This article presents a study on black market ACE-031 products and their detection by gel-electrophoresis and Western blotting. Of the 14 tested products, only 12 contained an ACVR2B-immunoreactive protein. However, mass spectrometry revealed that the products did not contain the ACVR2B-Fc fusion protein ACE-031 but instead the full-length human activin receptor IIB.

ABSTRACT

The usage of ACE-031 (Ramatercept), a dimeric fusion protein consisting of a human activin receptor IIB (ACVR2B) fragment linked to an Fc-part of human IgG1, is banned according to chapter S4.3 of the “WADA 2024 List of Prohibited Substances and Methods” due to its potential performance enhancing properties. While ACE-031 has not yet been pharmaceutically approved, it is sold as research chemical on the “black market” (BM). The article presents a study on BM ACE-031 products and its detection by gel-electrophoresis and Western blotting. Of 14 tested products, only 12 contained an ACVR2B-immunoreactive protein. Electrophoretic separation by SDS-PAGE also showed that the 12 ACVR2B-products contained many other proteins in addition to the main compound (ca. 58.4 kDa). Further analyses by mass spectrometry and immunoblotting revealed that the 12 products contained the full-length human activin receptor IIB instead of ACE-031. The absence of an Fc-fusion protein was further confirmed by treatment with IdeS protease, which was unable to cleave the BM products. In addition, it was demonstrated that the protocol we developed to detect luspatercept (another ACVR2B-Fc fusion protein) in human serum could also be successfully applied for the detection of BM ACE-031. Because administering black market products to human subjects was not ethically justifiable, a study was conducted with rats. In rat serum, BM ACE-031 was detectable up to 48 h post administration. However, due to the relatively high dose applied (10 mg/kg body weight) and possible differences in metabolism, the detection window may be different in humans.