Luspatercept Administration: Understanding the Detectability and Hematological Effects and in Males and Females
A single administration of subcutaneous luspatercept (0.25 mg/kg) is proposed for four healthy participants, two males and two females. While detection of luspatercept has been studied before by spiking standard into samples, the excretion profile of the drug has not yet been determined in an anti-doping setting. These excretion samples are vital for proper validation of the detection method(s) to be applied to athlete samples. Additionally, the detection window of the drug has yet to be determined in serum/plasma and DBS (and, if applicable, urine), which provides important information for results management authorities.
Finally, Phase I clinical data from luspatercept in healthy individuals suggests that there will be an effect on the hematological module of the ABP, if abused by athletes. As such, it is important to provide a well-characterized timeline of these changes.
The main objective of this study was to perform an administration of Reblozyl® (luspatercept-aamt), a newly approved drug to treat anemia, in healthy volunteers and evaluate the detection of luspatercept in serum, dried capillary blood spots (collected with the Tasso M20), and urine for antidoping purpose. Four volunteers, two males and two females, received one subtherapeutic dose of luspatercept (0.25mg/kg) followed 3 weeks after by a second dose. Samples were collected from before administration to 7 weeks after the second dose. Evaluation of Luspatercept detection in the samples was performed after an immunoextraction step with magnetic beads coated with anti-ActRIIB antibodies, followed by electrophoretic separation by SDS-PAGE and a single-blot and immunodetection using a biotinylated anti-ActRIIB. To propose a confirmation analysis, direct detection was also assessed by SDS/SAR-PAGE followed by double-blotting using a second ActRIIB detection antibody or by IEF-PAGE and single-blot. Indirect effects were examined by measuring endogenous EPO concentrations and by evaluating hematological parameters variations using the ABP model.
Despite the supraphysiological dose administered, intense signals were identified for luspatercept in serum from the day after the administration until the end of the study, 7 weeks after the second dose, and detection is likely possible for even longer time. This administration study also confirmed that the drug is excreted unchanged in urine and regularly eliminated, allowing detection in this matrix. 20μL-DBS also showed sufficient sensitivity to detect the drug until the end of the study. The three electrophoretic methods used in Anti-Doping laboratories: SDS-PAGE, SAR-PAGE and IEF-PAGE were all appropriate for both screening and confirmation and could be used for one or the other. They showed very similar sensitivity.
The impact of the luspatercept on indirect markers was evaluated: ABP approach could flag luspatercept administration in some subjects, especially when ABPS and HGB were both atypically increased, but the effects on RET% were limited and the time/amplitude of the effects varied between subject. Endogenous EPO expression was also not strongly affected and was not indicative of the use of an erythropoietic agent.
In conclusion, this study demonstrated that luspatercept can be detected for a long time using electrophoretic methods in all the matrices relevant for doping. Its survey can be easily implemented in antidoping laboratories.
Publication: Marchand A, Miller G, Martin L, Gobbo C, Crouch AK, Eichner D, Ericsson M. Detection of erythropoiesis stimulating agent Luspatercept after administration to healthy volunteers for antidoping purposes. Drug Test Anal. 2022 Jul 5. doi: 10.1002/dta.3341.