Biologics for Psoriasis: Classes
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Direct answer
Psoriasis was the first common disease decoded into a cytokine drug list, and the list has four shelves: tumour necrosis factor inhibitors (etanercept — a receptor-Fc fusion; infliximab — chimeric; adalimumab — fully human), the IL-12/23 p40 blocker ustekinumab, IL-17 blockers (secukinumab and ixekizumab against IL-17A; brodalumab against the IL-17 receptor) and selective IL-23 p19 blockers (guselkumab, risankizumab, tildrakizumab). IL-17 and IL-23 agents now clear skin most completely — PASI 90 in most patients — while anti-TNF drugs remain workhorses for psoriatic arthritis. Every start begins with the same screen: latent tuberculosis, hepatitis B, and live-vaccine status. In India, adalimumab and infliximab biosimilars carried these drugs from specialist-priced to broadly affordable.
What you must remember
- Anti-TNF details: etanercept 50 mg SC weekly (receptor-Fc fusion, binds TNF and lymphotoxin); infliximab 5 mg/kg IV at 0, 2 and 6 weeks then every 8 weeks (co-prescribe methotrexate against anti-chimeric antibodies); adalimumab 40 mg SC fortnightly (fully human).
- Ustekinumab: anti-p40, shared by IL-12 and IL-23; 45–90 mg SC at weeks 0 and 4, then every 12 weeks — the shared-subunit logic explains its Crohn's disease use.
- IL-17 class: secukinumab 300 mg and ixekizumab (anti-IL-17A); brodalumab blocks the IL-17 receptor — carrying a suicidal-ideation warning and a Crohn's disease contraindication, because IL-17 protects the gut mucosa.
- IL-23 p19 class: guselkumab, risankizumab, tildrakizumab — selective blockers with the deepest PASI 90/100 data currently, dosed at long intervals (risankizumab 150 mg SC at 0, 4, then every 12 weeks).
- Screening before every biologic: latent TB (IGRA or Mantoux plus chest X-ray; treat latent TB before starting), hepatitis B surface antigen and core antibody (reactivation), no live vaccines during therapy.
- Anti-TNF red flags: contraindicated in demyelinating disease and moderate-to-severe heart failure; lupus-like syndrome and paradoxical psoriasiform reactions occur.
- Immunogenicity: anti-drug antibodies reduce levels and trigger infusion reactions; methotrexate co-therapy blunts them for infliximab and adalimumab.
- India anchor: adalimumab, infliximab and etanercept biosimilars are marketed; the nomenclature code — "-ximab" chimeric, "-umab" human, "-cept" receptor fusion — is a viva staple.
Choosing by comorbidity, not by clearance rate
Skin-dominant psoriasis with no other diagnosis points to the IL-17 or IL-23 shelf, where PASI 90 approaches 70–90% and dosing is quarterly-ish — risankizumab and bimekizumab-class drugs lead the clearance tables. Add psoriatic arthritis and the choice widens rather than narrows: anti-TNF and IL-17 classes carry joint efficacy, while selective IL-23 p19 agents have mixed data in axial disease — a nuance worth stating. Add Crohn's disease and IL-17 agents exit entirely (brodalumab is formally contraindicated; secukinumab can provoke IBD), leaving ustekinumab or an anti-TNF — a genuine fork. A history of demyelination or heart failure deletes the anti-TNF shelf outright. Planned pregnancy favours certolizumab among anti-TNFs for its minimal placental transfer, or continued ustekinumab. The recurrent thrush patient cautions against IL-17 blockade, since that cytokine is the mucosa's antifungal guard. One organ-system inventory — skin, joints, gut, CNS, heart, infections, pregnancy — and the four shelves sort themselves; that inventory is the answer examiners actually grade.
Where students slip
The first slip is the brodalumab trap: IL-17 blockade's IBD contraindication is the single most examinable fact in the class, because it inverts the usual "biologics are interchangeable" instinct. The second is ustekinumab's target — students say "anti-IL-23" without noting it blocks the p40 subunit shared by IL-12, which is precisely why it also treats Crohn's. Third, the TB screening logic: anti-TNF drugs dissolve the granulomas that quarantine dormant bacilli, so screening is not bureaucratic ritual — and anti-TNF carries the highest reactivation signal among the shelves. Fourth, immunogenicity: loss of response at month nine is usually anti-drug antibodies, and the fix (methotrexate cover, dose escalation) is class-specific knowledge. Fifth, naming etanercept a monoclonal antibody — it is a receptor-Fc fusion protein, and the "-cept" suffix announces this. Finally, quoting PASI 75 when PASI 90/100 is the modern benchmark dates the answer by a decade.
Frequently asked questions
Why is brodalumab contraindicated in Crohn's disease?
IL-17 protects intestinal mucosal integrity, so blocking the IL-17 receptor can induce or worsen Crohn's disease.
What does ustekinumab block and why does that matter?
The p40 subunit shared by IL-12 and IL-23 — which is why one drug serves both psoriasis and Crohn's disease.
Why is methotrexate given with infliximab?
It suppresses anti-chimeric antibody formation, preserving infliximab levels and efficacy over time.
Which infections must be screened before starting any biologic?
Latent tuberculosis (IGRA or Mantoux plus chest X-ray) and hepatitis B — plus confirmation live vaccines are up to date beforehand.
Why is etanercept weaker in Crohn's disease than other anti-TNF agents?
As a soluble receptor it lacks membrane-bound TNF fixation and complement-mediated killing, delivering weaker mucosal effect than the antibodies.