Pfizer has once again put back the expiration date of its tender offer to buy King Pharmaceuticals.

In October, the US drugs giant offered $3.60 billion in cash, or $14.25 per share, to buy King, a premium of some 40%. The offer was previously scheduled to expire at midnight tomorrow, and it is now scheduled to expire on January 21; this comes after another extension in November.

As of December 14, 2010, approximately 116.5 million shares of King's common stock had been tendered, representing 46.6% of its outstanding shares. All terms and conditions of the offer are unchanged, Pfizer noted.

The rationale behind the deal is to get access to King's pain drugs portfolio. The acquisition should be accretive to Pfizer earnings by $0.02 per share in 2011 and 2012, and bring cost savings of at least $200 million by the end of 2013.

Meantime, earlier this week, George Lorch, 68, who has served as an independent director since 2000, was elected as Pfizer's non-executive chairman. The appointment comes a week after the sudden departure of Jeff Kindler as chairman and chief executive.