Stelara (ustekinumab) has one of the stronger long-term safety records among biologic medications, with clinical trials and real-world data now spanning up to 14 years. Side effect rates generally stay stable over time and don’t increase with continued use. That said, because the drug works by dialing down part of your immune system, there are specific risks worth understanding if you’re on it for years.
How Stelara Affects Your Immune System
Stelara blocks two immune signaling proteins (interleukin-12 and interleukin-23) that drive the inflammation behind psoriasis, psoriatic arthritis, Crohn’s disease, and ulcerative colitis. By targeting these specific proteins rather than broadly suppressing the immune system, it tends to cause fewer infections and complications than older biologics. But any drug that modifies immune function carries some long-term trade-offs.
Infection Risk Over Years of Use
Serious infections are the most closely watched risk with any biologic. In a pooled analysis of over 2,500 inflammatory bowel disease patients followed for up to five years, serious infections occurred at a rate of about 3.7 per 100 patient-years in the Stelara group, compared to 5.5 per 100 patient-years in the placebo group. In other words, Stelara patients actually had fewer serious infections than those on placebo during the study period, likely because uncontrolled inflammation itself raises infection risk.
Opportunistic infections, the kind that take advantage of a weakened immune system, were rare. Rates were 0.31 per 100 patient-years for Stelara users versus 0.53 for placebo. No serious anaphylactic reactions or serum sickness-like reactions were reported through five years of Crohn’s disease treatment or four years of ulcerative colitis treatment. Before starting Stelara, you’ll be screened for tuberculosis and other latent infections, since the drug could theoretically allow a dormant infection to reactivate.
Cancer and Malignancy Risk
This is the question most people on long-term biologics worry about. The data so far is reassuring. A 14-year follow-up study using Danish national health records found that psoriasis patients on Stelara did not have a statistically significant increase in cancer risk compared to patients on non-biologic treatments or other biologics. The rates of non-melanoma skin cancer were essentially identical between Stelara users and patients on conventional therapies.
In the pooled inflammatory bowel disease analysis, no cases of lymphoma were reported through five years of Crohn’s disease treatment or four years of ulcerative colitis treatment. Rates of other cancers (excluding non-melanoma skin cancer) were comparable between Stelara and placebo groups: 0.39 versus 0.32 per 100 patient-years. These numbers are low enough that the difference isn’t meaningful. Routine skin checks are still a sensible idea for anyone on long-term immune-modifying therapy, but Stelara doesn’t appear to carry the elevated lymphoma signal that concerned researchers with some earlier biologics.
Heart and Cardiovascular Safety
Early in Stelara’s history, there were theoretical concerns about cardiovascular events. A Swedish nationwide study spanning over 10 years and including more than 15,500 patients put this to rest. The risk of heart attack, stroke, or cardiovascular death in Stelara users was virtually identical to that of patients on three other commonly used biologics. Adjusted hazard ratios ranged from 1.07 to 1.19, none of which reached statistical significance. In the inflammatory bowel disease data, major cardiovascular events occurred at a rate of just 0.25 per 100 patient-years, similar to the placebo rate of 0.32.
Posterior Reversible Encephalopathy Syndrome
Stelara’s prescribing information lists a rare neurological condition called PRES, which involves sudden headaches, confusion, seizures, and vision changes caused by swelling in the brain. In practice, this is extraordinarily uncommon. As of the most recent case reports, only five cases have ever been documented in Stelara patients across all conditions. The large pooled IBD safety analysis reported zero cases through the entire follow-up period. If PRES does occur, it’s typically reversible once the drug is stopped and the swelling is treated. The suspected mechanism involves inflammatory changes that disrupt the barrier between blood vessels and brain tissue.
Antibody Development and Loss of Response
Over time, your immune system can develop antibodies against Stelara itself, which may reduce the drug’s effectiveness. In clinical trials, roughly 5 to 6% of patients on continuous Stelara therapy tested positive for these antibodies. The rate is relatively low compared to some other biologics.
However, a study specifically looking at inflammatory bowel disease patients who stopped responding found that 42% of them had developed antibodies to the drug, compared to only 6% of patients still responding well. Higher antibody levels correlated strongly with loss of response. This doesn’t cause dangerous side effects per se, but it means the drug gradually stops working for a small subset of people, which can feel like a side effect when your symptoms return after years of good control. If this happens, your doctor can check drug and antibody levels through blood tests to determine whether a dose adjustment or switch to another medication makes sense.
Injection Site Reactions
Stelara is given as a subcutaneous injection every 8 to 12 weeks (after an initial IV infusion for IBD patients). Injection site reactions, such as redness, swelling, or itching at the injection spot, occurred in about 1% of injections in clinical trials. This rate is quite low, partly because the injections are so infrequent compared to biologics given weekly or biweekly. These reactions don’t tend to worsen over time. Rare delayed skin reactions, including itchy, ring-shaped rashes on the trunk and limbs, have been reported in isolated cases but resolve within a couple of weeks.
What Five-Year Safety Data Shows Overall
The PHOENIX 2 trial followed psoriasis patients on Stelara for five years and found that safety event rates did not increase over time. About 70% of patients who started treatment completed the full five years, which is a strong retention rate for a biologic and suggests most people tolerate it well long-term. Event rates were comparable regardless of whether patients were on the lower or higher dose, and regardless of whether their dose needed adjusting along the way.
In the inflammatory bowel disease population, the overall rate of adverse events was actually lower in the Stelara group (347 per 100 patient-years) than in the placebo group (482 per 100 patient-years), as was the rate of serious adverse events (18.9 versus 29.4 per 100 patient-years). Nine deaths occurred among Stelara-treated IBD patients over the full study period, and all were determined to be unrelated to the drug.
The overall picture after more than a decade of real-world use is that Stelara carries a favorable long-term safety profile relative to other biologics. The risks that exist, particularly infections and the theoretical concern about malignancy, are present with all drugs in this class, and Stelara’s rates are consistently at the lower end. Regular follow-up appointments and periodic blood work help catch any issues early, but most people on Stelara for years experience stable, predictable treatment without accumulating new side effects over time.