Background/Purpose: Moderate-to-severe psoriatic arthritis (PsA) patients may be treated with biologics. Limited evidence is available about biologic utilization patterns outside approved doses. This study described the extent of dosing for etanercept (ETA), adalimumab (ADA), certolizumab (CER), golimumab (GOL), and ustekinumab (UST) among moderate-to-severe PsA patients who were biologic naïve versus (vs) previously treated with biologics.

Methods: Adult PsA patients in the MarketScan® claims database were identified between 01/01/2011‒12/31/2013 (identification period), with a 1-year follow-up and 3-month look-forward period (post-index period) ending 3/31/2015. Patients included had ≥1 PsA diagnosis using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code 696.0 and ≥1 pharmacy claim for ETA, ADA, CER, GOL, or UST during the identification period. Patients were considered treatment-naive if they had no prior biologic use or treatment-experienced if they had previous use of any biologic in the 6 months before the index date. Excluded patients had any other autoimmune disease indicated for treatment with biologics of interest. Intravenous biologic therapy was not evaluated due to lack of available data in MarketScan databases. Mean days of above-label use (daily maintenance dose ≥10% higher than indication), below-label use (daily maintenance dose ≤10% less than indication), and on-label use (daily maintenance dose ±10% than indication) per patient were described and stratified by treatment-naïve vs treatment-experienced patients.  

Results: This study identified 4245 PsA patients receiving biologic therapy: ETA (n=2342), ADA (n=1788), and GOL (n=115), respectively. Patients on CER (n=0) or UST (n=14) were not included due to small sample size and because both agents were only approved for PsA in late 2013. The majority of patients were male (~50-60%), with a mean age of ~50 years of age, and from the South of the United States. Across all three biologic patient cohorts examined, the majority of PsA patients were treatment-experienced, with ETA showing the highest proportion of patients with prior biologic use (67%), followed by GOL (57%) and ADA (56%) (Table 1). Treatment-experienced patients on ADA had greater mean days of above-label use compared to those naive to treatment (47 vs 19 days); however, treatment-experienced patients on ETA and GOL had fewer days of above-label use on average compared to naïve counterparts (ETA: 16 vs 20 days; GOL: 9 vs 16 days). Table 1. Mean days of above-label, on-label, and below-label use per patient per year

Conclusion: Above-label use was observed in PsA patients treated with ETA, ADA, and GOL; Prior biologic use seems to be a factor in above-label use of ADA versus other biologic cohorts.