Infliximab Indications: FDA Approvals and Off-Label Uses

Infliximab is approved for a broad range of inflammatory diseases, spanning gastroenterology, rheumatology, and dermatology. It works by targeting tumor necrosis factor alpha (TNF-alpha), a signaling protein that drives inflammation in conditions from Crohn’s disease to rheumatoid arthritis. Since its initial approval for Crohn’s disease in the late 1990s, its labeled uses have expanded steadily, and clinicians also prescribe it off-label for conditions like Behçet’s disease-related eye inflammation and Kawasaki disease in children. Understanding where infliximab fits, how well it performs for each condition, and what the trade-offs look like gives a clearer picture of why it remains one of the most widely used biologic therapies in the world.

How Infliximab Works

Infliximab is a chimeric monoclonal antibody, meaning part of its structure comes from mouse-derived protein and part from human protein. It neutralizes TNF-alpha by binding to both the free-floating (soluble) form circulating in the blood and the form anchored on the surface of immune cells. By locking onto TNF-alpha and preventing it from reaching its cellular receptors, infliximab effectively dials down the inflammatory cascade that damages tissue in autoimmune and chronic inflammatory diseases. It can also trigger the destruction of cells that produce TNF-alpha.¹

One detail that sets infliximab apart from some other TNF-blocking drugs is the way it binds. Infliximab attaches to both single units and clustered forms of soluble TNF-alpha, forming large, stable complexes. Some competing agents bind only the clustered form and create less stable connections. Each infliximab molecule can grab two TNF-alpha molecules, and up to three infliximab molecules can attach to a single TNF-alpha cluster.² This tight binding is part of why infliximab tends to produce rapid, noticeable improvements, sometimes within the first infusion or two.

Crohn’s Disease

Crohn’s disease was infliximab’s first approved indication, and it remains one of the most common reasons clinicians prescribe it. The drug is used for moderate to severe intestinal disease that has not responded well to conventional treatments like corticosteroids or immunomodulators. It is also specifically indicated for fistulizing Crohn’s, where abnormal tunnels form between the intestine and other structures like the skin around the anus. Published data show encouraging results for both fistula closure and for keeping patients in remission over time.³

The fistula picture is worth a closer look. A systematic review and meta-analysis of studies specifically focused on fistula outcomes found that TNF antagonists were about twice as effective as placebo for maintaining fistula remission. In studies where fistula healing was the primary endpoint, the drug also showed clear benefits for both inducing and sustaining fistula response.⁴ Fistulizing Crohn’s is one of the most debilitating forms of the disease, and infliximab is often the go-to biologic when fistulas do not respond to antibiotics or immunosuppressants alone.

Ulcerative Colitis

Infliximab is approved for moderate to severe ulcerative colitis that does not respond adequately to standard therapy. One of its more dramatic roles is as a rescue therapy in acute severe flares, where the alternative is often emergency surgery to remove the colon. In a randomized trial of patients facing that situation, those who received infliximab were significantly less likely to need a colectomy within three months: seven colectomies in the infliximab group versus 14 in the placebo group.⁵ A separate retrospective study found that roughly two-thirds of patients with acute severe disease who received infliximab avoided colectomy during their hospital admission.⁶

Cyclosporine is the main alternative rescue therapy in this setting. A meta-analysis comparing the two found no significant difference in colectomy rates at three or twelve months, and similar rates of adverse events and surgical complications.⁷ In practice, choice between the two often comes down to institutional experience and whether the patient has already tried one class of drug.

Rheumatoid Arthritis

Infliximab is approved for rheumatoid arthritis in combination with methotrexate, typically after methotrexate alone has not controlled the disease adequately. The landmark trial that established this pairing found that adding infliximab roughly tripled the clinical response rate compared to methotrexate alone, and it halted the radiographic progression of joint damage. In the methotrexate-only group, X-ray scores of joint erosion continued to climb; in the combination groups, they essentially flatlined.⁸

Even in early rheumatoid arthritis, before much joint damage has accumulated, the combination showed clear advantages. A controlled trial in patients with recent-onset disease found greater symptom improvement and significantly less radiographic progression at one year compared to methotrexate alone, along with better physical function scores.⁹ Infliximab is nearly always given alongside methotrexate in rheumatoid arthritis because the methotrexate reduces the body’s tendency to form antibodies against infliximab, keeping the drug effective longer.

Ankylosing Spondylitis

Ankylosing spondylitis is a chronic inflammatory condition primarily affecting the spine and sacroiliac joints. When nonsteroidal anti-inflammatory drugs are not enough, infliximab is one of the main biologic options. Around half of patients treated with infliximab and NSAIDs together achieve at least a 50 percent improvement in disease activity.¹⁰

MRI studies provide some of the most striking evidence for infliximab in this condition. A randomized, double-blind trial using MRI to measure spinal inflammation found near-complete resolution of inflammatory lesions in most patients receiving infliximab, while the placebo group showed essentially no change.¹¹ A follow-up study showed this improvement held up at two years: the number of inflammatory spinal lesions per patient dropped from roughly seven at baseline to about two after two years of treatment.¹² Whether this translates into genuine slowing of long-term structural damage to the spine is still being studied, but the inflammatory suppression is dramatic.

Psoriatic Arthritis and Plaque Psoriasis

Psoriatic arthritis sits at the overlap of rheumatology and dermatology, and infliximab addresses both sides of the disease. In the IMPACT trial, about two-thirds of infliximab-treated patients achieved meaningful joint improvement at 16 weeks, compared with only one in ten on placebo. Among those with significant skin involvement at baseline, about two-thirds achieved 75 percent or greater skin clearance, while none in the placebo group did. These improvements held through 50 weeks of continued treatment.¹³ Randomized trials confirm that infliximab controls both joint and skin manifestations of the disease.¹⁴

For plaque psoriasis without joint involvement, infliximab is approved as well. Phase III trials showed that a high percentage of patients with moderate to severe psoriasis achieved and sustained major skin clearance through one year of treatment.¹⁵ An earlier controlled trial noted particularly rapid improvement, with meaningful clearance appearing within weeks of the first infusion.¹⁶ Speed of onset is one of infliximab’s selling points in psoriasis, since some newer biologics take longer to reach full effect.

Pediatric Indications

Infliximab is approved for children and adolescents with Crohn’s disease and ulcerative colitis who have not responded adequately to conventional therapies. In pediatric Crohn’s disease, an open-label study of 112 children found that about 58 percent achieved remission during induction, and among those responders, more than half maintained remission with ongoing infusions every eight weeks. Children on infliximab also had fewer hospitalizations, fewer surgeries, and better growth, which matters because chronic inflammation can stunt development in young patients.¹⁷

In pediatric ulcerative colitis, a trial in 60 children found that about 73 percent responded to induction therapy. Among responders, those receiving infusions every eight weeks were roughly twice as likely to be in remission at one year compared to those on a less frequent schedule. Serious side effects were uncommon, and no deaths, malignancies, or opportunistic infections occurred during the study.¹⁸

Long-term data paint a more nuanced picture. A population-based study tracking children with inflammatory bowel disease on anti-TNF therapy found that the risk of treatment failure was highest in the first year and increased steadily over time. By five years, about 62 percent of pediatric Crohn’s patients on infliximab had experienced treatment failure, mainly from loss of response. Reassuringly, no cancers, deaths, or tuberculosis cases were reported during treatment.¹⁹ Loss of response is the central challenge with long-term infliximab use in any age group, and it connects directly to the question of drug monitoring, covered below.

Off-Label Uses

Beyond its approved indications, infliximab sees considerable off-label use in conditions where TNF-alpha plays a role but formal regulatory approval has not been pursued or granted.

Behçet’s Disease and Uveitis

Behçet’s disease can cause severe inflammation in the back of the eye (posterior uveitis) that threatens vision. In patients whose eye disease resisted standard immunosuppressants, infliximab produced rapid and lasting results. A 24-month follow-up study found that three-quarters of patients achieved complete remission by 12 months, and most of those remained in remission at two years. Visual acuity improved substantially, and the number of ocular attacks dropped dramatically after treatment.²⁰ Another long-term series reported that all treated patients achieved remission within two months, with most remaining attack-free and able to reduce their other immunosuppressive medications.²¹

Kawasaki Disease in Children

Kawasaki disease causes vasculitis in young children and is usually treated with intravenous immunoglobulin (IVIG). About 10 to 20 percent of children do not respond to the first round of IVIG, and infliximab has emerged as an alternative in those refractory cases. A randomized U.S. trial (KIDCARE) compared infliximab to a second dose of IVIG in resistant cases and found that 77 percent of infliximab-treated children had resolution of fever within 24 hours compared with 51 percent in the second-IVIG group. Hospital stays were also shorter by more than a day.²² A meta-analysis confirmed these findings, reporting that infliximab was associated with roughly five-fold higher odds of fever resolution and a shorter hospital stay compared to repeat IVIG.²³

Checkpoint Inhibitor-Induced Colitis

Cancer immunotherapy drugs like checkpoint inhibitors can cause severe colitis as a side effect. When steroids do not control the inflammation, infliximab has become one of the standard next-step treatments. A systematic review and meta-analysis found that infliximab was effective in about 81 percent of patients with checkpoint inhibitor-induced colitis, which was comparable to the other leading option, vedolizumab, at about 85 percent.²⁴

Sarcoidosis and Hidradenitis Suppurativa

In sarcoidosis that resists standard immunosuppressive treatment, infliximab has shown efficacy for extra-pulmonary manifestations (skin, joints, nervous system), with benefits sustained during prolonged therapy. Lung-related improvements were seen on imaging, though pulmonary function test results were less clear-cut.²⁵ For hidradenitis suppurativa, a painful skin condition involving recurring abscesses and draining lesions, a randomized crossover trial found that infliximab improved disease severity scores and quality of life compared to placebo.²⁶ Adalimumab rather than infliximab eventually received the formal approval for hidradenitis, but infliximab is still used off-label, especially in more severe cases.

Safety, Screening, and Common Side Effects

Because infliximab suppresses part of the immune system, infections are the headline safety concern. A systematic review and network meta-analysis found that patients on biologic therapies had a moderate increase in the risk of any infection and a roughly doubled risk of opportunistic infections. The risk of serious infections, however, was not significantly increased, and there was no clear increase in cancer risk, though follow-up periods were acknowledged to be limited.²⁷

Pre-treatment screening is critical. All patients should be tested for latent tuberculosis before starting infliximab, because the drug can reactivate dormant TB with potentially fatal consequences. Screening for hepatitis B is equally important, since viral reactivation has been documented under anti-TNF therapy. Despite clear guidelines, screening rates have historically been inadequate: one study found that only about two-thirds of patients were screened for TB and just a quarter for hepatitis B before their first dose.²⁸ Active infections, demyelinating neurological disorders, and severe heart failure are all contraindications.²⁹

Infusion reactions, ranging from mild flushing and headache to rare severe allergic responses, are another concern. These become more likely when patients develop antibodies against infliximab, which ties into the importance of drug monitoring discussed below.

Older Adults Face Higher Risks

Age matters with infliximab. Patients over 65 treated with anti-TNF therapy for inflammatory bowel disease have significantly higher rates of severe infections and mortality compared to younger patients or older patients not on these drugs.³⁰ A case series from one center was particularly sobering: all three patients over 60 who received anti-TNF therapy alongside other immunosuppressants developed serious infections, and all three died within a year. The infections included disseminated tuberculosis, Pneumocystis pneumonia, and cryptococcal meningitis.³¹ That case series is small, and not every elderly patient will have such outcomes, but it illustrates why the risk-benefit calculation shifts in this age group, especially when infliximab is combined with other immune-suppressing drugs.

Pregnancy and Newborn Considerations

Infliximab does not cross the placenta in meaningful amounts during the first trimester, but transfer becomes efficient during the late second and third trimesters. The drug can be detected in the infant’s blood for months after birth.³² This matters most for vaccination schedules. Because the infant is essentially carrying an immunosuppressant, live vaccines like rotavirus, BCG, and measles-mumps-rubella should be postponed. Guidelines recommend waiting until at least 12 months of age, or until drug clearance has been confirmed in the child’s blood.³³

Some clinicians try to time the last infusion before delivery to minimize how much drug reaches the fetus. Stopping infliximab early in the third trimester is one strategy, though this has to be balanced against the risk of the mother’s disease flaring during the final weeks of pregnancy. Inactivated vaccines (like those for diphtheria, tetanus, and whooping cough) are safe on the normal schedule regardless of infliximab exposure.

Therapeutic Drug Monitoring and Antibody Formation

One of the practical realities of infliximab therapy is that the body can develop antibodies against the drug, which reduce its effectiveness and increase the risk of infusion reactions. In a prospective study of patients receiving a biosimilar infliximab, about 11 percent developed anti-drug antibodies, and every patient who did had subtherapeutic drug levels.³⁴

An analysis of the NOR-DRUM trials quantified the clinical consequences. Patients who developed anti-drug antibodies were only about half as likely to be in remission at 30 weeks compared to antibody-free patients. They also experienced roughly double the rate of disease worsening over one year and were far more likely to have infusion reactions or need to stop infliximab altogether. Proactive therapeutic drug monitoring, where clinicians regularly check blood levels and adjust doses before problems develop, was associated with a lower risk of disease worsening and fewer infusion reactions, regardless of antibody status.³⁵ This is why many specialist centers now routinely measure infliximab trough levels and antibody concentrations rather than waiting for symptoms to worsen before investigating.

Biosimilars and Access

The original infliximab (Remicade) was one of the first biologics to face biosimilar competition, and several biosimilar versions are now widely available. A systematic review of studies in which patients switched from the original to a biosimilar found no clinically important differences in effectiveness or safety.³⁶ A phase III transition study in rheumatoid arthritis patients tracked outcomes through 78 weeks and confirmed that response rates, adverse event rates, and antibody formation were comparable whether patients stayed on the original, stayed on the biosimilar, or switched from one to the other.³⁷

Biosimilar availability has driven down costs considerably, making infliximab accessible to more patients and health systems. In some countries, institutional protocols now default to biosimilar infliximab for new starts and offer switching programs for patients already on the originator. The clinical evidence supports this as a safe practice.

Comparing Infliximab to Newer Biologics

As a drug that has been on the market for more than two decades, infliximab increasingly competes with newer biologics that target different inflammatory pathways. One question patients and clinicians frequently ask is whether a newer agent like vedolizumab, which targets gut-specific inflammation rather than TNF-alpha systemically, might be preferable in ulcerative colitis. A comparative study of biologic-naive ulcerative colitis patients found that short-term clinical response rates were essentially identical between infliximab and vedolizumab, at about 60 percent for each. One-year clinical remission rates were also similar. However, infliximab-treated patients had significantly higher rates of endoscopic remission at one year and were more likely to achieve steroid-free remission.³⁸

Infliximab’s broad mechanism, hitting TNF-alpha throughout the body rather than in one organ, is both its strength and its weakness. It means the drug works across a wide range of diseases, from eyes to joints to gut, but it also means immune suppression is more systemic, which drives the infection risks described above. Newer, more targeted agents may have narrower side effect profiles for certain conditions, but infliximab’s long track record, rapid onset, and extensive real-world data keep it firmly in the mix. For conditions like fistulizing Crohn’s disease or IVIG-resistant Kawasaki disease, where alternatives are limited and the evidence is deep, infliximab often remains first choice among biologics.