Later-Line Therapies Drive Biosimilar Prescriptions in Turkish Rheumatology Practices

Approximately 1 in 5 patients with rheumatoid arthritis (RA) or axial spondyloarthritis (axSpA) in Turkey were prescribed biosimilars rather than originator biologics, according to a new retrospective analysis from Erciyes University in Kayseri.¹

The findings, published in Scientific Reports, highlight how biosimilar use patterns remain modest overall but tend to increase in later treatment lines—offering insight into prescribing behavior in a country where biologics are fully reimbursed under national health insurance.

Researchers report that biosimilar use was not influenced by disease type but correlated with treatment sequence, shorter disease duration, and female sex. | Image credit: Zerophoto - stock.adobe.com

The study aimed to quantify biosimilar (BS) prescription rates and identify factors influencing clinicians’ decisions between biosimilars and reference biologic or targeted synthetic disease-modifying antirheumatic drugs (b/tsDMARDs). Although biosimilars have been available in Turkey for a decade, data on their uptake in rheumatology practice have been limited.²

“Our results indicate that disease duration, female sex, and the order of current therapy were the most important predictors of biosimilar prescription,” the authors wrote. “The use of biosimilars increased significantly as treatment lines progressed, reflecting both growing clinician familiarity and broader market availability.”

The investigators reviewed manual and electronic health records of 647 adults diagnosed with axSpA (n = 436) or RA (n = 211) who received at least 1 b/tsDMARD between May 1, 2023, and December 31, 2023. Patient inclusion required meeting the Assessment of SpondyloArthritis International Society or ACR/EULAR diagnostic criteria. Demographic, laboratory, and treatment-related data—including disease activity scores, duration of treatment, and medication sequence—were extracted.

Participants’ mean (SD) age was 48.1 (12.6) years, and 66% were women. All patients were insured through Turkey’s Social Security Institution, ensuring cost-free access to biologic and targeted synthetic therapies when clinically indicated. Available biosimilars during the study period included infliximab, etanercept, adalimumab, and rituximab, while a generic version of tofacitinib was also listed though not prescribed to any patient.

Across all patients, 21.2% received a biosimilar as their most recent b/tsDMARD prescription. Rates were similar between disease types—22.2% in axSpA and 19.0% in RA (P = .337)—suggesting that diagnosis did not significantly influence biosimilar uptake.

Patients with RA tended to be older and had a longer median disease duration (13 years vs 7 years; P < .001) than those with axSpA. Comorbidities, including hypertension, osteoporosis, diabetes, and dyslipidemia, were also more common in the RA group (all P < .05). The total duration of all b/tsDMARD use was significantly longer among individuals with RA (6.3 years) than those with axSpA (3 years; P = .001).

Among all biologic users, tumor necrosis factor (TNF) inhibitors dominated prescribing patterns, representing 80.7% of current treatments. Adalimumab was most frequently used in axSpA, while etanercept predominated in RA. In contrast, Janus kinase inhibitors such as tofacitinib or baricitinib were prescribed primarily for RA (16.6% of RA patients vs 0.2% of axSpA patients; P < .001).

Biosimilar use increased substantially with each successive treatment line. Patients who had received 5 or more distinct b/tsDMARDs showed the highest biosimilar prescription rate (39.7%), compared with just over 20% among those treated with their first biologic. Logistic regression revealed that female sex (OR, 1.70; 95% CI, 1.06-2.75), shorter disease duration (OR, 0.96; 95% CI, 0.92-0.99), and later treatment order (OR, 3.51; 95% CI, 1.06-11.60 for fifth-line or later use) were independently associated with biosimilar preference.

Interestingly, biosimilar users demonstrated higher disease activity measures at the time of data collection, including C-reactive protein and erythrocyte sedimentation rate levels. However, the researchers cautioned that these findings likely reflected the initiation of new therapy rather than reduced biosimilar efficacy. The median treatment duration for patients on biosimilars was zero years, indicating that many had recently started therapy.

Turkey represents one of the largest and fastest-growing pharmaceutical markets in the region, with national reimbursement policies facilitating broad access to biologic therapies. However, despite full coverage, prescriber behavior continues to favor reference biologics in early treatment stages. The authors suggested that clinician familiarity, patient comfort, and timing of biosimilar availability likely play roles in these trends.

Biosimilars have been shown globally to deliver comparable efficacy and safety to their originator counterparts while generating cost savings that expand patient access. In Europe, biosimilars account for roughly 70% of the TNF inhibitor market share, compared with far lower proportions in emerging markets. The Turkish findings therefore mirror an early stage of biosimilar integration into routine rheumatology practice.

“The increase in biosimilar use with subsequent therapy lines may reflect both increased physician confidence and accumulated experience over time,” the authors stated. “Wider education and awareness efforts could help normalize biosimilar prescribing earlier in the treatment sequence.”

The authors acknowledged several limitations, including the retrospective single-center design, lack of follow-up data on drug survival or switching outcomes, and exclusion of rheumatic diseases other than RA and axSpA. In addition, no socioeconomic analysis was performed, although uniform insurance coverage minimized cost disparities.

Future multicenter and longitudinal studies could clarify national trends and evaluate how biosimilar adoption impacts clinical outcomes and health care spending. As biosimilar availability expands, continued monitoring of prescription behaviors may help guide policy strategies to optimize equitable, cost-effective access to advanced therapies for inflammatory rheumatic diseases.

References

1. Kaplan H, Cengiz G, Kara H, Cüce İ, Kirnap M, Çaliş M. Analysis of data on biosimilar prescription rates in rheumatology practice from a reference center in Turkey. Sci Rep. 2025;15(1):28853. doi:10.1038/s41598-025-14816-0
2. Iskit AB. Key concepts in biosimilar medicines: What physicians must know. North Clin Istanb. 2022;9(1):86-91. doi:10.14744/nci.2021.84669