Accro Bioscience has dosed its first patient in a Phase IIb trial of AC-101, a selective RIPK2 inhibitor, for moderate-to-severe ulcerative colitis, setting up a 12-week clinical remission readout across roughly 50 sites. The mechanism is the bet worth watching: AC-101 targets the NOD/RIPK2 signaling pathway, which sits upstream of the inflammatory cascade rather than blocking a single cytokine or integrin. That separates it from the biologics that already crowd this space, including agents like vedolizumab, infliximab, and adalimumab, though whether a different pathway translates to better outcomes for patients who fail those agents is exactly what the IIb needs to answer.
The trial uses a three-arm design: two AC-101 dose cohorts against placebo, with clinical remission at Week 12 as the primary endpoint. Exploratory endpoints extend further, tracking histologic remission and whether remission holds during long-term treatment. That second layer matters because ulcerative colitis patients who achieve endoscopic remission but not mucosal healing tend to relapse faster. Including histology as an exploratory endpoint suggests Accro is already building toward a durability argument, not just an induction signal.
The Phase IIb does not arrive blind. Accro completed a Phase Ib proof-of-concept study in Chinese patients with moderate-to-severe UC, and those efficacy and safety results will be presented at UEG Week 2026 in Barcelona this October. Timing matters: the IIb’s enrollment is now open while the field gets its first look at AC-101’s Phase Ib data. A clean signal there will shape how investigators and potential partners read the larger trial. AC-101 also completed Phase I studies in healthy participants in both Australia and China with a favorable safety and pharmacokinetic profile, so the dose-selection rationale for the two IIb cohorts rests on a reasonably characterized base.
The ACG’s updated UC guidelines still anchor induction on corticosteroids and advanced therapies for moderate-to-severe disease, a standard that leaves real gaps for patients who cycle through biologics without durable remission. Whether AC-101 fills any of that gap comes down to what the Week 12 remission rates show across both dose arms versus placebo.
Jon Napitupulu is Director of Media Relations at The Clinical Trial Vanguard. Jon, a computer data scientist, focuses on the latest clinical trial industry news and trends.
