Solabegron (GW-427,353) is a drug which acts as a selective agonist for the β3 adrenergic receptor. It is being developed for the treatment of overactive bladder and irritable bowel syndrome. It has been shown to produce visceral analgesia by releasing somatostatin from adipocytes.,

Solabegron was discovered by GlaxoSmithKline and acquired by AltheRx in March 2011. Solabegron relaxes the bladder smooth muscle by stimulating beta-3 adrenoceptors, a novel mechanism compared to older established drug treatments for overactive bladder syndrome such as the anticholinergic agents. Astellas Pharma have developed the first commercially available β3 adrenergic receptor, mirabegron, which is now licensed in Japan and the US for overactive bladder. Mirabegron is not licensed for irritable bowel syndrome.

A Phase II study of Solabegron for overactive bladder (OAB) looked at 258 patients with moderate to severe incontinence experiencing an average of 4.5 wet episodes per day. Results demonstrated a statistically significant improvement with Solabegron as compared to placebo, as measured by the percent reduction of the number of wet episodes and the absolute number of daily voids.

A Phase II study for irritable bowel syndrome (IBS) evaluated 102 patients with IBS. Solabegron demonstrated significant reduction in pain associated with the disorder and a trend for greater improvement in the quality of life, compared to placebo.

Both Phase II studies indicated a tolerability profile for Solabegron that was similar to placebo. The OAB patients did not suffer from dry mouth, constipation, increase in heart rate or cognitive issues.

AltheRx is currently preparing to advance Solabegron into a large clinical study in OAB.

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