed proportion in each arm. Comparing these proportions can be expressed in different ways, including a risk difference, risk ratio, or odds ratio. Each measure answers a related but distinct question, so the numerical values should not be compared as though they were on the same scale.

What does the recalculated risk difference describe?

The posted recalculation expresses the contrast as a risk difference, with enoxaparin as the comparison arm relative to REGN7508. Its estimate is 0.102, and its interval endpoints are -0.006 and 0.210. A risk difference is an absolute contrast in event proportions. A value of zero corresponds to equal proportions; positive and negative values indicate opposite directions according to the stated arm ordering. The interval communicates uncertainty around the estimate, rather than identifying a guaranteed range for the true effect.

The recalculation is described as simple and unadjusted. It uses posted summary statistics rather than participant-level data and does not incorporate a model adjustment. The registry-reported estimate is a posterior odds ratio of 0.37, a different measure. The record does not state the sponsor’s model, prior assumptions, interval, or other inferential details, so the posterior result cannot be recreated from the posted summary figures alone.

What does a p-value tell the reader?

The recalculated unadjusted p-value is 0.04. In general, a p-value evaluates how compatible the observed data are with a specified null hypothesis under the assumptions of the test. It is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of a difference. The registry record does not report the sponsor’s p-value for the primary analysis. Because the displayed recalculation is unadjusted, the p-value does not account for testing across multiple outcomes unless an adjustment is explicitly included; such an adjustment is not reported.

Why do event counts matter?

The primary endpoint counts are 8 events among 113 participants in the REGN7508 arm and 10 among 58 participants in the enoxaparin arm, as indicated by the recalculation inputs. Binary outcomes with relatively few events can yield imprecise estimates: a small change in the number of observed events can materially affect the arm percentages and their contrast. That is one reason to consider the interval as well as the point estimate. The posted data do not include participant-level records, so alternative adjusted analyses or checks of individual observations cannot be carried out from the registry summary.

What is the relevance of the analysis population?

The primary population is modified intention to treat, defined as randomized participants who had an evaluable venogram, a confirmed venous thromboembolism, or both. This is not a statement that every randomized participant contributed to the endpoint analysis. In general, requiring evaluable outcome information can affect which participants are included and can introduce bias if inclusion is related to treatment assignment or outcome risk. Whether that occurred cannot be assessed from the available record. Reasons for missing or unevaluable assessments and their handling are not reported in the registry record.

What can be inferred from open-label randomization?

Randomization is intended in general to balance prognostic factors across assigned groups, especially when the number of participants is adequate. Open-label treatment means that assignment was not masked. Awareness of treatment can influence behavior, co-interventions, reporting, or assessment in general. The primary endpoint included adjudication, which can support consistent outcome classification, but the record does not describe the adjudication process or masking of adjudicators. It is therefore not possible to assess how outcome-assessment safeguards were implemented.

Finally, the registry lists one primary analysis and several additional outcomes, but a complete statistical analysis plan, multiplicity procedure, and original design assumptions are not reported in the registry record. These omissions limit evaluation of whether the reported analyses followed a prespecified hierarchy and how the sponsor’s inference should be interpreted beyond the stated results.

11. Confidence Intervals and Precision

The recalculated risk difference is 0.102, with interval endpoints of -0.006 and 0.210. The interval spans zero and extends to estimates on either side of it. This means the recalculated data do not pin down the direction and size of the contrast with high precision. The lower endpoint is slightly below zero, while the upper endpoint allows a larger positive contrast on the scale and ordering used in the recalculation. The interval is more informative about uncertainty than the point estimate alone.

The registry record does not state the confidence level for this recalculated interval. It also does not provide an interval for the sponsor’s posterior odds ratio of 0.37. Without an interval or other uncertainty summary for that reported analysis, its precision cannot be assessed from the registry entry. The two estimates use different scales and should not be combined or treated as direct substitutes.

Precision is limited in part by the number of observed primary events: 8 in the REGN7508 group and 10 in the enoxaparin group. The endpoint population sizes were 113 and 58, respectively. In general, estimates based on relatively few events can be sensitive to individual outcomes, and a wide interval signals that substantially different effects remain compatible with the data. The interval does not show which value is most likely without additional modeling assumptions, and it is not a forecast of the result of another study.

The unadjusted p-value of 0.04 addresses a different aspect of the data than the interval. It does not summarize the range of plausible effect sizes, and it does not eliminate uncertainty. In particular, it should not be interpreted in isolation from the interval, the registry’s separate posterior analysis, the limited event counts, and the absence of a reported multiplicity plan.

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 participants per arm, not total events. They are illustrations based on the observed effect, rather than the trial’s original design calculations. The listed assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The planning exercise considers detecting the full observed effect and smaller fractions of it.

The 80% power column gives the number of participants per arm that the illustration estimates would be needed for an 80% chance of detecting the specified effect under those assumptions, if that effect were the true one and the planning model applied. The 90% power column gives the corresponding per-arm planning number for a 90% chance. The displayed rows are planning for 100%, 75%, and 50% of the observed effect. For example, planning for 75% of the observed effect gives 262 participants per arm for 80% power and 350 participants per arm for 90% power. Planning for 50% gives 528 and 706 participants per arm, respectively. Planning for the full observed effect gives 162 and 216 participants per arm.

Smaller effects are harder to distinguish from random variation, so the illustration requires more participants per arm as the target effect becomes smaller. The figures are conditional on the stated assumptions and do not account for any additional design features that are not specified in the calculation. The original trial’s sample-size assumptions and justification are not reported in the registry record. These numbers are planning illustrations, not observed power: they do not measure the probability that the completed trial detected its effect after the results were known.

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, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.071; treatment proportion p₁ = 0.172; average p̄ = 0.122.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.4622 = 0.9059.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.4566 = 0.3843.
4. n = (0.9059 + 0.3843)² / (0.1016)² = 161.2, rounded up to 162 participants per arm for 80% power.

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

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
p0 <- 0.0707964601769911                          # control proportion
p1 <- 0.172413793103448                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

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

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(6454630)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 162 (80% power), 216 (90% power)
 75% of observed effect: n per arm = 262 (80% power), 350 (90% power)
 50% of observed effect: n per arm = 528 (80% power), 706 (90% power)
power.prop.test: 161.2 
Simulated power at n = 162 per arm: 0.819 (20000 replicates)

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

14. Analyses Reported by the Sponsor

The registry lists the sponsor’s primary analysis as a posterior odds ratio of 0.37. It does not provide an interval, confidence level, p-value, or method details for that estimate. The result is therefore best reported as the registry presents it, without assigning additional precision or reconstructing its underlying model.

The simple recalculation instead gives an unadjusted risk difference of 0.102, with interval endpoints of -0.006 and 0.210, and an unadjusted p-value of 0.04. These statistics summarize the posted event counts on a different scale from the posterior odds ratio. They are not the sponsor’s analysis and do not replace it. A risk difference and an odds ratio are not numerically interchangeable, and the posterior estimate may rely on methods and assumptions not detailed in the record.

The registry does not flag a discrepancy between its posted analysis and the recalculation. Still, the estimates should be kept distinct: the sponsor’s analysis is the registry-reported inferential result, while the recalculation is a transparent, unadjusted comparison of the posted summary data. Because the model specification and uncertainty summary for the sponsor result are absent, the record does not allow a full technical comparison or independent reproduction of that analysis.

15. Multiplicity, Missing Data and Analysis Populations

The registry identifies a primary endpoint and lists multiple additional outcomes. When statistical tests are conducted for several endpoints, the chance of at least one apparently unusual result can increase. General approaches to this problem include defining a hierarchy, adjusting significance thresholds, or treating additional analyses as exploratory. The registry record does not report which, if any, multiplicity approach was prespecified or used.

This omission is relevant to the recalculated unadjusted p-value of 0.04. It is a nominal result for a single unadjusted comparison, not a multiplicity-adjusted finding. The record also does not provide enough information to determine whether the sponsor’s posterior analysis incorporated any strategy for multiple outcomes. The posted posterior odds ratio is not accompanied by a p-value or a description of its decision rule.

The modified intention-to-treat population included randomized participants with an evaluable venogram, a confirmed venous thromboembolism, or both. The endpoint denominators are 113 for REGN7508 and 58 for enoxaparin. The registry record does not explain why other randomized participants were not included in those endpoint counts, whether any participants lacked assessable outcome data, or how missing or unevaluable venograms were handled. It also does not report sensitivity analyses for missing outcomes or the assumptions used in any such analyses.

In general, missing outcome data can affect both the estimated event proportions and the comparability created by randomization, particularly if availability of an assessment is related to treatment or risk. The record does not allow assessment of whether missingness was balanced between arms or whether the primary result is robust to alternative assumptions.

Other elements of the statistical plan are also not described: the original sample-size justification, interim analyses, any covariate adjustment, and detailed modeling choices for the sponsor’s analysis are not reported in the registry record. These gaps do not change the posted numbers, but they limit evaluation of prespecification, analysis reproducibility, and the strength of confirmatory claims.

16. Safety Results

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

Deaths

Other (non-serious) adverse events

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

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: diverticulitis (0.8%), joint dislocation (0.8%).

The registry’s safety counts use denominators of 120 for REGN7508 and 59 for enoxaparin, which differ from the primary endpoint population counts. It reports 2 participants with serious adverse events in the REGN7508 group and 0 in the enoxaparin group. Other adverse event counts are 8 and 6, respectively. The registry reports 0 deaths in each group.

These are descriptive counts within the recorded safety populations. They should not be treated as a direct comparison of risk without further information about event definitions, observation time, and analysis methods. The registry lists diverticulitis and joint dislocation among the leading serious event terms, each at 0.8%. The record does not provide details in this summary about severity grading beyond the serious classification or the relationship of individual events to treatment.

Differences in counts can be difficult to interpret in a study of this size, especially when events are uncommon. The absence of a recorded death does not establish the absence of other safety concerns, and the counts alone do not determine whether an event was caused by treatment. They describe what was recorded in the registry, not a causal assessment.

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

The posted results describe a randomized comparison of REGN7508 and enoxaparin for prevention of venous thromboembolism after elective unilateral total knee replacement. Through day 12, the registry reports primary endpoint percentages of 7.1% and 17.2%, respectively, in the endpoint population. The simple unadjusted recalculation gives a risk difference of 0.102 and an interval extending from -0.006 to 0.210. The registry also lists a posterior odds ratio of 0.37 but does not provide an interval or detailed method description.

These numbers do not establish that either treatment works or does not work. They are estimates from one phase 2 trial, with limited endpoint event counts and a short follow-up period. The interval around the recalculated difference reflects uncertainty, and the sponsor’s reported posterior estimate cannot be fully evaluated without its model and uncertainty information. The unadjusted p-value should not be mistaken for a complete account of the evidence, especially with multiple outcomes and no reported multiplicity plan.

The primary outcome combines asymptomatic thrombosis detected by venography with symptomatic deep vein thrombosis and pulmonary embolism. Consequently, the overall percentage does not show how each component contributed to the result. The registry does not report component-level primary results, detailed adjudication procedures, or the handling of unevaluable assessments.

The findings also do not establish how results would generalize beyond the studied population, setting, or outcome window. A completed study status indicates that the registry lists the trial as completed; it does not itself demonstrate that every planned analysis is available or that the results are definitive. Interpretation should distinguish the observed group percentages, the sponsor’s analysis, and the simple recalculation, while recognizing the unresolved questions about precision, missing data, and analysis planning.

18. Why This Trial Matters Statistically

This trial illustrates several core statistical issues in clinical research. First, the primary outcome is a composite that combines events identified in different ways, from asymptomatic findings on venography to symptomatic thrombosis and pulmonary embolism. A composite can make an outcome more inclusive, but the overall result can conceal variation across components. Knowing which components contributed is important for understanding what the endpoint represents.

Second, the record presents two forms of comparison: a sponsor-reported posterior odds ratio and a simple unadjusted risk difference. Both address the treatment-group contrast, but they use different scales and the registry provides different levels of detail for each. Readers need to separate the reported analysis from a summary-statistic recalculation and to avoid treating either measure as a complete description of uncertainty.

Third, event counts and precision matter. The primary comparison is based on relatively few events, and the recalculated interval includes zero. This draws attention to the distinction between an observed point estimate and the range of estimates compatible with the data. A p-value alone cannot convey that range or establish the importance of an effect.

Finally, the case highlights the importance of transparent reporting about analysis populations, missing assessments, multiplicity, and design assumptions. The registry defines the modified intention-to-treat population, but does not report key details about missing data or the original sample-size rationale. Statistical interpretation depends not only on the numerical results, but also on how outcomes were defined, who contributed data, and how uncertainty and multiple analyses were addressed.

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.
• Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.

Several limitations are specific to the posted record. The primary endpoint is a composite, but component-specific primary results are not reported. It is therefore not possible to determine from the record how much each type of venous thromboembolism contributed to the overall percentages. The registry provides the endpoint definition and timing but not detailed adjudication procedures or information about adjudicator masking.

The primary population is modified intention to treat rather than all enrolled participants. Although its inclusion rule is stated, participant flow and reasons for non-inclusion in the endpoint counts are not reported. Handling of missing or unevaluable venograms, any sensitivity analyses, and assumptions about unavailable outcomes are also not reported in the registry record.

The sponsor’s primary result is listed as a posterior odds ratio of 0.37 without an interval or method details. This limits assessment of its precision and prevents independent reconstruction from the registry summary. The simple recalculation uses posted summary data and is unadjusted; it cannot reproduce any participant-level model or account for covariates that may have been considered elsewhere.

The registry does not report the original sample-size justification, the statistical plan for interim analyses, or a multiplicity procedure. Multiple outcomes are listed, so the absence of a reported strategy complicates interpretation of unadjusted secondary comparisons. The endpoint observation period is through day 12, and the record does not establish longer-term outcomes. These limitations constrain the conclusions that can be drawn from this registry entry, without altering the reported counts and estimates.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: A Trial to Learn How Well REGN7508 Works for Preventing Blood Clots After a Knee Replacement in Adult Participants — NCT06454630.
• Registry record last updated 2026-05-27; status last verified 2026-05.
• Results first posted 2026-03-02.
• 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

NCT06454630 is a completed phase 2, multicenter, randomized, open-label, active-control, parallel-group study of REGN7508 versus enoxaparin after elective unilateral total knee arthroplasty. The registry lists enrollment of 179, a start date of 2024-06-27, and a primary completion date of 2024-11-19.

The primary outcome was the percentage of participants with confirmed, adjudicated venous thromboembolism through day 12. The posted percentages were 7.1% for REGN7508 and 17.2% for enoxaparin. The registry reports a posterior odds ratio of 0.37; a separate unadjusted recalculation reports a risk difference of 0.102, interval endpoints of -0.006 and 0.210, and p = 0.04.

The record also lists secondary clinical, safety, pharmacokinetic, laboratory, and immunogenicity outcomes. Details about the original sample-size rationale, multiplicity, missing-data handling, and the sponsor’s analysis methods are not reported in the registry record.