This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record.
1. Trial at a Glance
CARTITUDE-1 was a completed phase 1/2, single-group study evaluating JNJ-68284528 in participants with relapsed or refractory multiple myeloma. The registry reports 126 enrolled participants and one intervention: JNJ-68284528, a biological intervention.
| Feature | CARTITUDE-1 |
|---|---|
| Phase | Phase 1/2 |
| Condition | Multiple Myeloma |
| Population | Participants with relapsed or refractory multiple myeloma |
| Design model | Single group |
| Masking | None |
| Allocation | NA |
| Primary purpose | Treatment |
| Enrollment | 126 |
| Number of arms | 1 |
| Intervention | JNJ-68284528 (biological) |
| Status | Completed |
| Lead sponsor | Janssen Research & Development, LLC |
| Sponsor type | Industry |
| Start date | 2018-06-29 |
| Primary completion date | 2022-08-23 |
| ClinicalTrials.gov | NCT03548207 |
2. Clinical Question
The central clinical-statistical question was how participants with relapsed or refractory multiple myeloma responded to treatment with JNJ-68284528 and what adverse events occurred during the study period.
Population
Participants with relapsed or refractory multiple myeloma.
Intervention
JNJ-68284528, a chimeric antigen receptor T cell (CAR-T) therapy directed against B-cell maturation antigen (BCMA).
Comparator
The registry identifies a single-group design and one study arm; no comparator arm is reported.
Primary questions
What proportion of participants achieved a partial response or better according to IMWG criteria, and what adverse events occurred by severity?
3. Trial Design
No randomized comparator is reported.
The registry reports an unmasked study.
A comparative allocation scheme is not applicable to the single-group design.
The registry classifies the primary purpose as treatment.
JNJ-68284528
- Biological intervention
- Chimeric antigen receptor T cell (CAR-T) therapy
- Directed against B-cell maturation antigen (BCMA)
No comparator arm
- The design model is single group.
- The registry reports one study arm.
- No randomized control group is reported.
4. Endpoints
| Primary endpoint | Time frame | Registry definition |
|---|---|---|
| Phase 1b: Number of Participants With Adverse Events as Per Severity | Day 1 up to 45.2 months | An adverse event was any untoward medical occurrence in a clinical study participant administered a pharmaceutical product. Severity was graded according to NCI-CTCAE version 5.0, ranging from Grade 1 (Mild) to Grade 5 (Death). |
| Phase 2: Overall Response Rate (ORR) | Day 1 up to 45.2 months | ORR was the percentage of participants who achieved partial response (PR) or better according to international myeloma working group (IMWG) criteria. |
How the ORR definition works
The registry defines a partial response as a reduction of serum M-protein of greater than or equal to 50% together with reduction in 24-hour urinary M-protein by greater than or equal to 90% or to less than 200 mg per 24 hours. When serum and urine M-protein were not measurable, the criteria could instead use the difference between involved and uninvolved free light chain levels. If those measurements were also not measurable, a reduction in bone marrow plasma cells could be used when the baseline bone marrow plasma cell percentage was greater than or equal to 30%. When soft tissue plasmacytomas were present at baseline, a greater than or equal to 50% reduction in their size was additionally required.
5. Statistical Methodology
Descriptive analysis of adverse events
The phase 1b primary endpoint is the number of participants with adverse events according to severity. Because the endpoint is defined by counts of participants within severity categories, an appropriate analysis is descriptive tabulation of participants by adverse-event severity using the NCI-CTCAE version 5.0 grading framework reported in the registry.
The grade is a severity classification. An adverse event does not necessarily have a causal relationship with the intervention.
Proportion-based analysis of ORR
The phase 2 ORR endpoint is a binary response outcome summarized as the percentage of participants achieving PR or better according to IMWG criteria. For a single-group study, the natural statistical summary is the observed response proportion together with an appropriate confidence interval for that proportion.
The numerator represents participants meeting the prespecified PR-or-better definition. The denominator must correspond to the analysis population specified for the endpoint.
No treatment-effect comparison
Because CARTITUDE-1 is a single-group study, there is no randomized treatment-versus-control contrast. Consequently, a hazard ratio, risk ratio, odds ratio comparing randomized groups, or between-arm p-value is not an inherent feature of this design.
6. Planned Analysis
The registry reports results for the primary endpoints but does not provide posted statistical analyses in the ClinicalTrials.gov record. For the phase 1b safety endpoint, the relevant analysis would normally summarize the number of participants experiencing adverse events within each NCI-CTCAE severity grade over the specified Day 1 up to 45.2 months time frame. For the phase 2 ORR endpoint, the relevant analysis would normally estimate the proportion of participants achieving PR or better according to IMWG criteria, accompanied by a confidence interval describing statistical precision.
Phase 1b endpoint
Adverse events are categorized by severity using NCI-CTCAE version 5.0. The primary descriptive quantity is the number of affected participants in each severity category.
Phase 2 endpoint
ORR is defined as the percentage of participants achieving PR or better according to the detailed IMWG response criteria.
Confidence intervals
For a single-group response proportion, a binomial confidence interval is a natural way to quantify uncertainty around the observed proportion.
Interpretation
The analysis describes the observed experience of the treated study population rather than a randomized treatment effect.
7. Statistical Methods Explained
Why does a single-group trial change the statistical interpretation?
In a randomized comparative trial, the difference between treatment groups provides the basis for estimating a comparative treatment effect. CARTITUDE-1 has a single-group design, so there is no concurrent randomized comparator. The primary statistical task is therefore estimation and description of outcomes in the treated study population rather than estimation of a randomized between-group effect.
What does ORR measure?
ORR measures the proportion of participants who achieve a partial response or better under the prespecified IMWG criteria. It is a categorical efficacy endpoint: each participant is classified according to whether the response threshold was achieved during the defined assessment period.
Why does the definition of PR matter statistically?
The response definition determines who enters the numerator of the ORR. Here, the registry uses a hierarchy of measurements involving serum and urinary M-protein, free light chains, bone marrow plasma cells, and soft tissue plasmacytomas when applicable. A response proportion is only meaningful when the classification rule is applied consistently across participants.
What does an ORR confidence interval tell us?
A confidence interval around a single-group response proportion describes statistical uncertainty about the underlying response probability under the model and sampling framework used to construct the interval. It does not describe the range of responses that individual participants will experience.
Why is an adverse-event count different from an ORR?
Adverse-event severity is organized into clinical grades, while ORR reduces response status to whether a participant meets the PR-or-better criterion. The two endpoints therefore answer different questions: one characterizes safety events by severity, while the other summarizes antitumor response.
Why is there no hazard ratio for the primary ORR endpoint?
A hazard ratio is primarily a relative measure for time-to-event outcomes. ORR is a proportion measured over a defined period. In a single-group study, there is also no second randomized group against which a comparative hazard ratio could be calculated.
What does "adverse event" mean?
The registry defines an adverse event as any untoward medical occurrence in a participant administered a pharmaceutical product. Importantly, the definition does not require that the event be causally related to the intervention. Severity is separately graded from Grade 1 through Grade 5.
8. Safety
The registry reports serious adverse events by study population as the number affected divided by the number at risk. These figures span the Phase 1b US population, Phase 2 US population, and Phase 2 Japan population.
| Study population | Serious adverse events | Affected / at risk |
|---|---|---|
| Phase 1b (US Population) | Participants with serious adverse events | 11/29 |
| Phase 2 (US Population) | Participants with serious adverse events | 42/68 |
| Phase 2 (Japan Population) | Participants with serious adverse events | 1/9 |
Adverse-event severity as a statistical endpoint
The phase 1b primary endpoint is explicitly defined as the number of participants with adverse events according to severity. The registry specifies five severity grades: Grade 1, Mild; Grade 2, Moderate; Grade 3, Severe; Grade 4, Life-threatening; and Grade 5, Death related to the adverse event.
For safety interpretation, the distinction between frequency and severity is important. The number of participants experiencing an event and the grade assigned to that event provide different information. A participant-level count also differs conceptually from a count of the total number of events, because one participant can experience more than one adverse event.
9. Clinical Interpretation vs Statistical Interpretation
Statistical interpretation
The primary phase 2 efficacy endpoint is a single-group response proportion defined by IMWG criteria. The phase 1b primary endpoint is a participant count classified by adverse-event severity.
Clinical interpretation
The endpoints describe whether participants achieved a prespecified response and what adverse events occurred during follow-up. Neither endpoint alone summarizes every dimension of clinical benefit or risk.
The distinction is especially important because a single-group ORR does not establish how the intervention compares with another treatment. Historical comparisons may be informative in some research settings, but they are vulnerable to differences in eligibility criteria, disease characteristics, response assessment, follow-up, supportive care, and other factors. A concurrent randomized comparator provides a stronger basis for attributing differences to treatment assignment.
10. Interpreting a Single-Group Response Rate
An ORR estimate represents the observed proportion of participants who achieved PR or better according to the prespecified IMWG criteria during the defined assessment period. It is a descriptive estimate of response in the study population.
ORR does not mean that the same proportion of all patients with relapsed or refractory multiple myeloma would necessarily respond outside the study. It also does not measure the duration of response, overall survival, or a randomized treatment effect.
Because ORR is estimated from a finite number of participants, the observed percentage is subject to sampling uncertainty. A confidence interval quantifies that uncertainty; it does not represent a prediction interval for individual patients.
If a hypothesis test were performed for a single-group response rate, the p-value would quantify evidence against a specified null hypothesis under the chosen testing framework. It would not measure the magnitude of the response itself. The response proportion remains the direct measure of the observed effect.
11. Understanding the IMWG Response Definition
The registry's PR definition is not simply a general clinical judgment that a tumor has improved. It is a structured classification rule based on specified laboratory and disease measurements.
| Measurement pathway | Registry criterion for PR |
|---|---|
| Serum M-protein and urinary M-protein measurable | Greater than or equal to 50% reduction of serum M-protein and reduction in 24-hour urinary M-protein by greater than or equal to 90% or to less than 200 mg per 24 hours. |
| Serum and urine M-protein not measurable | Decrease of greater than or equal to 50% in the difference between involved and uninvolved free light chain levels. |
| Serum and urine M-protein and serum free light assay not measurable | Greater than or equal to 50% reduction in bone marrow plasma cells, provided baseline bone marrow plasma cell percentage was greater than or equal to 30%. |
| Soft tissue plasmacytomas present at baseline | Greater than or equal to 50% reduction in the size of soft tissue plasmacytomas was additionally required. |
This hierarchy illustrates why endpoint definitions matter in clinical-trial statistics. The response classification is constructed from clinically relevant measurements, but the measurement pathway can differ depending on what is measurable at baseline. Statistical analysis begins only after those clinical classification rules have been applied consistently.
12. Analysis Populations and Denominators
The registry reports 126 enrolled participants overall, while the serious-adverse-event summaries use population-specific denominators. Those denominators should be preserved when interpreting the safety results.
| Quantity | Reported value | Statistical significance |
|---|---|---|
| Total enrollment | 126 | Overall study population size |
| Number of arms | 1 | Single-group design |
| Phase 1b US safety denominator | 29 | Population-specific denominator |
| Phase 2 US safety denominator | 68 | Population-specific denominator |
| Phase 2 Japan safety denominator | 9 | Population-specific denominator |
Differences between an overall enrollment count and endpoint-specific denominators are not automatically errors. Clinical-trial endpoints can use different analysis populations or denominators depending on how the endpoint is defined and how participants are classified. The denominator is therefore part of the statistical result and should always accompany a reported proportion or affected-participant count.
13. Follow-Up and Time Frame
Study start
The registry lists 2018-06-29 as the study start date.
Primary endpoint assessment window
Both registered primary endpoints use a time frame of Day 1 up to 45.2 months.
Primary completion
The registry lists 2022-08-23 as the primary completion date.
Study status
The registry identifies the study as completed.
The endpoint time frame is important because a response percentage is meaningful only in relation to the period over which response was assessed. Likewise, adverse-event summaries depend on the observation period during which participants were monitored.
14. Why This Trial Matters Statistically
CARTITUDE-1 is a useful statistical teaching case because it illustrates how the appropriate analysis depends fundamentally on the design and endpoint. The study is not a two-arm randomized comparison; it is a single-group phase 1/2 study with a response proportion as a phase 2 primary endpoint and a severity-based adverse-event endpoint in phase 1b.
| Concept | How it appears in CARTITUDE-1 |
|---|---|
| Single-group design | One study arm is reported. |
| Phase 1/2 development | The study contains phase 1b and phase 2 primary endpoints. |
| Binary efficacy endpoint | ORR classifies participants according to whether PR or better was achieved. |
| Response criteria | PR is defined using IMWG criteria and specified laboratory and disease measurements. |
| Safety severity grading | Adverse events are graded from Grade 1 through Grade 5 under NCI-CTCAE version 5.0. |
| Denominator discipline | Safety results are reported with population-specific denominators. |
| Confidence intervals | Appropriate for describing uncertainty around an estimated single-group proportion. |
| No randomized comparator | A between-arm treatment effect cannot be estimated from this design. |
| Time frame | Both primary endpoints use Day 1 up to 45.2 months. |
15. Important Limitations and Interpretation Issues
- No concurrent comparator: the single-group design does not provide a randomized control group for estimating a treatment-versus-control effect.
- Single-group ORR: an observed response proportion describes the study population but does not by itself establish comparative efficacy.
- Endpoint-specific denominators: the serious-adverse-event results use denominators of 29, 68, and 9 for the reported populations and should be interpreted within those populations.
- Response classification: ORR depends on the detailed IMWG definition of PR or better, including alternative measurement pathways when M-protein or free light chain measurements are not measurable.
- Follow-up: both registered primary endpoints are defined over Day 1 up to 45.2 months, so the time frame is part of the interpretation.
- Safety versus efficacy: adverse-event frequency and response rate are distinct endpoints and should not be collapsed into a single numerical measure.
- External comparisons: comparisons with other studies are vulnerable to differences in populations, design, endpoint definitions, follow-up, and clinical management.
- Uncertainty: a point estimate alone does not communicate the sampling uncertainty surrounding a response proportion or safety rate.
16. What a Statistical Comparison Would Require
Understanding what is absent from a design can be as important as understanding what is present. A randomized treatment comparison requires at least two concurrently assigned groups and a prespecified method for comparing their outcomes. CARTITUDE-1 instead provides a single treated group.
What is estimable
The study can estimate the observed proportion achieving a defined response and summarize adverse events within the study population.
What is not a direct design feature
A randomized treatment-versus-control effect is not directly estimable because there is no comparator arm.
Why historical controls differ
A historical comparison does not reproduce the protection against confounding provided by concurrent randomization.
Why endpoint definition matters
Even a numerical comparison across studies can be misleading if response criteria, populations, assessment windows, or analysis populations differ.
17. Statistical Concepts in This Trial
The statistical structure of CARTITUDE-1 can be understood through a few core concepts.
18. Sources
- ClinicalTrials.gov: CARTITUDE-1 (NCT03548207).
- PubMed: PubMed record.
- PubMed: PubMed record.
- PubMed: PubMed record.
- PubMed: PubMed record.
- PubMed: PubMed record.
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19. Record Summary
CARTITUDE-1 is a phase 1/2, single-group study of JNJ-68284528 in participants with relapsed or refractory multiple myeloma. The registry reports 126 enrolled participants, one study arm, no masking, and a treatment primary purpose. Its registered primary endpoints address two distinct statistical domains: phase 1b adverse events classified by NCI-CTCAE version 5.0 severity and phase 2 overall response rate defined as the percentage of participants achieving partial response or better according to IMWG criteria.
The key statistical lesson is that study design determines what can be learned from an endpoint. A single-group ORR is an estimate of observed response in the treated study population, while the absence of a concurrent comparator means that the design does not directly estimate a randomized treatment effect. Similarly, safety results must be interpreted with their population-specific denominators and severity definitions. Careful attention to endpoint definitions, analysis populations, denominators, time frames, and statistical uncertainty is therefore essential when interpreting the study.