Pfizer has been boosted by the news that its investigational rheumatoid arthritis drug tofacitinib has met its primary endpoints in another late-stage trial.

The latest data on the drug, formerly known as tasocitinib, comes from the second of six Phase III studies being conducted on the novel, oral Janus kinase (JAK) inhibitor. The top-line results reveal that tofacitinib met its primary endpoints by showing statistically significant changes versus placebo in reducing signs and symptoms of RA after six months.

The drug also improved physical function at three months and demonstrated significantly greater disease remission at six months. The safety profile of tofacitinib was consistent with that seen previously in the clinical programme, and no new signals were detected. A full analysis of data will be submitted to a future scientific meeting.

The data comes four months after the first trial showed that tofacitinib showed signifcant response rates and improved physical functionality. Results from the other four studies are expected soon and Pfizer noted that orally administered tofacitinib is also being studied in psoriasis, renal transplant, Crohn’s disease and ulcerative colitis; a topical formulation is being investigated in psoriasis and dry eye disease.

Analysts believe that if approved, tofacitinib could be a big earner, with sales in the region of $2-$3 billion. This would go some way to softening the blow of generic competition to Pfizer’s cholesterol blockbuster Lipitor.

Furthermore, tofacitinab would provide serious competition to the RA big-sellers such as Abbott Laboratories' Humira (adalimumab), Pfizer/Amgen's Enbrel (etanercept) and Johnson & Johnson/Merck & Co's Remicade (infliximab) because it is an oral treatment; the others are injected or infused.