London, United Kingdom—Monitoring antidrug antibody formation in those receiving biologic disease-modifying antirheumatic drugs can inform treatment decisions in patients with rheumatic diseases. In particular, patients who developed antibodies to infliximab (Remicade) cross-reacted with the infliximab biosimilar CT-P13—marketed as Remsima or Inflectra—according to data from a multicenter, controlled study of patients with rheumatoid arthritis (RA) and spondyloarthritis (SpA) presented at the 2016 European League Against Rheumatism Annual Congress.
“These findings suggest that patients on branded infliximab should not be switched to the biosimilar, because cross-reactivity will increase the clearance of the biosimilar, potentially compromising therapeutic response and heightening the risk of infusion-related reactions,” stated Daniel Nagore, PhD, co-investigator of the study and an employee of Progenika-Grifols in Derio, Spain.
“Patients who develop antibodies on the reference product infliximab should be switched to a different biologic.… Gastroenterologists already monitor for antibodies in patients on biologics,” he added. “This study provides one more argument for therapeutic monitoring in rheumatic diseases.”
Infliximab is an anti–tumor necrosis factor (TNF) agent approved for the treatment of RA, SpA, plaque psoriasis, psoriatic arthritis, and inflammatory bowel disease. CT-P13, the first anti–TNF-α biosimilar, was approved for the same indications as infliximab by the European Medicines Agency in 2013, and by the FDA earlier in 2016.
A previous study showed that antibodies to branded infliximab cross-reacted with CT-P13 in patients with inflammatory bowel disease.
To investigate this question in rheumatic diseases, Dr Nagore and his co-investigators studied 250 patients currently being treated with Remicade for RA or SpA, and 77 infliximab-naïve controls. Among the controls, approximately 25% were healthy, and 75% had a rheumatic disease.
Patients were tested in parallel with 3 different bridging enzyme-linked immunosorbent assays that tested for antibodies to Remicade.
Antibodies to infliximab were detected in 126 (50.4%) patients receiving Remicade; all were positive for antibodies to infliximab on assays that used Remsima and Inflectra. Antibody levels to infliximab were statistically similar and highly correlated across all 3 assays. In addition, 100% of patients who tested positive for anti-infliximab antibodies also exhibited antibody reactivity to the biosimilar.
Patients who were antibody-positive had undetectable levels of infliximab, whereas those who tested antibody-negative had a median infliximab concentration of 1.7 mg/mL.
No associations were found between the presence of infliximab antibodies and type of rheumatic disease, or use of concomitant immunosuppressive therapies.
A subgroup analysis of patients taking adalimumab suggested that those patients could be safely switched to the infliximab biosimilar. All 3 assays were negative among 19 control patients who were receiving adalimumab and had anti-adalimumab antibodies.
Further studies are being planned to assess the potential for antibody formation in patients treated with assay biosimilars. Because of the availability of therapeutic ranges, antibody testing is widely used by gastroenterologists, Dr Nagore explained.
“Now that new assays are available for the medical community, this should be translated into therapeutic ranges in rheumatology as well,” he stated. “No optimal therapeutic window has been identified for rheumatologic diseases.”