# Mesalamine for Colorectal Cancer Prevention Programme in Lynch syndrome (MesaCAPP): a multicentre, multinational, randomised, two-arm, double-blind, phase II clinical study with mesalamine or placebo in carriers with Lynch syndrome – a study protocol

## TL;DR

This study tests whether mesalamine can prevent colorectal cancer in people with Lynch syndrome, a genetic condition that increases cancer risk.

## Contribution

The study introduces a phase II clinical trial protocol to evaluate mesalamine as a chemopreventive agent for Lynch syndrome carriers.

## Key findings

- The trial will assess mesalamine's effect on reducing colorectal neoplasia in Lynch syndrome carriers.
- Safety and tolerability of mesalamine will be evaluated over a 2-year period.
- Results will explore variations in drug effects based on age, sex, and cancer history.

## Abstract

Lynch syndrome (LS) carriers have a 20–46% lifetime risk of colorectal cancer (CRC) due to mismatch repair gene variants. Mesalamine (5-ASA, 5-aminosalicylic acid), used safely in patients with ulcerative colitis, may reduce CRC risk in LS by decreasing microsatellite instability, a key driver of LS-related cancer. This study evaluates 5-ASA’s efficacy as a tolerable chemopreventive drug, aiming to improve long-term CRC prevention in LS.

This multicentre, multinational, randomised, double-blind, two-arm, phase II clinical study will compare the effects of a 2-year daily intake of 5-ASA (2000 mg) to placebo in LS carriers. The primary objective is to assess whether mesalamine reduces colorectal neoplasia, both benign and malignant, compared with placebo in LS carriers, as detected by colonoscopy at the end of the treatment period (24 months±1 month) and on study completion. Secondary objectives include evaluating whether 5-ASA reduces neoplasia/tumour multiplicity and progression compared with placebo at specified time points, examining variations in the effects of 5-ASA versus placebo based on cancer history, sex and age (<45 years vs ≥45 years), and assessing the safety of 5-ASA in LS carriers.

The trial is currently open for enrolment, having received ethical approval from the Regional Ethical Review Board in Stockholm and funding from the Swedish Research Council. The study protocol is the finalised V.10.0 (11 April 2024), transitioned to the European Clinical Trials Information System. LS remains underdiagnosed, which may limit recruitment. The results are of global interest and will be published in peer-reviewed journals and presented at scientific conferences.

ClinicalTrials.gov: NCT04920149. EudraCT: 2019-003011-55. EU CT: 2024-514765-19-01.