A new ultra-sensitive test can detect CJC-1295 in horse blood down to 0.8 pg/mL, even though the peptide normally hides by binding to blood proteins.
0.8 pg/mLThe immuno-PCR assay can detect CJC-1295 bound to blood proteins at concentrations as low as 0.8 picograms per milliliter — far below what standard mass spectrometry can find
What the researchers found
Researchers developed an immuno-polymerase chain reaction (I-PCR) assay capable of detecting CJC-1295 — a growth hormone-releasing peptide — in horse blood at concentrations as low as 0.8 pg/mL. CJC-1295 is uniquely difficult to detect because it contains a reactive chemical group that covalently bonds to blood proteins, turning the peptide into a macromolecule that standard mass spectrometry screening cannot identify.
Using monoclonal antibodies specific to CJC-1295, the assay was validated in thoroughbred racehorses after administration of the drug. A screening threshold of 50 pg/mL was established to distinguish CJC-1295 from naturally occurring equine GHRH. The method confirmed detection of the peptide-protein conjugate in real-world samples.
Why it matters
CJC-1295 has been essentially invisible to standard drug testing because it binds to blood proteins and hides from conventional detection methods. This new assay closes that gap for equine sports, and the same approach could potentially be adapted for human anti-doping testing. It highlights how peptide drugs can be engineered to evade detection and how testing must evolve to keep up.
The numbers in context
detection limit 0.8 pg/mL · screening threshold 50 pg/mL · 30 amino acid peptide · validated in thoroughbred racehorses
How the study worked
Developed a pair of monoclonal antibodies targeting the CJC-1295 peptide, then built an immuno-PCR assay that amplifies the detection signal to identify CJC-1295-protein conjugates at extremely low concentrations. Validated by administering CJC-1295 to thoroughbred racehorses and testing blood samples.
Who was studied
Thoroughbred racehorses administered CJC-1295
What this study cannot tell us
The study focused on equine plasma, so direct applicability to human anti-doping testing would require additional validation. The 50 pg/mL threshold was set to avoid false positives from endogenous horse GHRH, but the threshold for human testing may differ. Sample size of horses tested was not specified in the abstract.
How to read the evidence
This is an original experimental study that developed and validated a novel detection assay in real-world equine samples. The methodology is rigorous but the scope is limited to equine testing.
When this study was published
Published in 2019 in Drug Testing and Analysis. The detection methodology remains relevant as CJC-1295 continues to be used illicitly in both animal and human sports.
The bigger picture
Performance-enhancing peptides represent a growing challenge for anti-doping authorities in both animal and human sports. CJC-1295's ability to covalently bond to blood proteins and evade mass spectrometry highlights how peptide design can outpace testing technology. This I-PCR approach demonstrates that antibody-based methods can close these detection gaps, and the same principle could be applied to other protein-conjugating peptide drugs.
Questions still open
- Could this immuno-PCR approach be adapted for human anti-doping testing to detect CJC-1295 in athletes?
- Are there other performance-enhancing peptides that use similar protein-conjugation strategies to evade detection?
- How long after administration does CJC-1295 remain detectable using this method?
Common questions
Why is CJC-1295 so hard to detect with standard drug tests?
How does the new immuno-PCR test work?
Read the original research
An immuno polymerase chain reaction screen for the detection of CJC-1295 and other growth-hormone-releasing hormone analogs in equine plasma.
Drug testing and analysis, 11(6), 804-812
Citation
Timms, Mark; Ganio, Katherine; Forbes, Grace; Bailey, Simon; Steel, Rohan. (2019). An immuno polymerase chain reaction screen for the detection of CJC-1295 and other growth-hormone-releasing hormone analogs in equine plasma.. Drug testing and analysis, 11(6), 804-812. https://doi.org/10.1002/dta.2554