What is ankylosing spondylitis and what are anti-TNF drugs?
Ankylosing spondylitis is a type of arthritis, usually in the joints and ligaments of the spine, but it may also affect other joints. Pain and stiffness occurs and limits movement in the back and affected joints. It can come and go, last for long periods, and be quite severe.
Anti-TNF drugs target a protein called 'tumor necrosis factor' that causes inflammation. These drugs suppress the immune system and reduce the inflammation in the joints, with the aim of preventing damage. Even though suppressing the immune system can make it slightly harder to fight off infections, it also helps to stabilize an overactive immune system.
The review shows that in people with ankylosing spondylitis, using anti-TNF drugs for up to 24 weeks:
- improves pain, function and other symptoms of ankylosing spondylitis;
- may increase the chance of achieving partial remission of symptoms of ankylosing spondylitis;
- probably slightly improves spinal inflammation, as measured by magnetic resonance imaging (MRI); and
- probably causes slightly more people to drop out of studies because of side effects.
We do not have precise information about side effects and complications, but in these short-term studies there was no evidence of an increase in serious adverse events. Possible side effects may include a serious infection (like tuberculosis) or upper respiratory infection. Rare complications may include certain types of cancer.
Best estimate of what happens to people with ankylosing spondylitis who take anti-TNF drugs for up to 24 weeks:
ASAS40 (40% improvement in pain, function, and inflammation as measured by morning stiffness, and patient overall well-being)
Compared to 13 people out of 100 who experienced an improvement with a placebo, among people who took:
- adalimumab: 46 people out of 100 experienced improvement (33% improvement);
- etanercept: 43 people out of 100 experienced improvement (30% improvement);
- golimumab: 38 people out of 100 experienced improvement (25% improvement); and
- infliximab: 53 people out of 100 experienced improvement (40% improvement).
Partial remission (defined as a value of less than 2 on a 0 to 10 scale in each of pain, function, and inflammation as measured by morning stiffness, and patient overall well-being)
Compared to 3 people out of 100 who experienced an improvement with a placebo, among people who took:
- adalimumab: 19 people out of 100 experienced partial remission (16% improvement);
- etanercept: 13 people out of 100 experienced partial remission (10% improvement);
- golimumab: 16 people out of 100 experienced partial remission (13% improvement); and
- infliximab: 47 people out of 100 experienced partial remission (44% improvement).
Physical function (lower score means better function; 0 to 10 scale)
Compared to a score of 5 in people who took placebo, among people who took:
- adalimumab, they rated their function to be 3.4 (16% improvement);
- etanercept, they rated their function to be 3.9 (11% improvement);
- golimumab, they rated their function to be 3.5 (15% improvement); and
- infliximab, they rated their function to be 2.9 (21% improvement).
Spinal inflammation as measured by magnetic resonance imaging (MRI)
Compared to people who took placebo, a small improvement in spinal inflammation was seen in:
- adalimumab (6% improvement);
- golimumab (2.5% improvement); and
- infliximab (3% improvement).
X-rays of the joints
Only one study looked at x-rays and found that joint changes were similar in both groups (detailed data not provided).
Side effects
When all the anti-TNF drugs were combined, 16 people out of 1000 dropped out of the study because of side effects compared to 7 people out of 1000 who took placebo (absolute increase 1%).
There may be little or no difference in the number of people who have a serious side effect with an anti-TNF drug compared to people who take a fake pill.
Authors' conclusions:
There is moderate to high quality evidence that anti-TNF agents improve clinical symptoms in the treatment of ankylosing spondylitis. More participants withdrew due to adverse events when on an anti-TNF agent but we did not find evidence of an increase in serious adverse events, though event rates were low and trials had a short duration. The short-term toxicity profile appears acceptable. Based on indirect comparison methodology, we are uncertain whether there are differences between anti-TNF agents in terms of the key benefit or harm outcomes.