A Study of Bomedemstat (IMG-7289/MK-3543) in Participants With Polycythemia Vera (IMG-7289-CTP-203/MK-3543-004): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of Bomedemstat (IMG-7289/MK-3543) in Participants With Polycythemia Vera (IMG-7289-CTP-203/MK-3543-004) (NCT05558696), a na phase 2 study. The primary outcome is Number of Participants With Adverse Events (AEs).

2. Clinical Question

3. Trial Design

This was a Phase 2, multi-center, open-label study of bomedemstat in participants with polycythemia vera. Its registry model is single group, with no allocation to separate treatment arms and no masking. Participants received daily bomedemstat for 36 weeks. At Week 36, those considered to be deriving clinical benefit and safely tolerating treatment could qualify for continued dosing through Week 52, at the investigator’s discretion.

The registry lists enrollment of 20 and identifies the primary safety population as participants who received at least one dose of study intervention. The primary endpoint covered adverse events up to approximately 52 weeks. This follow-up window is relevant when reading safety counts: it allows events to be recorded over the study period, but the record does not provide individual exposure times or event timing.

The study started on 2023-09-07, had a primary completion date of 2025-03-24, and is listed as completed. A completed status does not itself establish that all planned analyses or all outcome results are present in the registry record. The record describes objectives involving safety, efficacy, pharmacokinetics, and pharmacodynamics, but the statistical analysis plan and detailed methods for those objectives are not reported in the registry record.

Because this is a single-group, open-label study, its results describe outcomes among participants who received bomedemstat. They do not estimate a randomized difference between bomedemstat and a concurrent control. Without a comparator, changes in disease measures over time cannot by themselves separate an intervention effect from other explanations, such as the natural course of disease, participant selection, or changes in care. The registry record does not report an external-control analysis.

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: All participants who received at least one dose of study intervention

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 Number of Participants With Adverse Events (AEs), measured over Up to approximately 52 weeks.

The primary endpoint is the number of participants with one or more adverse events, assessed up to approximately 52 weeks. An adverse event is defined in the registry as an untoward medical occurrence temporally associated with use of the study intervention, whether or not it is considered related to that intervention. The endpoint therefore concerns occurrence during the study, not a determination that bomedemstat caused each event.

A participant-count endpoint is a straightforward way to describe how many people in the safety population experienced an event. It gives a clinically interpretable account of the reach of observed events within the treated group. It does not, by itself, describe how many events each participant experienced, how long events lasted, their severity, or their relationship to treatment. Those questions require additional information beyond a count of participants with one or more events.

The defined primary population includes participants who received at least one dose. The registry record lists 20 participants at risk in the bomedemstat safety group and reports adverse-event counts. It does not report a confidence interval or a comparative estimate for this endpoint. Since the design has no control group, the count is descriptive rather than an estimate of excess risk relative to another treatment.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a single-group study with an adverse-event count as the primary endpoint. The methods used to analyze this endpoint, beyond its definition and population, are not reported in the registry record. The distinction matters: a listed endpoint tells readers what outcome was intended, while a statistical analysis plan would specify how observations, missing data, follow-up, and uncertainty were handled.

What does a participant count convey?

A participant count records whether each participant experienced at least one event in the relevant category. This differs from counting every event: repeated events in the same person need not increase the number of participants affected. A count is therefore a measure of how many people had an event, not the total burden of recurrent events. The registry’s primary definition specifies one or more adverse events, but it does not report event-level frequency, duration, or timing.

Counts are often interpreted alongside the number of participants at risk, which describes the group from which those events arose. The safety record gives 20 at risk for the bomedemstat group. Even with a stated denominator, the count does not capture differences in follow-up time between individuals. Here, the primary endpoint timeframe is up to approximately 52 weeks, and the treatment description allows some participants to continue through Week 52. Individual exposure durations are not reported in the registry record.

How should a single-group result be understood?

In a single-group study, the observed count describes the treated cohort. A comparative treatment effect requires a reference outcome under a comparator condition, along with a method for making the groups comparable. This study has no separate comparator arm, and the registry lists no allocation. Consequently, a difference from an outside population or an assumed background rate would not be a randomized comparison. No such external comparison is reported in the registry record.

Open-label status means masking is listed as none. In general, lack of masking can affect the recording or interpretation of outcomes, especially when outcomes involve judgment. Adverse-event reporting also depends on how events are elicited, classified, and coded. The registry definition includes events regardless of whether they are judged related to treatment; it does not provide additional details on event ascertainment or adjudication.

What do thresholds and duration outcomes measure?

The secondary outcome descriptions include thresholds for hematocrit, platelet count, and white blood cell count. A threshold outcome classifies a participant according to whether a measure meets a stated cutoff. A duration outcome asks how long the condition persists, which is a different question from whether the cutoff was reached at a particular assessment. The record names duration outcomes for hematocrit, platelets, and white blood cells, but does not report their analysis methods or results.

For time-to-event or duration outcomes, follow-up may end before an event occurs or before the outcome can be fully observed. Statistical methods commonly account for such incomplete observation through censoring, but the method used for these outcomes is not reported in the registry record. No assumptions about censoring, event definitions beyond the listed outcomes, or time-to-event models should be inferred.

What do the planning illustrations mean?

The planning assumptions describe an illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is described as a fraction of the observed effect. These are planning assumptions, not evidence that the trial itself used a two-arm design: the actual registered study is single group. Nor do planning sample sizes represent observed power. They are hypothetical illustrations of sample sizes under the stated assumptions, not a retrospective measure of the study’s ability to detect an effect.

For binary outcomes, a normal approximation is a general method for planning around proportions. Its suitability depends on the data and assumptions; sparse event counts can make approximations less reliable. For time-to-event outcomes, the planning description uses total event counts under the Schoenfeld approach. These general methods do not establish what inferential procedure was used for the trial’s reported results. The statistical analysis plan, inferential tests, confidence-interval methods, and any adjustment for covariates are not reported in the registry record.

Over-dispersion is a general concern when observed variability exceeds what a simple model assumes. It can make uncertainty estimates too narrow if the model does not account for the extra variability. The registry entries do not indicate that an over-dispersion adjustment was used or was needed in this study. It would therefore be inappropriate to attribute a particular model or correction to the analysis.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Bomedemstat")
n      <- c(20)
events <- c(20)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Bomedemstat  20  20  100.0  83.2  100.0  83.9  100.0  83.9  99.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists multiple secondary outcomes in addition to the primary adverse-event endpoint. When several outcomes are examined, the chance of obtaining at least one apparently notable result can increase if each is tested separately without a plan for multiplicity. Statistical approaches can address this issue by defining a testing hierarchy, adjusting significance thresholds, or treating outcomes as descriptive. The registry record does not report whether any multiplicity procedure was planned or applied.

Numerical results for the listed secondary outcomes are not reported in the registry record. The record also does not provide p-values, confidence intervals, or an analysis plan for those endpoints. It is therefore not possible to determine from the available information which outcomes were analyzed, how comparisons across assessment times were handled, or whether reported inferences account for multiple testing.

Missing data can affect interpretation when participants do not complete follow-up or when a measurement is unavailable. The registry record does not report missingness, participant disposition by outcome, imputation methods, or sensitivity analyses. The design allowed qualifying participants to receive additional treatment through Week 52 at the investigator’s discretion, but the record does not state how differing treatment or observation durations were handled analytically.

The primary safety population is defined as all participants who received at least one dose. This definition clarifies who was intended to contribute to the primary endpoint, but it does not give details about the analysis population used for each secondary outcome. The registry record does not report an intention-to-treat population, a per-protocol population, or rules for handling participants with incomplete data. Such details should not be inferred from the completed status or from the endpoint descriptions.

12. 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: anaemia (5.0%), cardiac failure (5.0%), vertigo (5.0%), diverticulitis (5.0%), osteomyelitis acute (5.0%).

The safety record lists 8 participants with serious adverse events among 20 at risk and 20 affected participants in the other adverse-event category among 20 at risk. It also lists 1 death. These entries describe reported safety observations; they do not show whether events were judged related to bomedemstat. The primary adverse-event definition explicitly includes events whether or not they are considered related to the intervention.

The serious-event terms listed are Anaemia, Cardiac failure, Vertigo, Diverticulitis, Osteomyelitis acute, and Wound infection, each reported at 5.0%. The registry record does not report further details on event timing, duration, recurrence, severity beyond the serious classification, or individual outcomes. It does not state whether the death was related to treatment or provide a cause of death in the registry entries.

Serious adverse events are not synonymous with all adverse events. A serious-event count and a broader adverse-event count answer different safety questions, and the same participant can potentially contribute to more than one category. The listed counts should not be added together to produce a total. With no control group, these figures cannot establish whether event frequency was higher or lower than it would have been under another treatment or no study intervention.

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

The results mean that the registry records adverse events during follow-up in participants who received bomedemstat, including serious adverse events and a death. The endpoint and safety entries characterize what was observed in this study population. They do not by themselves establish that bomedemstat caused an event, nor do they estimate comparative safety against another treatment.

The study also set out to assess efficacy, pharmacokinetics, and pharmacodynamics, and the registry lists secondary outcomes for blood counts, hematocrit, thrombotic and hemorrhagic events, and spleen-volume reduction. The definitions describe what was to be evaluated, but the corresponding numerical results are not reported in the registry record. No conclusion about the direction or size of changes in those outcomes can be drawn from endpoint names alone.

In general, a treatment effect is a contrast between outcomes under different treatment conditions. A single-group study can describe a group’s observed outcomes, but it lacks the concurrent comparator needed for a randomized contrast. Changes during follow-up could have multiple explanations. The open-label design also means there was no masking, which may matter for outcomes involving assessment or reporting.

The enrollment and safety counts should be read as study-specific observations, not as precise estimates for all people with polycythemia vera. The registry record does not provide uncertainty intervals, participant characteristics, or detailed follow-up information needed to judge how well the observed data might generalize. A completed study status means the registry marks the study complete; it does not substitute for unreported efficacy results or an explanation of the analysis.

Thus, the record supports a descriptive reading of reported safety observations and the study’s intended outcome measures. It does not support claims about efficacy, causal attribution, comparative benefit or harm, or the probability of future outcomes beyond the observed study.

14. Why This Trial Matters Statistically

This study is statistically informative as an example of how to read a small, open-label, single-group clinical study without treating it as a controlled comparison. The registry identifies a defined primary safety outcome and a treated population, allowing the reported adverse-event counts to be interpreted in their intended context. It also makes clear that treatment continuation beyond Week 36 depended on clinical benefit, safe tolerability, and investigator discretion.

The study’s design and reporting illustrate why endpoint definitions and analysis populations matter. A count of participants with one or more adverse events is not the same as a count of all events, and it does not establish causality. Likewise, a threshold endpoint and a duration endpoint address different statistical questions, even when they concern the same laboratory measure. Readers need the analysis methods and numerical results to evaluate those outcomes; those details are not reported in the registry record.

The single-group design limits causal and comparative interpretation. This limitation is not repaired by statistical precision alone: even a narrow uncertainty interval around a treated-group estimate would not create a randomized control contrast. Conversely, a small number of observed events should not be read as proof of absence of risk. The posted safety counts describe the cohort, while the absence of a comparator limits the questions they can answer.

The listed planning assumptions also demonstrate the distinction between design illustrations and the actual trial. Hypothetical calculations based on observed effects and assumed two-arm allocation do not turn this registered single-group study into a two-arm experiment and do not represent observed power. Keeping that distinction explicit helps prevent planning quantities from being mistaken for trial findings.

15. 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 main trial-specific limitation is the absence of a comparator group. Since the study is single group and open label, its observed outcomes cannot provide a randomized comparison with another treatment or control condition. The design is therefore suited to describing observations in the enrolled cohort, but does not isolate the effect of bomedemstat from other possible explanations for changes or events.

The registry record does not report numerical efficacy results for the listed secondary outcomes. It also does not report confidence intervals, p-values, or detailed statistical methods for the outcomes. Without those details, the size and precision of any efficacy findings cannot be assessed from the available record. The completed status does not resolve this limitation.

The safety information is limited to participant counts and listed serious-event terms. The record does not provide event timing, duration, recurrence, individual exposure, cause of death, or attribution of events to treatment in the registry entries. The study’s follow-up was up to approximately 52 weeks, and continued treatment through Week 52 was conditional, but the registry does not describe how variation in exposure or follow-up affected analyses.

Participant characteristics, eligibility details, missing-data patterns, and outcome-specific analysis populations are not reported in the registry record. These omissions limit assessment of representativeness, completeness, and potential bias. The statistical analysis plan, including any adjustment for multiple outcomes or handling of incomplete measurements, is also not reported. Accordingly, conclusions should remain within the scope of the descriptive safety observations and the stated study design.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Study of Bomedemstat (IMG-7289/MK-3543) in Participants With Polycythemia Vera (IMG-7289-CTP-203/MK-3543-004) — NCT05558696.
• Registry record last updated 2026-05-07; status last verified 2026-04.
• Results first posted 2026-05-07.
• 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.

19. Record Summary

The registry record describes NCT05558696, a completed Phase 2, multi-center, open-label, single-group study of daily bomedemstat in participants with polycythemia vera. Enrollment was 20. Dosing was planned for 36 weeks, with possible continued treatment through Week 52 for eligible participants at the investigator’s discretion.

The primary endpoint was the number of participants with one or more adverse events up to approximately 52 weeks, among participants who received at least one dose. The safety record lists 8 participants with serious adverse events among 20 at risk, 20 affected participants in the other adverse-event category among 20 at risk, and 1 death. Numerical results for the listed efficacy-related secondary outcomes are not reported in the registry record.

The study started on 2023-09-07 and had a primary completion date of 2025-03-24. The registry record does not report the statistical analysis plan, missing-data methods, multiplicity handling, or comparative efficacy estimates.