Mumbai: Japanese drug maker Daiichi Sankyo will launch its open offer for an additional 20 per cent stake in Ranbaxy Laboratories on 16 August, Ranbaxy said in a filing with the Bombay Stock Exchange.

Tokyo-based Daiichi Sankyo, which agreed on 16 June to acquire 34.8 per cent from the Ranbaxy promoter group, had to delay the open offer, earlier scheduled for August 8, because of delay in getting clearance from the Securities and Exchange Board of India (SEBI).

Daiichi had made an open offer for acquiring up to 92.1 million shares, representing 20 per cent stake in Ranbaxy Laboratories, at a price of Rs737 each - the same rate it agreed to pay for the promoter shares.

The acquisition will cost Daiichi over Rs15,000 crore ($4.6 billion) and, on successful completion, the Japanese company would hold over 54.8 per cent stake in Ranbaxy, India's largest pharmaceutical company.

Together with the a portion of about $1 billion of preferential stock it agreed to acquire from the promoter group, Daiichi will hold over 58 per cent in Ranbaxy.

At Rs737 a share, Daiichi's open offer represents a premium of 53.5 per cent to Ranbaxy's average daily closing price on the National Stock Exchange for three-month ended 10 June.

The offer would expire on 4 September, instead of the previously scheduled 27 August, the filing added.

ICICI Securities is managing the open offer, while Nomura Securities is advising Daiichi Sankyo on the deal.

The Ranbaxy stock rose 0.5 per cent to Rs526.40 on the Mumbai market following the announcement of the open offer.