Comparison of Two Treatment Strategies in Inflammatory Bowel Disease: Biosimilar Adalimumab Monotherapy or in Combination with Azathioprine

Tumor necrosis factor-alpha (TNF-alpha) inhibitors, such as adalimumab (ADA) and infliximab, are among the most effective biological drugs for inducing and maintaining remission in patients with moderate to severe inflammatory bowel disease (IBD). Studies have shown that the effectiveness of infliximab is increased with the concomitant use of immunosuppressive drugs. However, little is known about ADA. Our aim was to compare the efficacy of monotherapy with biosimilar ADA and combination therapy with ADA+azathioprine (AZA) in IBD patients.

In this retrospective cohort study, the medical records of anti-TNF-naïve IBD patients referred to a tertiary hospital in Tehran during 2019-2020 who received biosimilar ADA (CinnoRA®) were reviewed. We compared the effectiveness of treatment, serum levels of ADA, anti-adalimumab antibodies, and laboratory data between the two monotherapy and combination therapy groups.

A total of 65 patients were enrolled. Fifty-six (86.2%) patients had ulcerative colitis, and the remaining had Crohn’s disease. 50 patients (76.9%) received combination therapy, and 15 (23.1%) were in the monotherapy group. The rate of clinical remission in the combination therapy group (50%) did not differ significantly from the monotherapy group (40%). The drug levels were in the therapeutic range (≥7.5 µg/mL) in 57.5% of patients in the combination therapy group and 76.9% of those in the monotherapy group. The antibody test result was positive in 40% of patients taking AZA+ADA and 10% of patients in the ADA group, neither were significantly different.

Adding AZA may not play a significant role in improving the therapeutic effectiveness of ADA in treating IBD.