A multicenter randomized, double-blind, placebo-controlled pilot study to assess the efficacy and safety of riociguat in systemic sclerosis-associated digital ulcers

Background To determine the effect of riociguat, an oral, selective soluble guanylate cyclase stimulator, on the net digital ulcer (DU) burden in systemic sclerosis (SSc). Methods Participants with SSc-related active or painful indeterminate DUs were recruited in a multicenter, double-blind, randomized, placebo-controlled, proof-of-concept trial. Eligible participants were required to have at least one visible, active ischemic DU or painful indeterminate DU at screening, located at or distal to the proximal interphalangeal joint and that developed or worsened within 8 weeks prior to screening. Participants were randomized 1:1 to placebo or riociguat in individualized doses (maximum of 2.5 mg three times daily) during an 8-week titration period, followed by an 8-week stable dosing period. This was followed by an optional 16-week open-label extension phase for participants with active DU/reoccurrence of DUs within 1 month of the end of the main treatment phase. The primary endpoint was the change from baseline to week 16 in net ulcer burden (NUB), analyzed using ANCOVA. Other endpoints included plasma biomarkers and proportion of participants with treatment-emergent adverse events (AEs). Results Seventeen participants (eight placebo, nine riociguat) were randomized at five centers. Six participants in each group transitioned to the open-label extension. Baseline characteristics were comparable between the treatment groups, except participants randomized to placebo were older and had longer disease duration (p < 0.05). At baseline, the mean (SD) NUB was 2.5 (2.0) in the placebo and 2.4 (1.4) in the riociguat. No significant treatment difference was observed in the change from baseline to 16 weeks in NUB (adjusted mean treatment difference - 0.24, 95% CI (- 1.46, 0.99), p = 0.70). Four participants experienced five serious AE (four in riociguat and one in placebo); none was considered related to study medication. Statistically significant elevation of cGMP was observed at 16 weeks in the riociguat group (p = 0.05); no other biomarkers showed significant changes. In the open-label extension, participants in the riociguat-riociguat arm had complete healing of their DUs. Conclusion In participants with SSc-DU, treatment with riociguat did not reduce the number of DU net burden compared with placebo at 16 weeks. Open-label extension suggests that longer duration is needed to promote DU healing, which needs to be confirmed in a new trial.