Yes, Stelara (ustekinumab) is a biologic medication. It belongs to a class of drugs called monoclonal antibodies, which are proteins engineered in a laboratory to target specific parts of the immune system. Stelara was first approved by the FDA in September 2009 and is manufactured by Janssen Biotech.
What Makes Stelara a Biologic
Biologics are different from conventional drugs in a fundamental way. Standard medications are typically small molecules made through chemical synthesis. Biologics are large, complex proteins produced using living cells. Stelara is specifically a human monoclonal antibody, meaning it was designed to mimic antibodies your immune system naturally produces. Its full molecular classification is a human immunoglobulin G1 kappa antibody, which is a type of protein structure found in the human immune system.
Because biologics are made from living cells rather than chemical reactions, they can’t be exactly replicated the way generic versions of conventional drugs can. Instead, near-identical versions called biosimilars go through a separate approval process. The FDA approved the first Stelara biosimilar, called Starjemza, in May 2025.
How Stelara Works in the Body
Stelara targets two specific immune system proteins: interleukin-12 (IL-12) and interleukin-23 (IL-23). These proteins act as signals that activate certain immune cells involved in inflammation. Both share a common building block called the p40 subunit, and Stelara works by binding to that shared subunit, blocking both proteins at once.
When IL-12 and IL-23 are overactive, they drive immune cells to multiply and release a cascade of inflammatory chemicals. This is what fuels the chronic inflammation behind conditions like psoriasis and Crohn’s disease. By intercepting these two signals before they can activate immune cells, Stelara dials down the inflammatory response at an early stage rather than trying to suppress the immune system broadly. This targeted approach is one of the key advantages of biologic therapies over older immunosuppressive drugs.
Conditions Stelara Treats
Stelara is FDA-approved for four conditions:
- Moderate to severe plaque psoriasis in adults and children ages 6 to 17
- Psoriatic arthritis in adults and children ages 6 to 17
- Crohn’s disease in adults
- Ulcerative colitis in adults
Its original 2009 approval covered only adult plaque psoriasis. The other indications were added over subsequent years as clinical trials demonstrated effectiveness in inflammatory bowel conditions and joint disease.
How Stelara Is Given
For psoriasis and psoriatic arthritis, Stelara is given as a subcutaneous injection (just under the skin) at week 0, again at week 4, and then once every 12 weeks. That’s roughly one injection every three months after the initial loading doses, which is less frequent than many other biologics.
Dosing depends on body weight. Adults weighing 100 kg (about 220 pounds) or less typically receive 45 mg per injection. Those over 100 kg receive 90 mg. Children ages 6 to 17 are dosed by weight as well, with those under 60 kg receiving 0.75 mg per kilogram of body weight.
For Crohn’s disease and ulcerative colitis, the treatment starts differently. The first dose is given intravenously in a clinic or infusion center. After that, maintenance doses of 90 mg are self-injected under the skin every 8 weeks, starting 8 weeks after the initial infusion.
Side Effects and Risks
The most common side effects are mild and include headache, fatigue, diarrhea, nasal congestion, sore throat, and dizziness. Redness or irritation at the injection site is also typical, especially early in treatment.
Because Stelara suppresses part of the immune system, it carries a higher risk of infections. Signs to watch for include fever, chills, cough, wounds that heal slowly, or a general feeling of being unwell. Any new or worsening symptoms of infection during treatment warrant prompt medical attention.
There is also a small increased risk of certain cancers, particularly skin cancers, associated with long-term immune suppression. Patients on Stelara are generally advised to limit sun exposure and monitor for new or changing skin growths. A rare but serious condition called posterior reversible encephalopathy syndrome (PRES) has been reported, with symptoms including sudden severe headache, confusion, vision changes, or seizures.
Screening Before Starting Treatment
Before you can begin Stelara, your doctor will order screening tests. Tuberculosis testing is standard practice for all biologics because suppressing the immune system can reactivate latent TB infections that have been dormant for years. This is done through a blood test or skin test. If you were born outside the U.S., have traveled to areas where TB is common, or have had close contact with someone who has active TB, you may need additional testing.
Your medical history will also be reviewed for any current infections, a history of cancer (particularly skin cancer), and previous exposure to chickenpox or herpes viruses, since these can flare during immune-suppressing treatment. These precautions are standard for biologics as a class, not unique to Stelara.