Patients with antibodies to infliximab also react to biosimiliar drug CT-P13, according to a study published online March 10 in the Annals of Rheumatic Diseases. The results dash hopes that the biosimiliar would be an option for patients who must switch from infliximab because they develop antibodies to the drug.
"Findings imply that [antibodies to infliximab]-positive patients treated with [infliximab] should not be considered for switching to a biosimilar treatment, since pre-existing [antibodies to infliximab] will interact with the new drug, enhance clearance and potentially lead to loss of response and infusion-related reactions," write M. Begoña Ruiz-Argüello, PhD, from the R&D Department, Progenika-Grifols, Derio, Spain, and colleagues.
The retrospective study looked at 250 consecutive patients who had been treated with infliximab for either rheumatoid arthritis or ankylosing spondylitis. Of those, 126 were enrolled after having been found to have antidrug antibodies during routine clinical testing. The investigators enrolled a balanced group of 124 patients who had been treated with infliximab but showed no evidence of antidrug antibodies in regular clinical testing.
In the study, the authors tested serum samples from the 250 infliximab-treated patients and 77 infliximab-naive control patients for antibody reactivity to infliximab and the biosimiliar CT-P13.
The test for infliximab antibodies was positive for 50.4% of the infliximab-treated patients, indicating that anti-infliximab antibodies crossreact with CT-P13. The results were consistent between three different assays used. In addition, no differences were found in the test results between patients with rheumatoid arthritis or ankylosing spondylitis.
Biosimiliars to infliximab have not yet been approved in the United States, but the products took a step closer to approval in February, when the US Food and Drug Administration's Arthritis Drugs Advisory Committee endorsed the biosimiliar's comparability to infliximab for treating Crohn disease in adult and pediatric patients and ulcerative colitis in adult patients, rheumatoid arthritis in combination with methotrexate, ankylosing spondylitis, psoriatic arthritis, and plaque psoriasis. The US Food and Drug Administration is expected to approve the biosimiliars this year.
For physicians currently treating patients with infliximab, the biosimiliars would provide a new option and potentially reduce treatment costs, explained Anisha Dua, MD, MPH, a rheumatologist at the University of Chicago in Illinois. But many physicians will likely wait for more information about the biosimiliars to emerge before using the drugs.
"There is going to be a delay between approval and physicians starting to use them because of concerns about exactly how similar the drugs are, the immunogenicity, and whether the safety parameters are going to be the same," Dr Dua told Medscape Medical News.
However, studies like the one from Dr Ruiz-Argüello and colleagues are starting to fill the gaps. Dr Dua said the fact that the authors found 100% agreement in tests with all three assays used in the study is reassuring and that the study included patients with both rheumatoid arthritis and ankylosing spondylitis. But she said that larger studies will be needed.
Although the study suggests there would not be a benefit in switching from infliximab to a biosimiliar for patients who develop antibodies to infliximab, it did not find such cross reactivity to adalimumab, Dr Dua noted. Serum from 19 patients being treated with adalimumab who had developed antibodies to the drug were tested for reactivity to infliximab and its biosimiliar, and none was found, the authors report. This might suggest switching adalimumab-reactive patients to CT-P13 might be an option, Dr Dua said. However, given the small number of patients with anti-adalimumab antibodies tested, further study is needed.
"People are going to want a lot more evidence to be comfortable," Dr Dua said.
Dr Ruiz-Argüello and several coauthors are employees of Progenika Biopharma SA.
Ann Rheum Dis. Published online March 10, 2016. Abstract
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