Study of Bomedemstat in Participants With Essential Thrombocythemia (IMG-7289-CTP-201/MK-3543-003): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study of Bomedemstat in Participants With Essential Thrombocythemia (IMG-7289-CTP-201/MK-3543-003) (NCT04254978), a na phase 2 study. The primary outcome is Number of Participants Who Experienced an Adverse Event (AE).

2. Clinical Question

3. Trial Design

This was a Phase 2, single-group, open-label study of bomedemstat in participants with essential thrombocythemia. The record lists Imago BioSciences, Inc., a subsidiary of Merck & Co., Inc., (Rahway, New Jersey USA) as sponsor. Enrollment was 73. The listed study start was 2020-09-08, the primary completion date was 2023-03-23, and the status is COMPLETED.

All participants were assigned to the bomedemstat group, which is described as receiving the drug daily for 169 consecutive days. Because there was no separate control group and masking was NONE, the study was not designed as a blinded comparison of bomedemstat against another intervention. The allocation field is NA; the registry record does not report a randomized allocation process.

The study description identifies safety and tolerability, as well as pharmacodynamic effects, as subjects of investigation. Its official title also names efficacy as an aim. The primary outcome reported in the results is the number of participants who experienced an adverse event, assessed over a timeframe of up to approximately 30 months. This outcome population is described as enrolled participants who received at least 1 dose. How the longer outcome timeframe relates to the listed 169 consecutive days of dosing is not reported in the registry record.

Other design details, including eligibility criteria beyond essential thrombocythemia, site locations, follow-up procedures and the basis for the enrollment target, are not reported in the registry record. The single-group design is central to interpretation: the observed events can be described within the treated group, but there is no concurrent control group in these results for estimating a comparative treatment effect.

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.

Initial Treatment Period (ITP)

Reasons for not completing this period:

Additional Treatment Period (ATP)

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All participants who were enrolled in the study and received at least 1 dose of study drug

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 Who Experienced an Adverse Event (AE), measured over Up to approximately 30 months.

The primary endpoint is the number of participants who experienced an adverse event. An adverse event is defined in the registry as an undesirable physical, psychological or behavioral effect during the study in conjunction with use of the drug or biologic, whether or not considered product related. The reporting window begins with the first dose and continues until completion of the study; the stated timeframe is up to approximately 30 months.

This kind of endpoint is used to describe the frequency of participants with reported events during treatment and study follow-up. Counting participants rather than event episodes answers whether a participant experienced an event, not how many separate events each participant had or how long each event lasted. The primary outcome population includes those enrolled who received at least 1 dose.

The record reports 72 participants with an adverse event among 73 at risk. This count does not, by itself, show that the drug caused the events. The definition explicitly includes events whether or not product related, and the registry does not report a causal attribution for the primary outcome. Nor does the endpoint measure efficacy or pharmacodynamic change. Specific definitions and results for other outcomes are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does a participant count capture?

The primary outcome is a binary participant-level measure: whether each participant experienced an adverse event during the specified observation period. A count of participants with at least one event summarizes how many people met that condition. It does not count every event episode, distinguish repeated episodes, or convey event duration. General statistical interpretation: binary outcomes are often summarized using the number of participants with the event and the number assessed. The posted result reports 72 participants with an adverse event among 73 at risk.

The endpoint’s definition is broad. It includes undesirable physical, psychological or behavioral effects in conjunction with study-drug use, whether or not considered product related. The record says observation runs from first dose through study completion, with a timeframe of up to approximately 30 months. Thus, the count is tied to the study’s event definition and observation window. Details about participant-level event adjudication, event collection procedures and handling of incomplete observation are not reported in the registry record.

Why does the design matter for interpretation?

General statistical explanation: a comparison group helps distinguish the outcome observed under an intervention from what might have occurred over the same period under another condition. Here, the design is single-group and the allocation field is NA. The results therefore describe the bomedemstat group, without an internal comparator for estimating a difference between groups. A count in one group is not, on its own, an estimate of the treatment’s causal effect.

The study is also open label, with masking recorded as NONE. General statistical explanation: when treatment assignment is known, expectations or clinical attention can potentially influence reporting or assessment, depending on how outcomes are collected. The registry record does not describe the assessment procedures well enough to determine whether or how that could have affected event recording. This is a limitation to keep in mind, not evidence that reported events were misclassified.

What do uncertainty and precision mean in this setting?

General statistical explanation: a confidence interval is a range of values compatible with the observed data under a specified statistical method. It conveys uncertainty around an estimate; a narrow interval generally indicates greater precision than a wide one. The registry record does not report a confidence interval or another uncertainty interval for the primary adverse-event result. No interval should be inferred from the participant count alone in this interpretation.

General statistical explanation: a p-value addresses how compatible data are with a specified null hypothesis under an analysis model; it does not measure the probability that a treatment works or caused an event. The registry record does not report a hypothesis test or p-value for the primary endpoint. Because there is no comparator group, a treatment-versus-control hypothesis test for this outcome is not presented in the record.

How should event categories be read?

The serious adverse event summary reports 27 affected participants among 73 at risk, alongside named event terms with percentages. The primary endpoint separately reports the number of participants with any adverse event. Serious events are a subset of safety information, but the registry record does not explain the relationship between every category in its summaries or state whether listed terms overlap within participants. The terms and percentages should therefore be read as reported, without adding them together or treating them as mutually exclusive categories.

General statistical explanation: event categories can overlap when one participant experiences multiple kinds of events. A count by term may refer to events or affected participants, depending on the registry’s definition. The record provides the term percentages but does not provide additional detail about overlap or the calculation method for those percentages. It also reports two deaths without giving their causes or treatment attribution.

What does the sample-size illustration represent?

The planning illustration is not the trial’s reported design justification. Its stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect to detect expressed as a fraction of the observed effect. General statistical explanation: sample-size calculations describe a planned amount of information under stated assumptions; they are not observed outcomes and do not show that a study had a particular probability of success. Such illustrations should not be interpreted as observed power. In this single-group study, the hypothetical two-arm assumptions do not describe the actual allocation. The trial’s own sample-size justification is not reported in the registry record.

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(73)
events <- c(73)
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  73  73  100.0  95.1  100.0  95.0  100.0  95.1  100.0

11. Multiplicity, Missing Data and Analysis Populations

The registry record describes three outcome measures and one analysis, but it does not report a multiplicity strategy. Multiplicity arises when several outcomes or statistical tests are considered: the chance of at least one apparently notable result can increase as more tests are conducted. General statistical explanation: prespecified priorities and adjustment methods can help readers understand how multiple comparisons were handled. No adjustment method, testing hierarchy or prespecified distinction among primary and secondary hypotheses is reported in the registry record. The primary outcome is identified as the number of participants who experienced an adverse event.

Missing-data handling is also not reported in the registry record. The primary outcome population is described as all participants enrolled who received at least 1 dose, and the adverse-event summary lists 73 at risk. The record does not explain how participants with incomplete follow-up, missing event information or early discontinuation were handled. It does not state whether the analysis used imputation, censoring, a complete-case approach or another method. These procedures should not be inferred from the reported denominator.

The registry identifies the primary endpoint population but does not give additional analysis-population definitions. Whether any other populations were used, and whether outcomes were assessed according to a separate analysis set, are not reported in the registry record. The record also does not report a statistical analysis plan, interim analyses, or adjustments for covariates. These absences limit assessment of how the reported result was selected and handled analytically; they do not establish that a particular method was or was not used outside the information in the record.

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: thrombocytopenia (5.5%), pneumonia (4.1%), gastrointestinal haemorrhage (2.7%), diverticulitis (2.7%), contusion (2.7%).

The serious adverse event summary reports 27 participants affected among 73 at risk. This is a participant count, not a count of all serious-event episodes. The record separately lists Thrombocytopenia, 5.5%; Pneumonia, 4.1%; Gastrointestinal haemorrhage, 2.7%; Diverticulitis, 2.7%; Contusion, 2.7%; and Arthralgia, 2.7% as leading serious-event terms. The percentages should be read as reported; the record does not state whether individual participants could appear under more than one term.

The record also reports two deaths. It does not report their causes, timing, or relationship to bomedemstat. A death count alone cannot establish whether deaths were treatment-related. Similarly, the listed serious-event terms and the overall serious-event count do not establish causation. The registry’s general adverse-event definition includes events whether or not considered product related, and no additional attribution details for these serious events are reported in the registry record.

These figures describe safety events recorded in this study group. With no separate comparator group, they do not show whether the frequency was higher or lower than it would have been under another treatment or no study drug.

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

The results provide a description of adverse events recorded among participants enrolled in this single-group bomedemstat study. The primary outcome reports 72 participants with an adverse event among 73 at risk. The serious adverse event summary reports 27 affected participants among 73 at risk, and the record lists two deaths. The serious-event terms and percentages add detail about the types of events recorded, but do not resolve cause or treatment attribution.

These observations do not demonstrate that bomedemstat caused every event, nor do they establish how the event experience compares with another treatment. The adverse-event definition explicitly includes events whether or not considered related to the drug. Without a separate comparison group, there is no concurrent reference for estimating a relative safety difference. Open-label conduct and the absence of reported assessment details further limit evaluation of how events were identified and classified.

The registry identifies efficacy and pharmacodynamics among the study’s aims, but corresponding results are not reported in the record details. The adverse-event endpoint does not answer whether a treatment changes disease outcomes or pharmacodynamic measures. It also does not describe the severity, duration or recurrence of all events at the participant level.

The record reports no confidence interval or comparative estimate for the primary outcome, so its statistical precision cannot be judged from an uncertainty interval. The findings are best understood as descriptive safety information from the participants and observation period reported. They should not be extended to populations, regimens or comparisons not described in the registry record.

14. Why This Trial Matters Statistically

This trial illustrates the distinction between describing events in a treated group and estimating a comparative treatment effect. Its single-group design can document the number of participants with adverse events during the study, but it cannot provide a direct comparison with an alternative condition. That design feature is essential when interpreting both the primary result and the serious-event summary.

The endpoint’s definition also matters. By including events whether or not considered product related, the primary count captures a broad safety experience rather than a count of events attributed to the drug. This makes the outcome useful as a general description of events recorded during treatment and follow-up, while requiring caution about causal interpretation. The reported serious-event terms add context but do not establish that treatment caused those events.

Statistically, the record also shows why counts and uncertainty estimates serve different purposes. Participant counts communicate what was observed in this study group; an uncertainty interval would help describe precision. No such interval is reported for the primary outcome. The absence of a comparator and the lack of reported inferential methods mean that comparative claims cannot be drawn from the recorded counts.

The listed sample-size illustration uses a hypothetical two-arm planning framework, whereas the actual study was single-group. General statistical interpretation therefore requires separating planning assumptions from the trial’s design and observed results. The registry record does not report the study’s own sample-size justification. These distinctions help readers assess what the safety data can describe and which questions remain unanswered.

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 principal trial-specific limitation is the absence of a control group. With a single group, the reported counts do not quantify how the adverse-event experience compares with another treatment or with no study drug. The open-label design, with masking recorded as NONE, is another limitation; details about event assessment and attribution are not reported in the registry record.

The primary outcome uses a broad adverse-event definition that includes events whether or not considered product related. The record does not report how treatment relatedness was assessed, how event severity was classified for the primary endpoint, or how repeated events were handled. Although the outcome timeframe is up to approximately 30 months and dosing is listed as 169 consecutive days, the relationship between treatment duration and observation is not explained.

The record reports no confidence interval, comparative estimate, hypothesis test or detailed statistical analysis plan for the primary outcome. Handling of missing data, incomplete follow-up and analysis populations beyond the stated primary population is not reported in the registry record. The sample-size illustration is based on a hypothetical two-arm framework and should not be mistaken for the design justification of this single-group study.

Finally, the record details summarized for this analysis do not include results for efficacy or pharmacodynamic outcomes, participant characteristics beyond the condition, or details about the two deaths. These omissions restrict interpretation to the reported adverse-event information and design features.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Study of Bomedemstat in Participants With Essential Thrombocythemia (IMG-7289-CTP-201/MK-3543-003) — NCT04254978.
• Registry record last updated 2026-05-04; status last verified 2026-04.
• Results first posted 2024-04-02.
• 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.

19. Record Summary

NCT04254978 is a completed Phase 2, single-group, open-label study of bomedemstat in participants with essential thrombocythemia. The record lists enrollment of 73, daily dosing for 169 consecutive days, a study start of 2020-09-08 and primary completion on 2023-03-23.

The primary endpoint counts participants who experienced an adverse event during a timeframe of up to approximately 30 months. The registry reports 72 participants with an adverse event among 73 at risk, and 27 participants with serious adverse events among 73 at risk. Two deaths are recorded. No separate comparator group is listed.

The results support a descriptive account of recorded events in the study group, not a controlled estimate of treatment effect. Attribution details, uncertainty estimates, missing-data procedures, the study’s sample-size justification and results for efficacy or pharmacodynamics are not reported in the registry record.