# A “Trial within a Cohort” platform for pediatric clinical trials on idiopathic nephrotic syndrome: scope, objectives, and design of the retrospective-prospective cohort PIN’SNP

## TL;DR

This paper introduces a new clinical research platform for studying pediatric idiopathic nephrotic syndrome in France, aiming to improve treatment through nested trials and longitudinal studies.

## Contribution

The first French national pediatric platform using the TwiCs model for INS research, enabling nested trials and observational studies.

## Key findings

- The PIN’SNP cohort will identify and describe INS cases in French pediatric centers.
- The platform supports prospective trials nested within a dynamic cohort to improve methodological and ethical standards.
- The TwiCs design facilitates communication and inclusion of patients in future therapeutic trials.

## Abstract

Idiopathic nephrotic syndrome (INS) in children is the most common glomerular disease and is characterized by recurrent relapses. There is no community consensus on the treatment of relapsing forms of nephrotic syndrome in children, unlike that for the initial presentation. To date, available treatments only enable relapsing patients to be maintained in remission, rather than modifying the course of the disease; therefore, more therapeutic trials are needed. The Société de Néphrologie Pédiatrique (SNP) decided to implement within its French centers a national coordinated long-term clinical research program for children treated for INS based on a Trials within Cohorts (TwiCs) model. The aim of this paper is to describe the PIN’SNP cohort and research program as well as the TwiCs design adapted to INS research in the French regulatory system.

This retrospective-prospective, multicenter research program will rely on a dynamic prospective cohort of children followed for an INS, known as the PIN’SNP cohort (i) to identify cases treated within SNP centers, (ii) to describe their clinical and epidemiological characteristics, and (iii) to provide a platform to nest prospective trials, and thus facilitate inclusion of patients in these future trials.

The PIN’SNP cohort is the first French national pediatric platform dedicated to the implementation of randomized nested trials along with longitudinal and observational studies on INS in children. The adaptation of the TwiCs design to inform all eligible patients/parents to each nested trial will facilitate methodological robustness and ethical acceptability and reinforce communication between investigators and participants.

number NCT04207580.

A higher-resolution version of the Graphical abstract is available as Supplementary information

A higher-resolution version of the Graphical abstract is available as Supplementary information

The online version contains supplementary material available at 10.1007/s00467-025-06676-7.