ustekinumab
Stelara (ustekinumab) is a monoclonal antibody from Janssen that blocks the p40 subunit shared by interleukin-12 and interleukin-23. It is used in plaque psoriasis, psoriatic arthritis, Crohn's disease, and ulcerative colitis in adults, and in plaque psoriasis and psoriatic arthritis in children from 6 years of age.
This page is based on US prescribing information for ustekinumab and the EMA medicine record for Stelara, cross-checked with the NCI Drug Dictionary; the mechanism is explained in plain language, and analogies are used only where they stay accurate.
How it works
Explains what the medicine does in the body, not dosing, side effects, or safety.
An analogy
IL-12 and IL-23 are two inflammatory orders issued by the immune system, and they share a common component, p40, like two machines that run on the same battery. Ustekinumab removes that shared battery, so both orders lose power at once.
In simple terms
Ustekinumab is given by injection and binds the p40 subunit shared by interleukin-12 (IL-12) and interleukin-23 (IL-23), two proteins that keep immune inflammation going. By blocking them, it calms the overactive immune responses behind plaque psoriasis, psoriatic arthritis, Crohn's disease, and ulcerative colitis.
In depth
Ustekinumab is a fully human IgG1 kappa monoclonal antibody that binds the p40 protein subunit common to interleukin-12 (IL-12) and interleukin-23 (IL-23). This prevents IL-12 and IL-23 from engaging their receptors, blocking downstream JAK-STAT signalling and the differentiation of naive CD4+ T cells into Th1 and Th17 effector subsets. The result is reduced immune-mediated inflammation in psoriasis, psoriatic arthritis, Crohn's disease, and ulcerative colitis.
See it in motion
A schematic animation of the mechanism — simplified for clarity, not drawn to scale.
How ustekinumab blocks two inflammatory signals at once
- Interleukin-12 (IL-12) and interleukin-23 (IL-23) are two inflammatory orders issued by the immune system, and they share a common component, p40.
- Ustekinumab binds the common component, p40, on both orders.
- Binding p40 prevents IL-12 and IL-23 from engaging their receptors, blocking downstream JAK-STAT signalling and the differentiation of naive CD4+ T cells into Th1 and Th17 effector subsets.
- The result is reduced immune-mediated inflammation in psoriasis, psoriatic arthritis, Crohn's disease, and ulcerative colitis.
Target: Interleukin-12/23 p40 subunit
A protein subunit shared by the cytokines IL-12 and IL-23 that helps drive the immune inflammation behind psoriasis and inflammatory bowel disease.
Approved uses
Approved uses differ by country and change over time. Always follow your local prescribing information.
Approved uses in United States
FDA- Moderate to severe plaque psoriasis in adults and pediatric patients 6 years of age and older who are candidates for phototherapy or systemic therapy
- Active psoriatic arthritis in adults and pediatric patients 6 years of age and older
- Moderately to severely active Crohn's disease in adults
- Moderately to severely active ulcerative colitis in adults
Approved uses in European Union
EMA- Moderately to severely active Crohn's disease in adults who have had an inadequate response with, lost response to, or were intolerant to either conventional therapy or a TNF-alpha antagonist
- Moderately to severely active Crohn's disease in paediatric patients from 2 years of age and older who have had an inadequate response to, or were intolerant to, either conventional or biologic therapy
- Moderately to severely active ulcerative colitis in adults who have had an inadequate response with, lost response to, or were intolerant to either conventional therapy or a biologic
- Moderately to severely active ulcerative colitis in paediatric patients from 2 years of age and older who have had an inadequate response to, or were intolerant to, either conventional therapy or a biologic
- Moderate to severe plaque psoriasis in adults who failed to respond to, or who have a contraindication to, or are intolerant to other systemic therapies including ciclosporin, methotrexate, or PUVA
- Moderate to severe plaque psoriasis in children and adolescents from 6 years of age and older who are inadequately controlled by, or are intolerant to, other systemic therapies or phototherapies
- Active psoriatic arthritis in adults, alone or in combination with methotrexate, when the response to previous non-biological disease-modifying anti-rheumatic drug (DMARD) therapy has been inadequate
Official sources
The statements on this page trace back to these records.
- Stelara (ustekinumab) — Summary of product characteristics and package leaflet, English version
European Medicines Agency
- openFDA drug label record for ustekinumab
U.S. Food and Drug Administration, openFDA
- NCI Drug Dictionary: ustekinumab
National Cancer Institute
This page explains how the medicine works — it isn’t the patient leaflet. For anything that applies to you, read the leaflet that came with your medicine or ask your pharmacist.
MedUnfold provides educational content and is not medical advice. Always follow your local prescribing information and healthcare professional.