As with all therapeutic proteins, there is potential for immunogenicity. The detection of antibody formation is highly dependent on the sensitivity and specificity of the assay. Additionally, the observed incidence of antibody (including neutralizing antibody) positivity in an assay may be influenced by several factors, including assay methodology, sample handling, timing of sample collection, concomitant medications, and underlying disease. For these reasons, comparison of the incidence of antibodies in the studies described below with the incidence of antibodies in other studies or to other infliximab products may be misleading.
Treatment with REMICADE can be associated with the development of antibodies to infliximab. An enzyme immunoassay (EIA) method was originally used to measure anti-infliximab antibodies in clinical studies of REMICADE. The EIA method is subject to interference by serum infliximab, possibly resulting in an underestimation of the rate of patient antibody formation. A separate, drug-tolerant electrochemiluminescence immunoassay (ECLIA) method for detecting antibodies to infliximab was subsequently developed and validated. This method is 60-fold more sensitive than the original EIA. With the ECLIA method, all clinical samples can be classified as either positive or negative for antibodies to infliximab without the need for the inconclusive category.
The incidence of antibodies to infliximab was based on the original EIA method in all clinical studies of REMICADE except for the Phase 3 study in pediatric patients with UC where the incidence of antibodies to infliximab was detected using both the EIA and ECLIA methods.
Immunogenicity in Adult Patients
The incidence of antibodies to infliximab in patients with RA and CD given a 3-dose induction regimen followed by maintenance dosing was approximately 10% as assessed through 1 to 2 years of REMICADE treatment. A higher incidence of antibodies to infliximab was observed in CD patients receiving REMICADE after drug-free intervals >16 weeks. In a PsA study in which 191 patients received 5 mg/kg with or without MTX, antibodies to infliximab occurred in 15% of patients. The majority of antibody-positive patients had low titers. Antibody development was lower among RA and CD patients receiving immunosuppressant therapies such as 6-MP/AZA or MTX. Patients who were antibody-positive were more likely to have higher rates of clearance, have reduced efficacy, and to experience an infusion reaction than were patients who were antibody negative [see Adverse Reactions (6.1)]. In the Ps Study II, which included both the 5 mg/kg and 3 mg/kg doses, antibodies were observed in 36% of patients treated with 5 mg/kg every 8 weeks for 1 year, and in 51% of patients treated with 3 mg/kg every 8 weeks for 1 year.
In the Ps Study III, which also included both the 5 mg/kg and 3 mg/kg doses, antibodies were observed in 20% of patients treated with 5 mg/kg induction (weeks 0, 2 and 6), and in 27% of patients treated with 3 mg/kg induction. Despite the increase in antibody formation, the infusion reaction rates in Studies I and II in patients treated with 5 mg/kg induction followed by every 8 week maintenance for 1 year and in Study III in patients treated with 5 mg/kg induction (14.1%–23.0%) and serious infusion reaction rates (<1%) were similar to those observed in other study populations. The clinical significance of apparent increased immunogenicity on efficacy and infusion reactions in Ps patients as compared to patients with other diseases treated with REMICADE over the long term is not known.
Immunogenicity in Pediatric Patients with Crohn’s Disease
In Study Peds Crohn’s, in which all patients received stable doses of 6-MP, AZA, or MTX, excluding inconclusive samples, 3 of 24 patients had antibodies to infliximab. Although 105 patients were tested for antibodies to infliximab, 81 patients were classified as inconclusive because they could not be ruled as negative due to assay interference by the presence of infliximab in the sample.
Immunogenicity in Pediatric Patients with Ulcerative Colitis
In the pediatric UC trial, 58 patients were evaluated for antibodies to infliximab using the EIA as well as the drug-tolerant ECLIA. With the EIA, 4 of 58 (7%) patients had antibodies to infliximab. With the ECLIA, 30 of 58 (52%) patients had antibodies to infliximab. The higher incidence of antibodies to infliximab by the ECLIA method was due to the 60-fold higher sensitivity compared to the EIA method. While EIA-positive patients generally had undetectable trough infliximab concentrations, ECLIA-positive patients could have detectable trough concentrations of infliximab because the ECLIA assay is more sensitive and drug-tolerant.
Adverse reactions, some with fatal outcomes, have been identified during post approval use of REMICADE in adult and pediatric patients. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
Postmarketing Adverse Reactions in Adults and Pediatric Patients
- Neutropenia [see Warnings and Precautions (5.6)] , agranulocytosis (including infants exposed in utero to infliximab), idiopathic thrombocytopenic purpura, thrombotic thrombocytopenic purpura.
- Interstitial lung disease (including pulmonary fibrosis/interstitial pneumonitis and rapidly progressive disease).
- Pericardial effusion, systemic and cutaneous vasculitis.
- Erythema multiforme, Stevens-Johnson Syndrome, toxic epidermal necrolysis, linear IgA bullous dermatosis (LABD), acute generalized exanthematous pustulosis (AGEP), new onset and worsening psoriasis (all subtypes including pustular, primarily palmoplantar), lichenoid reactions.
- Peripheral demyelinating disorders (such as Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, and multifocal motor neuropathy) transverse myelitis, and neuropathies (additional neurologic reactions have also been observed) [see Warnings and Precautions (5.9)].
- Acute liver failure, jaundice, hepatitis, and cholestasis [see Warnings and Precautions (5.4)].
- Serious infections [see Warnings and Precautions (5.1)] and vaccine breakthrough infection including bovine tuberculosis (disseminated BCG infection) following vaccination in an infant exposed in utero to infliximab [see Warnings and Precautions (5.13)].
- Malignancies, including leukemia, melanoma, Merkel cell carcinoma, and cervical cancer [see Warnings and Precautions (5.2)].
- Anaphylactic reactions, including anaphylactic shock, laryngeal/pharyngeal edema and severe bronchospasm, and seizure have been associated with REMICADE administration.
- Transient visual loss have been reported in association with REMICADE during or within 2 hours of infusion. Cerebrovascular accidents, myocardial ischemia/infarction (some fatal), and arrhythmia occurring within 24 hours of initiation of infusion have also been reported [see Warnings and Precautions (5.8)].
Postmarketing Serious Adverse Reactions in Pediatric Patients
The following serious adverse reactions have been reported in the post-marketing experience in pediatric patients: infections (some fatal) including opportunistic infections and tuberculosis, infusion reactions, hypersensitivity reactions, malignancies, including hepatosplenic T-cell lymphomas [see Boxed Warning and Warnings and Precautions (5.2)], transient hepatic enzyme abnormalities, lupus-like syndromes, and the development of autoantibodies.
The combination of REMICADE with other biological products used to treat the same conditions as REMICADE is not recommended [see Warnings and Precautions (5.10)].
An increased risk of serious infections was seen in clinical studies of other TNF blockers used in combination with anakinra or abatacept, with no added clinical benefit. Because of the nature of the adverse reactions seen with these combinations with TNF blocker therapy, similar toxicities may also result from the combination of anakinra or abatacept with other TNF blockers. Therefore, the combination of REMICADE and anakinra or abatacept is not recommended [see Warnings and Precautions (5.10)].
The concomitant use of tocilizumab with biological DMARDs such as TNF antagonists, including REMICADE, should be avoided because of the possibility of increased immunosuppression and increased risk of infection.
Specific drug interaction studies, including interactions with methotrexate (MTX), have not been conducted. The majority of patients in RA or CD clinical studies received one or more concomitant medications. In RA, concomitant medications besides MTX were nonsteroidal anti-inflammatory agents (NSAIDs), folic acid, corticosteroids and/or narcotics. Concomitant CD medications were antibiotics, antivirals, corticosteroids, 6-MP/AZA and aminosalicylates. In PsA clinical trials, concomitant medications included MTX in approximately half of the patients as well as NSAIDs, folic acid and corticosteroids. Concomitant MTX use may decrease the incidence of anti-infliximab antibody production and increase infliximab concentrations.
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