Pfizer Inc. (PFE) and Wyeth (WYE) have agreed to settle shareholder lawsuits that sought to rescind the drug makers' merger agreement, Wyeth said Thursday.

In a regulatory filing, Wyeth said lawsuits seeking class-action status were filed in the Delaware Court of Chancery and in federal and state court in New Jersey against Wyeth and members of its board of directors. The suits sought to invalidate Wyeth's January agreement to be acquired by Pfizer in a cash-and-stock deal then valued at about $68 billion.

In June, Wyeth and Pfizer reached an agreement in principle to settle the Delaware case, agreeing to include additional details about the deal in regulatory filings.

Wyeth and Pfizer continue to deny they have violated the law as alleged in the lawsuits, and they struck the settlement to avoid a delay in closing the deal, Wyeth said in its regulatory filing.

The deal is expected to close late in the third quarter or in the fourth quarter. The settlement is subject to approval by the Delaware Court of Chancery and other conditions.

Last month, Schering-Plough Corp. (SGP) and Merck & Co. (MRK) similarly reached settlements to end litigation by shareholders that sought to block Schering's takeover by Merck.

Separately, Wyeth disclosed it intends to file a lawsuit against generic manufacturer Apotex Inc. because Apotex filed for U.S. Food and Drug Administration approval to sell a generic version of Wyeth's Protonix heartburn drug before the patent expires. Sales of Protonix already have been hurt by the availability of generic versions in the U.S. from other companies.

Also, Wyeth said it reached a settlement of patent litigation with Wockhardt Ltd. (532300.BY) that allows Wockhardt to sell generic versions of antidepressant Effexor in June 2012, subject to earlier launch under limited circumstances but no earlier than January 2011. Wockhardt will pay Wyeth a percentage of profit from sales of the drug.

-By Peter Loftus, Dow Jones Newswires; 215-656-8289; peter.loftus@dowjones.com