# Assessing the efficacy, safety and utility of hybrid closed-loop glucose control compared with standard insulin therapy combined with continuous glucose monitoring in young people (≥16 years) and adults with cystic fibrosis-related diabetes (CL4P-CF study): protocol for an open-label, multicentre, randomised, two-arm and single-period parallel trial

## TL;DR

This study will compare hybrid closed-loop insulin delivery to standard insulin therapy with CGM in people with cystic fibrosis-related diabetes to see which better controls blood glucose.

## Contribution

The study introduces a trial evaluating hybrid closed-loop systems for managing cystic fibrosis-related diabetes, a novel approach in this patient population.

## Key findings

- Participants will be randomized to either hybrid closed-loop insulin delivery or standard insulin therapy with CGM.
- The primary outcome is the difference in time spent in the target glucose range between the two groups.
- Secondary outcomes include glucose metrics, lung function, and body mass index changes.

## Abstract

Cystic fibrosis-related diabetes (CFRD) is one of the most clinically impactful comorbidities associated with cystic fibrosis (CF). Current recommended management with insulin therapy is challenging due to variable daily insulin requirements and adds to the significant burden of self-management. This study aims to determine if hybrid closed-loop insulin delivery can improve glucose outcomes compared with standard insulin therapy with continuous glucose monitoring (CGM) in young people (≥16 years) and adults with CFRD.

This open-label, multicentre, randomised, two-arm, single-period parallel design study aims to randomise 114 young people (≥16 years) and adults with CFRD. Following a 2–3 weeks’ run-in period, during which time participants use a masked CGM, participants with time in target glucose range (3.9–10.0 mmol/L) <80% will be randomised to 26 weeks with hybrid closed-loop insulin delivery or standard insulin therapy with CGM. The primary outcome is the between-group difference in time in target glucose range (3.9–10.0 mmol/L) based on CGM levels during the 26-week study phase. Analyses will be conducted on an intention-to-treat basis. Key secondary outcomes are time above target glucose range (>10.0 mmol/L), mean glucose and HbA1c. Other secondary efficacy outcomes include glucose and insulin metrics, change in forced expiratory volume in 1 s and body mass index. Safety, utility, participant experiences and participant-reported outcome measures will also be evaluated. The trial is funded by the National Institute for Health and Care Research.

Ethics approval has been obtained from East of England–Cambridge South Research Ethics Committee. Results will be disseminated by peer-reviewed publications and conference presentations, and findings will be shared with people living with CF, healthcare providers and relevant stakeholders.

NCT05562492.