Ustekinumab: IL-12 and IL-23 Inhibitor for Psoriasis Crohns Disease and Colitis
Ustekinumab is a fully human IgG1 kappa monoclonal antibody that targets the shared p40 subunit of interleukin-12 (IL-12) and interleukin-23 (IL-23), two cytokines that play pivotal roles in the immunopathogenesis of several chronic inflammatory and immune-mediated diseases. By binding to p40, ustekinumab simultaneously prevents both IL-12 and IL-23 from interacting with their respective cell-surface receptors, thereby interrupting key inflammatory signaling pathways involved in T-cell differentiation and activation. This dual inhibitory mechanism distinguishes ustekinumab from biologics that target only a single cytokine.
Ustekinumab was first approved for the treatment of moderate-to-severe plaque psoriasis and has since gained regulatory approval for additional immune-mediated conditions including psoriatic arthritis, Crohn's disease, and ulcerative colitis. Its favorable dosing schedule, with maintenance injections every 12 weeks, and a well-characterized long-term safety profile have established it as an important treatment option in the management of these complex conditions. The availability of biosimilar versions of ustekinumab continues to expand patient access to this class of biological therapy.
Mechanism of Action
Ustekinumab specifically binds to the p40 subunit shared by IL-12 and IL-23, two cytokines produced primarily by activated dendritic cells and macrophages in response to inflammatory stimuli. IL-12 promotes the differentiation of naive T-helper cells toward the Th1 phenotype and drives the activation of natural killer (NK) cells, leading to interferon-gamma (IFN-gamma) production and cell-mediated immune responses. IL-23, on the other hand, is essential for the survival, expansion, and maintenance of Th17 cells, a T-helper cell subset that produces IL-17A, IL-17F, IL-22, and other pro-inflammatory mediators central to the pathogenesis of psoriasis and inflammatory bowel diseases. By blocking the p40 subunit, ustekinumab prevents both IL-12 from binding to its receptor (composed of IL-12R-beta-1 and IL-12R-beta-2) and IL-23 from binding to its receptor (composed of IL-12R-beta-1 and IL-23R). This simultaneous blockade of two interleukin axes substantially reduces both Th1-mediated and Th17-mediated inflammatory pathways. In psoriasis, this leads to normalization of keratinocyte proliferation and differentiation, clearance of skin plaques, and reduction of systemic inflammation. In inflammatory bowel disease, it reduces mucosal inflammation and promotes healing of the intestinal epithelium. The selectivity of ustekinumab for the p40-containing cytokines means it does not broadly suppress the immune system and preserves many protective immune functions.
Indications
Ustekinumab is approved for several chronic immune-mediated inflammatory conditions. For plaque psoriasis, it is indicated in adults with moderate-to-severe chronic plaque psoriasis who are candidates for systemic therapy, having failed or been intolerant to other systemic treatments including conventional agents such as methotrexate, ciclosporin, or phototherapy. It is also approved for pediatric patients aged 6 years and above with the same severity criteria. For psoriatic arthritis, ustekinumab is indicated in adults with active disease who have had an inadequate response or intolerance to a previous DMARD therapy; it addresses both the articular and dermatological components of the disease. In Crohn's disease, it is indicated for moderate-to-severely active disease in adults who have had an inadequate response to, or are intolerant of, conventional therapy or biological agents including TNF inhibitors. Similarly, for ulcerative colitis, ustekinumab is indicated for moderate-to-severe active disease in adult patients who have had an inadequate response, loss of response, or intolerance to either conventional therapy or a biologic agent. The breadth of these indications across dermatological and gastroenterological conditions highlights the central role of the IL-12/23 axis in chronic immune-mediated inflammatory diseases.
Dosage and Administration
The dosing regimen for ustekinumab differs depending on the indication and patient body weight. For plaque psoriasis in adults, the recommended dose is 45 mg administered subcutaneously at week 0 and week 4, followed by 45 mg every 12 weeks. For patients weighing more than 100 kg, a dose of 90 mg is recommended at the same intervals. For psoriatic arthritis, 45 mg subcutaneously at week 0 and week 4 is followed by 45 mg every 12 weeks; patients with co-existing moderate-to-severe plaque psoriasis weighing more than 100 kg may receive 90 mg. For Crohn's disease and ulcerative colitis, the induction dose is administered as a single intravenous infusion with the dose calculated based on body weight (approximately 6 mg per kilogram, with specific weight-band dosing: 260 mg for patients up to 55 kg, 390 mg for 55 to 85 kg, and 520 mg for more than 85 kg). Eight weeks after IV induction, subcutaneous maintenance dosing begins at 90 mg every 12 weeks. Patients who do not respond at week 16 may have their dosing interval reduced to every 8 weeks. Ustekinumab is available as a subcutaneous injection in pre-filled syringes for self-administration and as a concentrate for IV infusion for the induction dose in IBD.
Side Effects
Ustekinumab is generally well tolerated, with a safety profile established across large clinical trial programs and long-term observational data. The most commonly reported adverse effects include nasopharyngitis (common cold), upper respiratory tract infections, headache, and injection site reactions such as erythema, swelling, and mild pain. As an immunomodulatory biological agent, ustekinumab increases the risk of infections generally, including serious infections requiring hospitalization or intravenous antibiotic therapy, although the absolute rate of serious infections appears lower with ustekinumab than with some other biologics, particularly TNF inhibitors. Respiratory tract infections including bronchitis and sinusitis are common. Serious opportunistic infections are rare but have been reported and include tuberculosis and fungal infections; pre-treatment screening for TB is mandatory. Back pain, fatigue, and dizziness have been reported. Hypersensitivity reactions including urticaria, rash, and anaphylaxis, though rare, can occur and require immediate medical management. There have been postmarketing reports of serious skin conditions including exfoliative dermatitis and hypersensitivity vasculitis. The overall risk of malignancy does not appear substantially elevated based on clinical trial data, though long-term surveillance continues. Reversible posterior leukoencephalopathy syndrome (RPLS), a neurological condition, has been reported very rarely.
Interactions
As a biological medicine, ustekinumab is not metabolized by cytochrome P450 enzymes and does not participate in pharmacokinetic interactions with small-molecule drugs through enzymatic pathways. However, several clinically important considerations apply. Live attenuated vaccines should not be administered during ustekinumab treatment or within the period following its discontinuation until immunological recovery is sufficient; this is because immunosuppression may allow disseminated infection with vaccine organisms. Non-live vaccines can be administered, though immune responses may be attenuated. Concomitant use of ustekinumab with other immunosuppressive biologics, including TNF inhibitors, IL-17 inhibitors, or IL-23 inhibitors, is not recommended due to the risk of excessive immunosuppression and infection without established additional clinical benefit. In inflammatory bowel disease, ustekinumab is often used after failure of TNF inhibitors, and the washout period between such agents should be managed carefully. Concomitant immunomodulatory agents such as azathioprine, 6-mercaptopurine, or methotrexate may be continued during ustekinumab therapy based on clinical judgment, as combination therapy has been used in some settings, though evidence for additional benefit is limited in most indications. There are no specific restrictions on concomitant use of most conventional medications.
Special Notes
Before initiating ustekinumab therapy, comprehensive pre-treatment evaluation is required. Tuberculosis screening using a tuberculin skin test or an interferon-gamma release assay, together with a chest X-ray, must be performed and latent TB treated before starting ustekinumab. Hepatitis B serology should be checked as reactivation of hepatitis B has been reported in patients receiving biologics, though less commonly than with TNF inhibitors. Live vaccines must be updated before starting therapy; patients should not receive live vaccines during treatment. Regular monitoring for signs of infection, including at each scheduled visit, is important throughout treatment. Ustekinumab is a fully human antibody, which reduces the risk of immunogenicity and formation of anti-drug antibodies compared to chimeric or humanized antibodies, contributing to its sustained efficacy over time. Patients with malignancy, either active or in remission, should be evaluated carefully before starting ustekinumab in consultation with the relevant oncology team. Ustekinumab should be stored in the refrigerator at 2 to 8 degrees Celsius, protected from light and away from heat. Subcutaneous injections should be self-administered by patients after appropriate training by healthcare professionals, rotating injection sites between the thighs, abdomen, and upper arms.
Related Topics
Frequently Asked Questions
How does ustekinumab differ from other biologics used in psoriasis?
Ustekinumab targets the p40 subunit shared by IL-12 and IL-23, positioning it differently from TNF inhibitors (adalimumab, etanercept), IL-17 inhibitors (secukinumab, ixekizumab), and selective IL-23 inhibitors (risankizumab, guselkumab). By simultaneously blocking both IL-12 and IL-23, it inhibits both Th1 and Th17 inflammatory pathways, providing broad immunomodulatory effects. In clinical practice, its every-12-week subcutaneous maintenance dosing represents a practical advantage for patients. Compared to selective IL-23 inhibitors such as risankizumab, some data suggest slightly lower skin clearance rates with ustekinumab, while its long-term safety record is well established. The choice among biologics depends on individual disease characteristics, comorbidities, prior treatment history, and patient preference, and should be made in consultation with a dermatologist or gastroenterologist.
Why is the first dose for inflammatory bowel disease given intravenously?
For Crohn's disease and ulcerative colitis, the induction dose of ustekinumab is administered as an intravenous infusion to achieve rapid and high drug concentrations in the systemic circulation and at the site of intestinal inflammation. The IV route bypasses first-pass metabolism concerns and provides immediate, reliable drug exposure, which is particularly important in patients with active mucosal disease who may have impaired subcutaneous absorption due to edema or local tissue alterations. The single IV induction dose has been shown in clinical trials to produce faster induction of remission and mucosal healing compared to subcutaneous induction. Following successful IV induction, maintenance therapy transitions to subcutaneous self-injection every 12 weeks, providing a convenient long-term treatment schedule.
Can ustekinumab be used in patients who previously failed TNF inhibitors?
Yes, ustekinumab is specifically approved and widely used in patients who have had an inadequate response to, or cannot tolerate, TNF inhibitors such as adalimumab or infliximab. In Crohn's disease particularly, ustekinumab demonstrated efficacy in clinical trials that included a high proportion of patients who had previously failed anti-TNF therapy, a group often referred to as anti-TNF inadequate responders. Clinical response rates in this population remain meaningful, making ustekinumab a valuable second-line or third-line biologic option in inflammatory bowel disease. Similarly, in psoriasis and psoriatic arthritis, ustekinumab can be used after insufficient response to TNF inhibitors. The transition from one biologic to another requires a washout period managed by the treating specialist to balance residual immunosuppression against disease activity risk.
Sources
- European Medicines Agency (EMA): Stelara (ustekinumab) Summary of Product Characteristics, current version.
- Feagan BG et al. Ustekinumab as Induction and Maintenance Therapy for Crohn's Disease. N Engl J Med. 2016.
- Griffiths CEM et al. Comparison of ustekinumab and etanercept for moderate-to-severe psoriasis. N Engl J Med. 2010.