UK drugmaker Alizyme is set to kick off a Phase III programme for its obesity drug cetilistat after concluding discussions with the US Food and Drug Administration.

The agency has accepted its plan for a pivotal trial of cetilistat looking at the compound’s role in the treatment of weight-gain in patients with type 2 diabetes.

The drug’s safety and efficacy in this setting were demonstrated in a recently-completed Phase II programme involving patients in Europe, Japan and the USA.

The Phase III programme will recruit around 4,000 patients and look at treatment with the drug for one year in a series of placebo-controlled studies. It is scheduled to start in the first half of 2007.

The primary endpoint in the study will be the proportion of patients losing at least 5% of their body weight compared to placebo, while absolute weight loss will also be measured.

Alizyme said that the safety and efficacy of cetilistat has been established in Phase I and II trials. The drug demonstrated a similar level of efficacy to Roche's Xenical (orlistat), it added, but has a more favourable tolerability profile.

Xenical’s initial promise as a blockbuster failed to materialise because of some side effect problems, but the drug has still been a useful earner for Roche. It brought in sales of 363 million Swiss francs in the first half of this year, a rise of 12% after a period of flagging sales growth. Last year’s tally for the drug was 635 million francs, a rise of 5% over 2004.

But the big question mark for prescription sales of Xenical, as well as the future potential of cetilistat, will come after GlaxoSmithKline launches an over-the-counter version of orlistat under the Alli brand, an event scheduled for later this year.

In January, an FDA advisory committee recommended approval of orlistat 60mg capsules as an OTC weight-loss medication, to be used three times daily in combination with a low-fat diet in adults, and the agency granted the application ‘approvable’ status in April. GSK already co-promotes Roche's Xenical 120mg as a prescription product alongside Roche in the USA.