In what is rapidly developing as a new trend that could have a major impact on generic manufacturers, Pfizer says it will introduce a copycat version of the antidepressant Zoloft that will be priced below generics. The move follows Merck's announcement that it plans to roll out a cheap copycat of the blockbuster cholesterol drug Zoloft. Drug makers have become increasingly aggressive in their response to the onslaught of generic competition. In Pfizer's case, the company has a subsidiary that is rolling out the cut-rate drugs. That goes one step beyond the typical "authorized generic" that has emerged to compete for the market after a drug loses patent protection. And it represents a lethal brand of competition for generic makers who are also hard pressed by fierce competition. Insurers, meanwhile, are likely to love the price war. Article (WSJ sub. req.)