(Adds comments from AbbVie, analysts; details, updates shares)
Sept 11 (Reuters) - AbbVie Inc said on Monday two patients died in a late-stage trial of its rheumatoid arthritis drug but that the deaths were not linked to the drug, which met the study's main goals.
The trial was evaluating two doses of the drug upadacitinib - 15 mg and 30 mg - in patients with moderate to severe rheumatoid arthritis, who did not adequately respond to or were intolerant to other anti-rheumatic drugs.
Upadacitinib, a once-daily pill, belongs to a class of drugs known as JAK inhibitors, which block inflammation-causing enzymes called Janus kinases and are being used to treat rheumatoid arthritis among other diseases.
Rheumatoid arthritis, a chronic inflammatory disease in which the immune system attacks tissues in the joints, affects more than 23 million people.
"Following the second positive phase 3 trial ... we believe this drug has the potential to be the best-in-class JAK inhibitor. We remain comfortable with its safety profile, " Jefferies analyst Jeffrey Holford wrote in a client note.
If approved, Upadacitinib could reduce AbbVie's dependence on its flagship rheumatoid arthritis treatment Humira, which generated more than $16 billion in sales last year.
The drugmaker said the reason for one of the deaths was unknown, while the second patient died due to heart failure and presumed pulmonary embolism, or blood clots in the lungs.
"At the time of initial report, both events were considered by the investigator as having no reasonable possibility of being related to the study drug," AbbVie's spokeswoman Jillian Griffin told Reuters.
Eli Lilly and Co's rival rheumatoid arthritis drug, baricitinib, also a JAK inhibitor, hit a roadblock in April when the U.S. Food and Drug Administration declined to approve it, calling for an additional clinical study.
Three months later, Lilly said the FDA was concerned about a small, but increased number of potentially dangerous blood clots seen in baricitinib patients in clinical trials, outlining a likely multi-year delay for the drug.
Pfizer Inc's Xeljanz is the only approved JAK inhibitor in the United States to treat rheumatoid arthritis.
AbbVie's shares were marginally down in morning trading on Monday. (Reporting by Divya Grover in Bengaluru; Editing by Shounak Dasgupta and Saumyadeb Chakrabarty)