Safety, Tolerability, Ascending Dose and Dose Frequency Study of rhHNS Via an IDDD in MPS IIIA Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety, Tolerability, Ascending Dose and Dose Frequency Study of rhHNS Via an IDDD in MPS IIIA Patients (NCT01155778), a randomized phase 1, phase 2 study. The primary outcome is Number of Treatment Emergent Serious Adverse Events (SAE).

2. Clinical Question

3. Trial Design

This was a Phase I/II study of rhHNS administered by the intrathecal route through a surgically implanted IDDD in patients with MPS IIIA. Its stated purpose was to assess safety and tolerability with ascending doses and differing dose frequencies. Treatment was planned once monthly, or every two weeks for the highest monthly total, for 6 months.

The registry describes allocation as randomized and masking as none, while identifying the study model as single-group. It lists three active dose arms: 10 mg monthly, 45 mg monthly, and 45 mg every 14 days for a monthly total of 90 mg. Each arm has four participants in the posted results. No placebo or untreated comparison group is listed, so the design does not support a controlled comparison against no study drug.

The registry reports enrollment of 12, a completed status, and a primary completion date of 2012-09-01. The primary safety follow-up extends to week 30. The treatment-emergent period was defined from IDDD implantation surgery through the last follow-up contact, 30 (±7) days after end-of-study procedures. The registry does not report the rationale for the dose selection, the details of the randomization procedure, or a sample-size justification.

Secondary outcomes covered changes from baseline in developmental quotient using BSID III, KABC II, and VABS-II; disability scores; behavior; movement assessment; and several quality-of-life instruments. Their listed assessment times range from Week 22 to Week 26. These outcomes broaden the descriptive scope of the study, but the registry does not provide posted analyses for them in the record summarized by these results.

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: Study enrolled 12 participants and 4 participants were included in each of the 3 dose groups.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Safety population was defined as all enrolled participants who received at least 1 dose (full or partial) 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 Treatment Emergent Serious Adverse Events (SAE), measured over Baseline to week 30 (follow-up).

The primary endpoint is the number of treatment-emergent serious adverse events from baseline to week 30, including follow-up. It is a count of events, not a score of symptom severity or a measure of change in function. The registry defines an adverse event as an untoward medical occurrence after study drug administration, without requiring a causal relationship to treatment. An event is serious if it results in outcomes such as death, initial or prolonged inpatient hospitalization, a life-threatening experience, persistent or significant disability or incapacity, or a congenital anomaly, or is considered significant for another reason.

For safety research, event counts can identify the burden of serious events observed during the defined monitoring period. They are relevant in a study whose stated purpose is safety and tolerability, particularly when treatment involves an implanted delivery device and repeated intrathecal administration. However, a count alone does not show whether events were caused by treatment, how long they lasted, how severe they were beyond meeting the serious-event definition, or whether they were concentrated in a particular participant. The registry does not report an event-level breakdown sufficient to answer all of those questions.

The treatment-emergent window begins at IDDD implantation surgery and continues to the last follow-up contact, 30 (±7) days after end-of-study procedures. Consequently, the endpoint’s observation period includes device surgery and follow-up as well as the treatment period. The registry’s definition does not attribute every counted event to rhHNS.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry posts the primary endpoint as a count of serious adverse events, with a separate result for each dose arm. A count outcome records how many events were observed during a defined period. It differs from a binary outcome, which would record whether each participant experienced at least one event, and from a rate, which would relate events to time at risk. The posted primary results are event totals; they should not be restated as participant counts or rates.

In general, count outcomes can include repeated events in the same participant. As a result, the total count may be larger than the number of participants who experienced an event. The separate serious-event participant figures make this distinction visible in this record. Neither type of summary describes the timing of events, the number of repeat events per person, or the duration of follow-up for each participant. Those details are not reported in the registry record.

The registry reports no inferential analysis results for the primary count outcome. There are no posted confidence intervals or p-values for the arm-specific results. A confidence interval, in general, is a range that expresses the statistical uncertainty around an estimate under a specified method and assumptions. Without one, readers cannot use the posted event counts to assess a formal interval of uncertainty. A p-value, in general, measures how compatible data are with a specified statistical null model; it is not a measure of clinical importance or proof that a treatment caused an outcome. No primary p-value is reported in the registry record.

Count data are often analyzed using statistical models designed for event counts. In general, a Poisson model assumes that the variability in counts follows a particular relationship with the mean. When observed variability is greater than that assumption allows, over-dispersion may be present; methods that account for it can avoid overstating precision. Repeated events within the same participant can also make observations dependent rather than independent. The registry does not report a count model, an over-dispersion assessment, a repeated-event method, or any other statistical analysis plan for this endpoint. It is therefore not possible to determine whether those issues were addressed in a sponsor analysis.

The study is described as randomized, but its model is listed as single-group and its posted arms are three dose regimens without a placebo or untreated arm. Random assignment can help balance groups when a comparative design is specified, but the record does not describe the randomization method or the intended statistical comparison. The arm-specific counts can be read descriptively; the registry does not report a test of differences among doses or a causal contrast.

The sample-size information associated with the record is described as planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Such calculations are prospective planning illustrations, not observed power and not evidence that this study had adequate power. The record does not report its own sample-size justification or design assumptions. In addition, the posted primary outcome is a count across three dose arms, whereas the stated planning assumptions refer to a two-arm comparison. No arm-comparison analysis is reported, and no recalculation is presented.

The study includes multiple secondary outcomes measured at different time points and with different instruments. In general, examining many outcomes can increase the chance that at least one result appears noteworthy by chance if testing is repeated without adjustment. Statistical methods can address this through a prespecified testing hierarchy or multiplicity adjustment, but the registry does not report such a plan. Because secondary results are not posted as analyses in this record, there is no basis for interpreting their statistical significance or adjusting it.

Interpretation also depends on the analysis population. The primary safety population is defined as enrolled participants who received at least one full or partial dose. This definition identifies who is eligible for inclusion in the safety summaries, but the registry does not report the number actually included by arm, the handling of missing observations, or whether anyone discontinued or had incomplete follow-up. The posted arm sizes and event results can be described as recorded; they do not allow a reconstruction of participant-level analysis methods.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists numerous secondary measures spanning development, disability, behavior, movement, and quality of life, with assessments at several time points. Testing many outcomes can increase the chance of a false-positive finding when each is examined independently. In general, multiplicity is handled through prespecified methods such as a testing hierarchy or an adjustment to the significance threshold. The registry record does not report a multiplicity strategy, and no secondary analysis results are posted in this record. It is not possible to determine whether a multiplicity plan was used outside the registry record.

The primary safety population includes enrolled participants who received at least one full or partial dose. The registry does not report how missing outcomes were handled, whether all participants completed follow-up, or whether analysis populations differed across outcomes. It also does not report a missing-data method, imputation procedure, or sensitivity analysis. These omissions matter because incomplete observation can affect event ascertainment and the interpretation of measures assessed at later visits.

The registry reports four participants per dose arm, but it does not provide participant-level event histories or detailed exposure time. The primary endpoint is an event count over a period that includes IDDD implantation and follow-up. Without timing and exposure details, the record does not support a rate comparison or an assessment of whether follow-up differed across participants. The randomization method, analysis plan, and any planned interim analyses are not reported in the registry record.

11. 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: device breakage (25.0%), device component issue (25.0%), device failure (25.0%), postoperative wound infection (25.0%), viral infection (25.0%).

The primary safety result counts treatment-emergent serious adverse events over baseline to week 30, including follow-up. The posted event totals are 5 for the 10 mg arm, 3 for the 45 mg arm, and 2 for the 90 mg arm. These are not the numbers of participants who had at least one serious event. The separate participant figures are 3 of 4, 3 of 4, and 1 of 4, respectively. Other adverse events affected 4 of 4 participants in each arm.

These summaries should be kept distinct: one participant can experience more than one event, so event totals and affected-participant counts are not interchangeable. The registry lists six serious-event terms at 25.0% each, but the denominator for those percentages is not reported in the registry record. The event terms do not establish causality; the registry’s adverse-event definition does not require a causal relationship with study treatment. The record also does not report event timing, individual event histories, duration, or an attribution assessment. Deaths are not reported in the registry record, which should not be read as confirmation that none occurred.

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

The posted results establish that serious adverse events were counted during the specified treatment-emergent period in each dose arm. They also distinguish the total number of events from the number of participants affected. The listed results provide a descriptive account of safety observations among the small groups represented in the registry record.

They do not establish that rhHNS caused the events, that a particular dose caused more or fewer events, or that the event pattern would be the same in a larger population. The registry has no placebo or untreated arm listed, and it reports no inferential comparison among doses. The counts therefore cannot separate events associated with treatment from those associated with IDDD surgery, the device, the underlying condition, or other causes. The listed serious-event terms identify recorded categories, not proven causes.

The primary endpoint is not a measure of developmental benefit or disease progression. Although the study lists secondary measures of development, disability, behavior, movement, and quality of life, their analysis results are not posted in this record. The safety counts cannot answer whether those outcomes changed. Nor can they establish a benefit-risk balance, because the record does not provide posted comparative evidence of benefit alongside the safety data.

The appropriate statistical interpretation is consequently narrow: the registry reports event totals and affected-participant summaries for three dose regimens over a defined observation period. Small groups and the absence of reported uncertainty estimates limit precision. The results are useful as a description of what was recorded in this study, but they do not support broad conclusions about comparative safety, causation, or clinical effectiveness.

13. Why This Trial Matters Statistically

This study is statistically informative because it illustrates the distinction between an event count and the number of people who experience an event. The primary results count serious adverse events, while the separate safety summary counts affected participants. Those quantities can differ when participants experience repeated events. Keeping them separate prevents the event total from being misread as the number of affected people.

The record also shows why the design and the analysis need to be interpreted together. Although randomized allocation is listed, the model is described as single-group and the arms are dose regimens without an untreated or placebo comparator. The arm-specific numbers can therefore describe what was observed, but they do not by themselves estimate a controlled treatment effect. In particular, a numerical difference between dose arms is not a formal dose-response result without an appropriate analysis and information about uncertainty.

Finally, the endpoint includes a period beginning with IDDD implantation surgery and ending after follow-up. That definition captures events during a clinically relevant safety window, but it also means that event counts may encompass more than the period of drug administration. Device and postoperative terms in the record underscore the importance of event attribution and timing, details that are not fully reported. For researchers, this trial highlights how definitions, denominators, repeated events, follow-up, and missing analysis details shape the meaning of a safety summary.

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 registry record does not report a statistical analysis plan, the randomization procedure, or the rationale for the sample size. It also does not describe how the three dose arms were intended to be compared. The record identifies randomized allocation but a single-group model, with no placebo or untreated arm listed. These features limit interpretation of arm-to-arm patterns as comparative evidence.

Each dose arm has four participants, so the posted summaries represent small groups. The registry provides event counts and affected-participant figures but no confidence intervals, p-values, event rates, or participant-level histories. It does not report event timing, repeat-event details, individual follow-up duration, or attribution to treatment, surgery, or device. The event-term percentages are listed without a reported denominator. Deaths are not reported in the registry record.

The observation period includes IDDD implantation surgery as well as treatment and follow-up. The primary count therefore does not isolate events during drug exposure. The registry does not report missing-data handling, completion by arm, or sensitivity analyses. While secondary outcomes are listed, their analysis results are not posted in this record. These limitations mean the available results are a descriptive safety account rather than a complete comparative or causal analysis.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Safety, Tolerability, Ascending Dose and Dose Frequency Study of rhHNS Via an IDDD in MPS IIIA Patients — NCT01155778.
• Registry record last updated 2021-06-14; status last verified 2021-05.
• Results first posted 2018-12-12.
• 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

NCT01155778 is a completed Phase I/II study of intrathecal rhHNS delivered through an IDDD to patients with MPS IIIA. The registry lists randomized allocation, no masking, and a single-group model. Three dose regimens are posted, with four participants per arm. Treatment was planned for 6 months.

The primary endpoint is the number of treatment-emergent serious adverse events from baseline to week 30, including follow-up. Posted event counts are 5, 3, and 2 across the 10 mg, 45 mg, and 90 mg arms. Separate safety data report serious events affecting 3 of 4, 3 of 4, and 1 of 4 participants, and other adverse events affecting 4 of 4 participants in each arm.

The record lists secondary developmental, behavioral, disability, movement, and quality-of-life measures, but does not post their analysis results. It does not report inferential analyses, uncertainty intervals, the sample-size rationale, multiplicity methods, or missing-data handling. The results are descriptive and do not establish causality or a comparative treatment effect.