A Study of Recombinant Vaccinia Virus in Combination With Cemiplimab for Renal Cell Carcinoma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of Recombinant Vaccinia Virus in Combination With Cemiplimab for Renal Cell Carcinoma (NCT03294083), a randomized phase 1, phase 2 study. The primary outcome is Number and Percentage of Participants With Adverse Events From Pexa-Vec Administered by IV Infusions or IT Injections in Combination With IV Cemiplimab.

2. Clinical Question

The study, NCT03294083, is a Phase 1b/2a trial in renal cell carcinoma. Its stated primary outcome counts participants with adverse events from Pexa-Vec administered by intravenous infusion or intratumoral injection in combination with intravenous cemiplimab. The safety description includes treatment-emergent adverse events, Grade 3 or greater adverse events, serious adverse events, laboratory toxicity, events requiring discontinuation of study agents, and deaths.

The study also names progression-free survival, disease control rate, and overall survival as secondary outcomes. The registry record does not report numerical results for those outcomes here, so the clinical question addressed by the posted figures is limited to safety counts. They do not establish a comparative benefit or harm estimate between treatment strategies.

3. Trial Design

This was a randomized, open-label, parallel-group Phase 1b/2a study. It is described as a multicenter, dose-escalation and safety/efficacy evaluation trial. The registry record lists an enrollment of 95 and a completed status. The recorded study start was 2018-06-19, and primary completion was 2023-02-16.

The study had a dose-escalation stage followed by an expansion stage. In Part 1, the listed Pexa-Vec dose groups were 3 x 10^8 pfu and 1 x 10^9 pfu, administered by intravenous infusion once per week for 4 treatments. The brief summary says the dose-escalation stage was intended to determine the maximum feasible Pexa-Vec dose in combination with cemiplimab, with dose-limiting toxicities informing enrollment at the listed dose levels. Further details of the first dose group’s cemiplimab schedule are not reported in the registry record.

In the expansion, Part 2-Arm A used intratumoral Pexa-Vec every 2 weeks for 3 treatments with intravenous cemiplimab every 3 weeks. Arm B used cemiplimab every 3 weeks, with intratumoral Pexa-Vec to be given after disease progression while cemiplimab continued. Arms C and D used intravenous Pexa-Vec once per week for 4 treatments with intravenous cemiplimab every 3 weeks. The posted arm descriptions do not give a distinct dose for Arms C and D.

Although the allocation is listed as randomized, the randomization method, allocation ratio, and details of how participants were assigned among the stages and expansion arms are not reported in the registry record. No masking was used. The arms differ in route and timing of Pexa-Vec, and the cemiplimab-alone arm allowed later Pexa-Vec; these features matter when interpreting any direct contrast. The posted safety counts should therefore be read within their named groups, not as a single uniform comparison.

4. Participant Flow and Accounting

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

Before assignment: A total of 141 patients were screened for eligibility prior to group assignment, which included 8 patients for Part 1 and 133 patients for Part 2. Of these, 46 patients failed the screening process (2 patients in Part 1 and 44 patients in Part 2). Consequently, a total of 95 eligible patients were enrolled and assigned to the study groups (6 patients in Part 1 and 89 patients in Part 2).

Overall Study

Analysis population for the primary outcome, as defined in the registry: The safety group had 88 subjects and the ITT group had 89 subjects, which is the correct value as the table safety group had 88 subjects (Arm B 16 subjects).

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.

Only the first 6 of 7 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Number and Percentage of Participants With Adverse Events From Pexa-Vec Administered by IV Infusions or IT Injections in Combination With IV Cemiplimab, measured over Through study completion without survival follow-up period, an average of 1 year.

The primary endpoint counts participants with adverse events associated with Pexa-Vec by intravenous infusion or intratumoral injection in combination with intravenous cemiplimab. The registry description says safety is assessed through the incidence, severity, and frequency of treatment-emergent adverse events, Grade 3 or greater adverse events, serious adverse events, laboratory toxicity, adverse events requiring discontinuation of study agents, and deaths. Severity is graded using National Cancer Institute Common Terminology Criteria for Adverse Events Version 5.0.

A participant count is a way to describe how many people in a group had an event, rather than how many separate event episodes occurred. In general, this type of endpoint is used in safety studies because it summarizes whether harms were observed in participants during exposure to treatment. It does not by itself describe the duration of an event, its timing, or the number of repeated episodes in one person. Those details may require separate outcome listings.

The stated monitoring period begins with the first dose, continues through treatment up to a maximum of 1 year, and extends up to 28 days after the last dose. The primary outcome timeframe is described as through study completion without the survival follow-up period, with an average of 1 year. The record does not provide a single overall endpoint estimate, confidence interval, or test comparing treatment groups. The available adverse-event group listings should therefore be interpreted as descriptive safety information rather than as a quantified causal comparison.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a randomized, open-label, parallel-group design, but it does not report a detailed statistical analysis plan. The outcome information consists of counts by group and descriptive percentages for selected serious adverse-event terms. No inferential analysis is listed. The discussion below explains general statistical principles relevant to such results; it does not attribute unreported methods to this study.

What a participant count describes

A participant count records how many people in a group experienced an event during the specified observation period. The count is meaningful alongside its group denominator: for example, the posted serious-event figures pair an affected-participant count with the number at risk. A count alone does not communicate the full observation time for each person, the number of repeated episodes, or whether events began before or after a particular treatment. The registry outcome description gives an overall safety monitoring window, but person-level exposure and event timing are not included in the listed summaries.

Counts are especially useful in safety reporting because rare or serious events should remain visible even when a group is small. They can also be unstable as estimates of an underlying event frequency: a change in the outcome of one person can noticeably alter a small group’s summary. For that reason, the arm-level counts are best read as descriptive observations. The record does not report uncertainty intervals around these counts.

What a confidence interval would add

In general, a confidence interval gives a range of values compatible with the data and the method used to estimate an outcome. It communicates statistical precision, not certainty that the true value lies within a particular interval. A narrow interval generally indicates greater precision than a wide one, under the assumptions of the method. No confidence intervals for the safety counts or comparative effects are reported in the registry record, so their precision cannot be assessed using interval estimates from the posted results.

Why group comparisons need care

A randomized design can support a causal comparison when the groups, outcome definitions, follow-up, and analysis are clearly specified and the comparison is conducted as planned. Here, the trial has sequential dose escalation and an expansion with several Pexa-Vec routes and treatment schedules. The cemiplimab-alone arm also allows Pexa-Vec after disease progression. These features mean that a simple contrast between group counts would not necessarily represent a single, consistent treatment contrast across the full study. The randomization method, assignment details, and statistical comparison plan are not reported in the registry record.

In general, a treatment-effect estimate summarizes the contrast between defined groups, while an adjusted estimate accounts for specified covariates through a stated model. The posted material does not give a comparative estimate, an adjustment model, a hypothesis test, or a prespecified contrast. It would be inappropriate to infer one from the separate arm counts or to describe the displayed values as evidence of statistical significance.

Multiplicity and multiple outcomes

Multiplicity arises when many outcomes, comparisons, time points, or analyses are examined. In general, making many statistical tests can increase the chance of finding an apparently notable result by chance if the analysis does not account for the testing strategy. This study names several secondary outcomes and includes multiple study groups, but the registry record does not report a multiplicity adjustment, hierarchy of hypotheses, or analysis plan describing how such issues were handled. The listed serious adverse-event terms are descriptive; their percentages should not be read as the result of a set of formal tests.

Missing data and follow-up

In general, missing outcome information can affect interpretation when participants have incomplete follow-up, discontinue treatment, or are not assessed at the same times. The registry record describes the safety monitoring window, but the posted summaries do not state how missing safety assessments were handled or whether every participant completed the full window. They also do not report a missing-data analysis. A completed study status does not, by itself, establish complete outcome data for every participant.

The record identifies a safety group of 88 subjects and an ITT group of 89 subjects. It also contains a note that refers to Arm B as 16 subjects, while the adverse-event listing gives 15 at risk for Part 2-Arm B. The relationship between these figures is not explained in the registry record. This makes it important to preserve the specific denominators attached to the posted group results and not silently substitute one population count for another.

Over-dispersion and model choice

In general, over-dispersion occurs when observed variability exceeds what a statistical model assumes. It can make standard errors too small and intervals or tests misleading if not addressed. This is most relevant when a model is used for event counts or rates. No count model, rate analysis, dispersion estimate, or model-based comparison is reported for these safety results, so over-dispersion cannot be assessed from the posted figures. The displayed summaries are participant counts, not a fitted event-rate model.

The registry includes a planning illustration based on a stated observed effect and assumptions, but such illustrations are not observed power and do not replace a trial’s own design justification. The trial’s sample-size justification and a detailed account of its own analysis plan are not reported in the registry record. Thus, the available information supports a descriptive reading of safety counts and leaves important questions about precision, comparisons, missingness, and multiplicity unresolved.

10. Multiplicity, Missing Data and Analysis Populations

The posted outcome material includes a safety endpoint and names progression-free survival, disease control rate, and overall survival as secondary outcomes. It also reports several arms and selected serious adverse-event terms. The registry record does not report a statistical hierarchy for these outcomes, a multiplicity adjustment, or a plan specifying which comparisons were confirmatory. In general, when investigators examine multiple outcomes or comparisons, interpretation depends on how that multiplicity was handled. No conclusion about formal control of false-positive findings can be drawn from the descriptive listings.

The record describes safety and ITT populations as 88 and 89 subjects, respectively. The safety adverse-event group listing gives 15 at risk for Part 2-Arm B, while a note in the primary outcome population description refers to Arm B as 16 subjects. The registry record does not explain the difference. The adverse-event counts should therefore be reported with their listed arm denominators, and the stated overall populations should not be treated as interchangeable.

The monitoring description specifies follow-up from first dose through treatment, up to a maximum of 1 year, and up to 28 days after the last dose. However, the posted summary does not state how many participants had complete assessments, how missing safety information was handled, or whether any participants were excluded from a particular analysis. An ITT population is identified, but its use for the safety endpoint is not described in detail.

In general, missingness can affect interpretation if participants with incomplete follow-up differ from those with complete observation. No missing-data method, sensitivity analysis, or detailed accounting of incomplete follow-up is reported in the registry record. These limitations constrain interpretation of both safety frequencies and the named secondary outcomes.

11. 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: atrial fibrillation (33.3%), sepsis (33.3%), cancer pain (33.3%), spinal cord compression (13.3%), haematuria (7.1%).

The serious adverse-event listings give, for each named group, the number at risk and the number reported as affected. Read them as group-specific counts: Part 1 at 3 x 10^8 Pfu lists 2 of 3; Part 1 at 1 x 10^9 Pfu lists 1 of 3; Part 2-Arm A lists 6 of 15; Part 2-Arm B lists 6 of 15; Part 2-Arm C lists 11 of 30; and Part 2-Arm D lists 11 of 28. The figures describe participants, not the total number of serious-event episodes.

The separate category labelled other adverse events lists 3 of 3, 3 of 3, 15 of 15, 15 of 15, 30 of 30, and 28 of 28, respectively. Keep this category distinct from the serious-event counts as the registry presents it. The record also lists deaths by group, but does not give the cause or treatment attribution for each death in these summaries. A death count should not automatically be interpreted as a treatment-related death.

The percentages attached to selected serious-event terms are presented without a denominator explanation in the registry record. They should be read as posted, not recalculated or compared as if they were arm-specific risks. In general, safety counts describe observed events over a defined monitoring period; they do not establish causation or comparative risk by themselves.

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

The posted data show that serious adverse events and other adverse events were recorded in the named study groups, and they report death counts by group. They also list selected serious adverse-event terms with percentages. These results are relevant to describing the safety experience recorded during a study of Pexa-Vec and cemiplimab. The outcome description specifies monitoring from first dose through treatment, up to a maximum of 1 year, and up to 28 days after the last dose.

These counts do not show that a particular event was caused by Pexa-Vec, cemiplimab, or their combination. The posted figures do not provide individual event timing, attribution, or a comparative analysis. Nor do they establish that one arm had more or fewer events in a way that can be interpreted as a causal difference. The arms differ in route and treatment schedule, and the cemiplimab-alone group could receive Pexa-Vec following progression.

The outcome is safety-focused. Although progression-free survival, disease control rate, and overall survival are named as secondary outcomes, their numerical results are not reported in the material. The listed safety counts cannot answer whether treatment changed those efficacy outcomes. They also cannot establish a treatment recommendation or a treatment benefit.

In general, statistical precision matters when interpreting apparent differences. The record does not provide confidence intervals or formal comparative tests for these safety summaries. Several groups have small listed denominators, which means that each observed participant can substantially affect the descriptive count. This is a limitation of what the displayed summaries can establish, not a reason to reinterpret them as evidence for or against a treatment.

The most defensible reading is therefore narrow: the registry reports these event counts for the named groups, under the stated safety monitoring framework. The size and design of the study, the lack of a reported comparative analysis, and the unresolved population-count detail limit conclusions about differences between arms. A completed registry status does not fill in outcome analyses or explanations that are not reported.

13. Why This Trial Matters Statistically

This trial is statistically notable because it brings together dose escalation and an expansion stage with several treatment schedules. The posted design includes intravenous and intratumoral Pexa-Vec, cemiplimab alone, and combination treatment. The cemiplimab-alone arm could later add intratumoral Pexa-Vec after disease progression. These features create distinct treatment strategies rather than one straightforward two-arm comparison across the entire study.

The design illustrates why outcome definitions and analysis populations matter. The primary endpoint is safety-oriented and counts participants with adverse events, while the record also lists efficacy-related secondary outcomes. The reported safety group and ITT group have different stated sizes, and the Arm B population note does not match the number at risk in its adverse-event listing. Analysts need to preserve those distinctions rather than assuming all counts refer to the same population.

It also demonstrates the difference between descriptive and inferential evidence. The registry reports observed counts and selected percentages, but no comparative effect estimates, uncertainty intervals, or hypothesis tests for these figures. Descriptive safety data can convey what was recorded; without a reported contrast and its precision, they do not provide a statistical ranking of the arms.

Finally, this record shows the limits of relying on a registry summary alone. It gives the study’s stages, some schedules, outcome definitions, and selected safety counts, but does not report the full statistical plan, detailed missing-data handling, or multiplicity strategy. For biostatisticians and clinical researchers, those gaps are central to judging what the reported results can support. The appropriate statistical account is therefore careful, group-specific, and explicit about what remains unreported.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The safety summaries are not accompanied by comparative effect estimates, confidence intervals, or hypothesis tests. The registry record therefore does not quantify the precision of the arm-specific counts or support a formal between-arm interpretation. Several listed groups have small denominators, and the posted outcomes remain descriptive.

The population information is not fully reconciled. The primary outcome description states that the safety group had 88 subjects and the ITT group had 89 subjects. It also includes a note referring to Arm B as 16 subjects, while the adverse-event group listing gives 15 at risk for Part 2-Arm B. The reason for this discrepancy is not reported in the registry record. The group-specific figures should be read with the denominators attached to those listings.

The registry record does not provide the randomization procedure, allocation ratio, arm assignment details, or a full statistical analysis plan. It does not report how missing safety assessments were handled, whether follow-up was complete for all participants, or how the secondary outcomes were analyzed. A multiplicity strategy is also not reported. The record names several outcomes, but numerical results for progression-free survival, disease control rate, and overall survival are not present.

Some treatment descriptions are incomplete. The Part 1 description for the 3 x 10^8 pfu group ends before the cemiplimab schedule is fully stated, and the posted descriptions for Arms C and D do not identify a distinct Pexa-Vec dose. The record’s percentages for selected serious-event terms do not explain their denominators. In addition, the death listings do not provide cause, timing, or treatment attribution. These omissions limit clinical and statistical interpretation of the posted safety figures.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A Study of Recombinant Vaccinia Virus in Combination With Cemiplimab for Renal Cell Carcinoma — NCT03294083.
• Registry record last updated 2026-06-18; status last verified 2026-05.
• Results first posted 2026-06-18.
• 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.

18. Record Summary

NCT03294083 is a completed, randomized, open-label, parallel-group Phase 1b/2a study of Pexa-Vec with cemiplimab in metastatic or unresectable renal cell carcinoma. It included a dose-escalation stage and an expansion stage with intravenous or intratumoral Pexa-Vec schedules, as well as a cemiplimab-alone arm that could receive Pexa-Vec after progression.

The primary outcome counts participants with adverse events. The registry posts group-specific serious and other adverse-event counts, death counts, and selected percentages for serious-event terms. It identifies a safety group of 88 subjects and an ITT group of 89 subjects, but the Arm B count is not consistent across the population note and adverse-event listing.

The record does not report comparative safety estimates, confidence intervals, formal tests, or numerical results for the named secondary outcomes in the material. Its posted counts describe recorded events; they do not by themselves establish causation or differences between treatment strategies.