Randomised clinical trial: a phase 1b study of GB004, an oral HIF‐1α stabiliser, for treatment of ulcerative colitis

Summary Background Epithelial barrier dysfunction contributes to a dysregulated intestinal immune response in ulcerative colitis (UC). GB004 is an orally administered, small molecule, gut‐targeted stabiliser of hypoxia‐inducible factor‐1α, a transcription factor with protective roles at the epithelial layer of the inflamed gut. Aims To evaluate safety, pharmacokinetics, pharmacodynamics and efficacy of GB004 in patients with active UC. Methods This double‐blind, placebo‐controlled study randomised patients 2:1 to receive an oral solution of GB004 120 mg or placebo once daily for 28 days. Eligible patients had a Robarts Histopathology Index score ≥4 with neutrophils in the epithelium, total Mayo Clinic score 3‐12, Mayo Clinic endoscopic subscore ≥1, and blood in the stool, despite treatment with 5‐aminosalicylates, corticosteroids or immunosuppressants. Results Thirty‐four patients were randomised. GB004 120 mg for 28 days was generally well‐tolerated. Adverse events occurred in 27.3% (3/11) and 39.1% (9/23) of patients in the placebo and GB004 groups respectively. Nausea and dysgeusia were most commonly reported in the GB004 group (0% for placebo and 21.7% [5/23] and 13.0% [3/23] respectively for GB004). There were no treatment‐related serious adverse events or deaths. GB004 exhibited minimal accumulation, with higher colonic concentrations relative to plasma. Exploratory pharmacodynamic and efficacy analyses demonstrated GB004 target engagement and numerically higher proportions of patients achieving improvement in multiple measures of disease activity, respectively, at day 28 for GB004 compared to placebo. Conclusion Results from this phase 1b trial support evaluation of the full therapeutic potential of GB004 for the treatment of UC. A phase 2 study (NCT04556383) is ongoing. Clinicaltrials.gov NCT03860896. Defective barrier function is believed to be central to the pathogenesis of inflammatory bowel disease. GB004 is an orally administered, small molecule, gut‐targeted stabiliser of hypoxia‐inducible factor‐1α, a transcription factor with protective roles at the epithelial layer of the inflamed gut. In this phase 1b (NCT03860896), first‐in‐patient study involving patients with ulcerative colitis (UC), GB004 was well tolerated and exhibited low systemic exposure. Exploratory biomarker and efficacy results support the biologic relevance and therapeutic potential of this novel approach for the treatment of UC.