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.
Why this grade: The study uses in vitro incubation in serum and urine to characterize metabolism and validates an analytical detection method; no human or animal subjects were studied in vivo.
AOD9604 is a peptide consisting of the C-terminal fragment of human growth hormone from amino acids 177-191 with an additional tyrosine residue at the N-terminus of the peptide. It is reported to mimic the lipolytic properties of growth hormone without the diabetogenic side effects. Therefore, AOD9604 may be used as a performance enhancing drug and is banned by the World Anti-doping Agency (WADA). The peptide is available on several Internet websites and was recently identified in confiscated vials in the USA. To detect abuse of the peptide in athletes, a solid-phase extraction method was validated in urine with a limit of detection of 50 pg/mL. The method has good linearity, precision (<20%), specificity and recovery (62%). Six potential metabolites of the peptide were identified after incubation of AOD9604 in serum and urine. Quantification of the metabolites in serum identified a single metabolite, consisting of amino acids CRSVEGSCG, which is significantly more stable than the other metabolites or the parent compound. Screening for AOD9604 and the stable metabolite may potentially allow an increased window of detection.
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