Cosentyx (secukinumab) is not a TNF inhibitor. It belongs to a different class of biologic drugs called IL-17A inhibitors. While both types reduce inflammation and treat some of the same conditions, they work through entirely different pathways in the immune system.
How Cosentyx Actually Works
Cosentyx is a fully human monoclonal antibody that targets a specific inflammatory protein called interleukin-17A (IL-17A). By binding to IL-17A, it prevents this protein from attaching to its receptor on cells, which blocks a chain reaction that would otherwise trigger inflammation in the skin, joints, and spine.
TNF inhibitors, by contrast, block a different inflammatory protein called tumor necrosis factor-alpha (TNF-α). The most common TNF inhibitors include Humira (adalimumab), Enbrel (etanercept), Remicade (infliximab), Cimzia (certolizumab pegol), and Simponi (golimumab). These drugs have been on the market longer and are often the first biologic prescribed for inflammatory conditions, partly because biosimilar versions have brought their costs down.
Both IL-17A and TNF-α eventually activate the same core inflammatory switch inside cells (a transcription factor called NF-κB), which is why blocking either one can reduce symptoms in overlapping conditions. But the upstream signals, the receptors involved, and the downstream effects differ enough that some patients respond well to one class and not the other.
What Cosentyx Treats
The FDA has approved Cosentyx for six conditions:
- Moderate to severe plaque psoriasis in patients 6 years and older
- Active psoriatic arthritis in patients 2 years and older
- Ankylosing spondylitis in adults
- Non-radiographic axial spondyloarthritis in adults with objective signs of inflammation
- Enthesitis-related arthritis in children 4 years and older
- Moderate to severe hidradenitis suppurativa in adults
Several of these conditions, particularly psoriatic arthritis and ankylosing spondylitis, overlap with conditions treated by TNF inhibitors. That overlap is a big reason people wonder whether Cosentyx is in the same drug class. It isn’t, but it competes in many of the same treatment spaces.
How It Compares to TNF Inhibitors for Psoriasis
Head-to-head comparisons suggest Cosentyx at its standard 300 mg dose outperforms the TNF inhibitor adalimumab (Humira) for plaque psoriasis. A network meta-analysis found that at 16 weeks, patients on Cosentyx were about 42% more likely to achieve a 75% improvement in their psoriasis severity score and roughly twice as likely to reach 90% improvement compared to those on adalimumab. That advantage held and even widened at 24 weeks.
Against infliximab (Remicade), the results were closer. At 12 weeks, the two drugs performed comparably. By 16 and 24 weeks, Cosentyx pulled ahead with statistically significant advantages in skin clearance, though the gap was smaller than with adalimumab.
These numbers don’t mean Cosentyx is universally “better.” Individual responses to biologics vary considerably, and some patients do well on a TNF inhibitor for years without needing to switch.
Infection Risk Differences
One of the practical reasons the distinction between these drug classes matters is their safety profiles, particularly around infections. TNF inhibitors carry a well-known risk of reactivating latent tuberculosis, which is why you’ll be screened for TB before starting one. In a large observational study from the Nordic countries, no cases of tuberculosis were recorded among patients on Cosentyx, while small numbers of cases appeared across each of the TNF inhibitors.
There has been theoretical concern that blocking IL-17A could increase susceptibility to fungal infections, since IL-17 plays a role in the body’s defense against fungi. In practice, fungal infection rates on Cosentyx were low (about 1.1% of patients) and only slightly higher than rates seen with TNF inhibitors (ranging from 0.4% to 0.7% depending on the specific drug). Overall infection rates between the two classes were similar.
Dosing and Administration
Cosentyx is given as a subcutaneous injection, meaning you inject it under the skin rather than receiving it through an IV. The standard schedule starts with weekly injections for the first five weeks (at weeks 0, 1, 2, 3, and 4), then shifts to once-monthly maintenance injections starting at week 8. Most patients self-inject at home using a prefilled pen or syringe after initial training.
This is a different rhythm than some TNF inhibitors. Adalimumab, for example, is typically injected every two weeks without a loading phase. Infliximab requires IV infusions at a clinic. The loading phase with Cosentyx is designed to build up drug levels quickly, which can mean faster initial results for skin clearance.
Switching Between Drug Classes
If you’ve tried a TNF inhibitor and it stopped working or never worked well enough, switching to an IL-17A inhibitor like Cosentyx is a common next step. Because the two classes target different proteins, a patient who doesn’t respond to one may respond to the other. Current treatment guidelines from major rheumatology and dermatology societies recognize this as a valid strategy, though they don’t specify a single best approach after a biologic fails. The decision typically depends on your specific condition, how you responded to previous treatments, and what side effects you experienced.
The reverse is also true. Some patients start on Cosentyx and later switch to a TNF inhibitor if needed. Moving between these classes, rather than trying another drug within the same class, gives you a mechanistically distinct option rather than a second attempt at blocking the same protein.