Ranbaxy Laboratories on Tuesday said that the open offer by the Japanese drug maker Daiichi Sankyo for acquiring an additional 20 per cent stake in it will commence on August 16.

Pursuant to the Securities and Exchange Board of India (Sebi) letter dated August 4, giving its observations on the draft letter of offer filed, the open offer would open on August 16, instead of earlier scheduled August 8, Ranbaxy Laboratories said in a filing to the Bombay Stock Exchange.

Daiichi's open offer price at Rs 737 per share represents a premium of 53.5 per cent to Ranbaxy's average daily closing price on the National Stock Exchange for three-month ended June 10, the Japanese firm had earlier said in a statement.

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

Last week, Daiichi Sankyo had deferred its open offer following delay in regulatory approvals. While, yesterday the Japanese drug maker had received approvals from the market regulator SEBI and Foreign Investment Promotion Board for the acquisition of 34.8 per cent stake in the Ranbaxy.

Earlier on June 16, Daiichi, which had agreed to acquire the promoters' 34.8 per cent stake in Ranbaxy, had made an open offer for acquiring up to 9.21 crore shares, representing 20 per cent stake at a price of Rs 737 each.

On successful completion, Daiichi would hold over 58.09 per cent stake in Ranbaxy. ICICI Securities is the manager to the offer.

Daiichi had announced the acquisition of a majority stake of more than 50 per cent in Ranbaxy for over Rs 15,000 crore. The acquisition is expected to complete by March 2009.

Post acquisition, Ranbaxy would continue to be listed in India. Shares of Ranbaxy were trading at Rs 524.45, up 0.09 per cent in the morning trade on the BSE.