MSX 2 MSX-2 is a selective adenosine A2A receptor antagonist used in scientific research.It is a xanthine and a derivative of the non-selective adenosine receptor antagonist caffeine.MSX-2 has poor water solubility, which has limited the use of MSX-2 itself.Water-soluble ester prodrugs of MSX-2, including MSX-3 (a phosphate ester prodrug) and MSX-4 (an amino acid ester prodrug), have been developed and used in place of MSX-2.
