Lexicon Pharmaceuticals has successfully completed a Phase I clinical trial of LX1033, an orally-delivered small molecule drug candidate for the treatment of diarrhoea-predominant irritable bowel syndrome.

LX1033 is designed to act locally in the gastrointestinal tract by reducing the serotonin available for receptor activation without affecting serotonin levels in the brain.

Study endpoints included safety and tolerability together with pharmacokinetic and pharmacodynamic parameters consisting of measures of both plasma and urinary 5-hydroxyindoleacetic acid biomarker.

The randomised, placebo-controlled trial, which involved eight healthy volunteers, showed that LX1033 was safe and well tolerated at all doses and produced a significant reduction in serotonin synthesis compared to placebo, as measured by both plasma and urinary 5-hydroxyindoleacetic acid.

Lexicon now plans to move LX1033 forward in to a Phase II study in patients with diarrhoea-predominant irritable bowel syndrome.