Background/Purpose: A biosimilar product is a biological product highly similar to another FDA-approved biological product, reference product, and has no clinically meaningful differences in safety and effectiveness from the reference product. While four biosimilars have been approved by the FDA in rheumatology in 2016-2017, only one biosimilar infliximab-dyyb (IFX-b) has launched. We have evaluated early uptake of IFX-b in RA following its approval in April 2016 and launch in November 2016.

Methods: Symphony Health longitudinal prescription and medical claims data was used to evaluate the uptake of IFX-b relative to its reference product infliximab (IFX) from biosimilar approval through Q1 2017. The database contains claims records for 279 million unique patients representing an estimated 63% of specialty prescriptions, 58% of medical claims, and 25% of hospital claims in the US. Duration of therapy was defined as days from biologic initiation to the last administration. Time to treatment discontinuation (TTD) was defined as months from biologic initiation to switch or last administration + 90 days if no other biologic was administered. Duration of therapy was described with a Kaplan-Meier curves. Patient characteristics were evaluated using frequencies for categorical and mean and standard deviation (SD) for continuous variables.

Results: Of the 78,481 patients who initiated a biologic/biosimilar therapy for RA since IFX-b approval, 90 (0.1%) were treated with IFX-b and 5,178 (6.6%) were treated with IFX. The first patient started IFX-b in May 2016 and 78 IFX-b patients (86.7%) started in Q1 2017. Of the patients treated with IFX-b, 66 (73.3%) were female, 58 (64.4%) were 65 or older, 1 patient was commercially insured, the rest were with unknown insurance status, 31 (34.4%) were previously treated with IFX, 56 (62.2%) received IFX-b as their first biologic. Mean (SD) age for IFX-b patients was 65.9 (12.4) compared to 55.0 (16.7) for infliximab patients (p<0.0001). Mean (SD) number of prior biologics was 0.5 (0.8) for IFX-b and 0.5 (0.9) for IFX patients. Median (mean) duration was 1.0 (4.5) days for IFX-b and 60.0 (101.2) for IFX (Log Rank P<0.001) due to late IFX-b adoption.

Conclusion: Adoption of IFX-b in the US so far has been low and has not yet significantly impacted the reference biologic. The majority of IFX-b patients received it as first biologic, however a third of them switched from IFX. Duration of therapy on IFX-b is relatively short due to delayed launch. Future monitoring of IFX-b uptake is warranted especially as other approved biosimilars prepare for launch.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/real-world-utilization-of-biosimilars-for-management-of-rheumatoid-arthritis-ra-in-the-us/