Background/Purpose:

The use of biologic therapy in psoriatic arthritis (PsA) has altered the disease course and has been shown to reduce disease activity. Data comparing the clinical characteristics of PsA patients and their biologic therapy switching patterns are sparse.  We sought to compare baseline characteristics at biologic initiation between patients who go on to switch biologic therapy and those who do not switch in the setting of a real-world US registry population.

Methods:

Patients with a current diagnosis of PsA in the CORRONA registry, a large observational registry population in the US, who initiated a biologic were followed for two years to identify whether or not they switched to second biologic. We did not restrict this analysis to patients who were biologic-naïve at initiation.  We defined non-switchers as those who either continued to use initial biologic for the entire follow-up period, or discontinued their initial biologic but did not add a second biologic. Measures of disease activity including MD and patient global assessment of disease, tender and swollen joint counts, CDAI, presence of enthesitis or dactylitis, and MD and patient global assessment of skin were evaluated at initiation and at the end of the observation period. P-values comparing non-switchers to switchers were calculated using the Mann-Whitney-Wilcoxon test to account for skewed distribution of disease activity measures.

Results:

In this population, mean age at PsA onset was 42.4 years: 42.6 for non-switchers and 41.2 for switchers. Median duration of PsA was 6 years:  7 for non-switchers, and 5 for switchers. 54.6% were bio-experienced (53.7% for non-switchers and 58.3% for switchers) and the majority of the population (79.7%) did not switch to another drug (Non-switchers were 451 vs 115 switchers). Switchers had significantly higher mean MD and patient assessment of disease activity, higher mean tender and swollen joint counts, higher mean CDAI and Physician assessment of skin.  Patient assessment of skin (23.7 versus 24.9) was not found to be statistically different. 

Conclusion:

At initiation, patients who go on to switch biologic therapy had worse disease activity compared to those who did not switch.  Rheumatologists appear to switch biologics based on their assessment of both arthritis and skin related disease activity.

Table 1. Comparison of Non-Switchers and Switchers.

	Non-Switchers N=451 Mean (SD)	Switchers N=115 Mean (SD)	P-value
Physician Global Assessment	17.6 (16.6)	26.1 (20.8)	<.001
Patient Global Assessment	29.2 (24.0)	41.0 (26.8)	<.001
Tender Joint Count	2.7 (4.8)	5.3 (6.9)	<.001
Swollen Joint Count	2.6 (4.3)	4.1 (5.6)	0.002
CDAI	10.0 (9.6)	16.3 (13.1)	<.001
Physician Assessment of Skin	28.0 (30.8)	37.3 (27.6)	0.006

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-characteristics-of-patients-who-switch-biologic-therapy-within-the-first-two-years-results-from-a-large-us-registry-population/