# Clinical trials for Wolfram syndrome neurodegeneration: Novel design, endpoints, and analysis models

## TL;DR

This paper introduces a new clinical trial design for Wolfram syndrome that reduces sample size needs using historical data and multivariate analysis.

## Contribution

The novel trial design combines historical controls, run-in data, and multivariate endpoints to improve efficiency in rare disease trials.

## Key findings

- Using historical controls and run-in data can achieve over 80% power with 30 participants per group.
- Inconsistent placebo progression rates require up to 50 participants per group to maintain statistical power.
- Multivariate endpoints and existing data resources can expedite drug development for rare diseases.

## Abstract

Wolfram syndrome, an ultra-rare condition, currently lacks effective treatment options. The rarity of this disease presents significant challenges in conducting clinical trials, particularly in achieving sufficient statistical power (e.g., 80%). The objective of this study is to propose a novel clinical trial design based on real-world data to reduce the sample size required for conducting clinical trials for Wolfram syndrome.

We propose a novel clinical trial design with three key features aimed at reducing sample size and improve efficiency: (i) Pooling historical/external controls from a longitudinal observational study conducted by the Washington University Wolfram Research Clinic. (ii) Utilizing run-in data to estimate model parameters. (iii) Simultaneously tracking treatment effects in two endpoints using a multivariate proportional linear mixed effects model.

Comprehensive simulations were conducted based on real-world data obtained through the Wolfram syndrome longitudinal observational study. Our simulations demonstrate that this proposed design can substantially reduce sample size requirements. Specifically, with a bivariate endpoint and the inclusion of run-in data, a sample size of approximately 30 per group can achieve over 80% power, assuming the placebo progression rate remains consistent during both the run-in and randomized periods. In cases where the placebo progression rate varies, the sample size increases to approximately 50 per group.

For rare diseases like Wolfram syndrome, leveraging existing resources such as historical/external controls and run-in data, along with evaluating comprehensive treatment effects using bivariate/multivariate endpoints, can significantly expedite the development of new drugs.