GSK2586184, a JAK1 selective inhibitor, in two patients with ulcerative colitis.

Tofacitinib, a non-selective Janus kinase (JAK) inhibitor, is effective in inducing clinical and endoscopic remission in patients with active ulcerative colitis (UC). Tofacitinib inhibits cytokine signalling through blockade of JAK1, JAK2, JAK3 and tyrosine kinase 2 (TYK2). Adverse events including neutropenia and anaemia resulting from JAK2 inhibition have been observed in actively treated patients. By selectively targeting JAK1, such adverse events could be expected to be avoided. This open label study was designed to enrol 15 patients with UC, however the trial was discontinued after two inclusions due to safety concerns with the agent in a parallel trial for systemic lupus erythematosus. GSK2586184 was administered in two patients with moderate-to-severe UC. The JAK1 selective inhibitor GSK2586184 was well tolerated and induced clinical and endoscopic response in two patients with moderate-to-severe UC. In addition, treatment with GSK2586184 decreased histology scores and faecal calprotectin levels at early withdrawal.