Thymosin β4 is a small acetylated protein consisting of 43
amino acids with a monoisotopic mass of 4,960.49 Da (inset
in Fig. 6). In vivo, this hormone plays an important role in the
regulation of cell migration, proliferation, and differentiation.
Due to its anti-inflammatory effects and positive influence on
angiogenesis, reepithelialization, and wound healing, thymosin
β4 is of great interest both for the pharmaceutical industry
and possibly athletes in sports [41, 42]. A synthetic form of
thymosin β4, called RGN-352, was developed for the treatment
of acute heart attacks, cardiac tissue damage, and the
management of multiple sclerosis and already tested in clinical
trials. But as the manufacturer was not GMP compliant,
the clinical assessment of the drug was stopped before the
studies were completed [43]. Nevertheless, an acetylated fragment
of thymosin β4 comprising amino acids 17–23 [44] is
distributed online as “TB-500” [35]. Although intended only
for veterinary use, the online provider advertises performanceenhancement
due to an increasedmuscle growth, strength, and
endurance, as well as an improved tissue repair and reduced
inflammation [45]. In order to test for authenticity, one of
these preparations was purchased online from DB Genetics
(Santa Cruz, CA, USA) and analyzed for the declared ingredient
[Fig. 4b]. Surprisingly, the analysis of the black market
product yielded thymosin β4 instead of TB-500. Figure 6
shows the HRMS product ion mass spectrum of [M+6H]+ at
m/z 828 of the sixfold charged acetylated thymosin β4, and
the elemental composition as well as accuratemasses of the band
y-ions are summarized in Table 1. This finding further
corroborates the above-made statement that drug candidates
without clinical approval are distributed.
