Priority 9 from the Psoriatic Arthritis PSP

UNCERTAINTY: Why do treatments stop working well against psoriatic arthritis, and when they lose effectiveness, what's the best way to regain control of psoriatic arthritis? (JLA PSP Priority 9)
Overall ranking 9
JLA question ID 0108/9
Explanatory note This question aims to generate evidence to understand why drug based treatments that have been working well stop working for some people with psoriatic arthritis. This is often referred to as 'treatment failure'. Some people with psoriatic arthritis can experience 'treatment failure' multiple times. Also, if this happens, what treatments should be offered to regain control of their psoriatic arthritis symptoms as quickly as possible? Should the ordering of treatments be based upon specific patient characteristics? 
Evidence

This is an area of uncertainty. No systematic reviews or guidelines identified. 
Health Research Classification System category Inflammatory and immune system
Extra information provided by this PSP
Original uncertainty examples When first-line treatment for spondyloarthritis has failed, what is the most effective and cost-effective ordering of systemic biological disease-modifying anti-rheumatic drugs to treat with and does this ordering change based on particular patient characteristics?  
Submitted by 4 uncertainties submitted 
PSP information
PSP unique ID 0108
PSP name Psoriatic Arthritis
Total number of uncertainties identified by this PSP. 46  (To see a full list of all uncertainties identified, please see the detailed spreadsheet held on the JLA website)
Date of priority setting workshop 12 July 2021