Development and validation of a ligand-binding assay for quantification of the F(ab') antivenom of Daboia russelii siamensis in human serum and its application to a phase I clinical study.

Daboia russelii siamensis accounts for most of snakebite mortalities in China, yet, specific treatment against the venom toxins is absent in clinical practice. The F(ab') antivenom of Daboia russelii siamensis is manufactured and approved for the clinical trial in China. To satisfy the need for clinical pharmacokinetic research, this study aimed to develop a ligand binding assay (LBA) for the quantification of F(ab') antivenom of Daboia russelii siamensis in human serum. A diverse combination of conditions was optimized based on the fitness of the calibration curve and selectivity. The established LBA undergoes thorough method validation according to the guidelines of regulatory authorities. In the calibration range 1.0-64 μg/mL, the correlation coefficient r was from 0.9970 to 1.000, indicating good fitness. Accuracy and precision were within ± 20%. Dilution linearity was observed in the ultra-high quality-control (QC) samples (500 μg/mL). In addition, the assay was free from hook effect, the endogenous interferences and exogenous interferences. The QC samples were stable under different handling and storage conditions. The validated assay was successfully applied to a phase I clinical study of the F(ab') antivenom of Daboia russelii siamensis in Chinese healthy volunteers. The peak concentrations exhibited dose-proportionality. In conclusion, this study provides a novel and reliable LBA method for the clinical pharmacokinetic research of F(ab') antivenom of Daboia russelii siamensis. It will facilitate further clinical trials in treating the snakebite of Daboia russelii siamensis.