UPDATE NO. 3
Subject: Request for amendment and harmonization of completed clinical trial record — IRCT20100922004794N12
Dear IRCT Administration Team,
We respectfully request amendment and harmonization of the record for the clinical trial IRCT20100922004794N12, entitled “Formulation of Levothyroxine plus slow-release Liothyronine preparation for treatment of hypothyroidism (Clinical trial Phase 2 & 3).”
The Phase 3 component of this trial has now been completed. During preparation of the final Phase 3 manuscript, we performed a detailed reconciliation of the current IRCT record with the final Phase 3 protocol and identified several residual inconsistencies originating from earlier versions of the registration.
We wish to emphasize that all substantive Phase 3 methodological decisions described in this amendment were made before recruitment of the first Phase 3 participant and before any Phase 3 outcome data were available. The present request is therefore intended to harmonize the public registry with the final pre-recruitment Phase 3 protocol and actual trial conduct; it does not represent changes made in response to study results.
Secondary outcomes
Serum TSH, total T3, total T4, FT3, FT4 and the derived T3/T4, T3/FT4, and FT3/FT4 ratios were prespecified secondary biochemical outcomes.
The proportion of participants with a T3/FT4 ratio within the predefined reference range of 65–145 was also a prespecified secondary biochemical analysis and should be added to the registered outcomes.
Phase 3 treatment groups
The final Phase 3 trial consisted of two randomized parallel treatment groups:
1. LT4 monotherapy.
2. LT4 plus slow-release liothyronine.
The previously planned age- and sex-matched euthyroid control group was removed before Phase 3 recruitment. Although this deletion is already mentioned in the IRCT update history, the previous normal-control description remains in another section of the current registry. We respectfully request that this residual entry be removed or designated as superseded.
Intervention and dose titration
Participants allocated to combination treatment started therapy with LT4 plus SR-T3 at an initial SR-T3:LT4 dose ratio of approximately 1:5. The absolute starting doses were individualized according to each participant's thyroid hormone replacement requirement. The 1:5 ratio represented the initial treatment ratio and was not intended to remain fixed throughout follow-up. During the dose-adjustment period, LT4 and SR-T3 doses were individually titrated according to biochemical response, and consequently the SR-T3:LT4 dose ratio could change during follow-up. SR-T3 tablets containing 15, 20, and 25 μg were available for individual dose titration. LT4 tablets containing 50, 75, and 100 μg were also available.
During the initial dose-adjustment phase, LT4 and SR-T3 doses were individually titrated according to biochemical response in order to maintain serum TSH within approximately 0.5–5.0 mU/L. In participants receiving combination treatment, the serum T3/FT4 ratio and the intended balance between LT4 and SR-T3 exposure were also considered during titration.
We therefore request that the intervention section be revised to describe the starting regimen and subsequent individual titration rather than implying that the 1:5 ratio remained fixed throughout the study.
LT4 monotherapy group
Participants assigned to the control group received individualized LT4 replacement according to their pretrial replacement requirement and biochemical response, with dose adjustment when required to maintain euthyroidism. The control arm was not restricted to a fixed dose of 100 μg LT4 throughout follow-up. We therefore request correction of the registry section that currently describes a fixed 100-μg/day LT4 regimen.
Placebo and masking
Participants randomized to LT4 monotherapy received a matching placebo corresponding to SR-T3 in order to maintain double blinding. Active SR-T3 and placebo tablets were matched in physical appearance, taste, smell, and packaging. The current IRCT record contains an internal inconsistency in which the masking description correctly states that the control group received placebo instead of SR-T3, whereas another field states “Placebo: Not used.” We therefore request that the placebo field be corrected to indicate placebo used.
Eligibility criteria
The Phase 3 study included adults aged 20–75 years with hypothyroidism who were euthyroid on stable LT4 treatment before randomization. The final pre-recruitment exclusion criteria also included pregnancy or planned pregnancy and clinically important cardiovascular conditions, including unstable cardiovascular disease and cardiac arrhythmia.
We additionally request clarification of the cancer-related eligibility wording so that the registry clearly distinguishes previous definitively treated thyroid cancer resulting in hypothyroidism from current or active malignancy, according to the final Phase 3 protocol.
Follow-up period
The Phase 3 intervention and follow-up period was 48 weeks, approximately 12 months, with principal assessments at baseline, 6 months, and 12 months and additional biochemical monitoring during the initial dose-adjustment period. We request correction of the isolated registry reference to “24 weeks,” which is inconsistent with the final Phase 3 protocol.
Cardiovascular safety assessments
Prespecified cardiovascular safety monitoring included resting heart rate, blood pressure, and serial electrocardiography. ECG variables included heart rate, RR interval, PR interval, QRS duration, QT interval, corrected QT interval, and clinically important rhythm and conduction abnormalities. ECG assessments were performed at baseline, 6 months, and 12 months.
We request that these ECG assessments be added to the registered safety procedures and outcomes.
Pharmacogenetic assessments
The Phase 3 Pharmacogenetic analyses evaluated the candidate variants: rs225014, rs12885300, rs225015, and rs17606253.
We request replacement of the current broad genetic description and reference to whole-genome sequencing with the actual candidate-variant analysis and laboratory methodology used in the study.The final laboratory method will be entered once all laboratory details have been confirmed:
Patient preference
Patient treatment preference was assessed during follow-up and at study completion. We request correction of the registered assessment timing where necessary.
We therefore request completion of the following fields:
Actual recruitment start date: 2024.12.03
Actual recruitment end date: 2024.12.08
Final participant/final study visit date: 2025.12.10
Post-trial treatment
Following completion of assigned study treatment, participants were returned to conventional LT4 replacement therapy and followed until biochemical euthyroidism was re-established.
We respectfully request that the above amendments be incorporated while preserving the original registration history and dates of previous protocol updates. The purpose of this amendment is to provide a complete, accurate, and transparent public record of the final Phase 3 protocol and actual study conduct. We again confirm that the substantive Phase 3 methodological decisions described above were established before Phase 3 recruitment began and before any Phase 3 outcome data were available.
Please let us know if supporting documents, including dated protocol versions, ethics approvals, investigational-product documentation, or study records, are required.