Secukinumab Mechanism of Action: How Secukinumab Works | Elicit

Secukinumab Mechanism of Action

How Secukinumab (Cosentyx) Works: Selective IL-17A antagonist that blocks IL-17A–IL-17 receptor interaction and downstream proinflammatory mediators.

Last updated:

March 2026

Quick Summary

Secukinumab (Cosentyx) is a fully human monoclonal antibody that binds specifically to interleukin-17A (IL-17A), a proinflammatory cytokine implicated in chronic immune-mediated inflammatory disorders. It selectively targets IL-17A by inhibiting its interaction with the IL-17 receptor, neutralizing IL-17A activity, and reducing release of proinflammatory cytokines, chemokines, and mediators of tissue damage. This mechanism supports its use across plaque psoriasis and several spondyloarthritis-spectrum diseases and hidradenitis suppurativa.

Properties

Details
Generic Name Secukinumab
Brand Names Cosentyx
Drug Class IL-17A antagonist (interleukin-17A modifier; monoclonal antibody)
Primary Target Interleukin-17A (IL17A)
Approved Indications Moderate-to-severe plaque psoriasis (adults and pediatric patients ≥6 years), psoriatic arthritis (PsA), ankylosing spondylitis (AS), non-radiographic axial spondyloarthritis (nr-AxSpA), enthesitis-related arthritis
Key Effect Neutralizes IL-17A activity and reduces release of proinflammatory cytokines, chemokines, and mediators of tissue damage

Development History

Secukinumab (development code AIN457) was discovered and developed by Novartis Pharmaceuticals as a fully human IgG1κ monoclonal antibody engineered to selectively bind and neutralize interleukin-17A (IL-17A), a pro-inflammatory cytokine centrally elevated in psoriatic lesions and the synovium of spondyloarthropathies. Unlike the upstream IL-23/p40 target of ustekinumab or the pan-TNF approach of etanercept, secukinumab was designed to intercept IL-17A directly, preventing it from engaging the IL-17 receptor and thereby blocking downstream keratinocyte activation, neutrophil recruitment, and the chemokine cascade that sustains plaque formation. The antibody was constructed as a fully human sequence with minimal immunogenicity—anti-drug antibody incidence remained below 1% across phase III populations—and formulated for both subcutaneous and intravenous administration with a half-life supporting monthly maintenance dosing after an initial weekly loading phase.

The pivotal approval program comprised two Phase 3 double-blind trials, ERASURE (NCT01365455) and FIXTURE (NCT01358578), enrolling 738 and 1,306 patients with moderate-to-severe plaque psoriasis, respectively. Both trials used co-primary endpoints of PASI 75 and IGA 0/1 at week 12. In ERASURE, secukinumab 300 mg achieved PASI 75 in 81.6% of patients versus 4.5% on placebo; in FIXTURE, the 300 mg arm reached 77.1% versus 44.0% for etanercept and 4.9% for placebo—demonstrating superiority over both comparators. The FDA granted approval on January 21, 2015 for adults with moderate-to-severe plaque psoriasis, making Cosentyx the first IL-17A inhibitor to receive regulatory clearance in the United States. Japan had granted the first global approval in December 2014 for psoriasis and psoriatic arthritis.

Label expansions followed in rapid succession across the spondyloarthritis spectrum. On January 15, 2016, the FDA approved Cosentyx for both active ankylosing spondylitis (AS) and active psoriatic arthritis (PsA), supported by the MEASURE 1 and MEASURE 2 trials in AS (subcutaneous secukinumab 150 mg meeting the primary ASAS20 endpoint at week 16) and the FUTURE 1 and FUTURE 2 trials in PsA (ACR20 response rates approximately 50–54% versus 15–18% for placebo). In 2020, the FDA approved Cosentyx for non-radiographic axial spondyloarthritis (nr-axSpA) based on the PREVENT trial, which demonstrated significant reduction in ASDAS disease activity versus placebo. The label now spans five indications—moderate-to-severe plaque psoriasis, PsA, AS, nr-axSpA, and enthesitis-related arthritis in pediatric patients—with the most recent FDA supplement activity recorded in 2025–2026 covering additional formulation and population expansions per the Drugs@FDA BLA 125504 record.

Detailed Mechanism of Action

Pharmacokinetics and tissue distribution. After subcutaneous administration, secukinumab reaches systemic circulation with an absolute bioavailability of approximately 73%, and absorption follows a first-order process with an estimated absorption rate constant of 0.18/day. Consistent with the behaviour of a large IgG1-kappa antibody, the drug exhibits limited extravascular distribution: in a typical 90-kg patient, serum clearance is approximately 0.19 L/day with a central compartment volume of 3.61 L and peripheral volume of 2.87 L. Steady-state peak exposure occurs at a Tmax of approximately 6 days after dosing, and the terminal half-life averages approximately 27 days, supporting target engagement across monthly dosing intervals. Like other IgG antibodies, secukinumab is cleared primarily through FcRn-mediated recycling and proteolytic catabolism rather than renal elimination. Distribution into the clinical target tissue is rapid: dermal interstitial fluid concentrations reach 28–39% of contemporaneous serum levels within 7–14 days of a single 300 mg dose, providing a pharmacokinetic rationale for early cutaneous responses.

Primary target and initial binding event. Secukinumab is a fully human IgG1-kappa monoclonal antibody that selectively binds and neutralizes IL-17A, preventing its interaction with the IL-17 receptor. IL-17A signals through a heterodimeric receptor complex composed of IL-17RA and IL-17RC; by sequestering free IL-17A in the extracellular space, secukinumab eliminates the ligand-dependent trigger for receptor complex activation and the downstream signalling cascade that follows.

Receptor-proximal signalling disruption. In the intact pathway, receptor ligation drives recruitment of the adaptor protein Act1 to the IL-17 receptor via homotypic SEFIR–SEFIR domain interactions. This Act1–receptor engagement enables downstream wiring: Act1 recruits TRAF6 through its TRAF-binding motifs, initiating canonical inflammatory signalling. TRAF6 activation leads to TAK1/IKK-mediated phosphorylation and degradation of IκBα, releasing NF-κB dimers for nuclear translocation. In parallel, the pathway activates mitogen-activated protein kinase cascades including ERK, p38, and JNK, as well as C/EBP family transcription factors, broadening transcriptional output. IL-17 signal transduction additionally branches into TRAF6- and TRAF5-dependent cytokine and chemokine programmes: TRAF6 primarily drives representative cytokine outputs such as IL-6, while TRAF5 drives chemokine outputs such as CXCL1. By neutralising IL-17A upstream, secukinumab prevents Act1 recruitment and simultaneously blunts both the cytokine and chemokine arms.

Gene expression consequences. Downstream of NF-κB and MAPK activation, a key transcriptional node in keratinocytes is IκBζ (encoded by NFKBIZ), whose mRNA rises within hours of IL-17A stimulation and is required for subsequent induction of beta-defensins, IL-19, and CSF3. IL-17A also controls gene expression post-transcriptionally: signalling through an Act1–TRAF2–TRAF5 complex stabilises target mRNAs via HuR and related factors, prolonging chemokine and cytokine protein production beyond the initial transcriptional wave. Counter-regulation is provided by Regnase-1, which degrades actively translated IL-17 target transcripts including Il6 and Nfkbiz, limiting the amplitude of inflammation.

Feed-forward loop and clinical translation. In vivo, Act1/CIKS signalling in keratinocytes drives neutrophilic microabscess formation and sustains a feed-forward loop that amplifies IL-17A and IL-17F production by dermal γδ T cells. Airway epithelial studies show that IKKi is required for IL-17-induced neutrophilia and pulmonary inflammation, illustrating how this kinase connects IL-17 receptor engagement to the recruitment of innate effectors in barrier tissues. Blocking IL-17A with secukinumab breaks this amplification circuit, reducing keratinocyte activation, epidermal hyperproliferation, neutrophil infiltration, and the sustained Th17-driven cytokine environment that characterises plaque psoriasis, psoriatic arthritis, and ankylosing spondylitis.

Clinical Relevance

Approved Indications

Key Drug Interactions (Mechanism-Based)

Contraindications

Emerging Indications

Immunology

Clinical Trials of Secukinumab

Trial Name Phase N Enrolled Intervention Indication Primary Endpoint Key Result Status
PREVENT Phase 3 randomized 555 Subcutaneous secukinumab 150 mg with or without a loading dose vs. placebo. Active non-radiographic axial spondyloarthritis (nr-axSpA) The proportion of patients achieving at least a 40% improvement in the Assessment of SpondyloArthritis international Society criteria (ASAS40) at Week 16. At week 16 in the CRP+/MRI+ subgroup, the ASAS40 response rate was significantly higher with secukinumab compared to placebo (52.3% vs. 21.8%; P < 0.0001), representing an absolute difference of 30.5 percentage points. Completed
JUNIPERA Phase 3 randomized 86 Patients aged 2 to 17 received open-label subcutaneous secukinumab (75 mg for <50 kg, 150 mg for ≥50 kg), and Week 12 responders were randomized to continue secukinumab or switch to placebo every 4 weeks. Juvenile psoriatic arthritis (JPsA) and enthesitis-related arthritis (ERA) Time to disease flare in the double-blind treatment period (Week 12 to Week 104). Secukinumab significantly delayed the time to disease flare compared to placebo, reducing the risk of flare by 72% over two years (HR 0.28; P<0.001). In the JPsA subgroup, the flare risk was reduced by 85%. Completed
SUNSHINE Phase 3 randomized 541 Secukinumab 300 mg administered subcutaneously every 2 weeks (SECQ2W) or every 4 weeks (SECQ4W) versus placebo. Moderate-to-Severe Hidradenitis Suppurativa Proportion of patients achieving a Hidradenitis Suppurativa Clinical Response (HiSCR) at Week 16. The primary endpoint was met. At Week 16, a higher proportion of patients achieved a Hidradenitis Suppurativa Clinical Response (HiSCR) with secukinumab 300 mg Q2W (45.0%) compared to placebo (33.7%; P=0.0070). The Q4W dosing group also showed a higher response rate (41.8%) vs placebo. Completed
SUNRISE Phase 3 randomized 543 Secukinumab 300 mg administered subcutaneously every 2 weeks (SECQ2W) or every 4 weeks (SECQ4W) versus placebo. Moderate-to-Severe Hidradenitis Suppurativa Proportion of patients achieving a Hidradenitis Suppurativa Clinical Response (HiSCR) at Week 16. Both secukinumab dosing arms met the primary endpoint. At Week 16, a higher proportion of patients achieved a Hidradenitis Suppurativa Clinical Response (HiSCR) with secukinumab 300 mg Q2W (42.3%) and Q4W (46.1%) compared to placebo (31.2%; P=0.0149 and P=0.0022, respectively). Completed
FUTURE 5 Phase 3 randomized 996 Subcutaneous secukinumab 300 mg or 150 mg with a loading dose, 150 mg without a loading dose, or placebo. Active Psoriatic Arthritis The primary endpoint was the proportion of patients achieving an American College of Rheumatology 20 (ACR20) response at week 16. At 2 years, the rates of no radiographic progression (change in vdH-mTSS ≤0.5) were 89.5% in the 300 mg group, 82.3% in the 150 mg with loading dose group, and 81.1% in the 150 mg no-load group. The mean change in vdH-mTSS was lowest in the 300 mg group (0.10). Completed
CLARITY Phase 3b randomized 1102 Secukinumab 300 mg subcutaneous was compared head-to-head with ustekinumab (45 mg or 90 mg based on weight). Moderate-to-Severe Plaque Psoriasis Co-primary endpoints were superiority of secukinumab over ustekinumab for PASI 90 and IGA mod 2011 0/1 responses at Week 12. At Week 12, secukinumab was superior to ustekinumab for PASI 90 response (66.5% vs. 47.9%; P<0.0001) and IGA mod 2011 0/1 response (72.3% vs. 55.4%; P<0.0001). At 52 weeks, secukinumab remained superior for PASI 90 (73.2% vs 59.8%). Completed
EXCEED Phase 3b randomized 853 Secukinumab 300 mg subcutaneous was compared head-to-head with adalimumab 40 mg subcutaneous in biologic-naïve patients. Active Psoriatic Arthritis The proportion of patients achieving at least a 20% improvement in the American College of Rheumatology response criteria (ACR20) at week 52. The primary endpoint of superiority for ACR20 response at week 52 was not met. ACR20 was achieved by 67% of secukinumab patients versus 62% of adalimumab patients (p=0.0719). In a subset with active psoriasis, secukinumab was superior for combined ACR50 and PASI 100 response (28.2% vs. 17.7%; P=0.006). Completed

Secukinumab Competitive Landscape

This table shows how Secukinumab compares to other IL-17 inhibitors and biologic therapies for inflammatory conditions. Each entry breaks down the representative drugs, their molecular targets, and how they actually work in the body.

Drug Class Representative Drug(s) Primary Molecular Target Mechanism of Action Key Efficacy Outcomes Route & Dosing Safety / Risk Profile Key Limitations
TNF-alpha inhibitors "Infliximab (Remicade), Adalimumab (Humira), Etanercept (Enbrel)" Tumor Necrosis Factor-alpha (TNF-α) Binds to and neutralizes both soluble and membrane-bound TNF-α. In Crohn's disease, a single infliximab dose led to a clinical response in 65% of patients vs 17% for placebo. Varies by agent; includes IV infusion every 4-8 weeks and subcutaneous injection every 1-2 weeks. Carries a boxed warning for increased risk of serious infections and malignancies. Common adverse events include upper respiratory infections. Primary non-response occurs in 20-40% of patients; monitoring required for serious infections.
IL-17 inhibitors "Secukinumab (Cosentyx), Ixekizumab (Taltz), Bimekizumab (Bimzelx)" Interleukin-17A (IL-17A), Interleukin-17F (IL-17F) Binds to and neutralizes IL-17 cytokines or blocks the IL-17 receptor. In plaque psoriasis, IL-17 inhibitors demonstrate high efficacy, with PASI 90 rates at Week 12-16 ranging from 59% to 91%. Subcutaneous injection, loading dose followed by maintenance dosing every 2 to 8 weeks. Most common adverse reactions include nasopharyngitis and upper respiratory infections. Increased risk of mucocutaneous candidiasis. Not recommended for patients with active inflammatory bowel disease. Dosing is generally more frequent than for IL-12/23 inhibitors.
IL-23 inhibitors "Guselkumab (Tremfya), Risankizumab (Skyrizi), Tildrakizumab (Ilumya)" The p19 subunit of Interleukin-23 (IL-23) Selectively binds to the p19 subunit of IL-23, inhibiting its interaction with the IL-23 receptor. In Crohn's disease, guselkumab achieved clinical remission in 59% of patients; in psoriasis, PASI 90 response rates are high, approximately 70-73%. IV infusion or subcutaneous injection for induction, followed by maintenance injections every 4, 8, or 12 weeks. Common adverse reactions include respiratory infections and injection site reactions. Liver enzyme monitoring required. Efficacy may be superior to ustekinumab in biologic-experienced patients, but not in biologic-naïve.
JAK inhibitors "Tofacitinib (Xeljanz), Upadacitinib (Rinvoq), Filgotinib (Jyseleca)" Intracellular Janus kinases (JAK1, JAK2, JAK3, TYK2) Blocks the JAK-STAT signaling pathway, reducing inflammatory gene expression. In ulcerative colitis, upadacitinib induction achieved clinical remission in 26-33% of patients. Oral tablets or solution, once or twice daily. Carries a boxed warning for serious infections and increased mortality. Common adverse reactions include upper respiratory infections. Not recommended for use with biologic DMARDs or other potent immunosuppressants.
TYK2 inhibitors "Deucravacitinib (Sotyktu)" Tyrosine kinase 2 (TYK2) regulatory domain Allosterically inhibits TYK2 by binding to its regulatory domain. In plaque psoriasis trials, deucravacitinib achieved PASI 75 in 53-58% of patients. Oral, 6 mg once daily. Common adverse reactions include upper respiratory infections and herpes simplex. Not recommended for use with other potent immunosuppressants.

Open Research Questions