Abatacept, formerly known as CTLA4Ig, achieved the primary endpoint in both of the Phase III trials, which are due to be presented to the annual meeting of the American College of Rheumatology later this week. The drug achieved a 20 per cent improvement in the signs and symptoms of rheumatoid arthritis, as measured according to the ACR's 'ACR 20' standard.
T cell costimulatory pathways are believed to play important roles in the pathogenesis of various autoimmune diseases. Abatacept is a novel fusion protein that blocks a costimulation signal that activates T cells by inhibiting an interaction between them and antigen-presenting cells (APCs) known as CD28-B7.
The first trial (AIM), lasting a year, tested abatacept in patients who had failed to respond to methotrexate, a commonly used disease-modifying antirheumatic drug (DMARD). The trial showed that 73.1 per cent of patients taking abatacept plus methotrexate achieved an ACR 20 response, compared to 39.7 percent taking methotrexate plus placebo.
The second trial (ATTAIN), lasting six months, tested patients who had failed to respond to biological therapy with inhibitors of tumor necosis factor (TNF), a class that includes Johnson & Johnson's Remicade (infliximab), Amgen's Enbrel (etanercept) and Abbott Laboratories' Humira (adalimumab).
This trial showed that 50.4 percent of patients taking abatacept together with another treatment in the same class as methotrexate achieved an ACR 20- response. Only 19.5 per cent of patients taking abatacept plus placebo achieved this objective.
The first trial reveals that, as with all other biologics tested to date, abatacept in combination with methotrexate is more effective than methotrexate alone, while the second study reveals it can have valuable effects in patients who have failed to respond to biological therapies.
The results of AIM also showed that abatacept could have a positive effect on the progression of the disease, measured by looking at radiographs of joint erosions and joint space narrowing.
The results come at a time when Bristol-Myers Squibb has been struggling with a pipeline that the Wall Street Journal memorably said was 'considered the worst in the business', earlier this year.
In addition, the firm has been recovering from an accounting scandal and increased competition to some of its products from cheaper generics. It is also set to see sales of its biggest-selling product, the cholesterol fighter Pravachol (pravastatin), lose US patent protection in 2006.
Analysts estimate abatacept could generate annual sales ranging from $500 million to more than $1 billion if it is approved.
The drug is one of three late-stage products that B-MS has in its pipeline. The others are muraglitazar for diabetes and entecavir for hepatitis B.