Among the companies whose shares are expected to see active trade in Wednesday's session are Celgene Corp., RPM International and Guidant Corp.

After Tuesday's closing bell, Celgene Corp. (CELG) said the Food and Drug Administration has approved its drug Revlimid, and that Chief Executive John Jackson will retire on May 1 and be replaced by Sol Barer. Jackson will remain chairman, and Robert Hugin will take over from Barer as president and chief operating officer. The Summit, N.J.-based company said due to a later-than-expected FDA approval for Revlimid, it now sees 2005 earnings of 36 cents to 38 cents a share. Celgene also declared a 2-for-1 stock split with a record date of Feb. 17.

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Bristol-Myers Squibb's (BMY) rheumatoid-arthritis drug Orencia finally received U.S. regulatory approval.

Chesapeake Energy Corp. (CHK) said it has extended its offer to exchange its 6.5% senior notes due 2017 for any and all of its outstanding 6.5% senior notes due 2017 that were issued on Aug. 16 in a private offering. The offer had been scheduled to expire Dec. 23.

Guidant Corp. (GDT) received a warning letter from the Food and Drug Administration regarding a September inspection of its cardiac device manufacturing facility in St. Paul, Minn., the company said.

NRG Energy Inc. (NRG) said it has agreed to acquire Dynegy Inc.'s (DYN) 50% ownership interest in West Coast Power LLC, a joint venture with ownership in power plants totaling 1,800 megawatts in Southern California. In addition, NRG agreed to sell to Dynegy its 50% interest in Rocky Road Power LLC, a 330-megawatt, natural gas-fired peaking facility in East Dundee, Ill. NRG will pay Dynegy a net purchase price of $160 million. The transactions, which are conditioned upon one another and subject to approval from the Federal Energy Regulatory Commission, are expected to close in the first quarter, the company said.

Pfizer (PFE) said it bought a 12% stake in genomics firm Perlegen Sciences, marking its latest move to enter the emerging field of personalized medicine.

RPM International Inc. (RPM) said its earnings for the fiscal 2006 second quarter, excluding asbestos charges, will be below last year's due to effects associated with the Gulf Coast hurricanes. The specialty coatings company's outlook includes a charge of 5 cents a share in the quarter. Before charges related to asbestos liabilities, RPM said it expects quarterly per-share earnings of 22 cents to 24 cents, compared with 31 cents last year.

Weyerhaeuser Co. (WY) said it has reached agreements to settle all the remaining "opt out" cases in its linerboard antitrust litigation, except for one plaintiff. The Federal Way, Wash.-based forest products company said the settlements will result in an after-tax charge of $25 million, or 10 cents a share, in the fourth quarter. The settlements deal with cases brought by customers who elected to opt out of the class action lawsuit and pursued litigation on their own.