Treatment of mildly to moderately active ulcerative colitis with a tryptase inhibitor (APC 2059): an open-label pilot...

Mast cells isolated from the colonic mucosa in active ulcerative colitis appear to be partially degranulated, suggesting the release of tryptase.

To investigate the safety and activity of APC 2059, a highly specific tryptase inhibitor, in the treatment of ulcerative colitis.

This was an open-label, Phase 2, multicentre pilot study in patients with mildly to moderately active ulcerative colitis, with a disease activity index of 6-9 on a 12-point scale. Fifty-six adults received 20 mg APC 2059 subcutaneously twice daily and 53 completed 28 days of treatment. The primary end-point was response, defined as a final disease activity index of < or = 3. Supplementary analyses were also performed.

Sixteen (29%) of 56 patients responded. Five (9%) showed complete remission (disease activity index=0). Twenty-seven (49%) improved, with a final disease activity index of < or = 3 or a four-point reduction. Improvement or normalization in each category of the disease activity index was as follows: stool frequency, 64%; bleeding, 64%; endoscopy, 50%; physicians' rating, 63%. There were no significant relationships between outcome and pharmacokinetics. The most common adverse events were related to the injection site (32.1%).

In this pilot study, the tryptase inhibitor APC 2059 was safe and there was evidence of activity in the treatment of ulcerative colitis.