What Are the Factors for Starting Anti-TNF Inhibitor Biosimilars in RA and AS?

Analysis of a Korean health insurance database found the type of institution and physician specialty were the most important factors favoring the use of anti—tumor necrosis factor (anti-TNF) biosimilars in rheumatoid arthritis (RA) and ankylosing spondylitis (AS). Additionally, patients with RA who were taking glucocorticoids or who had comorbidities were less likely to receive biosimilars.

The study, published recently in PLoS One, aimed to provide insight into the real-world patterns of biosimilar initiation in patients with RA and AS in Korea by identifying patient characteristics and other factors associated with starting biosimilars using a logistic regression model.

Korea’s reimbursement guidelines for patients with rheumatic diseases recommend biosimilars as equivalent to their originators. However, in real-world clinical practice, a patient’s age or comorbidities may influence physicians’ willingness to prescribe a biosimilar. Furthermore, in the real-world, patients are not blinded. Patient concerns regarding biosimilars can contribute to reluctance to use biosimilars as well as a possible nocebo effect.

Using the Korean National Health Insurance Service (NHIS) database, researchers identified patients with RA or AS who had used anti-TNF agents from their initial approval of these biologics in 2004 through 2017. Between 2012, when the first biosimilar anti-TNF inhibitors were approved in Korea, to 2017, the rate of biosimilar use among patients prescribed TNF inhibitors increased to 16.5%.

To determine factors for initiating biosimilars, the researchers identified 4216 patients with RA and 2338 with AS who started anti-TNF inhibitors between 2013 and 2017.

Type of institution: Hospitals and clinics were factors for starting biosimilars, as opposed to tertiary or general hospitals. The authors hypothesize this could be due to simpler administrative procedures in hospitals or clinics.

Physician specialty: Prescribing from internal medicine (including rheumatology), orthopedics, and other specialties was investigated, and internal medicine departments were a factor for starting biosimilars. The authors say this is perhaps due to differences in knowledge or acceptance of biosimilars by physicians in different specialties.

Regional differences: There was more biosimilar use in metropolitan areas and in other cities compared to Seoul. This could be due to regional differences in marketing by pharmaceutical companies as well as knowledge and opinions of clinicians, the researchers say.

Use of biosimilars in combination with other medications: Regarding the influence of use of other medications, in RA, patients who used methotrexate were more likely to initiate biosimilars, whereas those who used oral glucocorticoids were less likely to initiate biosimilars, possibly reflecting patient and physician uncertainty about the effectiveness of biosimilars used in combination with glucocorticoids.

Comorbidities: Using an index measurement of comorbidities, patients with RA who had higher levels of comorbidities were less likely to initiate biosimilars, likely reflecting patient and physician concerns about the safety of biosimilars, according to the authors.

ICBP registration: Registration with the Individual Copayment Beneficiaries Program (ICBP) for rare and intractable diseases was also a factor in RA; these patients were less likely to initiate biosimilars. ICBP was used as a marker of economic status, as patients registered with ICBP pay only 10% of their medical expenses as copayment. Household income, however, was not a significant factor. The authors say these findings suggest that lower cost sharing was associated with the selection of more expensive drugs.

Patient characteristics associated with biosimilar use in AS were unclear. The authors conclude that a general lack of knowledge about interchangeability of originators and biosimilars, and about switching to biosimilars, may inhibit the prescription of biosimilars. They recommend further observational and clinical research in a variety of patients to improve knowledge and potentially increase acceptance and prescription of biosimilars.

Reference

Sung YK, Jung SY, Kim H, et al. Factors for starting biosimilar TNF inhibitors in patients with rheumatic diseases in the real world. PLoS One. [published online January 24, 2020]. doi:10.1371/journal.pone.0227960.