Therapeutic Drug Monitoring Has Promise for Improving Psoriasis Outcomes, Study Suggests

There is increasing evidence to suggest that therapeutic drug monitoring (TDM) will allow for more tailored and rational use of biologics in psoriasis, according to a recent study.

For patients with inflammatory bowel disease (IBD) and rheumatoid arthritis (RA), adequate serum concentrations of biologics have been linked with sustainable clinical responses, and now, there is growing evidence to suggest that TDM is beneficial in psoriasis as well.

When it comes to biosimilars, however, there is a lack of data in using TDM. The published TDM data focuses on the use of infliximab biosimilars in IBD and RA, with studies suggesting that biosimilar switching is feasible, with few adverse events.

One study sought to determine if patients with IBD with or without measurable infliximab (Remicade) antibodies for their cross reactivity to the biosimilar Remsima. All 56 patients who tested negative for anti-Remicade antibodies tested negative for antibodies to the biosimilar; all 69 patients who tested positive for anti-Remicade antibodies also tested positive for antibodies to Remsima. In addition, the antibody titres against both the originator and the biosimilar were strongly correlated (P <.001). Similarly, another study reported that 27 patients with varied rheumatological conditions switched from infliximab to a biosimilar and had no significant difference in infliximab serum levels and disease activity for up to 12 months after the switch.

The study proposed a treatment algorithm for TDM of biologics for psoriasis, as there is a need for evidence-based and cost-effective use of biologics, given the high prevalence of psoriasis, the impact on patients’ lives, and the cost of the therapy, the researchers said. Not all patients respond to therapy, or they may stop responding over time, despite the development of medications targeting anti-tumor necrosis factor agents as well as interleukin (IL)-23, IL-22 and IL-17.

The researchers conducted a literature review on the TDM of anti-TNFs (adalimumab, infliximab, and etanercept), IL12/23 antagonists (usekinumab, guselkumab, and tildrakizumab) and IL-17 inhibitors (secukinumab, ikekizumab). While target therapeutic ranges for biologics are preferred, so far this has only been explored in adalimumab, the researchers said.

For adalimumab, the incidence rates of anti-adalimumab antibodies in psoriasis have ranged from 6.5% to 45%. The most recent report of a therapeutic range for adalimumab trough levels range from 3.51-7.00 mg/L.

For etanercept, the researchers wrote that it appears to exhibit immunogenicity less often than other biologics, with anti-etanercept antibodies observed in 0%-18.3% of patients.

For ustekinumab, anti-ustekinumab antibodies (AUA) have been reported in 3.8%-6.0% of patients. In addition, serum ustekinumab concentrations are affected by weight, with lower serum concentrations observed in heavier patients.

The researchers said additional research is needed, especially for newer biologics, to evaluate target therapeutic ranges. For instance, little is known about the TDM of secukinumab and ixekizumab; both selectively bind and neutralize interleukin-17A, the primary effector of Th17 cells. The same is true of guselkumab and tildrakizumab, which target interleukin-23.

While the researchers said they recommend the measurement of biologic serum trial concentrations and anti-drug antibody levels in routine clinical practice when possible, they noted that can be challenging, especially if patients take medication in the office but may skip doses in between visits.

Reference

Liau MM, Oon HH. Therapeutic drug monitoring of biologics and psoriasis (published online July 5, 2019). Biologics. doi: 10.2147/BTT.S188286.