Oral deucrictibant for prophylaxis of hereditary angioedema attacks (CHAPTER-1): primary analysis of a randomised, double-blind, placebo-controlled, phase 2 trial

Background Hereditary angioedema is a bradykinin-mediated, rare condition characterised by recurrent and potentially life-threatening attacks of subcutaneous and submucosal swelling. Bradykinin B2 receptor antagonism is a proven mechanism for on-demand treatment of attacks, but no evidence exists on its effects when used prophylactically. Deucrictibant is an investigational orally bioavailable bradykinin B2 receptor antagonist. We aimed to evaluate the efficacy, safety, and tolerability of two dose regimens of oral deucrictibant administered as prophylaxis against hereditary angioedema attacks. Methods CHAPTER-1 was a multicentre, double-blind, placebo-controlled, randomised, phase 2 trial conducted in two parts, a double-blind placebo controlled first part and an open-label second part, with only part 1 reported here. Part 1 recruited adults (aged 18–75 years) with hereditary angioedema type 1 or 2 from 37 sites (university hospitals and accredited angioedema centres) across North America, Europe, and Israel. Patients required a documented history of three or more attacks within the last 3 consecutive months before screening or two or more during the screening period (up to 8 weeks) to be eligible. An interactive response technology system randomised eligible patients 1:1:1 to receive oral deucrictibant 20 mg daily, 40 mg daily, or matching placebo for 12 weeks. Randomisation to treatment groups was stratified by the baseline attack rate. Patients, investigators, site personnel, and the sponsor were blinded to treatment assignment. Masking was achieved with identically appearing deucrictibant and placebo capsules. The primary endpoint was the time-normalised number of investigator-confirmed attacks per 4 weeks (monthly attack rate) from weeks 1 to 12 and was assessed using the intention-to-treat set. The endpoint was analysed by comparing each deucrictibant group with the placebo group using a Poisson generalised linear model with a log link function and Pearson's χ 2 scaling of SEs to account for potential dispersion. The safety analysis set included all patients who were randomly assigned and who received one or more doses of study drug (deucrictibant or placebo). CHAPTER-1 is registered with ClinicalTrials.gov (NCT05047185) and is now complete. Findings Between March 9, 2022, and June 19, 2023, 44 patients were screened. Of 34 patients who were randomly assigned, 11 patients received deucrictibant 20 mg, 12 patients received deucrictibant 40 mg, and 11 patients received the placebo, with a median follow-up of 85·0 days (IQR 84·0–86·0). 21 (62%) patients were female, 13 (38%) were male, and 34 (100%) patients were White. The least squares mean monthly attack rate (primary analysis) was 0·40 (95% CI 0·18–0·92) for deucrictibant 20 mg, 0·30 (0·11–0·81) for deucrictibant 40 mg, and 1·93 (1·30–2·88) for placebo; percent reduction in attack rate compared with placebo was 79·2% (95% CI 47·2–91·8) for deucrictibant 20 mg (p=0·0010) and 84·5% (95% CI 53·8–94·8) for deucrictibant 40 mg (p=0·0008). Treatment-related treatment-emergent adverse events were experienced by two (18%) patients receiving deucrictibant 20 mg, one (8%) patient receiving deucrictibant 40 mg, and one (9%) patient receiving the placebo; all were mild in severity (grade 1) and did not require dosing modification of the study drug. There were no serious adverse events or deaths in any treatment group. Interpretation To the best of our knowledge, this trial provides the first clinical evidence and proof-of-concept for bradykinin B2 receptor antagonism as a therapeutic approach for the prevention of hereditary angioedema attacks and supports further investigation of oral deucrictibant for bradykinin-mediated angioedema. Funding Pharvaris.