UPDATED: FDA advisers sign off on Pfizer's arthritis pill

Pfizer took one step closer to an FDA approval of a potential blockbuster. Today an FDA advisory committee endorsed the company's drug, tofacitinib, as a safe and effective treatment for patients with rheumatoid arthritis. Yet there are plenty of doubts about whether the agency will take the recommendation.  

The Arthritis Drug Advisory Committee voted 8-2 in favor of approval of the experimental arthritis pill, which could become the first disease-modifying oral drug against the autoimmune disorder in more than a decade and the first JAK inhibitor to hit the U.S. market for this disease, according to Pfizer ($PFE). The company has asked for approval for the drug as a second option for the thousands of RA patients who don't respond to existing injectable meds such as Abbott's ($ABT) Humira and Amgen's ($AMGN) Enbrel. The FDA action date for the application is in August.

Pfizer has a lot riding on the approval of tofacitinib. The U.S. drug giant has lost exclusivity for the mega-blockbuster Lipitor, U.S. sales of which fell by 71% in the first quarter. Tofacitinib is among a handful of prospects in the company's pipeline that could bring more than $1 billion in annual sales and help replace declines in Lipitor revenue. Several analysts estimate sales of the drug to hit $1 billion or more by 2015 if approved this year.

Yet the FDA could spoil Pfizer's blockbuster plans for the drug. The agency's staff reported this week that there were more cases of cancer and infections in patients who took the drug in studies, and they noted that the X-ray method used to measure the impact of the drug on patients' disease wasn't sufficient for the agency to judge the efficacy of the treatment. However, the arthritis panel of non-agency experts voted unanimously that the efficacy of the drug was sufficient for approval. 

"The committee ultimately viewed the safety profile of tofacitinib as acceptable; however, several panelists suggested that tofacitinib should be approved for use in patients who have failed other available treatment options, including anti-TNF inhibitors," analysts at Cowen wrote in a note to investors today. "We continue to expect tofacitinib to be approved in aTNF-refractory patients for whom there is still a great unmet medical need."

Pfizer has plenty of opponents in race to develop new oral RA meds. Behind Pfizer, Eli Lilly ($LLY) and Incyte ($INCY) are developing a rival JAK inhibitor for treating RA, and AstraZeneca ($AZN) and Rigel ($RIGL) are in late-stage development of an oral med to combat the disease. Pfizer was predictably upbeat about its own program after today's panel nod.

"We are pleased with the Committee's positive evaluation of the tofacitinib data and its decision to recommend approval," Dr. Yvonne Greenstreet, senior vice president and the head of Medicines Development Group for Pfizer Specialty Care, said in a statement. "The RA patient population needs additional treatment options, and Pfizer looks forward to working with the FDA on next steps as it completes its review of the tofacitinib application."

- here's Pfizer's release
- check out Reuters' report
- see the Wall Street Journal's article

UPDATED: Added additional details about FDA review of tofacitinib, analyst comments and other aspects of the program.