(419) Evaluating the Real-World Effects of Biosimilar Introduction on Stable Patients with Rheumatologic and Inflammatory Bowel Diseases: A Three-Month Post-Switch Analysis

Background: : The expanded availability of adalimumab biosimilars is accelerating transitions from the originator. Biosimilars improve cost-containment and have demonstrated similar effectiveness and safety compared to originators in clinical trials. Real-world evidence is needed to highlight outcomes for patients stable on an originator who switch to a biosimilar.

Objective: : Evaluate biosimilar switches and patient outcomes (adverse events and dose escalations) in rheumatology or inflammatory bowel disease (IBD) patients who switched to an adalimumab biosimilar.

Methods: : A single-center, retrospective review was conducted. Included patients were switched to an adalimumab biosimilar by a rheumatology or IBD provider between January and June 2024 and had been stable on the originator (same dose and frequency with no dose escalations) for at least 3 months before switching. Patients were excluded if they never started the biosimilar. Patients were followed for 3 months after biosimilar initiation. Outcomes included number of dose escalations, number of adverse effects or worsening of symptoms, number of switches (branded to unbranded product or another biosimilar) post-biosimilar initiation, and reason for switch. Data were analyzed using descriptive statistics.

Results: : Included patients (n=269) were predominantly White (89%) females (61%) with a median age of 46 years (interquartile range [IQR]= 35-56 years). Top three indications for adalimumab were rheumatoid arthritis (n=84, 31%), Crohn’s disease (n=84, 31%), and psoriatic arthritis (n=37, 14%). Most patients initiated adalimumab-adaz (n=193, 72%) upon switching from adalimumab originator. Post-biosimilar initiation, 13 patients (n=5%) had a dose escalation with a median of 82 days (IQR = 30-153) from biosimilar initiation to escalation. Ten patients (4%) reported experiencing an adverse event with 66 patients (25%) experiencing worsening symptoms or flares. Almost half of patients required a second switch (n=130, 46%) to unbranded adalimumab-adaz (n=108/130, 83%), back to the adalimumab originator (n=10/130, 8%), or to a non-adalimumab product (n=5/130, 4%). Medication availability/stock issues (n=104/130, 81%) was the most common reason for the second switch.

Conclusions: : Biosimilars were well tolerated during the first 3 months of therapy with a low number of patients experiencing adverse events, however 25% of patients stable on adalimumab originator experienced worsening symptoms or flares. Many patients stable on adalimumab originator who switch to an adalimumab biosimilar require subsequent switches within 3 months, using clinic/pharmacy resources.

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