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.