Time-Scale Target Parameters and Two-Step Estimation in Longitudinal Trials for Progressive Diseases

Area of Science:

• Biostatistics
• Clinical Trial Methodology
• Neurodegenerative Disease Research

Background:

• Progressive diseases like Alzheimer's necessitate early treatment intervention to maintain patient function.
• Current clinical trial analyses often use mean differences at fixed time points, which may obscure early treatment benefits.
• Interpreting the clinical relevance of small mean differences in early disease stages is challenging.

Purpose of the Study:

• To introduce novel target parameters for quantifying treatment effects on a time scale in longitudinal studies.
• To provide methods for estimating these parameters, applicable to both randomized and non-randomized treatment scenarios.
• To enhance the interpretation of treatment efficacy in progressive neurological disorders.

Main Methods:

• Development of target parameters measuring treatment effects in terms of time saved or percentage slowing of disease progression.
• Proposal of general two-step estimators for these parameters, utilizing standard longitudinal data analysis methods in the first step.
• Implementation of the second step for inference in the TCT R package, followed by asymptotic property analysis and simulation studies.

Main Results:

• The proposed two-step estimators provide a robust framework for analyzing time-scale treatment effects.
• The methodology was successfully applied to a phase 2/3 clinical trial for Alzheimer's disease.
• The analysis yielded significant additional insights into the treatment effect beyond traditional metrics.

Conclusions:

• The novel time-scale parameters offer a more clinically relevant measure of treatment efficacy in progressive diseases.
• The proposed estimation methods are versatile and can be implemented using existing statistical software.
• This approach improves the understanding and communication of treatment benefits, particularly for early-stage interventions in Alzheimer's disease.