In addition to antidrug antibody levels, measuring serum drug levels of a biosimilar of etanercept may help evaluate clinical efficacy in patients with ankylosing spondylitis (AS), according to study findings published in Clinical Rheumatology. 

Researchers analyzed 60 Chinese patients with AS who received the etanercept biosimilar, yisaipu (YSP). The biologic was given subcutaneously at a dose of 50 mg once weekly and serum drug levels, antidrug antibody levels, and other clinical markers were obtained at 4, 12, and 24 weeks after the start of therapy. Advanced statistical techniques were used to determine the effective serum drug levels in study patients. Moreover, clinical efficacy was defined by achieving an AS Disease Activity Score based on C reactive protein (ASDAS-CRP) <2.1.

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After analysis, the researchers found that patients with an ASDAS-CRP score ≥2.1 showed significantly reduced drug levels vs patients with a score ≤2.1. In addition, the minimum effective serum levels of participants who achieved an ASDAS-CRP score ≥2.1 were 2.32, 2.12, and 2.36 μg/mL, at 4, 12, and 24 weeks, respectively. 

With respect to safety, the investigators reported that participants with antidrug antibodies had increased tumor necrosis factor-α levels and reduced serum drug levels.

“Detecting serum drug levels and antidrug antibody levels might facilitate estimation of the clinical efficacy and adjustment of medication regimen during etanercept biosimilar therapy in Chinese patients with AS,” wrote the researchers.

“In the future, we intend to increase the number of patients and extend the monitoring duration to discover the significance of YSP and [antidrug antibody] levels in clinical practice,” they concluded.

Reference

Dong Y, Li P, Xu T, Bi L. Effective serum level of etanercept biosimilar and effect of antidrug antibodies on drug levels and clinical efficacy in Chinese patients with ankylosing spondylitis [published online February 12, 2019]. Clin Rheumatol. doi:10.1007/s10067-018-04424-x