Eli Lilly and Co and Incyte Corp said their experimental drug was effective in reducing painful symptoms associated with rheumatoid arthritis after 52 weeks of treatment.
The drug, baricitinib, is part of a new family of medicines called JAK inhibitors that block enzymes believed to be involved in the inflammatory process.
If approved, the pill will compete against injected rheumatoid arthritis drugs that currently dominate the market. Pfizer Inc's Xeljanz was the first such pill to hit the shelves last year.
Lilly and Incyte had released trial data on baricitinib last year after 12 and 24 weeks of treatment.
Lilly also started late-stage trials after the drug showed positive results after 24 weeks of treatment.
Patients who completed week 24 were eligible to receive either the 4 mg or 8 mg once daily dose through week 52.
Of the 196 patients in the study, 71 percent showed a 20 percent improvement in rheumatoid arthritis symptoms.
"In the long-term extension, the clinical improvements observed at week 24 were sustained through 52 weeks in (rheumatoid arthritis) patients," the companies said in a statement.
Rheumatoid arthritis is an autoimmune disorder that causes inflammation and damage to the joints and surrounding tissues.
Lilly shares closed at $51.78 on the New York Stock Exchange on Wednesday, while Incyte shares closed at $20.55 on the Nasdaq.
(Reporting by Pallavi Ail in Bangalore; Editing by Roshni Menon)