TNF inhibitors, or blockers, are safer than previously thought for patients with ankylosing spondylitis (AS) and may have fewer unwanted side effects than non-steroidal anti-inflammatory drugs (NSAIDs), the standard first-line therapy for AS, a retrospective study has found.
Ankylosing spondylitis (AS) is a type of arthritis that usually affects the joints and ligaments of the spine. Its hallmark sign is inflammation of the sacroiliac joints, where the base of the spine (the sacrum) meets the pelvis (iliac bone). Pain and stiffness occur, limiting patients’ movement. These symptoms can come and go, last for long periods, and become more severe.
TNF inhibitors (TNFi), or anti-TNF therapy, have been a mainstay in arthritis treatment, including AS. These medications block the activity of an immune protein called tumor necrosis factor (TNF) alpha. When present in excess, this protein leads to the damaging joint inflammation characteristic of arthritic diseases.
By blocking TNF alpha, these therapies suppress the immune system and reduce joint inflammation, preventing damage. Even though this effect can make it slightly harder to fight off infections, it also helps stabilize the overactive immune system characteristic of people with arthritis.
While the majority of safety studies on TNF inhibitors have been performed in rheumatoid arthritis (RA) patients, it seems their use in patients with ankylosing spondylitis “may be safer than previously thought,” researchers say.
The researchers retrospectively analyzed the medical history of 150 AS patients referred to a center in Poland, to determine the frequency of adverse events in those treated (103 patients) as compared to those not treated with TNF inhibitors (47 patients).
Patient interviews and medical records were collected between September 2016 and March 2018. Data included prior and current use of traditional disease-modifying antirheumatic drugs (DMARDs) and TNF inhibitors, as well as current use of other medications.
The most commonly used TNF inhibitors were adalimumab (49.51%; sold under the brand Humira, among others) followed by etanercept (sold as Enbrel) and etanercept biosimilar SB4 (27.18%; sold as Benepali, among others), golimumab (17.48%; sold as Simponi), infliximab biosimilar CT-P13 (4.85%; sold as Remsima and Inflectra), and certolizumab (0.97%: sold as Cimzia).
No differences in the incidence of adverse events, serious adverse events, infections, and opportunistic infections were noted between TNFi-treated and non-treated groups, recalled over the three months prior to patient interviews.
However, noninfectious adverse events were less common in TNFi-treated patients, with abdominal pain the most common.
Except for acute infectious diarrhea — which was also less frequent in patients treated with TNF inhibitors — the differences in incidence rates of specific infections were not significant. Women were more than twice as likely as men to have adverse events.
TNF inhibitors also seemed more efficient to control disease activity. Treated patients had significantly lower AS activity and disability scores as measured by various disease activity scales (BASDAI, ASDAS, and BASFI).
Blood markers of inflammation — C-reactive protein and erythrocyte sedimentation rate — were also lower in TNFi-treated patients.
In the TNFi-treated group, 54% of patients achieved remission or low disease activity compared to less than 11% in those not treated with TNFi.
“TNF inhibitors show a good safety profile in ankylosing spondylitis patients,” the researchers said, adding that treatment with TNF inhibitors “may be better tolerated than standard first-line treatment with NSAIDs.”
But the researchers warned that the short period of observation of this study “could only detect frequent [adverse events], but not others that happen during the [prolonged] use of TNFi.”
“Large, real-world cohorts with long-term prospective observation would be the most appropriate for studying adverse effects of TNFi in AS patients, as adverse effects in this particular group seem to be rare,” they concluded.
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