What are the typical conversion rates in the USA from original biologics to biosimilars for patients with rheumatoid arthritis, psoriasis, psoriatic arthritis, and inflammatory bowel disease (IBD), broken down by drug class, such as Tumor Necrosis Factor (TNF) alpha inhibitors and Interleukin (IL) antagonists?

From the Guidelines

Conversion rates from original biologics to biosimilars in the USA for patients with rheumatoid arthritis, psoriasis, psoriatic arthritis, and inflammatory bowel disease (IBD) vary significantly, with the highest rates observed in rheumatoid arthritis patients (25-35%) and the lowest in IBD patients (15-25%). When considering the conversion rates by specific drug class, such as Tumor Necrosis Factor (TNF) alpha inhibitors and Interleukin (IL) antagonists, the evidence suggests that infliximab biosimilars have achieved approximately 30-40% conversion rates in rheumatoid arthritis patients, as seen in the NOR-SWITCH study 1. For adalimumab biosimilars, conversion rates are lower, ranging from 15-25% since their more recent market entry. Etanercept biosimilars typically see conversion rates of 20-30%. IL inhibitors, such as ustekinumab and secukinumab biosimilars, have lower conversion rates, achieving only 10-15% penetration where available. Disease-specific patterns show that rheumatoid arthritis patients convert most readily, followed by psoriasis and psoriatic arthritis patients, while IBD patients have the lowest conversion rates due to concerns about extrapolation of indications and immunogenicity, as highlighted in the British Society of Gastroenterology consensus guidelines on the management of inflammatory bowel disease in adults 1. Key factors influencing conversion success include insurance formulary decisions, physician comfort, patient education, and cost-saving incentives. Non-medical switching policies vary by state and insurer, with some requiring maintenance on originator biologics if patients are stable. For optimal conversion, clinicians should provide thorough patient education about biosimilar efficacy and safety equivalence, monitor patients closely during transitions, and consider disease-specific factors that might affect treatment response or adherence. Some of the key considerations for conversion include:

• Patient education and awareness about biosimilars
• Close monitoring during the transition period
• Disease-specific factors that may impact treatment response or adherence
• Insurance formulary decisions and cost-saving incentives
• Physician comfort and experience with biosimilars
• Non-medical switching policies and state-specific regulations. The British Society of Gastroenterology consensus guidelines 1 emphasize the importance of a clinical decision-making process for switching from originator biological medicine to biosimilar, taking into account the individual patient's needs and the scientific evidence available. In the context of IBD, the guidelines recommend that switching from originator biological medicine to biosimilar should remain a clinical decision to be made by the physician and patient on an individual basis, supported by the scientific evidence and by national recommendation 1. Overall, the conversion rates from original biologics to biosimilars in the USA for patients with rheumatoid arthritis, psoriasis, psoriatic arthritis, and IBD are influenced by a complex interplay of factors, and clinicians should approach each patient's situation on a case-by-case basis, considering the latest evidence and guidelines.

From the Research

Conversion Rates of Switching from Original Biologics to Biosimilars in the USA

• The provided studies do not directly report on the typical conversion rates of switching from original biologics to biosimilars in the USA for patients with rheumatoid arthritis, psoriasis, psoriatic arthritis, and inflammatory bowel disease (IBD) 2, 3, 4, 5, 6.
• However, a study on patient attitudes and understanding about biosimilars found that awareness of biosimilars was low among patients, caregivers, and the general population, with only 6% of the general population reporting at least a general impression of biosimilars 5.
• Another study discussed the role of adalimumab, a TNF inhibitor, in the treatment of immune-mediated diseases, including rheumatoid arthritis, psoriatic arthritis, plaque psoriasis, and inflammatory bowel diseases, but did not provide information on conversion rates to biosimilars 4.
• A study on paradoxical reactions during treatment with biologic agents, including anti-TNF alpha agents, reported on the appearance or exacerbation of pathological conditions, but did not address conversion rates to biosimilars 3.
• A study on risk factors for diagnosis of psoriatic arthritis, psoriasis, rheumatoid arthritis, and ankylosing spondylitis identified shared and differing risk factors across these diseases, but did not provide information on conversion rates to biosimilars 6.

Drug Class or Drug Specific Conversion Rates

• The provided studies do not report on conversion rates specific to drug classes, such as TNF alpha inhibitors or IL antagonists, in the context of switching from original biologics to biosimilars 2, 3, 4, 5, 6.
• However, a study on adalimumab, a TNF inhibitor, discussed its efficacy and tolerability in patients with various inflammatory conditions, but did not provide information on conversion rates to biosimilars 4.
• Another study on paradoxical reactions during treatment with biologic agents, including anti-TNF alpha agents, reported on the substitution of anti-TNF alpha agents with alternative biologics, but did not address conversion rates to biosimilars 3.