Detection and in vitro metabolism of AOD9604.
This study focused on developing analytical methods to detect AOD9604 — a synthetic peptide derived from the C-terminal fragment (residues 177–191) of human growth hormone with an added N-terminal tyrosine — in biological samples for anti-doping purposes. AOD9604 is reported to mimic the lipolytic effects of growth hormone without diabetogenic side effects, making it a candidate performance-enhancing drug banned by WADA. Researchers validated a solid-phase extraction method for detecting AOD9604 in urine, achieving a limit of detection of 50 pg/mL with acceptable linearity, precision (below 20%), specificity, and recovery (62%). The study also characterized in vitro metabolism by incubating AOD9604 in serum and urine, identifying six potential metabolites. Quantification in serum revealed one notably stable metabolite — a peptide fragment consisting of the amino acid sequence CRSVEGSCG — that persisted longer than both the parent compound and other metabolites. The authors suggest that screening for both AOD9604 and this stable metabolite could extend the detection window in doping controls. Limitations include the in vitro nature of the metabolic data, meaning real-world metabolic behavior in human subjects in vivo remains uncharacterized.