A Phase I/II, Open-label Study of Ofatumumab Added to Chlorambucil in Previously Untreated Japanese Patients With Chronic Lymphocytic Leukemia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Phase I/II, Open-label Study of Ofatumumab Added to Chlorambucil in Previously Untreated Japanese Patients With Chronic Lymphocytic Leukemia (NCT01563055), a na phase 2 study. The primary outcome is Number of Participants Who Developed Toxicity Requiring Discontinuation From Study Treatment During Cycle 1.

2. Clinical Question

The question is therefore a short-term tolerability question for the combination, rather than a randomized estimate of how its outcomes differ from another treatment. The registry summary also names safety, efficacy and pharmacokinetic profile as study aims. Secondary outcomes include response, progression-free survival, overall survival, time to response, duration of response, time to next CLL therapy, constitutional symptoms and ECOG performance status. Those outcomes broaden the study’s descriptive scope, but their inclusion in the outcome list does not establish that results are reported for them.

3. Trial Design

The registry record describes a Phase I/II, open-label study, while its phase classification is Phase 2. The study began in 2012-04, had primary completion in 2014-11, and is marked completed. Enrollment was 10. Its single-group model, allocation listed as NA, and absence of masking indicate that the registry record does not describe a randomized, masked comparison. The sole listed group received ofatumumab plus chlorambucil.

The population was Japanese patients with previously untreated CLL. The intervention description specifies ofatumumab as an infusion and chlorambucil as tablets. The regimen description gives ofatumumab as 300mg on day 1 and 1000mg on day 8 in cycle 1, followed by 1000mg on day 1 in subsequent 28-day cycles. Chlorambucil is described as 10mg/m2 by mouth on days 1–7 of each 28-day cycle. Treatment duration is described as a minimum of 3 cycles until best response or a maximum of 12 treatment cycles.

The primary outcome concerns toxicity requiring discontinuation during cycle 1, from treatment start through Week 4. The registry record also lists 55 outcome measures and several secondary outcomes, including response assessments, survival outcomes and measures of symptoms and performance status. The presence of these listed outcomes does not itself provide their findings. Analysis results are not reported in the registry record, and the primary endpoint count is not reported in the registry record.

Further design details—including the eligibility criteria, recruitment procedures, specific dose-modification rules beyond the brief treatment description, and the rationale for the enrollment target—are not reported in the registry record. A detailed statistical analysis plan, including planned methods for the secondary outcomes, is also not reported in the registry record. The record’s brief description identifies tolerability, safety, efficacy and pharmacokinetic profile as aims, but does not give further methodological detail for those aims.

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: This study consisted of two parts. In part A of the study, the eligible participants (par.) were enrolled to assess the tolerability of ofatumumab with chlorambucil. After confirmation of the tolerability, Part B of the study was initiated. The total number of participants in Part A and Part B was 10.

Overall Study

Analysis population for the primary outcome, as defined in the registry: All Subjects Population: all participants who received at least one dose of investigational product.

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 Developed Toxicity Requiring Discontinuation From Study Treatment During Cycle 1, measured over From start of treatment through Cycle 1 (Week 4).

The primary endpoint counts participants who developed toxicity requiring discontinuation from study treatment during cycle 1, from the start of treatment through Week 4. It is a participant count, not a measure of the severity of every adverse event, the total number of events, or the duration of treatment. The registry description says that discontinuation-causing toxicity was determined using predefined withdrawal criteria, but those criteria are not reported in the registry record.

This endpoint is used to address early tolerability of the combination. A treatment-related withdrawal is a consequential event for participants’ ability to continue the assigned regimen, so an early count can describe whether the regimen was sufficiently tolerated to proceed during the initial cycle. The registry’s stated criterion classified treatment as tolerable when 0 of 3 participants, or <=2 of 6 participants, developed toxicity requiring discontinuation in cycle 1. These criteria are stated in the outcome description; they do not substitute for the actual observed endpoint result.

The observed number meeting the endpoint, along with any estimate of its uncertainty, is not reported in the registry record. The record also does not report the detailed adjudication process or explain whether other forms of treatment interruption were counted. The endpoint therefore identifies a defined early tolerability question, but the posted information does not establish how many participants experienced the event or how precisely the event frequency can be estimated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a single-group study and reports no analysis results. A detailed statistical analysis plan is not reported in the registry record. The explanations below are general statistical context for interpreting the registered design and outcomes, not a claim about methods actually used in this trial.

What does a single-group design estimate?

In a single-group study, observed outcomes describe the participants who received the study regimen. Without a concurrent comparator group, the study does not directly estimate how outcomes would differ under another treatment. Changes over time or outcomes observed after treatment may be clinically interesting, but attributing them to treatment requires caution because other explanations cannot be separated using a randomized within-trial comparison. In this record, allocation is NA, masking is none, and the model is single group.

Open-label describes a study in which treatment assignment is not masked from participants and study personnel. Lack of masking can influence subjective assessments, decisions to discontinue, and reporting or ascertainment of symptoms. The degree to which any such influence occurred is not reported in the registry record. A clearly defined outcome and consistent assessment rules can aid interpretation, but the full withdrawal criteria and assessment procedures are not reported in the registry record.

How should a participant count be read?

The primary outcome is a count of participants who experienced toxicity requiring discontinuation during the stated cycle 1 window. A count communicates how many people met the event definition in the analyzed population. It is distinct from an event count, since one participant may experience more than one event, and it is distinct from a time-to-event measure, which incorporates when an event occurs and how long participants are observed. The primary endpoint result itself is not reported in the registry record, so the count cannot be interpreted further.

For a binary outcome, statistical uncertainty is often expressed with a confidence interval around an event proportion. General interpretation: a confidence interval describes a range of values compatible with the data under the statistical method and assumptions used. It is not a guarantee that the true value lies in a particular interval. With a small participant group, uncertainty can be substantial, and interval methods can behave differently when event counts are low. No confidence interval for the primary endpoint is reported in the registry record.

What do the stated tolerability criteria mean?

The outcome description gives a criterion of 0 of 3 participants, or <=2 of 6 participants, with toxicity requiring discontinuation in cycle 1. These are decision thresholds stated in the registry outcome description. They should not be mistaken for observed results: the record does not report the actual number of participants meeting the endpoint. Nor does the description state how the criterion was used in decisions beyond defining the stated tolerability standard.

Why are secondary outcomes methodologically different?

The secondary outcomes include binary participant counts, response measures, and time-to-event outcomes such as progression-free survival, overall survival, duration of response and time to next CLL therapy. General explanation: a time-to-event analysis uses both event timing and follow-up information, and can account for participants whose event has not been observed by the end of their available follow-up. Such participants are commonly described as censored, meaning the event time is only partly known. The registry record does not report the analysis methods, event counts, follow-up distributions or censoring details for these outcomes.

Response assessments can also depend on assessment criteria, timing and reviewer. The registry lists complete response assessments by the IRC, IRC with CT, and investigator, and other outcomes assessed by the IRC or investigator. The record does not report the assessment criteria or explain the role of each reviewer. Results from different assessors should not be assumed to be interchangeable without information about their methods and agreement.

What does over-dispersion mean in general?

General explanation: over-dispersion occurs when observed variation in count data is greater than expected under a chosen statistical model. It can make model-based uncertainty estimates too small if the extra variability is ignored. The primary endpoint is a participant count, but no model for it is reported, and the record does not state that an over-dispersion adjustment was used. This general issue should not be read as evidence that over-dispersion was present in this study.

What can be inferred from the listed analysis information?

The record lists 55 outcome measures and reports no analyses. This means the registry entry, as summarized, does not provide analysis results to evaluate. It does not establish whether analyses were carried out elsewhere, whether outcomes were measured but not posted, or why results are absent. The statistical plan, handling of missing observations, analysis populations beyond the primary population description, and any planned interim analyses are not reported in the registry record. No inferential method or adjustment for multiple outcomes can therefore be attributed to this trial from 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("Ofatumumab + Chlorambucil")
n      <- c(3)
events <- c(0)
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  Ofatumumab + Chlorambucil  3  0  0.0  0.0  70.8  0.0  56.1  0.6  60.2

11. Multiplicity, Missing Data and Analysis Populations

The record lists 55 outcome measures, including the primary tolerability outcome and secondary outcomes spanning response, survival, treatment timing, symptoms and performance status. When many outcomes are assessed, the chance of observing at least one apparently unusual result can increase if each is tested separately. General statistical practice may address this multiplicity through a prespecified hierarchy, adjusted significance thresholds, or emphasis on estimation and confidence intervals. The registry record does not report a multiplicity strategy, any hierarchy among secondary outcomes, or an analysis plan specifying how results were to be interpreted.

The record reports no analyses. Thus it does not provide the results needed to assess whether outcomes were analyzed, whether the analysis set differed by outcome, or whether missing observations affected the findings. The primary population is described as all participants who received at least one dose of investigational product. The approach to missing data, withdrawals, incomplete outcome assessments and censoring is not reported in the registry record.

General explanation: missing data can affect interpretation when participants with unavailable outcomes differ from those with observed outcomes. A complete-case analysis uses only participants with recorded data for an outcome; other approaches may make additional assumptions. Those assumptions matter because missingness can change estimates and uncertainty. No missing-data method or sensitivity analysis is reported in the registry record, so none should be presumed.

The trial’s small enrollment and broad list of outcomes make transparent reporting of the analysis population and outcome availability particularly important for interpretation. The registry record does not report these details for the secondary outcomes. The absence of posted analyses also means that conclusions about multiplicity, missingness, or the consistency of results across outcomes cannot be drawn from the available record.

12. Safety Results

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

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: spinal compression fracture (10.0%), hypoxia (10.0%).

The serious-adverse-event summary for the ofatumumab-plus-chlorambucil group lists 10 participants at risk and 2 affected. The top serious adverse-event terms are spinal compression fracture at 10.0% and hypoxia at 10.0%. The other-adverse-event summary lists 10 participants at risk and 10 affected. These are counts and percentages as recorded; they are not measures of treatment effect relative to a control group.

Serious adverse events and other adverse events are separate summary categories. The record does not report the event-level detail needed to determine whether participants experienced multiple events, when events occurred, how long they lasted, whether they resolved, or how investigators assessed their relationship to treatment. It also does not report a complete narrative of severity or management. The two listed serious terms should therefore be read as selected terms in the registry summary, not as a complete description of every serious event.

The deaths field has no reported value. Deaths are not reported in the registry record; this should not be interpreted as confirmation that no deaths occurred. Likewise, the listed safety counts cannot determine whether events were caused by the regimen. These summaries describe recorded safety information for a group of 10 participants, without a comparator that could support a comparative safety estimate.

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

The registry record documents a small, open-label, single-group study of ofatumumab plus chlorambucil in previously untreated Japanese patients with CLL. It defines an early tolerability outcome based on toxicity requiring discontinuation during cycle 1 and states a threshold for considering treatment tolerable. It also lists a range of secondary outcomes and includes selected adverse-event summaries.

What the record does not establish is the observed result for the primary endpoint. The number of participants who developed toxicity requiring discontinuation during cycle 1 is not reported in the registry record. No estimate or confidence interval for that outcome is reported either. The stated tolerability criterion must not be treated as evidence that the criterion was met.

The record also cannot establish a comparative treatment effect. There is no separate control group, and the study is described as single group with allocation NA. Selected adverse-event counts describe events in the treated group, but they do not show how those counts compare with an alternative treatment or with an untreated counterfactual. The secondary outcomes are listed, but numerical findings and analyses for them are not reported in the registry record.

General statistical interpretation: estimates from a small study can be imprecise, and absence of a reported result is not the same as evidence of no effect or no event. Here, because the primary result is absent, even a descriptive event frequency for the endpoint cannot be evaluated. The safety summaries permit only a limited description of reported counts and terms; they do not reveal full event histories or establish causality.

The appropriate reading is therefore bounded: the registry record describes the treatment regimen, study design, endpoint definition and selected safety counts, but does not provide the primary outcome result or analyses needed to assess efficacy, uncertainty, or comparative benefit and harm. No conclusion about treatment effectiveness follows from the information reported.

14. Why This Trial Matters Statistically

Statistically, the trial illustrates the distinction between registering an outcome and reporting its result. The primary endpoint is specified in practical terms: toxicity requiring treatment discontinuation during cycle 1. The registry also gives a tolerability threshold. Yet without the observed endpoint count, readers cannot assess whether that threshold was met, estimate an event frequency, or judge the uncertainty around it. A well-described endpoint is valuable, but it cannot substitute for an outcome estimate.

The design also clarifies the limits of a single-group study. A cohort receiving one regimen can contribute descriptive information about treatment exposure and observed events. It does not provide the randomized contrast needed to estimate how outcomes differ from another treatment. This is especially important when interpreting safety counts: recorded adverse events are informative descriptions, but a comparator is needed to assess relative frequency under comparable conditions.

The entry’s 10 participants and 55 listed outcome measures also make complete reporting important. Clear denominators, outcome-specific analysis populations, follow-up information, missing-data methods and analysis plans help readers distinguish observed evidence from unresolved questions. Those details are not reported in the registry record, and analyses are not reported there.

The record therefore offers a useful statistical teaching example in restraint: distinguish registered aims from posted findings, distinguish event counts from comparative effects, and do not infer absence of events from an absent result. These principles apply broadly to clinical trial interpretation, particularly when the available record includes outcome definitions and selected safety data but no analysis results.

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 most direct limitation is that the primary endpoint result is not reported in the registry record. Although the endpoint window and tolerability criterion are described, the observed count of participants with toxicity requiring discontinuation is absent. No estimate of uncertainty is reported, so the primary tolerability outcome cannot be quantitatively interpreted.

The trial is described as single group, open-label and unmasked, with no separate comparator. It therefore cannot provide a randomized within-trial comparison of treatment outcomes. Open-label assessment can also be relevant when outcomes involve clinical judgment or decisions to discontinue, although the extent of any influence is not reported in the registry record.

Enrollment was 10. The record does not report a sample-size justification, so the basis for this enrollment target is not known. Eligibility criteria, detailed assessment procedures, withdrawal rules, dose modification rules, duration of follow-up and outcome-specific analysis populations are not reported in the registry record. The complete statistical analysis plan, missing-data methods, interim analyses and multiplicity strategy are also not reported in the registry record.

The registry lists 55 outcome measures but reports no analyses. Numerical findings for the secondary outcomes are not reported in the registry record. Safety information is limited to selected summaries; deaths, event timing, duration, relatedness, severity detail and participant-level event patterns are not reported in the registry record. The record thus supports a description of the registered design and selected safety counts, but leaves key questions about outcomes, precision, analysis and completeness unresolved.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Phase I/II, Open-label Study of Ofatumumab Added to Chlorambucil in Previously Untreated Japanese Patients With Chronic Lymphocytic Leukemia — NCT01563055.
• Registry record last updated 2015-08-10; status last verified 2015-07.
• Results first posted 2015-08-10.
• 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

NCT01563055 is a completed, open-label, single-group study of ofatumumab plus chlorambucil in previously untreated Japanese patients with CLL. The title describes a Phase I/II study, and the registry phase classification is Phase 2. Enrollment was 10. The listed regimen used ofatumumab infusion and chlorambucil tablets.

The primary outcome was the number of participants with toxicity requiring discontinuation during cycle 1, through Week 4. The registry record states a tolerability threshold but does not report the observed primary endpoint count or analysis results. It lists 55 outcome measures and secondary outcomes including response, survival, symptoms and performance status.

The serious-adverse-event summary lists 2 affected participants among 10 at risk; spinal compression fracture and hypoxia are each listed at 10.0%. The other-adverse-event summary lists 10 affected among 10 at risk. The record does not report a comparator, analysis plan, or detailed results for the primary and secondary outcomes.