Researchers looked at trials done up to June 2014 on the effect of anti-TNF drugs (adalimumab (Humira®), etanercept (Enbrel®), golimumab (Simponi®), and infliximab (Remicade®)) on ankylosing spondylitis. They found 21 trials with 3308 participants. Most studies were funded by pharmaceutical companies.
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.
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.
TNF (tumor necrosis factor)-alpha inhibitors block a key protein in the inflammatory chain reaction responsible for joint inflammation, pain, and damage in ankylosing spondylitis.
To assess the benefit and harms of adalimumab, etanercept, golimumab, and infliximab (TNF-alpha inhibitors) in people with ankylosing spondylitis.
We searched the following databases to January 26, 2009: MEDLINE (from 1966); EMBASE (from 1980); the Cochrane Central Register of Controlled Trials (CENTRAL; 2008, Issue 4); ACP Journal Club; CINAHL (from 1982); and ISI Web of Knowledge (from 1900). We ran updated searches in May 2012, October 2013, and in June 2014 for McMaster PLUS. We searched major regulatory agencies for safety warnings and clinicaltrials.gov for registered trials.
Randomized controlled trials (RCTs) comparing adalimumab, etanercept, golimumab and infliximab to placebo, other drugs or usual care in patients with ankylosing spondylitis, reported in abstract or full-text.
Two authors independently assessed search results, risk of bias, and extracted data. We conducted Bayesian mixed treatment comparison (MTC) meta-analyses using WinBUGS software. To investigate a class-effect of harms across biologics, we pooled harms data using Review Manager 5.
We included twenty-one, short-term (24 weeks or less) RCTs with a total of 3308 participants; 18 contributed data to the MTC analysis: adalimumab (4 studies), etanercept (8 studies), golimumab (2 studies), infliximab (3 studies), and one head-to-head study (etanercept versus infliximab) which was unblinded and considered at a higher risk of bias. The risk of selection and detection bias was low or unclear for most of the studies. The risk of selective outcome reporting was low for most studies as they reported on outcomes recommended by the Assessment of SpondyloArthritis international Society. We found little heterogeneity and no significant inconsistency in the MTC analyses. The majority of the studies were funded by pharmaceutical companies. Most studies permitted concomitant therapy of stable doses of disease-modifying anti-rheumatic drugs, non-steroidal anti-inflammatory drugs, or corticosteroids, but allowances varied across studies.
Compared with placebo, there was high quality evidence that patients on an anti-TNF agent were three to four times more likely to achieve an ASAS40 response (assessing spinal pain, function, and inflammation, as measured by the mean of intensity and duration of morning stiffness, and patient global assessment) by six months (adalimumab: risk ratio (RR) 3.53, 95% credible interval (Crl) 2.49 to 4.91; etanercept: RR 3.31, 95% Crl 2.38 to 4.53; golimumab: RR 2.90, 95% Crl 1.90 to 4.23; infliximab: RR 4.07, 95% Crl 2.80 to 5.74, with a 25% to 40% absolute difference between treatment and placebo groups. The number needed to treat (NNT) to achieve an ASAS 40 response ranged from 3 to 5.
There was high quality evidence of improvement in physical function on a 0 to 10 scale (adalimumab: mean difference (MD) -1.6, 95% Crl -2.2 to -0.9; etanercept: MD -1.1, 95% CrI -1.6 to -0.6; golimumab: MD -1.5, 95% Crl -2.3 to -0.7; infliximab: MD -2.1, 95% Crl -2.7 to -1.4, with an 11% to 21% absolute difference between treatment and placebo groups. The NNT to achieve the minimally clinically important difference of 0.7 points ranged from 2 to 4.
Compared with placebo, there was moderate quality evidence (downgraded for imprecision) that patients on an anti-TNF agent were more likely to achieve an ASAS partial remission by six months (adalimumab: RR 6.28, 95% Crl 3.13 to 12.78; etanercept: RR 4.24, 95% Crl 2.31 to 8.09; golimumab: RR 5.18, 95% Crl 1.90 to 14.79; infliximab: RR 15.41, 95% Crl 5.09 to 47.98 with a 10% to 44% absolute difference between treatment and placebo groups. The NNT to achieve an ASAS partial remission response ranged from 3 to 11.
There was low to moderate level evidence of a greater reduction in spinal inflammation as measured by magnetic resonance imaging though the absolute differences were small and the clinical relevance of the difference was unclear: adalimumab (1 trial; -6% (95% confidence interval (CI) -12% to 0.05%); 1 trial: 53.6% mean decrease from baseline versus 9.4% mean increase in the placebo group), golimumab (1 trial; -2.5%, (95% CI -5.6% to -0.7%)), and infliximab (1 trial; -3% (95% CI -4% to -2.4%)).
Radiographic progression was measured in one trial (N = 60) of etanercept versus placebo and it found that radiologic changes were similar in both groups (detailed data not provided).
There were few events of withdrawals due to adverse events leading to imprecision around the estimates. When all the anti-TNF agents were combined against placebo, there was moderate quality evidence from 16 studies of an increased risk of withdrawals due to adverse events in the anti-TNF group (Peto odds ratio (OR) 2.44, 95% CI 1.26 to 4.72; total events: 38/1637 in biologic group; 7/986 in placebo) though the absolute increase in harm was small (1%; 95% CI 0% to 2%).
Due to low event rates, evidence of the effect of individual TNF-inhibitors against placebo or for all four biologics pooled together versus placebo on serious adverse events is inconclusive (moderate quality; downgraded for imprecision). For all anti-TNF pooled versus placebo based on 16 studies: Peto OR 1.45, 95% CI 0.85 to 2.48; 51/1530 in biologic group; 18/878 in placebo; absolute difference: 1% (95% CI 0% to 2%).
Using indirect comparison methodology, and one head-to-head study of etanercept versus infliximab, wide confidence intervals meant that results were inconclusive for evidence of differences in the major outcomes between different anti-TNF agents. Regulatory agencies have published warnings about rare adverse events of serious infections, including tuberculosis, malignancies and lymphoma.