Niclosamide Enema for Active Distal Ulcerative Colitis: A Phase 1, Open-Label Study

Oral and rectal formulations of 5-aminosalicylic acid are the first-line therapy for mild-to-moderate, distal ulcerative colitis (UC), but such a treatment is not effective in one-third of patients. Niclosamide is a small molecule, developed and approved as an orally administered drug to treat helminthic infections, with an excellent safety profile. Preclinical work showed that niclosamide is an anti-inflammatory agent, thereby providing the rationale to explore its safety and efficacy in patients with UC. This phase 1, open-label trial was aimed at assessing the safety of niclosamide formulated as an enema in patients with mild-to-moderate, distal UC, who relapsed on maintenance therapy with oral and/or rectal 5-aminosalicylic acid.

Seventeen patients with active UC received niclosamide enema (150 mg/60 mL) twice a day for 6 weeks. The primary endpoint was the safety of niclosamide treatment. Secondary endpoints included clinical remission and improvements in endoscopic Mayo/histologic scores. Endoscopic remission percentages exclude participants meeting criteria at baseline for endoscopic remission.

Niclosamide was well tolerated by all 17 patients that were enrolled and treated. No serious adverse event was registered. Fifteen mild adverse events were registered in 6 patients and considered to be unrelated to the treatment. Clinical remission was achieved in 10 (59%) of 17 patients. Improvements of endoscopic Mayo score and histologic Geboes score were seen in 7 (58%) of 12 and 7 (41.2%) of 17 patients, respectively.

Niclosamide enema treatment is safe and well tolerated. Niclosamide improves clinical symptoms and endoscopic/histologic signs of UC; however, appropriately designed placebo-controlled clinical trials are required to confirm efficacy.