Psoriasis Biologics: How They Work, Which to Choose, and What to Expect

Why Biologics Changed Psoriasis Treatment

Before biologics, moderate-to-severe psoriasis treatment relied on methotrexate, cyclosporine, and phototherapy. These approaches suppress immune function broadly, carry significant organ toxicity risks, and produce inconsistent results. Most patients cycled between treatments as efficacy waned or side effects accumulated.

Biologics work differently. They are engineered proteins (monoclonal antibodies or fusion proteins) that block specific cytokines driving psoriatic inflammation. This targeted approach delivers higher efficacy with a narrower side effect profile [1].

The shift from “managing psoriasis” to “clearing psoriasis” started with TNF inhibitors in the early 2000s and accelerated dramatically with IL-17 and IL-23 inhibitors in the 2010s and 2020s.

The Four Biologic Classes

TNF-Alpha Inhibitors

The original psoriasis biologics. TNF-alpha is a pro-inflammatory cytokine involved in many immune pathways.

Agents: Adalimumab (Humira), etanercept (Enbrel), infliximab (Remicade), certolizumab pegol (Cimzia)

Efficacy: PASI 75 response in 40-65% of patients at 12-16 weeks. Lower than newer classes but still effective for many patients [2].

Advantages: Longest track record (20+ years of safety data). Biosimilars available for adalimumab and infliximab, reducing cost significantly. Also treat psoriatic arthritis effectively.

Limitations: Higher infection risk than IL-17/IL-23 inhibitors. Require TB screening. Secondary failure (loss of response over time) occurs in 20-40% of patients due to anti-drug antibody formation. Not the top choice for skin clearance alone anymore.

IL-12/23 Inhibitors

Agent: Ustekinumab (Stelara)

Ustekinumab blocks the p40 subunit shared by IL-12 and IL-23. This dual blockade was the first step beyond TNF inhibition for psoriasis.

Efficacy: PASI 75 in 66-76% at 12 weeks. PASI 90 in roughly 40-50% [3].

Advantages: Dosing every 12 weeks after loading (convenient). Good safety profile over 10+ years. Weight-based dosing allows optimization. Effective for both skin and joint disease.

Limitations: Outperformed by IL-17 and IL-23 inhibitors in head-to-head trials. Used as a biosimilar option in many markets now that the patent has expired.

IL-17 Inhibitors

IL-17 is the central effector cytokine in psoriatic plaque formation. Blocking it produces rapid, dramatic skin clearance.

Agents: Secukinumab (Cosentyx), ixekizumab (Taltz), brodalumab (Siliq), bimekizumab (Bimzelx)

Efficacy: PASI 90 in 55-75% at 12-16 weeks. Bimekizumab, which blocks both IL-17A and IL-17F, achieves the highest skin clearance rates of any biologic currently available, with PASI 100 (complete clearance) in 58-68% of patients at 16 weeks in the BE VIVID and BE READY trials [4].

Advantages: Fastest onset of action among biologics (visible improvement within 1-2 weeks for some patients). Highest overall clearance rates. Strong evidence for nail psoriasis.

Limitations: Increased risk of Candida infections (oral and mucosal) due to IL-17’s role in mucocutaneous immunity. Incidence is 1-5% for most IL-17 inhibitors and 10-15% for bimekizumab (usually mild, oral thrush responding to antifungals). Brodalumab carries a boxed warning for suicidal ideation (based on a small number of events in trials). Not recommended for patients with inflammatory bowel disease.

IL-23 Inhibitors

IL-23 sits upstream of IL-17 in the psoriatic inflammatory cascade. Blocking it disrupts the pathogenic Th17 cell response without fully eliminating IL-17 signaling from other sources.

Agents: Guselkumab (Tremfya), risankizumab (Skyrizi), tildrakizumab (Ilumya)

Efficacy: PASI 90 in 65-75% at 16 weeks. Risankizumab and guselkumab are the top performers in this class [5].

Advantages: Excellent durability of response. Some patients maintain clearance even after stopping treatment (suggesting potential immune “resetting”). Dosing every 8-12 weeks after loading. Lower Candida risk than IL-17 inhibitors. Potentially suitable for patients with concurrent IBD. Emerging evidence for psoriatic arthritis (risankizumab recently approved for PsA).

Limitations: Slightly slower onset than IL-17 inhibitors (peak response at 16-24 weeks rather than 12). Newer agents with less long-term safety data than TNF inhibitors.

Head-to-Head Trial Results

Several large randomized trials have directly compared biologics:

Key takeaway: IL-17 inhibitors clear skin faster (better at weeks 4-16), while IL-23 inhibitors show durable long-term superiority (better at weeks 48-52). Bimekizumab currently holds the highest overall clearance rates [6].

Choosing the Right Biologic

Biologic selection depends on more than just efficacy percentages. Patient-specific factors that influence the decision:

• Psoriatic arthritis: TNF inhibitors and IL-17 inhibitors have the strongest joint data. IL-23 inhibitors (risankizumab, guselkumab) are gaining PsA evidence.
• Inflammatory bowel disease: Avoid IL-17 inhibitors (can worsen IBD). TNF inhibitors and IL-23 inhibitors are preferred.
• Recurrent Candida infections: Favor IL-23 inhibitors over IL-17 inhibitors.
• Injection frequency preference: IL-23 inhibitors offer the longest dosing intervals (every 8-12 weeks maintenance).
• Speed of clearance: IL-17 inhibitors, particularly bimekizumab and ixekizumab, clear skin fastest.
• Cost and insurance: Biosimilar adalimumab and infliximab are significantly cheaper. Step therapy requirements may mandate trying a TNF inhibitor first.
• Needle anxiety: Infliximab (IV infusion in clinic) avoids self-injection entirely.

What Starting a Biologic Looks Like

Before starting any biologic, your dermatologist will order baseline labs and screening:

• Complete blood count (CBC)
• Hepatic function panel
• Hepatitis B and C serologies
• Tuberculosis screening (QuantiFERON-Gold or PPD skin test)
• HIV test (sometimes)
• Pregnancy test (if applicable)

After screening, most biologics follow a loading dose schedule (more frequent injections for the first few weeks) before transitioning to maintenance dosing. For example, secukinumab requires weekly injections for the first 5 weeks, then every 4 weeks. Risankizumab requires two loading doses at weeks 0 and 4, then every 12 weeks.

Most patients self-inject at home using prefilled syringes or autoinjector pens. Injection site reactions (redness, mild pain, swelling) are common initially but typically diminish over time.

Long-Term Safety: What the Data Shows

Long-term registry data and extension studies provide reassuring safety signals for most biologics:

• Infection risk: Slightly elevated compared to placebo, but serious infections remain uncommon (1-2 per 100 patient-years across classes). Upper respiratory infections are the most common.
• Malignancy: No increased cancer risk demonstrated in long-term registries for any biologic class [7]. The theoretical concern about immune suppression and cancer surveillance has not materialized in real-world data.
• Cardiovascular: TNF inhibitors may reduce cardiovascular events in psoriasis patients (psoriasis itself is a cardiovascular risk factor). IL-17 and IL-23 inhibitor cardiovascular data is neutral.
• Pregnancy: TNF inhibitors (particularly certolizumab, which does not cross the placenta) have the most safety data. IL-17 and IL-23 inhibitors are being studied, but current practice is to stop biologics before or during pregnancy.

When Biologics Fail

Primary failure (no response by week 16) occurs in 10-25% of patients depending on the biologic. Secondary failure (initial response followed by loss of efficacy) affects another 10-30% over several years.

Options when a biologic stops working:

• Switch within the same class (e.g., secukinumab to ixekizumab)
• Switch to a different class (e.g., IL-17 to IL-23 inhibitor)
• Add a conventional systemic (methotrexate can improve biologic response and reduce anti-drug antibodies)
• Combination with topical therapy for residual plaques

Cost and Access

Biologics are expensive. List prices range from $30,000-$70,000 per year in the United States. Practical cost depends on insurance, step therapy requirements, and manufacturer copay assistance programs.

Most manufacturers offer copay cards that reduce out-of-pocket costs to $0-$25/month for commercially insured patients. For uninsured patients, patient assistance programs can provide biologics at no cost based on income eligibility.

Biosimilars (available for adalimumab, etanercept, and infliximab) have reduced costs by 15-40% and are therapeutically equivalent to their reference products.

Related Reading

• Psoriasis: The Evidence-Based Guide (Pillar)
• Scalp Psoriasis: Causes, Treatments, and What Actually Clears It
• Psoriasis Diet: Anti-Inflammatory Foods That Actually Help
• Guttate Psoriasis: Triggers, Treatment, and Recovery

References

1. Menter A, Strober BE, Kaplan DH, et al. Joint AAD-NPF guidelines of care for the management and treatment of psoriasis with biologics. J Am Acad Dermatol. 2019;80(4):1029-1072. doi:10.1016/j.jaad.2018.11.057
2. Reich K, Nestle FO, Papp K, et al. Infliximab induction and maintenance therapy for moderate-to-severe psoriasis: a phase III, multicentre, double-blind trial. Lancet. 2005;366(9494):1367-1374. doi:10.1016/S0140-6736(05)67566-6
3. Leonardi CL, Kimball AB, Papp KA, et al. Efficacy and safety of ustekinumab, a human interleukin-12/23 monoclonal antibody, in patients with psoriasis: 76-week results from a randomised, double-blind, placebo-controlled trial (PHOENIX 1). Lancet. 2008;371(9625):1665-1674. doi:10.1016/S0140-6736(08)60725-4
4. Gordon KB, Foley P, Krueger JG, et al. Bimekizumab efficacy and safety in moderate to severe plaque psoriasis (BE READY): a multicentre, double-blind, placebo-controlled, randomised withdrawal phase 3 trial. Lancet. 2021;397(10273):475-486. doi:10.1016/S0140-6736(21)00126-4
5. Gordon KB, Strober B, Lebwohl M, et al. Efficacy and safety of risankizumab in moderate-to-severe plaque psoriasis (UltIMMa-1 and UltIMMa-2): results from two double-blind, randomised, placebo-controlled and ustekinumab-controlled phase 3 trials. Lancet. 2018;392(10148):650-661. doi:10.1016/S0140-6736(18)31713-6
6. Reich K, Papp KA, Blauvelt A, et al. Bimekizumab versus secukinumab in plaque psoriasis. N Engl J Med. 2021;385(2):142-152. doi:10.1056/NEJMoa2102383
7. Asgari MM, Wu JJ, Gelfand JM, et al. Validity of diagnostic codes and prevalence of psoriasis and psoriatic arthritis in a managed care population. Pharmacoepidemiol Drug Saf. 2013;22(8):842-849. doi:10.1002/pds.3436