Clinical Data William Sandborn, M.D., Chief of the Division of Gastroenterology of University of California San Diego, presented data at the UEGW Virtual Week 2020 from the successful Phase 1b translational medicine study of GB004 in mild-to-moderate ulcerative colitis, or UC.The Phase 1b study evaluated safety, tolerability, and pharmacokinetics over 4 weeks of treatment in patients with active UC despite treatment with 5-aminosalicylate (5-ASA) therapy. In addition to trends disclosed earlier this year, the presentation included newly disclosed data on the reduction of an important inflammatory biomarker in IBD, fecal calprotectin, and the resolution of rectal bleeding, which is considered to be an objective measure of disease activity.

GB004’s differentiated mechanism of action was also highlighted in a second poster summarizing data from two pre-clinical studies. In a human monolayer assay, GB004 demonstrated superior protection of barrier integrity compared to tofacitinib, a pan-JAK inhibitor approved for the treatment of moderate-to-severe UC. In a separate mouse organoid study, GB004 induced HIF-1α-dependent genes, including barrier function genes such as Claudin 1, which were elevated in patients in the Phase 1b trial, further validating GB004’s mechanism of action.Gossamer has begun screening patients in a global Phase 2 study of GB004 in patients with active ulcerative colitis despite treatment with 5-ASA (NCT04556383). Up to 195 subjects are expected to be enrolled, randomized evenly across two dose arms of GB004 and placebo.
The primary endpoint of the study is clinical remission at week 12. Patients will continue blinded treatment through week 36, after which they will have the option to roll onto an open-label extension. Additional endpoints such as mucosal healing, histologic remission, clinical response, and disease clearance also will be assessed.