MSX-3

MSX-3 is a water-soluble phosphate ester prodrug of MSX-2, a xanthine derivative, and functions as a selective antagonist of the adenosine A2A receptor. It is used primarily in scientific research to study the pharmacology of adenosine receptor antagonism, including in preclinical animal models examining motivation, effort-related behavior, and dopamine interaction. MSX-3 itself possesses some adenosine receptor affinity, likely reflecting *in vitro* dephosphorylation to release MSX-2. It is structurally related to caffeine but is markedly more selective for A2A receptors than for A1 or A2B, and is inactive at A3 receptors. It is developed for intravenous (not oral) use due to its water solubility, improving on MSX-2 which had poor solubility[1][3][5].