NEW YORK (AP) — Pfizer Inc. said Thursday its experimental oral treatment for rheumatoid arthritis has met key goals in two midstage studies by improving tender and swollen joints. In a study involving 384 participants, various doses of the CP-690,550 drug candidate prompted responses in 49 percent to 75 percent of patients, compared with 28.8 percent of patients taking placebo. Another study involving 136 patients yielded similar results. “This compound could represent a promising advance in rheumatoid arthritis treatment for patients who need an alternative to currently available therapies,” said Dr. Michael Berelowitz, Pfizer’s senior vice president of clinical development and medical affairs for the specialty care unit. While the drug is still years away from market, it could eventually become a key competitor to several blockbuster treatments. A key advantage would be that it is taken orally, instead of injected like current treatments such as Abbott Laboratories’ Humira, Johnson & Johnson’s Remicade, and Wyeth and Amgen Inc.’s Enbrel. Enbrel topped all others in 2008 with sales of $3.4 billion. Belgian drug developer UCB recently gained approval for its injectable treatment Cimzia. It has already been approved to treat gastrointestinal Crohn’s disease. The Pfizer results were presented at the 10th annual congress of the European League Against Rheumatism in Copenhagen. The main results are taken from a 12-week analysis of a six-month study and confirm prior positive midstage study data, the company said. Pfizer is also currently conducting a late-stage clinical trial on the drug candidate.