Cosentyx (secukinumab) is a biologic medication approved to treat six inflammatory conditions: plaque psoriasis, psoriatic arthritis, ankylosing spondylitis, non-radiographic axial spondyloarthritis, enthesitis-related arthritis in children, and hidradenitis suppurativa. First approved by the FDA in 2015, it works by blocking a specific immune protein called interleukin-17A (IL-17A) that drives inflammation in the skin, joints, and spine.
How Cosentyx Works
IL-17A is a signaling molecule your immune system uses to coordinate inflammation. In autoimmune and inflammatory conditions, the body overproduces IL-17A, which triggers a cycle: it tells skin cells, joint tissue, or other structures to ramp up their inflammatory response, and those tissues then release more signals that keep IL-17A production going. Cosentyx is a lab-made antibody that latches onto IL-17A and neutralizes it, breaking that loop.
In psoriasis specifically, IL-17A drives the rapid overgrowth of skin cells that forms thick, scaly plaques. Blocking it leads to measurable reductions in inflammation within the first week of treatment, with continued improvement through the first 12 weeks. The same inflammatory pathway plays a central role in the joint erosion of psoriatic arthritis, spinal inflammation in ankylosing spondylitis, and the painful skin abscesses of hidradenitis suppurativa.
Plaque Psoriasis
Cosentyx is approved for moderate to severe plaque psoriasis in patients 6 years and older who are candidates for systemic therapy or phototherapy. In clinical trials, adult participants had psoriasis covering at least 10% of their body surface area. The standard adult dose is 300 mg injected under the skin once a week for the first five weeks (weeks 0 through 4), then once every four weeks as a maintenance dose. Some patients may use a lower 150 mg dose on the same schedule.
This is the condition Cosentyx was originally developed for, and it remains one of the drug’s primary uses. Pediatric dosing for children ages 6 and older is weight-based, with lower doses for smaller patients.
Psoriatic Arthritis
Psoriatic arthritis causes joint pain, swelling, and stiffness, often alongside skin symptoms of psoriasis. Cosentyx is approved for active psoriatic arthritis in patients 2 years and older. For adults, the typical starting dose is 150 mg, either with a loading phase (weekly for five weeks, then monthly) or simply once every four weeks from the start. If symptoms persist, the dose can be increased to 300 mg monthly.
The flexibility in dosing reflects that psoriatic arthritis varies widely in severity. Patients with both significant joint disease and skin involvement may benefit from the higher dose, since 300 mg is the standard for psoriasis.
Ankylosing Spondylitis and Spinal Inflammation
Ankylosing spondylitis (AS) is a type of arthritis that primarily affects the spine, causing chronic back pain, stiffness, and over time potentially fusing vertebrae together. Cosentyx is approved for active AS in adults, with the same dosing options as psoriatic arthritis: 150 mg with or without a loading phase, with the possibility of increasing to 300 mg if needed.
A related condition, non-radiographic axial spondyloarthritis (nr-axSpA), causes similar spinal symptoms but hasn’t yet produced visible joint damage on X-rays. It does show objective signs of inflammation on MRI or through blood markers. Cosentyx is approved for this condition as well, at 150 mg with or without the loading phase. This approval matters because nr-axSpA is often an earlier stage of spinal inflammatory disease, and treatment can help manage pain and stiffness before structural damage occurs.
Enthesitis-Related Arthritis in Children
Enthesitis-related arthritis (ERA) is a form of juvenile arthritis that causes inflammation where tendons and ligaments attach to bone, along with joint swelling. Cosentyx is approved for children 4 years and older with active ERA. This condition can affect the hips, knees, and feet, and in some cases progresses to involve the spine in a pattern similar to adult ankylosing spondylitis.
Hidradenitis Suppurativa
The newest addition to the list, approved in October 2023, is moderate to severe hidradenitis suppurativa (HS) in adults. HS causes painful, recurring lumps and abscesses in areas where skin rubs together, such as the armpits, groin, and under the breasts. These lesions can rupture, form tunnels under the skin, and lead to scarring.
The dosing for HS follows the same loading schedule as psoriasis: 300 mg weekly for five weeks, then every four weeks. If the response isn’t adequate, the maintenance frequency can be increased to every two weeks. Before this approval, treatment options for HS were limited, making Cosentyx one of only a few biologics available for the condition.
What Treatment Looks Like
Cosentyx is given as a subcutaneous injection, meaning it goes just under the skin rather than into a vein. Most patients learn to self-inject at home using a prefilled pen or syringe. The injection sites are typically the thigh, abdomen, or upper arm, and you rotate between them to avoid irritation.
The loading phase for most conditions involves weekly injections for the first month, which front-loads the medication to build up therapeutic levels faster. After that, you settle into a maintenance schedule of one injection every four weeks for most conditions. Because Cosentyx suppresses part of the immune system, you’ll need screening for tuberculosis before starting and ongoing monitoring during treatment.
Common Side Effects
The most frequently reported side effects in clinical trials were upper respiratory infections (cold-like symptoms, sore throat, runny nose) and diarrhea. Upper respiratory infections and nasopharyngitis occurred in up to about 15% of patients. Diarrhea, nausea, headache, fatigue, and back pain each occurred in 1% to 10% of patients.
Because Cosentyx partially suppresses immune function, it increases susceptibility to infections. Fungal infections, urinary tract infections, and oral herpes each occurred in 1% to 10% of trial participants. A small number of patients (about 1%) developed low white blood cell counts, specifically a type called neutrophils that help fight bacterial infections. Skin reactions like hives, eczema flares, or acne were also reported at low rates.
Serious infections are uncommon but possible. People with active infections should not start Cosentyx, and those with a history of Crohn’s disease or ulcerative colitis should be aware that new cases or flares of inflammatory bowel disease have been reported during treatment.