MRI Parameters as Biomarkers in Cystic Fibrosis (FEMPTO)

Overview

Cystic fibrosis (CF) is an inherited condition that affects several organs, including the gut. People with CF often experience uncomfortable digestive symptoms such as bloating, gas, abdominal pain, and constipation. The root cause is that the gut produces thicker-than-normal mucus, which slows things down and makes it harder for the bowel to work properly. Current treatments such as laxatives, enemas, or surgery can be inconvenient and don't always work well. There is a real need for better options, and for a clearer understanding of how the CF gut behaves and responds to treatment. This study will use MRI, a non-invasive imaging technique, to look at how fluid moves through the gut in adults with CF and the impact of linaclotide. Linaclotide is a licensed medication used to treat chronic constipation and irritable bowel syndrome. It works by encouraging the gut to release more fluid, helping things move more easily. It acts locally in the gut and is not absorbed into the bloodstream. Early research suggests it may help in CF in a way that does not rely on correcting the underlying genetic fault, making it a promising avenue to explore. Participants will include people with different bowel habits, including those who tend towards constipation and those who tend towards diarrhoea. The scans will help researchers check whether certain MRI measurements can reliably detect changes in gut fluid and movement. This is a feasibility study; its main objective is to test whether these MRI measurements are useful and practical, and support a sample size calculation, in future CF studies investigating linaclotide effects.

Background: The recent James Lind Alliance priority setting listed "How can we relieve gastro-intestinal symptoms, such as stomach pain, bloating and nausea?" as number 3 priority despite treatment with CFTR modulators. The investigators have shown using magnetic resonance imaging (MRI) that pwCF have abnormal small bowel contents which empty more slowly into the colon. This is most likely due to impaired pancreatic, biliary and intestinal secretions leading to hyperviscosity of contents. Linaclotide is a drug which stimulates bicarbonate secretion in the small intestine which has been shown to accelerate transit in mice models of CF but not in patients. Its action would be predicted to reduce mucus viscosity and normalise small bowel contents and transit. Aims: to perform a mechanistic pilot study using MRI to show that linaclotide normalises small bowel contents and transit times. Methods: A randomised, placebo-controlled trial of linaclotide in pwCF. Linaclotide 290ug will be taken on the day before and on the MRI study day. Patients will then undergo serial MRI scanning for 6 hours following dosing at time T 0 , with a standard rice pudding meal at time T60 and a second 700kcal meal at T 300 minutes with the final scan at time T360minutes as the investigators have done previously. The investigators will measure small bowel water content (SBWC) as well as time for chyme to enter the colon (orocaecal transit time \[OCTT\]) and T1 ascending colon(T1AC), a measure of colonic water content. Primary endpoint: SBWC AUC 0-6hours . Secondary endpoints: change in SBWC after second meal from T300 to T360 ( ∆ SBWC), OCTT, T1 AC AUC 0-6 hours, bowel frequency and stool consistency on study day and the following 3 days. Impact: If successful this will provide a mechanistic rationale for a full 12 week clinical study of linaclotide as adjunctive treatment for pwCF.