sanofi-aventis is to retrieve all rights to its anti-obesity pill Acomplia in Japan from Astellas Pharma as part of its aim to strengthen its presence in the country, the world's third largest drugmaker said here.

Astellas, Japan's second largest drugmaker, and France's sanofi agreed to accelerate the transfer of rights from a joint-venture between the two companies. The transfer will be implemented by June, sanofi said in a statement.

Acomplia, also known as rimonabant and sanofi's biggest drug hope, is subject to marketing approval in the United States and Europe. In Japan, rimonabant is in phase IIB clinical trials.

sanofi has said it expects to launch the drug in the second half of this year, later than it had originally hoped after the US health authority asked Sanofi for extra information on the treatment and rejected it as an anti-smoking aid.

sanofi has estimated that Acomplia could yield annual sales of about $3 billion as studies showed it also helps lower blood sugar levels in obese diabetics and boost good HDL cholesterol which helps lower the risk of cardiovascular diseases.