Efficacy and safety of setmelanotide, a melanocortin-4 receptor agonist, in patients with Bardet-Biedl syndrome and Alström syndrome: a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial with an open-label period

Abstract

Background: Impaired cilial signalling in the melanocortin-4 receptor (MC4R) pathway might contribute to obesity in patients with Bardet-Biedl syndrome and Alström syndrome, rare genetic diseases associated with hyperphagia and early-onset severe obesity. We aimed to evaluate the effect of setmelanotide on bodyweight in these patients.

Methods: This multicentre, randomised, 14-week double-blind, placebo-controlled, phase 3 trial followed by a 52-week open-label period, was performed at 12 sites (hospitals, clinics, and universities) in the USA, Canada, the UK, France, and Spain. Patients aged 6 years or older were included if they had a clinical diagnosis of Bardet-Biedl syndrome or Alström syndrome and obesity (defined as BMI >97th percentile for age and sex for those aged 6-15 years and ≥30 kg/m² for those aged ≥16 years). Patients were randomly assigned (1:1) using a numerical randomisation code to receive up to 3·0 mg of subcutaneous setmelanotide or placebo once per day during the 14-week double-blind period, followed by open-label setmelanotide for 52 weeks. The primary endpoint, measured in the full analysis set, was the proportion of patients aged 12 years or older who reached at least a 10% reduction in bodyweight from baseline after 52 weeks of setmelanotide treatment. This study is registered with ClinicalTrials.gov, NCT03746522.

Findings: Between Dec 10, 2018, and Nov 25, 2019, 38 patients were enrolled and randomly assigned to receive setmelanotide (n=19) or placebo (n=19; 16 with Bardet-Biedl syndrome and three with Alström syndrome in each group). In terms of the primary endpoint, 32·3% (95% CI 16·7 to 51·4; p=0·0006) of patients aged 12 years or older with Bardet-Biedl syndrome reached at least a 10% reduction in bodyweight after 52 weeks of setmelanotide. The most commonly reported treatment-emergent adverse events were skin hyperpigmentation (23 [61%] of 38) and injection site erythema (18 [48%]). Two patients had four serious adverse events (blindness, anaphylactic reaction, and suicidal ideation); none were considered related to setmelanotide treatment.

Interpretation: Setmelanotide resulted in significant bodyweight reductions in patients with Bardet-Biedl syndrome; however, these results were inconclusive in patients with Alström syndrome. These results support the use of setmelanotide and provided the necessary evidence for approval of this drug as the first treatment for obesity in patients with Bardet-Biedl syndrome.

Funding: Rhythm Pharmaceuticals.

Figure 1.

Disposition of pivotal and supplemental patients with BBS and Alström syndrome. BBS, Bardet-Biedl syndrome. ^aSafety analysis set includes patients who received ≥1 dose of study drug (setmelanotide or placebo). ^bPlacebo-controlled analysis set includes randomized patients who received ≥1 dose of placebo or setmelanotide and had baseline data. ^cFull analysis set includes randomized patients who received ≥1 dose of setmelanotide and had baseline data.

Figure 2.

(A) Body weight percent change in the exploratory cohort of patients with BBS ≥18 years old (n=15). (B) Body mass index Z score absolute change in pivotal patients with BBS <18 years old (n=16). ATB, active treatment baseline (defined as last measurement before the first dose of setmelanotide; ie, Week 0 for setmelanotide group and Week 14 for placebo group). ^aData shown by study visit do not include data imputed for patients who received <52 weeks of setmelanotide at time of analysis. ^bPopulation sizes ranged from 7 to 15, with n=12 at 52 weeks on active treatment. ^cPopulation sizes ranged from 8 to 16, with n=14 at 52 weeks on active treatment. Error bars are the standard deviation.