A subsidiary of Abbott Laboratories has started a cash tender offer for Facet Biotech Corp., the drug and medical products company said Tuesday.

Earlier this month, Abbott said it had agreed to buy Facet for about $450 million in cash, in order to increase expanding its access to biotechnology drugs, including a potential treatment for multiple sclerosis.

Abbott is offering $27 per share, a 67 percent premium to Facet's $16.21 closing stock price on March 9, the day the deal was announced.

The acquisition has been approved by both companies' boards and is expected to close in the second quarter.

Abbott, based in North Chicago, Ill., has valued the deal at about $722 million, less Facet's projected cash and marketable securities at closing of approximately $272 million.

Abbott's buyout follows last December's rejection by Facet shareholders of a bid worth $17.50 per share for the company by Biogen Idec.

Abbott's tender offer is being made by Amber Acquisition Inc. and is set to expire on April 19 unless extended. There is no financing condition tied to the tender offer.

Shares of Facet, based in Redwood City, Calif., were down a penny at $26.97 in morning trading. Abbott shares slipped 2 cents to $53.85.