Efficacy and safety of linaclotide in treating functional constipation in paediatric patients: a randomised, double-blind, placebo-controlled, multicentre, phase 3 trial.

Background: Linaclotide, a guanylate cyclase C agonist, has been approved in the USA for the treatment of chronic idiopathic constipation and irritable bowel syndrome with predominant constipation in adults. We aimed to assess the efficacy and safety of linaclotide in paediatric patients aged 6-17 years with functional constipation.

Methods: This randomised, double-blind, placebo-controlled, multicentre, phase 3 study was done at 64 clinic or hospital sites in seven countries (USA, Canada, Israel, Italy, the Netherlands, Ukraine, and Estonia). Patients aged 6-17 years who met modified Rome III criteria for functional constipation were randomly assigned (1:1), with a block size of four and stratified by age (6-11 years and 12-17 years), to receive either oral linaclotide 72 μg or placebo once daily for 12 weeks. Participants, investigators, and data assessors were masked to assignment. The primary efficacy endpoint was change from baseline (CFB) in the 12-week frequency rate of spontaneous bowel movements (SBMs; occurring in the absence of rescue medication on the calendar day of or before the bowel movement) per week and the secondary efficacy endpoint was CFB in stool consistency over the 12-week treatment period; efficacy and safety were analysed in all patients in the randomised population who received at least one dose of study intervention (modified intention-to-treat population and safety population, respectively). The study is registered with ClinicalTrials.gov, NCT04026113, and the functional constipation part of the study is complete.

Findings: Between Oct 1, 2019, and March 21, 2022, 330 patients were enrolled and randomly assigned to linaclotide (n=166) or placebo (n=164). Two patients in the linaclotide group did not receive any treatment; thus, efficacy and safety endpoints were assessed in 328 patients (164 patients in each group). 293 (89%) patients completed the 12-week treatment period (148 in the linaclotide group and 145 in the placebo group). 181 (55%) of 328 patients were female and 147 (45%) were male. At baseline, the mean frequency rate for SBMs was 1·28 SBMs per week (SD 0·87) for placebo and 1·16 SBMs per week (0·83) for linaclotide, increasing to 2·29 SBMs per week (1·99) for placebo and 3·41 SBMs per week (2·76) for linaclotide during intervention. Compared with placebo (least-squares mean [LSM] CFB 1·05 SBMs per week [SE 0·19]), patients treated with linaclotide showed significant improvement in SBM frequency (LSM CFB 2·22 SBMs per week [0·19]; LSM CFB difference 1·17 SBMs per week [95% CI 0·65-1·69]; p<0·0001). Linaclotide also significantly improved stool consistency over placebo (LSM CFB 1·11 [SE 0·08] vs 0·69 [0·08]; LSM CFB difference 0·42 [95% CI 0·21-0·64]; p=0·0001). The most reported treatment-emergent adverse event (TEAE) by patients treated with linaclotide was diarrhoea (seven [4%] of 164 vs three [2%] of 164 patients in the placebo group) and by patients treated with placebo was COVID-19 (five [3%] vs four [2%] in the linaclotide group). The most frequent treatment-related TEAE was diarrhoea (linaclotide: six [4%] patients; placebo: two [1%] patients). One serious adverse event of special interest (treatment-related severe diarrhoea resulting in dehydration and hospitalisation) occurred in a female patient aged 17 years in the linaclotide group; this case resolved without sequelae after administration of intravenous fluids. No deaths occurred during the study.

Interpretation: Linaclotide is an efficacious and well tolerated treatment for functional constipation in paediatric patients and has subsequently been approved by the US Food and Drug Administration for this indication.

Funding: AbbVie and Ironwood Pharmaceuticals.