Europe’s number one drugmaker Sanofi-Aventis says it is pulling back under its wing all Japanese rights to its anti-obesity and anti-smoking pill, Acomplia (rimonabant), from Astellas Pharma, under a move designed to strengthen the firm’s foothold in the country.

Astellas and Sanofi have agreed to speed up the transfer of rights to the drug, which is currently in Phase II clinical trials in Japan, from a joint venture between the two groups, and they expect this move to complete by June.

Acomplia is an important element in Sanofi-Aventis' strategy to overcome generic erosion of sales of some of its key players, including the antihistamine Allegra (fexofenadine), the diabetes drug Amaryl (glimepiride), Arava (leflunomide) for arthritis and DDAVP (desmopressin).

But earlier this year the group was forced to put back the drug’s expected launch after it received an approvable letter from the US Food and Drug Administration (FDA) requesting extra information on the agent, making a delay inevitable. A market introduction had been pencilled for the first half of this year but is now expected in the second half.

Sanofi certainly has high hopes for the product, recent clinical trials of which showed that it helped patients achieve a weight loss of 5% or more over two years, a "modest but sustained reduction in weight," according to the group. And overall, including both the weight loss and smoking cessation markets, Acomplia is expected to generate peak annual sales of around $3 billion.