Cobitolimod for moderate-to-severe, left-sided ulcerative colitis (CONDUCT): a phase 2b randomised, double-blind, placebo-controlled, dose-ranging induction trial

Background: Cobitolimod is a topically administered, DNA-based oligonucleotide that activates Toll-like receptor 9 (TLR9), and previous research has shown clinical efficacy in patients with moderate-to-severe ulcerative colitis. Here we assessed the efficacy and safety of different dose regimens of cobitolimod for induction therapy in patients with moderate-to-severe, left-sided ulcerative colitis. Methods: CONDUCT was a randomised, double-blind, five-arm, placebo-controlled, dose-ranging phase 2b study that recruited patients with moderate-to-severe, left-sided ulcerative colitis, with inadequate response to conventional or biological therapies, from 91 hospitals or outpatient clinics in 12 European countries. Eligible patients had a Mayo score of 6–12 with a centrally read endoscopic subscore (modified to exclude friability from grade 1) of 2 or higher and no individual subscore of less than 1, and confirmation of left-sided disease. Patients were randomised (1:1:1:1:1; block size of ten) via a computer-generated schedule and centralised interactive voice and web response system to receive rectal enemas of cobitolimod at 31 mg, 125 mg, or 250 mg at weeks 0 and 3 (2 × 31 mg, 2 × 125 mg, and 2 × 250 mg groups), cobitolimod at 125 mg at weeks 0, 1, 2, and 3 (4 × 125 mg group), or placebo. Randomisation was stratified by current glucocorticosteroid and previous tumour necrosis factor inhibitor treatment. Patients and all study personnel were masked to treatment allocation. The primary endpoint was the proportion of patients achieving clinical remission (Mayo subscores for rectal bleeding of 0, for stool frequency of 0 or 1 [with ≥1-point decrease from baseline], and for endoscopy of 0 or 1 [excluding friability]) at week 6. The primary analysis (based on intention to treat) and safety analysis were done in all randomly assigned patients who received at least one dose of active study drug or placebo. In this exploratory study, statistical tests were one-sided; p values