INTRODUCTION
Emerging therapies for many chronic inflammatory dermatologic diseases, including hidradenitis suppurativa (HS), use monoclonal antibodies (biologics) to target inflammation. Currently, best evidence for HS treatment exists for adalimumab, an injectable TNF-α inhibitor.1 Evidence also exists for infliximab as well as other biologics that modulate the interleukin (IL-17, IL-12, IL-23, IL-1), and complement pathways with clinical trials ongoing.2-5 However, adalimumab is only effective in about 50% of patients, and this efficacy is measured by 50% or greater reduction in lesion count, not 100% disease clearance.1,6 Large randomized controlled studies evaluating infliximab’s efficacy in HS have yet to be performed.7
Similar to the use of biologics in other inflammatory diseases, HS patients may fail biologic therapy initially (primary non-response) or lose response over time (secondary loss of response).8-9 Given the high cost, the high failure rate of anti TNF-α agents, and likelihood of more biologics entering clinical practice, a treatment strategy that ascertains failures early and optimizes therapy is critically needed.
Similar to the use of biologics in other inflammatory diseases, HS patients may fail biologic therapy initially (primary non-response) or lose response over time (secondary loss of response).8-9 Given the high cost, the high failure rate of anti TNF-α agents, and likelihood of more biologics entering clinical practice, a treatment strategy that ascertains failures early and optimizes therapy is critically needed.
One potential reason for loss of response and therapy failure are anti-drug antibodies (ADAbs). All monoclonal antibodies are immunogenic, meaning the immune system may recognize these medications as "non-self" and form antibodies against them.10 These ADAbs have been implicated in suboptimal and loss of response in patients using biologic medications.10-11
Therapeutic drug monitoring (TDM) is the measurement of drug and ADAb serum levels to inform decisions about dose optimization. TDM can be performed routinely (proactively) or when patients do not respond to the therapy (reactively).9
